Practical Yacht Navigator 0679508074, 9780679508076

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yacht navigator practical Kenneth

SI2-50

This is a complete manual on how to navigate any type of small vessel

and

coastwise

across the sea in today's

It is a modern book for modern boating people who want to learn fast by means of clear diagrams and

circumstances.

photographs, which are supported by a

comprehensive

text.

Two-color

used throughout to give numerous examples of fixing the yacht's position, emphasizing the essential knowledge needed on tides, coping with fog, understanding the all-important steering compass and a host of other facets of the small craft navigator's illustrations are

activities.

How

to use small

radar

sets is dealt with,

as are techniques with the almost

universal echo sounder

and

logs

sailing

and

transistorized

computers for those that

have them. More basic means of calculating where the boat is and where to head for next are not forgotten. The author keeps in mind that the type of boat and the method of propulsion may van widely, but there is a clear explanation of the pilotage problem encountered by the cruising yacht when she is beating to windward. -

The book

is

ideal

when studying who has

navigation. But the reader

not

the time or inclination to attend special instruction, will find here the to

go

to sea

without getting

knowledge

lost.

BOSTON PUBLIC LIBRARY

yacht navigator practical

yacht navigator practical Kenneth

Wilkes

DAVID McKAY COMPANY,

NEW YORK

INC.

Practical

Yacht Navigator

Copyright

©

1

978 by

All rights reserved,

H.

Kenneth Wilkes M. R.I.N.

including the right

to reproduce this book, or parts thereof, in

any form, except

brief

quotations

First

American

for the inclusion of

in a

review.

edition,

1

978

Congress Catalog Card Number: 77-75995 ISBN: 0-679-50807-4 Library of

J 97?/-

Printed

/

in

Great Britain

Contents

1

Lost on the water

9

2.

The mariner's map

3.

Equipment to

4.

More on instruments

66

5.

North, south, east, west

73

6.

To shape

82

7.

Plotting the course

8.

How

9.

This

a

high is

10.

How

11.

Radar

16

find the

way

course

is

92

the tide

96

?

the position

1 1

134

some

144

windward

155

for

2.

Sailing to

1

3.

Log books

1

175

Coastal passage

16. Blinded but not lost

63

167

14. Off to sea 5.

4

the radio helps

1

1

36

:

fog

!

182

17. Traverse tables

191

18. Celestial navigation

197

Index

204

^^~

Publisher's note Practical Yacht Navigator has had world

being

first

lives in

published

in

1

wide

sales since

973. The author. Kenneth Wilkes,

England and some of

practice of coastal navigation

his is

examples, although the similar everywhere,

borrowed considerably from European usage. This edition has been extensively rewritten by Roger Marshall. It preserves the attractive format and approach of the earlier edition, but makes the contents of immediate application to all who sail the coasts of the United States and Canada.

Line illustrations: Bill

Streets

Log book examples: Peter Milne

Photographs: Peter

Johnson except

for

U.S. Coastguard 25. 26, 150.

Roger Marshall 26 J. R.

(left).

28, 29

Hughes 151. 152. House 67. EMI Marine 149, 152

Kelvin

Simrad 141

1

Lost on the Water

.

great fun until

Boating

is

along

sunshine and

in

a

you are

lost.

Sailing

spanking breeze, or with

the engine purring sweetly,

is

what many

expect to do on a Sunday afternoon.

It is

sailors

one

thing to do this with the shore half a mile off and

landmarks, perhaps houses and fields moving it can be quite frightening to have sun and reliable engine, but with sight all round and no indication of

slowly past, but the

same

fine

only water

where

to

in

go

in a

boat which

is

hijacked.

Just before you were going ashore on Sunday after a fine weekend, along came some escaped criminals, bound up your hands and tied a handkerchief around your eyes and confined you with your head up the quarter berth. You heard the engine start and the sails hoisted and away they went. Six hours later they woke you up: they were feeling slightly seasick and had not the faintest idea where they were. If you would navigate them, so they said, they would strike some sort of bargain. Well, what do you do next? If you had only used your boat for afternoon sailing and always very close to familiar landmarks then you would be just as frightened as the hijackers. On the other hand there is no need to be a super mathematician or a puzzle solver to be able to take quick charge of this situation and learn to navigate. You only need to be a practical

evening

yacht navigator.

:

navigating your yacht.

next.

Imagine yourself

all sorts of things you would do, even though the hijackers had kept no record of what they had been doing up to that instant. You would look for certain things around the horizon, you would look at your watch to see what time had elapsed, you would look at the compass and you would look at the charts. Then two or three courses of action would suggest themselves. You would be choosing one of them away you go

There are

Let's hope this sort of dramatic situation never happens, but the circumstances are not unlike those the yacht navigator and he may be the owner or the skipper deals with at times during

—

—

the season.

My own

first

attempt

at a

passage out of sight

of land did not involve hijackers sort of run that scores of yachts

time every season a simple run :

across Long Island

New

Haven.

I

Sound from

It was just the make for the first of about 20 miles !

Port Jefferson to

penciled a line on the chart joining

two places. This gave me a course to steer on the boat's compass. The distance seemed rather difficult to calculate because the chart did not have a scale of miles to the inch like a road map. Someone in the yacht club said that it was best to sail by night because lighthouses flashed out, making it easy to find where you were. memorized the characteristics of two prominent

these

I

lighthouses.

^™

^^^™

practical yacht navigator Off

we went on

a reach. Later than had expected appeared dead ahead, which took Haven lighthouse. The only problem was I

a flashing light

to be

New

I

were a bit more than the four seconds apart they were supposed to be. Behind the lighthouse could see a pattern of red and white 4 sec. flashing buoys. So using a dim flashlight searched on the chart around the entrance to New Haven harbor and found a series of buoys that seemed to correspond to what lay ahead. felt sure we were approaching the entrance to the channel correctly. Almost at once heard the sound of breaking water on all sides. then did probably the only sensible thing had done all night: stood out to sea and hove-to. By daylight could clearly see the light at Branford reef which had mistaken for the New Haven lighthouse. We were several miles east of our destination. During the night we had stood into the reefs around the Thimble Islands, and the broken water had that the flashes

I

I

I

I

I

I

I

I

I

I

heard

was

the fast east-going tide rushing over

shoal rocks. Fortunately, the rocks had been well

below the surface and we had come to no harm. With fair, we reached New Haven with no further problems. But had the seas turned rough or the visibility deteriorated we might have been in serious trouble. Shortly after, met a man who told me of a trip he made from Oyster Bay to Saybrook. Mistaking a buoy on the western end of Long Sand Shoal for one on the eastern end, he almost sailed into the Hen and Chickens. Fortunately, he realized his error upon seeing the lighthouse at Saybrook breakwater. He, too, came to no harm, but if the weather had turned bad it may have been otherwise. Incidents of this sort probably happen many and a bit times every season. With fine weather of luck no damage is done but a lot of time may be wasted. But if the weather turns foul, then the trouble starts. At best a very anxious time is had the weather remaining

I

—

10

—

by

all,

and

at

worst disaster may

Many

strike.

rescues by lifeboat are a result of navigation

which has gone haywire. The yachtsman does not have to learn navigation like a merchant marine officer, but his navigational problems are basically the same. Courses of study and examinations suitable for the yachtsman are discussed in Chapter 19. But it is not

at all

necessary to take these to gain a grasp of

navigational matters.

It is

practical ability that he

needs.

A may

cursory glance at a text book on navigation give the impression that the subject

is

and calls for a lot of mathematics and complex calculations. In fact, navigation is based on common sense and a little very elementary difficult

geometry. Early sailors managed to navigate without the advantage of study they were" able to do so by observation of the results of wind and tide, by deductions based on what they saw, and by amassing experience. All that a text book can do is to point out the problems, and indicate solutions: this reduces the time required to amass

—

experience.

Now here is an important point. Most people soon master the principles in any navigation problem quite quickly, but fail to reach the correct answer. It is because they are inaccurate. They make mistakes

in

simple addition or subtraction,

add when they should subtract, or pick up the wrong figure from a table. More students fail examinations by making silly, simple mistakes than by not knowing the principles involved. The trouble is that this happens more often at sea, than when practicing on land. It may be argued that a degree or so error in a course does not matter as one can seldom steer to that accuracy. This is true. But if one is careless and it an error is just as likely to be 1 0° as 1 °

—

then becomes serious

if

not dangerous.

It is

lost particularly important to right

—

plus or minus

ensure that signs are

— since an error

the sign

in

produces an error of double the figure. If a is applied the wrong way the variation of 1 0° which makes 20 miles course will be 20° wrong error on a 60 mile passage. The golden rule which it is most strongly recommended should be followed in every navigation problem is:

W

—

Check every figure, and every sign "name" N or S, E or W.

every

—

(

+

or —),

Check every addition subtraction by "adding back").

Do

not

own

is

no reason

should not use your

know

"wake co. 21 0° mistake has been made by the wrong

what they mean,

e.g.

and figure when checked.

USE any answer till every figure

has been

exactly

Many

T."

a

figure being

picked up, or misunderstood.

When

some

writing

figures

down which need

subtraction or addition, ensure they are written

plumb under each other. Again this speeds the work and helps accuracy. These may seem obvious or trivial points, but experience shows that they pay handsome

Good

navigation calls for meticulous

attention to detail

and

neat, accurate writing

than any high degree of technical

ticked as checked.

more

ability.

Pilotage Pilotage

is

a

name given

to

such things as

directing a vessel into or out of a harbor,

estuary or

This procedure should be followed

when

working out exercises at home or at sea, and when working "for real." It is a temptation to press on with calculations particularly at sea to get a speedy answer, without "wasting time" checking. But if the checking is done while the table-book or tidal atlas, or whatever, is open and to hand, it only takes a moment, and will save a lot of unnecessary work in re-calculating if the first answer is obviously wrong. If it is not obviously wrong, possibly hours of unnecessary sailing may be involved, and even danger incurred, all through omitting to check at each stage. So right from the start, make it routine to check and tick every figure and calculation. Your work will be made easier, and the risk of error reduced, if you write clearly and neatly, and do not omit captions. Do not overwrite a wrong figure, but cross it out and put the new figure

—

—

By "caption" has just been written

clearly.

why you

abbreviations, provided you

dividends.

and subtraction (check

Tick every sign

There

on the water

is

—

of what 21 0° true.

meant the meaning e.g.

wake course

river.

Position and direction are

ascertained by eye using local

knowledge

or

coupled with use of the compass, particularly in poor visibility or by night. There is no time for, and little necessity for, plotting the ship's course on the chart, the operation calling chart,

for

knowledge

of the position in relation to the

channel, of buoys and other navigational marks,

and

for the ability to identify these objects as seen.

In

many designated

"Pilotage" areas regulations

commercial vessels (or vessels over a stated tonnage) to employ a certificated pilot. Yachts are not obliged to carry pilots (except in require

all

a

very few specific places).

Ayachtsmansailing on Long Island Soundsayfrom Stamford to Mystic, Connecticut would use pilotage, determining his course by reference to buoys and landmarks. He would not require to pre-determine courses to steer nor to plot his position on the chart in daylight and normal weather. Nevertheless,

many

of the features of navigation

essential

on

a longer

which

are

passage may be used, and

in

11

^^— practical yacht navigator

Fig

1

.

They

This

is

what meridians

are.

Known,

are by definition "great circles."

too, as longitude.

Fig 3. When these are combined, the result is system of reference over the seas of the world, latitude

Fig 2.

12

Parallels of latitude.

and longitude.

a natural in

terms of

lost

poor

visibility or at

night

may be

A

necessary.

knowledge of the buoyage systems, the proper use of the echo sounder (or leadline). The direction of tidal streams, the use of leading lights and marks, port entry signals and the recognition of navigational Pilotage calls for thorough

marks by their lights at night These are all dealt with later

is

also necessary.

Navigation as a general subject There are some words used over and over again and their explanation is as follows: Position. its 1

A

position can be described

in

terms of

relation to a stated object, e.g. "position,

may be

not close to an easily identified object,

it

more

and

precisely described by

longtitude of which more

its

in a

latitude

The meridian which

passes through Greenwich

termed the prime

Any number

named

The

latitude of a position

of meridians can be drawn, at

any

either at the center of the earth, along

meridian on which longitude

lies.

it

A

direction in the business of navigating

can be described as a line between the observer and an object, or between two objects or positions. The direction of an object is defined in terms of the angle between the object and some

"datum"

line.

The

direction of

observer,

is

therefore the

The meridians on south

commonly used

a chart

all

run true north and

— they join the two poles. line

If

the angle

representing a bearing and a

is measured, this is a true bearing. Bearings are normally measured in 360° notation, measuring the angle from true north (the meridian,

meridian

it)

(Fig 1.)

by the

is

or

"bearing."

in

meridian

one object

position from another position, or from the

A

Any

(Fig 3.)

minutes which the meridian on which it lies is east or west of the prime meridian, 0° (Greenwich

or a line parallel to

figure).

therefore stated as

given as the degrees and

is

(all give the same named by this angle, in degrees and minutes, and is named east or west, and can be any angle up to 1 80° E or 1 80° W.

the equator, or at either pole

is

being a given number of degrees and minutes north or south of the equator, measured along the

between the

0°.

desired angular distance from the prime meridian

measured

(Fig 2.)

Direction.

cuts the center of the earth).

is

of

can be drawn, cutting every meridian at right angles, and each passing through a given point on any meridian. The angular distance of any parallel of latitude is measured along a meridian, or at the center of the earth, from the equator towards either pole, and is named north or south, and any angle up to 90°.

in a circle,

minute of arc are recorded in decimals, e.g. 50° 25i being written 50°25'.5. The equator is a great circle girding the earth exactly midway between north and south geographic poles. A straight line which passes through both the north and south geographical pole is a meridian. It cuts the equator at right angles, and is half a great circle (a circle which

meridian, and

parallel to

Any number

meridian).

(60') in a degree. Fractions of a

is

drawn

a line

minute.

There are 360 degrees (360°)

60 minutes

is

parallels of latitude

Its

Cape May lighthouse." When

miles east of

parallel of latitude

the equator and girding the earth.

on the water

clockwise round to the degrees may therefore be anything from to 359 (always measured clockwise), and may be designated true bearing bearing.

bearing

suffix T, e.g.

090°

T. (Fig 4.)

See page

1

5.

13

i^^^™™^"""""^""" practical yacht navigator Bearings are given clockwise

Fig 4.

degrees.

Relative bearings from ship's head: 45°

Fig 5.

to port Fig 6.

in

and 90° to starboard. Relative bearings as given by the Navy:

45° and 260°.

If

the bearing

measured

is

in

shown by

relation to the

magnetic compass, then this will usually differ from the true bearing because compass north usually differs from true (geographic) north. A compass bearing is always shown with the suffix C, e.g. 090° C. (see Chapter 5). A bearing which is related to the direction of the yacht's head (the direction she is going) is called a relative bearing. Used often to give a quick indication of a general direction, it does not direction of north as

Fig 4.

a

compass bow," or "buoy seen 90° abeam to starboard" are examples of relative bearings. (Fig 5.) The United States Navy gives relative bearings based on 360 degrees. For instance, a relative bearing of 45 degrees indicates 45° from dead ahead to starboard, while a relative bearing of 260 degrees indicates 1 00° from dead ahead to port. (Fig 6.) require the observer to refer to true or north. "Vessel seen

Fig 5.

45° on

port

Distance. All distances are measured (or sea) miles. 1

Fig 6

14

^

The

nautical mile

cables, normally

shown

is

in

nautical

divided into

as decimals of a mile,

The nautical mile is, be definition, the distance of one minute of arc measured along the meridian. As the earth is not a perfect sphere, this distance varies between 6 046 ft at the equator and 6 1 08 ft at the pole, 2 miles 4 cables

is

written 2.4 M.

lost but for practical purposes the average

mean value of 6 080 over 200 yards.

taken at a fraction

Note that the nautical mile

ft.

is

longer than the statute mile of 5 1

5 per cent), which

is

on the water

now

The cable

is

a

appreciably

280

feet (over

an arbitrary measurement

is

fixed in the sixteenth century.

Speed The

unit

used

always the knot, (abbreviations

is

kn or K), which

is

one

nautical mile

in

one hour.

Depths The old 6

feet.

depth

unit of

Fractions are

the fathom (fm), being

is

shown

as fathoms and feet.

Thus 1 A represents 7 fms 4

ft.

The new unit of depth, used on most new charts and new editions of older ones, is the meter (m). Fractions are of a meter.

shown

in

decimeters or decimals

Thus 8 7 indicates 8.7 meters.

m

denotes meters denotes nautical miles. This may well apply to the same object when navigating, for instance a lightship may be 21 m high and visible 14 M away. Note: small

capital

M

Bearings on charts and All

bearings

line

bearing

seaward).

lists of lights

shown with no 1

All

suffix (e.g. "lights in

74°" are true bearings (from

show true many and pilot books show

Admiralty charts

bearings, without the suffix T, but

"yachtsman's" charts bearings and courses magnetic (e.g. 095° mag). To guard against error, it is advisable to put T against

all

true bearings

which you write down,

from those which may be magnetic or compass. This is explained more fully in Chapter 5.

to distinguish clearly

15

2.

A

The Mariner's Map

chart is a mariner's map. It shows him where safe for him to sail— amd more important-

is

shows where

it

is

and harbors and

not.

It

shows the

it

of water

and even

So you can map, and

enables the navigator to form an accurate picture of the area

Once

shown.

the knack of "reading" a chart

are given easily

meaning by

their shapes.

by abbreviations or

remembered

after a

initials,

little

U.S Naval

Institute.

Bowditch, American Practical Navigator, U S Navy Hydrographic Office, Publication No. 9 Reed's Nautical Almanac (partial information only).

Types of chart Charts may be broadly

classified

between

Navigational charts for keeping a track of a ship's position and for determining courses to be 1

steered.

acquired the yachtsman can visualize even a strange area m advance. He knows what to expect before he gets there, knows where the dangers lie, where the safe channels are, and can navigate in confidence. Like a good book, the more one reads it the more one knows about the subject. But a chart contains so much information that quite a lot of it has to be written in a form of shorthand Much of this takes the form of symbols which indicate their

,

each

other so that he can shape a course from one to another. A mass of "signposts" in the form of landmarks are given so that he can fix his position m relation to them. The shape of the coastal hills cliffs, sand dunes and the general "picture" of the coast are all shown. The depths

a

Chart No. 1 Nautical Chart Symbols and Abbreviations, National Oceanic and Atmospheric Administration. Dutton's Navigation and Piloting,

various ports

their positions relative to

the nature of the sea bed are given. see a chart is far more than simply

and only one meaning, and one has to learn to be extremely careful to recognize the exact message being conveyed. This applies particularly to the shape and color of buoys shown, the precise type of light of a given lighthouse, and so on This only comes with practice, and the reader is recommended to study a chart or charts in detail identifying every mark or symbol and checking with the list of symbols and forms given in publications such as:

is

Non-Navigational charts such as 2.

for special

purposes

(a) Routing charts showing details of winds weather, principal shipping routes.

(b) Lattice charts for position finding

by radio

aids. (c) Radio beacon charts. (d) Tidal stream charts and atlases. (e) Charts of isogonic variation and

other

specialized information.

Other data

which

are

practice.

A

very clear understanding of what a chart shows is important for safe navigation. Each

symbol and abbreviation has one precise meaning 16

Navigational charts the United States, navigational charts are published by several different agencies. The principle ones are the National Ocean Survey of the National Oceanicand Atmospheric Administration In

a

the mariner's :

map

(Department of Commerce), the Hydrographic Center of the Defense Mapping Agency (Department of Defense), the U.S. Coast Guard, and the U.S. Naval Oceanographic Office. In most cases, the publishing agency distributes the charts to local sales agents in U.S. and foreign ports.

The National Oceanic and Atmospheric Administration produces complete catalogs of charts, listing

each by number and area covered.

Nautical Chart Catalog

1

covers the Atlantic and

Gulf coasts, while Catalog 2 covers the Pacific coast

and Catalog 3 covers Alaska. They are available from any authorized distributors. Other chart sources for boats sailing

American

in

waters are the U.S. Geological Survey (Department of the Interior), the Mississippi River

and

district offices of

the U.S.

Engineers for charts of

many major

Although these agencies are sources than those

when :

listed

they are useful

Commission,

Army Corps

rivers.

important chart

less

above, there

in fulfilling

of

and

lakes

may be

times

the yachtsman's

particular chart requirements.

Other countries also produce good charts, especially large-scale charts of their local waters.

The

British Admiralty charts, published by the Hydrographic Department (British Ministry of Defense), are very widely used. Over 6,000 are

published, covering the world. They are available

from

agents

official chart

in

most

large ports.

Chart projections The earth is an "oblate spheroid," slightly flattened at

cartographer

is

Fig 7. For navigation we need a flat chart, but the earth roughly spherical. So every attempt to make a chart is a

that

is,

a

sphere

top and bottom. The

reproducing the surface of this sphere, or it, on a flat piece of paper. (Fig 7.) It is

clearly impossible to flatten out an

or a large piece of it

compromise.

faced with the problem of a portion

of

or stretching

is

in

one

orange skin

— without either cutting

some way. The same

a section of the earth's surface.

— it

applies to

Whatever he does, 17

practical yacht navigator is bound to distort the area some ways. There are several methods

the cartographer

depicted

in

of "projecting" the earth's curved surface onto a flat

plane.

The

principal projections used in

them on the same scale towards the top of the chart. It will at once be apparent that the space between 1 0' on the chart towards the top is greater than

it

was

at the

bottom,

navigation are Mercator's projection and the

the northern hemisphere (or less

gnomonic

hemisphere).

projection.

A

Mercator projection On a sphere (the earth)

of latitude are lines all parallel to the equator and thus to each other, and are equally spaced. But

the (vertical) meridians, though also straight and cutting each parallel of latitude at right angles,

meet

at

all

the poles and are therefore tapering

together as they approach either pole.

globe on a flat draws his meridians all vertical and parallel to each other, and spaced equally apart. To prevent distortion of the shapes of the land, he expands the distance between

To represent

a section of the

the chart

is

of

of the southern

between two points on a called a rhumb line. Although not the shortest distance between the two points, there is negligible difference between this and a straight line

Mercator chart

the (horizontal) parallels

if if

is

Great Circle course if the distance is less than about 500 miles, in latitudes less than about 60° N or S, and can safely be disregarded for coastal navigation. In practice, all coastal and short passages are laid off on the chart as rhumb lines or straight lines on a Mercator chart. (Fig 9.)

surface, the cartographer

parallels of latitude to

correspond with the amount

he has pulled the meridians apart to make them parallel. Thus, while the shape of each part of a chart

is

correct, the scale varies gradually

top and bottom of the chart. (Fig

8.)

between

The

A

straight line

meridian

at

the

on

same

a

Mercator chart cuts each

angle, so that true bearings

of the line will remain unchanged along its length. (b) The shortest distance between two points on a

sphere

is

a

whose plane

portion of a Great

Circle (a circle

cuts the center of the earth). This

appear as a curved line on a Mercator chart, bowed away from the equator. (c) Distances on the chart must be scaled off from the latitude scale (on vertical edges of the chart), and level with the part being measured as the scale varies. Check this by placing the dividers on, say, 1 0' of latitude near the bottom of the chart. Then, without disturbing the dividers, place will

1

projection

Charts on the

Gnomonic

Projection are only used

for very high latitudes (polar charts), for plotting

long-distance Great Circle tracks, and other special purposes. The meridians radiate out from the nearer pole, and the parallels of latitude appear as

circumferences or arcs of circles whose centers are at the nearer pole. On these charts a Great Circle track appears as a straight line, cutting

practical effects of this are: (a)

Gnomonic

meridian

at a different angle,

would appear

as a curved

while

line,

a

rhumb

bowed from

each

line

the

nearer pole. (Fig 10.)

A

shipmaster, requiring to shape a great circle

more miles apart so as to minimize his mileage would use a gnomonic chart. He would draw in a straight line between the ports, pick up the latitude and longitude of a series of points along this line, and transfer these points to a mercator chart. Joining these points would produce a course between two ports

a

thousand

or

bending round. He could then determine the positions where an alteration of course should then be made to maintain series of short straight lines

.

the mariner's Fig 8.

Flat chart actually represents surface of sphere.

Fig 9.

In

Mercator projection,

a

course can be

map

laid off as a

straight line but distances are distorted from north to south.

Curved line represents great "ordinary chart."

Fig 10.

Gnomonic

by straight curved

line,

his position

circle.

This

is

the projection of an

projection: great circle

is

now represented now becomes

but straight course on Mercator

along the great

a long passage,

whether

sails a great circle

A yacht on power, seldom

circle line.

sail or

course, preferring to pick a

course or series of courses to take advantage of favorable winds and currents, and so avoid areas of adverse conditions such as areas of fog, stormy weather.

ice

and

Non-navigational charts 1

Routing charts are published

oceans. There

is

for

each of the each month

a separate chart for

in the year for each ocean. These show Winds. The directions and strengths of the winds likely to occur at a large number of positions over the chart. At each position symbols indicate the percentage of winds of varying directions and strengths to be expected. Ice Limits. Areas of fog, with percentage

incidence, sea temperatures, etc.

Main shipping routes (and distances) between a number of ports. Ocean currents, directions and rates of flow.

These charts are not suitable for plotting the They are essential for

ship's position or track.

trans-ocean passages. 2. Lattice charts.

These are charts overprinted

with "lattices" of lines or curves which enable the ship's position to be determined from radio signals

19

.

:

practical yacht navigator received from certain specific navigational radio

nearly 7 miles to the inch. (As the scale of a

The message received indicates the intersecting lines on which a ship's position lies. There are a number of systems, each requiring

the area being measured, this ratio

stations.

designed for that Chapter 1 0. 3. Radio beacon charts show all radio beacons, some linking together those operating on a use of the particular

in

common

frequency. They

beacons

are best situated to use for position

show which

radio

in a given area. These are discussed in Chapter 10. 4. Tidal stream charts and atlases. A description and instructions for use appear in Chapter 6.

finding

Charts of isogonic variation. These

number

show

a

each passing through all points having a given magnetic variation. Variation is fully discussed in Chapter 5. 6. Co-tidal and co-range lines charts. Tables are available which predict the times of high water and low water at a number of ports (see Chapter 8). Co-tidal and co-range lines charts enable the height of tide at positions well offshore to be calculated. These are of use where it is desired to correlate a depth found by echo-sounder with depths shown on the chart at positions some miles from a port. of lines

is

shown

as at

a stated latitude).

When

lattice chart

system. These are discussed

5.

Mercator chart varies according to the latitude of

selecting a chart the scale

visualized by noting

how wide

is

more

easily

apart are the

degrees and minutes of latitude

shown

in

the

mind that 1 minute is 1 nautical mile, and 1 degree is 60 miles. There are three main scales of chart. 1 Harbor plans. These are drawn to the largest scale and cover a single harbor or estuary, showing the greatest detail. They are drawn on gnomonic projection, but this has no practical significance for navigation. Scales are between 2 and 1 inches (50 and 250 mm) to the mile. 2. Coastal charts to various scales, for example Port approach charts covering 1 2 to 24 miles across. Large scale coastal charts covering about 50 M vertical borders, bearing in

of coast.

Medium 1

00

M

scale coastal charts covering about

of coast.

Small scale coastal charts covering about 200

M

of coast. 3.

Ocean

charts to a very small scale spanning

1-2,000 M or more. The yachtsman will

find a harbor plan helpful

for navigation in large harbors containing

Scale of charts The scale of a chart is the relationship of a distance on the chart to the distance it represents on the land (or sea) depicted. A large scale chart shows, say, a river a mile wide very large on the chart, while a small scale chart would show the same river very small. The scale of a chart is shown, usually near the title, as a ratio or fraction, e.g.

that

1

:

on

500,000 or

1

500,000'

would

charts covering his usual sailing area, and

medium

scale charts covering any proposed or likely

passages he may make.

The amount

of detail

shown on

a chart

naturally varies with the scale of the chart

indicate

1 inch on the 500,000 inches, or

this chart, a distance of

chart depicts a distance of

20

This

sandbanks, shoals, or channels (such as Miami harbor or Newport harbor), but in many cases port approach charts will provide quite sufficient detail. He should have a few large scale coastal

larger the scale the

coastal chart

may

more

not

detail.

show

all

A

— the

small scale

the buoys

in

harbors and estuaries, and details of lighthouses

map

the mariner's (their

exact characteristics and arcs of

visibility

may be omitted or be incomplete). For this reason, medium or large scale charts must be used when closing the land and sectors

and

(if

any)

to identify lights

scale chart

is

and objects.

If

no

large

available for a particular piece of

coast, details should be

Guard Light

List,

found

in

the U.S. Coast

the pilot for the area, and

the appropriate edition of Reed's Nautical Almanac.

Care latitude

is

called for in reading the scales of

and longitude printed on the

vertical

and horizontal margins of the chart respectively. The spacings, and the meanings of the graduations vary with the different scales used. Refer to Fig 1 1 On the small scale on the left, each graduation marks one minute of latitude, each five minutes being alternately with and without a .

On the medium scale shown, each one minute is alternatively "plain" or "bar," and there are five spaces marked within each minute. Each small graduation therefore represents 0.2 of a minute. On the large scale shown on the right, each minute has been divided into ten parts, so each small graduation represents one tenth of a bar.

art

CSS

|

minute.

Always read the degrees first, (taking the lower number of the two degrees which lie on each side

20'

of the position), then the minute, noting carefully

I

the minute numbers printed. Note also what each smallest graduation represents.

A

little

practice

is

necessary. 31

Depth of water on a chart The coastal areas of a chart show the height of hills and peaks near the shoreline, with contour

I:

20'

lines

connecting

all

points of a similar height.

This information enables the navigator to form a

mental picture of surrounding landforms.

In

addition, the sea areas of a chart give the heights

4V Fig

1 1

.

4tf

Latitude scales

Each minute of latitude

49*.

on charts. Small, medium, and one mile.

is

of prominent ocean landmarks, such as lighthouses. They also show a vast number of "soundings" (the measured depths at various places on the ocean floor which are permanently or nearly permanently

large scale.

covered with water), as well as "drying heights" (the heights of all features of the seabed that are periodically uncovered at low tide). 21

1

practical yacht navigator

Because the level of the sea is continually changing as the tide rises and falls, some common reference level must be used to measure land heights and sea depths. The reference level used to record soundings (and drying heights) is called the chart datum. On most current charts, the chart datum is some average lowest level to which the tide falls. This low water average can be calculated in several ways. Three of the most common methods are mean low water, mean lower low water, and mean low water springs. Mean low water (MLW), used on charts of the Atlantic and Gulf coasts, is the average height of all low tides at a particular place. Mean lower low water (MLLW), used on charts of the Pacific coast, is the average

two

height of the lower of the particular place.

daily tides at a

And mean low water

(MLWS), used on most

British

springs

Admiralty charts,

is

would

when The

new and

their highest

and lowest).

moons when

full

tides are at

of the time the actual depth

is

either equal to or

higher than the sounding. But depending upon the reference level used, tides can also

fall

occasionally

below the charted depth. The actual depth is

always the charted depth

of the

PLUS

the

height of the tide at that particular time. In

contrast to the low water

datum used

feet

rest of

above the water only

mean high water

used to measure the

level

heights of land objects

generally a high water

average. Like the chart datum, however, this

mean high water and

the actual depth of the water

at that particular time.

Units of measurement vary charts.

Many

still

among

different

current charts measure depths

is

also printed in purple along the border.

The heights

of land objects as well as drying

heights are always measured

in feet

when

fathoms and feet. Drying heights are distinguished by an underline for example, 6 means a drying height of 6 feet. When meters are used to specify soundings, heights are also given in meters. Again drying heights are underlines 4 means 0.4 meters above chart datum. On the sea areas of most charts, places of similar depth are connected by depth contours (or fathom in

—

—

blue tints

is

22

feet high

usually

—

the darker the tint, the used to indicate depth shallower the water. These tints are separated by depth contours, which are either dashed or dotted depending upon the depth, or broken at intervals and the depth written in.

generally) setting

00

in

fathoms and feet. But this system is now changing as soundings on new charts are converted to meters and decimeters. To avoid confusion, the depth unit used on a particular chart is always specified. For instance, "soundings in fathoms, depths under 1 fathoms in fathoms and feet" might be written under the title of an older chart. And on a newer chart, the unit of measurement used for soundings

the reference level for recording land heights, a 1

00

the vertical distance between

or

Movement of water on the chart A current is a movement of water always

lighthouse marked on the chart as

1

MINUS

PLUS

average can be calculated in various ways. The one used on most charts of the United States is mean high water (MHW), which is the average height of is all high tides at a particular location. When

MHW

depth.

the time, the exact height of the

lines). In addition, a series of

to record

soundings, the reference is

00

soundings are given

The actual depth of the water at a certain place and time is therefore seldom the same as the sounding marked on the chart at that location. Most

water, then,

1

lighthouse lantern above sea level would be feet

the average height of low water at the time of spring tides (at the

actually be

the tide rose to the

in

non-tidal rivers,

(or

one direction. This is found and in oceans. The Gulf Stream

in

the mariner's

map

before using a lighthouse for establishing one's

an example of an ocean current. It is marked on old charts with a feathered arrow and on new charts by a wavy arrow. The rate may be

characteristics are determined without

shown

This involves counting the flashes and timing their

is

A

beside the arrow.

in figures,

tidal

current runs alternately

directionsand

at

in

one

of

two

varying ratesof speed. Detailsoftidal

currents are given

in

booklets published by the

National Oceanic and Atmospheric Administration,

Ocean Survey,

National

and

in

in

Reed's Nautical Almanac,

Eldridge Tide and Pilot Book. Eldridge

period,

best light

probably the most widely used source of information on tidal currents along the Atlantic coast. It

number of reference which have particularly fast-moving tides. These tables predict the times of current change, the direction and average maximum velocity for flood and ebb tides, and an indication of the days on which the currents will be at their strongest (spring tides) and their weakest (neap tides). The direction and velocity of tidal currents at over 300 other locations are listed separately, and the times of current change at these places can be extrapolated from one of the reference includes current tables for a locations

station tables. Eldridge also includes hourly

is

it

essential that the light's exact

is

a stop

major bays, sounds, and harbors along the Atlantic seaboard.

for the

the time from the start of one series of

flashes (or eclipses) to the start of the next cycle.

(Or from the finish of one cycle to the finish of

wise to check several complete appears that the same characteristics are not being repeated exactly, continue to check till consistent results are obtained. Never assume a light is the one expected, always check carefully. Many ships have come to grief through cycles.

It is

If it

failure to identify a light or

they see

On

is

Navigational marks

large scale charts,

a large

They

number

of

are the

mariner's "sign posts." But just as a road sign post

must be read to be of any value, so must any navigational mark be identified, and its message

The lighthouse It

characteristics of

the

same

is

the mark usually seen at the

tells

us

area have the

name by the No two lighthouses

its

its light.

same

1

29.

a lighthouse light does

round the horizon, the arcs of be shown by fine or pecked lines, and the arc or arcs will be given in the "Pilot" or sailing directions. The arcs are given in degrees as seen from the ship (NOT from the lighthouse). not shine

all

A medium

or small-scale chart

abbreviated details of a

in

characteristics, but

light.

If

small scale chart states "Fl(2)

some

1

may

for

only

show

example the

5 sec

WR"

it

arc or arcs the color

be white and over others red. If the arcs shown, then it is essential to consult a large-scale chart showing the respective arcs by pecked lines. If none is available, light lists give the arcs of visibility of many such lighthouses. will

are not

On

a small-scale chart

may be

written

ft 20 M more detail: Harbor of Refuge Light Fl W, 2R sector Red from 325° to 351° and 127° to 175° covers Hen and Chicken and Brown Shoals. If no large-scale chart showing these sectors

Harbor of Refuge

but the light

read.

greatest range.

if

visibility will

seen

Charts covering coastal waters and the approaches

and harbors contain

assuming that the one

the one they seek. See page

indicates that over

navigational marks and buoys.

It is

watch. The period of a

(Fig 12.)

current charts or simplified current diagrams

to ports

any doubt.

necessary over several cycles.

if

done with

the next.)

is

tidal

position

lists

Lt Fl

5 sec 72

give

is

23

practical yacht navigator available the arcs should be

drawn on the

The simplest way

is

protractor with

to

do

this

Weems

center on the lighthouse, and

its

N point

oriented with the

chart.

to place the

to south. Then, using

the outer figures on the protractor, mark off the

angles and describe arcs as that the bearings are from

the diagram. Note

in

seaward to the

lighthouse.

Some lights at entrances to rivers or harbors show colored sectors to indicate the safe channel.

When when seen

A

in

far to

one side

pair of lighthouses (or lights)

when

a safe

they are

By day

approach. The nearer

a lighthouse

only be identified by

the Fig 1 2. A light with sectors of different colors, in this case white and red. Yachts passing along the courses shown would see red. then red and white together in a narrow sector, then white. On charts and in books, sectors in degrees are given as seen from ship. In this case red might be from 255° (at right hand edge) to 45° (at bottom left edge).

where the

hills is

is

light

is

they

always

the higher.

shows no

its

the neighboring coast, is

may be placed

in line (in "transit")

the lower; the back light

This

or the other the light

will turn to either red or green.

so that

mark

the channel the light seen will be white;

too

lights

and can

general appearance and its hills

ability to

and

silhouette.

"read" the contours of

though one would sometimes

of value,

be navigating by objects closer to the eye (i.e. beacons, buoys and the shore line). Light vessels and light floats (which are basically

unmanned

because they turn

light vessels)

on

sectors but have their characteristics

Most have hull. All

a

in

the

name

cannot,

their

moorings, have

own

individual light

same way

painted

in

as lighthouses.

bold

letters

on the

U.S. coastal lightships are painted red;

gradually these are being replaced by "Texas towers" or large automatic navigation buoys. There is no obligation for a yacht to sail only indeed, it is frequently prudent to in a channel proceed just outside the channel so as to be out of the way of large commercial vessels, but the chart should be studied to ensure there will be sufficient depth and no other dangers. (In busy waterways there may be laws prohibiting shoal

—

24

the mariner's

map

The Ambrose Light located off New York harbor is a good illustration of a modern "Texas tower." These towers have replaced traditional lightships in areas. For the navigator, a Texas tower provides an unmistakable daylight identification. light

many

2«*5

practical yacht navigator

Execution Rock Light in Long Island Sound. This the few manned lighthouses still in operation.

is

one

of

frequently decide to leave a port or starboard hand

buoy on the "wrong"

side.

Buoyage system

The Hillsboro This tower

is

Inlet Light near Fort Lauderdale. Florida. an example of a lattice structure with a

central stair cylinder.

from obstructing the passage of vessels which, because of their draft, must remain in the channels). The yachtsman still needs to be able to recognize the buoys to ensure a safe passage. But he will draft vessels (such as yachts)

26

Buoys and many beacons indicate their meaning, and their position in relation to channels, shoals and dangers by their appearance, namely, by their shapes by by by by in

their colors their

numbers

their lights

(if

(if

any)

any), colors and characteristics

their fog signals

(if

any)

accordance with internationally agreed systems. The two principal systems are the lateral and

the cardinal.

In a lateral

number, and

light

which

a vessel

on

a

system, the color, shape,

buoy

indicate the side on

should proceed

when

entering a

-

the mariner's

map

harbor, or proceeding in the same direction as the main flood stream. (When leaving a harbor, or proceeding in the opposite direction to the main

fiood stream, this side

is

naturally reversed.) In a

cardinal system, the color, shape,

buoy

indicate the direction of the

the danger

it

marks.

Different countries use lateral or

and light on a buoy in relation to

some

version of either the

the cardinal system, or a combination of

the two. The United States uses the lateral system, as does Canada. In Europe, Britain uses the lateral

system, although the colors that mark the

two

of a channel are the reverse of those

in

used

sides

A lateral system similar to Britain's is found along most of the European continent, with some minor differences. France, however, employs combination of the lateral and cardinal systems. And the cardinal system is also used along other America.

Fig

1

3.

chart.

A

Fig

1

an estuary as depicted on a to identify each buoy

The yachtsman should be able

and know

4.

night.

typical entrance to

a

its

purpose.

What you

The

see

when approaching the same harbor is as shown in Fig 1 3. Some

boat's position

buoys are obscured by the land and there is no visible indication of distance. Pick three lights you are sure of, get a fix. use the compass, and then check again as you draw nearer. Do not rely on your sense of direction.

at

Alt. Fl.

W.

andG-

FI.W. 6 sec .-

^Qk.FI.W.

-FIR

4sec -

Mo(A)W.

OCCLOWOCC

Qk. FI.W.

FI.W.

HIGH

-FIR. 4 sec.

Qk. FIR.

27

practical yacht navigator

BUOYAGE

Odd numbered

A

bell

bell

buoy.

buoy. The steel float carries a short skeleton

tower in which the bell is mounted. In open water bell buoys are sounded by the motion of the waves: when sited where smooth water prevails they are operated by compressed gas or electric hammers.

Can buoy

28

(port side), unlighted.

— the mariner's

A buoy

is

a navigational

map

mark more closely

associated with a small vessel than with

commercial ships. While big

craft are

watching on

their radar, or their bridge officers are relying

shore marks easily visible to them, the fisherman or yachtsman closes a buoy, reads

name

or

checks

its

light flash

and says

"We

its

are right

here." Officially, however, reliance should not be

placed on buoys, for they can drag moorings, if in exposed positions. And since buoys unmanned, if a light goes out of order, some time may go by before it is fixed. In the U.S. lateral system of buoyage, red buoys

especially are

(nuns or lighted) indicate the starboard side of a channel when a boat is inbound. An easy way to An

remember

intracoastal marker

this

is

the rule "red-right-returning" the :

red channel markers should be kept to the right

when A nun buoy with

even number (starboard

side),

unlighted. These are constructed of steel plates, with the part above water shaped like a cone.

returning from a trip to sea. Red buoys have even numbers, which increase from seaward, and if lighted the light is either red or white. Black buoys

(cans or lighted) indicate the port or left side of a channel when a boat is inbound. They carry odd numbers, which also increase from seaward, and if lighted the light is either green or white. Another buoy in the U.S. lateral system is the mid-channel marker, which has black and white vertical stripes. In terms of shape, it may be a can, a nun, or a lighted buoy, and it may also have a letter painted on it. Boats may pass a mid-channel marker on either side, but they should always stay close to it. A red and black horizontally banded buoy marks either a channel junction or an obstruction that may be passed to port or starboard. The preferred side, however, is indicated by the color of the top band keep the buoy to port if the ton band is black and to starboard if the top band is red. A red and black banded marker may be a can, a nun, or a lighted buoy, and it may be lettered.

29

^^B Lateral

PORT SIDE

System seen

entering from seaward.

ODD NUMBERED AIDS FIXED

FLASHING

OCCULTING QUICK FLASHING LIGHTED BUOY

CAN

WHITE OR GREEN

MID-CHANNEL NO NUMBERS — MAY BE LETTERED

MORSE CODE WHITE ONLY

CAN

NUN

LIGHTED

STARBOARD SIDE NUMBERED AIDS

EVEN FIXED

FLASHING

OCCULTING QUICK FLASHING LIGHTED

WHITE OR RED

30

NUN

Lateral

System

INTERRUPTED QUICK FLASHING

JUNCTIONS AND OBSTRUCTIONS — NO NUMBERS — MAY BE LETTERED

CAN PREFERRED CHANNEL TO STARBOARD

LIGHTED

BUOYS HAVING NO LATERAL SIGNIFICANCE— ALL WATERS

LIGHTED

CHANNEL TO PORT

NO NUMBERS — MAY BE LETTERED

w

$

5 FIXED

FLASHING OCCULTING

(ORANGE)

(YELLOW)

(WHITE)

SPECIAL

QUARANTINE AREA

ANCHORAGE

PURPOSE

NUN PREFERRED

$

AND

(BLACK/WHITE) SPECIAL

(GREEN WHITE)

PURPOSE

DREDGING

ANY COLOR EXCEPT GREEN AND RED

31

:

5

.

practical yacht navigator

European coastlines flanked by

reefs or isolated

the light

To eliminate these disparities in European buoyage systems, over a three year period beginning in 1 977 the countries of northern and western Europe are adopting a new combined cardinal and lateral system. But in the meantime, this gradual conversion may only add to the confusion for visiting American yachtsmen. So before sailing in European waters, always study the buoyage system currently being used in any given area.

Reading the chart The area covered by a chart in general terms, e.g. "Long

is

stated

Island

the

in

Sound

title

— eastern

studying a chart in detail, get a broad idea of the scale of distances by studying part." Before

is

omitted

—

is

it

3 flashes every this

consulted. The

full

book must be

characteristics might then be

found as "GpFI(3) 30 sees 1 80 ft 20 M" (1 80 ft high, visible 20 M from height of eye of 1 5 ft). When transferring a position from one chart to another (as when plotting a course which extends over two charts, or when transferring from a smallscale chart to a large-scale chart after making a landfall) pick up the latitude and longitude of the position to be transferred, on both charts. Check this by relating the position to some object shown on both charts such as a particular buoy. Before starting work on a chart, rub out all old pencil markings from earlier work (hence the use of a soft pencil).

From time

to time the characteristics of

Next, note carefully whether depths are marked

navigational lights (lighthouses and buoys) are

fathoms,

changed, fresh wrecks occur or are found, and so on. These and similar alterations are promulgated in "Notices to Mariners," issued daily and weekly, and it is important that charts are periodically brought up to date ("corrected") by a chart agent. Charts should be handed in for correction at least once a year, and preferably before a passage is

feet, or meters.

This

is

stated clearly

and on new charts "Depths in meters" is also printed in magenta color in the margin. Check also what the various depth contour lines indicate, and what tinting is used to denote shoal water of various depths. Get the "feel" of the area by noting (a) The type of coastline. Are there high hills near the coast? Or cliffs, sand dunes. Are there

below the

chart's

title,

(b)

The general depths near the shore.

shore steep-to (deep water close

Is

in) or

the

shelving

gradually?

if

1

(c) How much detail is shown. The smaller the scale (the more area depicted) the less detail, and

vice versa. Are the

undertaken.

Books and tables The following books

off-lying rocks or shoals?

full

characteristics of

navigational lights given?

A

all

small scale chart

may

will

be found most useful,

not essential.

Tide tables covering the whole area

likely to

coastal areas of the United States. Also,

Book contains

tide information for the eastern seacoast.

lighthouses, e.g. GpFI(3) 20

2.

M—

i.e.

the period of

be

sailed. The National Oceanic and Atmospheric Administration, National Ocean Survey publishes tide tables and tidal charts for almost all the

show any characteristics of the lights of buoys, and may only give abbreviated ones of not

32

1

knowledge

essential for positive identification, either a

large-scale chart or a pilot

the latitude scale.

in

is

seconds or every 30 seconds? As

dangers.

Eldridge Tide and Pilot

The U.S. Coast Guard Light

List.

detailed

Volume

I

the mariner's ;overs the Atlantic coast (from

Maine

to

South

into suitable

sequence and each chart arranged with its title and number on the near-side upper edge. Each group may be

Vlississippi River system.

conveniently stored

books contain a nass of sailing information on different areas Df the country, but they are compiled principally with commercial vessels in mind. Of greater value :o the yachtsman are the numerous sailing directions, many written by famous and axperienced yachtsmen for areas frequented by

canvas, or preferably a

folio

/achts.

remainder.

Volume

II

covers the Atlantic and

groups of about

3ulf coasts (from !

90fl

The charts should be divided

South Carolina to Texas). Volume II is the Pacific coast and Pacific Islands, Volume IV the Great Lakes, and Volume V the

arolina).

n be

folded.

map

3.

U.S. coast "pilots." These

4.

Reed's Nautical Almanac for American coasts.

5.

Dutton's Navigation and Piloting

is

in

which they

case,

now

are likely to be required,

jseful reference for celestial navigation work.

in a "folio," flat,

using either a

zip-up clear plastic

available for this purpose. List the

and stick the list inside each can be read without opening the case. Any individual chart can then be found easily by leafing through the near-side edges, and can be withdrawn without disturbing the charts

in

each

so that

folio,

it

After use, a chart should be folded in the original creases

also a

six or so, possibly in the

proper

and replaced,

right

way

up, in

its

folio.

Care of charts Charts are not inexpensive. If well looked after, and returned to the chart agent for correction annually, a chart should last several seasons. The chart in use should be kept as dry as possible and when working in wet gear remove headgear and spread a dry towel along the nearside edge. Some navigators cover the chart in use with a sheet of perspex and write in chinagraph. This certainly protects the chart, but Flat

zip-up cases are available

They are

a

good

in

two

charts can be

inserted, back-to-back, so that both

A

can be read

plastic.

yacht's stock of charts

dozen or

inaccurate.

idea for holding a chart in the

cockpit for pilotage. Indeed,

through the

is

clear plastic.

may number from

a

up to perhaps fifty. It is well worth arranging and indexing them to facilitate finding the one required. All National Ocean Survey charts fold naturally to about 1 6 in. x 24 in. or less, and the area of water covered and the chart number is printed on one edge, visible when so,

33

:

practical yacht navigator

CHART MEANINGS A

chart

shows the following things by means

of special 1

.

symbols and abbreviations.

Dangers, including rocks, rocks awash level of chart

2.

datum, wrecks,

light

may be shown

frequency and

number of flashes. Buoys and beacons. Symbols and

—

Flashing

Fl.

and lights. Fog signals: abbreviations

S-L

Fl.

Qk.FI.

Short and Long Flashing

Quick flashing

more flashes Occ.

at

Occulting

— a short

flash.

— a rate of 60 or

a minute.

— or being eclipsed.

Light being interrupted by a

for type of

sound, number of blasts. Harbor features. Anchorage, berth,

period of darkness less than the

dock

intervals.

period of

etc.

Buildings: to distinguish appearance.

7.

Type of bottom: abbreviations mud, rock etc. Topographical features:

hills,

Iso.

Coast features:

Alt.

contours,

sandhills, mudflats

light

darkness, at regular intervals.

— successive flashes

RG, or

RW)

at regular

Group Flashing

— two or more

flashes repeated at regular intervals.

Gp.Occ.

is its first

— equal periods of

intervals.

Gp.FI.

of a light

regular

(or eclipses) alternate in color

Radio and Radar: stations, beacons, buoys, masts etc.

The color

light, at

Alternating

(e.g. cliffs,

etc.

Lights.

Isophase

and

for sand,

trees, rivers etc.

10.

— a single flash

followed by a long

6.

8.

one of the

regular intervals.

abbreviations indicating the shape, color

4.

to have

following "characteristics" (see also Fig 80) F. Fixed a steady light.

Lights, abbreviations indicating the type of light flash(es), color,

3.

at

overfalls.

A

—

Group Occulting two

light

more

identifying feature. All lights are white unless

interrupted by

symbol states a color: R Red G Green White (with other color) Y Yellow

periods of darkness at regular

W

34

B Blue Or Orange Vi

Violet

Am Amber

or

intervals. I.

Qk.FI.

Interrupted Quick Flashing

— quick

flashes interrupted by periods of

darkness.

the mariner's

Fog Signals. Many lighthouses, light vessels, and some navigational buoys give sound signals in fog (some buoys in clear weather also). A fog signal can be identified by the type of sound made and by its characteristics (number and frequency of the light floats,

sound). (Abbreviations used on charts

shown

in

brackets).

Siren (siren)

Whistle

Medium power

high or low

Type of bottom. Information as to whether the bottom is sand, rock or shingle etc. is chiefly of

when about

to anchor or kedge. This guide to the holding one can expect. On rare occasions a position may be verified by reference to the material on the bottom, but this requires the use of a leadline and a lead "armed" with tallow or grease to which particles will adhere. The principal abbreviations used interest

will give a

are:

note, or a combination of both.

s

Sand

Sn

Shingle

Uses compressed air. Usually on offshore buoys.

M

Mud

P

Ml

Marl

St

Pebbles Stones

CI

Clay

Wd

Seaweed

Sh Ck

(whis) Bell (B)

If

power-operated, a single

If

5-30

materials,

sees.

wave-actuated, irregular and

may

not sound

in flat

calm.

fne

fine

crs

coarse

sft

soft

Strong low note terminating

(dia)

distinctive "grunt."

hrd

hard

Horn (horn]

Several types with different

sm

small

by different mechanisms, such as diaphragm or reed.

Nautophone

High note,

like reed. Electric.

(nauto)

Gong (gong)

Medium

or

low pitched

resounding tone.

Gun (gun)

Explosive signal.

Chalk

in

some

of these

such as

Diaphone

tones and pitches. Operate

Shells

Adjectives are used to qualify

stroke at regular intervals of 1

map

would be shown as fneS. Radio and Radar. The ability to locate on the chart the positions of radio beacons, Consol stations, and (with radar) buoys fitted with radar reflectors, and racons will enable the maximum value to be obtained from the RDF set (or radar). These are all marked on charts with their respective abbreviations. Fine sand

35

3.

Certain equipment and instruments are necessary for navigation, but these

or elaborate.

do not have

recommend

I

to be costly

starting with the

minimum, only adding as more experience suggests. Let us divide the instruments into lists

two

— instruments for the chart table and

"deskwork" aboard

or ashore.

Instruments for the chart table Chart table, with adequate lighting and storage for charts.

Note books, navigator's log book. Pencils 2B and HB, pencil sharpener. Compasses and dividers, 6 in. to 7 in. to

(1

50

mm

180 mm).

Parallel Rule,

1

5

in.

to

1

8

in.

(400

mm to

460 mm).

Weems

protractor, or other chart protractor.

Magnifying

glass.

For use at home, recommend a piece of plywood about \ in. (1 2 mm) thick, about 30 in. x 24 in. (750 mm x 600 mm), with fold-back clips or thumb tacks (drawing pins) to secure charts. I

This avoids spoiling a table with compass- point holes. try to

size, at least

36

30

possible, arrange for reasonable seating

if

—

when

the yacht

is

heeled over.

Make

suitable provision for your instruments and books,

be ready to hand and

so that they

will

keep sliding

off the table.

Good

will

lighting

not

is

important, with provision to reduce glare back towards the helmsman. He wants all the nightvision possible, and any glare will spoil this. A fitting consisting of a small bulb on a flexible stalk is excellent. Some have a tiny shade fitted which can be adjusted to eliminate unwanted light scatter. Convenient chart storage can be provided by a shallow tray, about 2-3 inches deep, with the chart table forming the hinged lid.

Note books Without adequate note books there is a tendency to rely on memory, or to use scraps of paper. If it is worth writing down it is worth preserving to see

Chart table

Aboard,

Again,

you may spend a long time at it. In suitable cases on a sailing yacht, try to arrange a strong strap which can be easily fixed, perhaps with a Swedish snap-shackle, so as to support you in your seat

instruments for the yacht. The former are required for

Way

Equipment to find the

arrange a chart table of adequate

in.

x 24

in.,

or larger

if

possible.

what went wrong

memory

next time.

last time, or to refresh

One book

for navigational matters to

position to be

reckoning

Few in

is

worked up

enable the ship's

at

essential. This

one's

specially reserved

any time by dead is

the yacht's log book.

navigators will agree on the ideal layout, but

Chapter

1

3,

one layout which has proved

Forward facing chart table (on Swan 37 class). Note ample deep stowage for gear. Instrumentation fills almost all available space on partial bulkhead.

effective in practice

is

Whatever layout you

described

find

in detail.

most convenient to you

should be used consistently.

most unlikely you will find exactly what you want in a readymade printed book, so if not, rule your own, with your columns and captions. Get a supply run off on a copier (preferably Xerox or similar) and put them in a filing folder. Let no one use this but yourself anyone else is quite likely to make a mess of it.

—

It is

Pencils Always use 2B

(soft) pencils on your charts. Old can be rubbed out, but a hard pencil is difficult to remove and permanently marks the chart and good charts are not cheap. Buy a box of 2B pencils while you are about it. HB or H pencils can be used for log entries and other work this should not require erasure, and a hard

entries

—

—

pencil stays sharp longer.

sharpener

is

a

must

A

small pencil

— your 2B pencils soon blunt, 37

What can be achieved

as a chart table on a small yacht (this is Nicholson 30). Note athwartships bookcase, pencil and dividers rack, navigator's light and easy view of electronic equipment. Data such as tides, code flags and deviation are pinned up for quick reference. From left to right these are log and speedometer, depth sounder, radio and DF receiver. On the chart is a Sestral-Luard chart protractor, which enables compass courses and bearings to be read off. after setting variation and deviation a

into the face of the protractor.

38

equipment

Athwartship's chart table on a 42 ft sloop {Morning Cloud II. by Rt. Hon. Edward Heath). Considerable chart working area and stowage. Neon light depth sounder top right, where it is visible from the cockpit. Wiring is behind panel.

when owned

39

•

practical yacht navigator

and you want accurate

lines

and figures on the

"chisel" point.

matchbox,

chart.

is

Compasses

Parallel rules

These should be not less than six or seven inches overall, and of good quality. It is well worth getting those made of stainless steel cheap ones soon rust aboard a yacht. Do not get the draftsman's "bow" compasses which must be adjusted by turning a screw they take too long to alter. The kind of compass that can be worked with one hand is easiest. Keep the pencil lead in compasses sharp preferably a wedge-shaped or

This

—

—

—

line

is

A

bit of

sandpaper, or even a

useful to fine-up the edge.

and plotters

the traditional instrument for transferring a

from one position to another on the chart,

transferring a course or bearing line to a

rose to find

its

bearing or direction, for reading

and longitude, and similar tasks. There are other methods of doing these, and some navigators dislike parallel rules on the grounds that there is a risk of the rule slipping and giving a false result. However, a off or plotting the latitude

Motor

cruiser

wheel house

with chart table on starboard side.

40

for

compass

equipment

Fig 16.

steps to

To find true bearing compass rose.

of line

AB,

parallel rule

is

taken

in

Using a parallel rule to obtain a bearing (true only). Rule has center point on meridian, is then closed to give 220' reading of bearing on which it was first aligned. Fig 15.

41

practical yacht navigator long ruler it

is

often wanted, and for this use alone

is

worth

A Weems and

Plath parallel rule

excellent type. This

along

its

is

is

an

engraved with degree marks

with a protractor, or the compass rose. One edge of the parallel rule is placed along the line the is required. The rule is then ("walked") till the zero point on moved in steps one edge is exactly on any meridian (vertical graticule). The bearing is then read from the

bearing of which

Read the exact

engraved on the scale. Longitude is found in a similar manner, but the parallel rule is placed vertically on the chart and first aligned on a meridian the vertical lines on the chart. The rule is then "stepped" across till one edge cuts the point and either the top or bottom horizontal scale on the

—

chart.

The longitude

is

then read off the scale.

same

point on the other edge cut by the

The

both the point and the vertical latitude

latitude

edges, which enables the user to dispense

meridian.

rule cuts

scale on either side of the chart.

place.

its

must be "closed" before

rule

reading, otherwise a false reading will result. (Fig

A

15

)

type of parallel rule preferred by This

roller rule.

a roller

is

a

wide

straight

having non-skid knurling

These make

it

chart so that

it

some

edge at

is

the

with

fitted

each end.

possible to slide the rule across the

remains

parallel to its original

position, thus enabling lines to be transferred parallel

from any position on the chart.

parallel plotter

is

one

To obtain the bearing

(or direction) of a line

the chart by reference to a

one edge line.

A Weems

of the best of this type.

compass

on

rose, place

of the parallel rule accurately along the

Holding

this

edge

firmly,

open the other "leg" compass

of the rule in the direction of the nearest

rose on the chart.

Move

alternate "legs," keeping

the other "leg" firmly on the chart,

till

one edge

of

the rule exactly cuts the center of the rose. Read the bearing

in

degrees, from the point on the

outer ring of the rose cut by the

same edge

of the

rule. (Fig 16.)

To

find the latitude of a point

on the

chart,

place one edge of the parallel rule accurately on

the parallel of latitude (the horizontal lines printed across the chart) nearest to the point. (Fig 1

7.)

Move

alternate "legs" of the rule (keeping the

other leg firmly on the chart)

42

till

one edge

of the

Fig

1

7.

latitude

Finding latitude of a point by starting

and using

parallel rule.

at a parallel of

equipment Instead of using a parallel rule to plot a course,

some yachtsmen

prefer to use

two

triangles.

Weems

and Plath manufactures a pair of 45 degree triangles with a protractor engraved along the longest edge of each.

To

find a bearing using triangles,

place the edge of one triangle along the desired

course

Then place the edge of the second one of the edges of the first

line.

triangle against

so that the

can be

first

slid

along

until

it

reaches the center of the compass rose.

Now

read

the bearing (true or magnetic) where the triangle cuts the outer part of the rose.

Another method of picking up latitude and is by using

longitude quite quickly and easily the dividers.

To

find the latitude, place

one

divider point on the position being measured,

and

the other on the nearest parallel of latitude ruled

on the chart and as nearly as possible immediately above or below the position. Without disturbing the dividers, now place one leg on the same parallel of latitude on the vertical scale on the chart margin, and the other leg on the scale. Read the point just found on the scale. (Fig 1 8.) For longitude, repeat the process using the nearest

meridian (vertical

These

are

a course.

some

line) to

the position. (Fig 19.)

of the instruments used to lay off

Whichever you

select,

become

familiar

with their use so that you can work quickly and accurately even

in

the worst weather.

Dividers If

the distance being measured on the chart

exceeds the pencil

opening of the dividers (Fig 20.), between the two places. Then,

full

in a line

using that part of the latitude (vertical) scale roughly parallel with the places, pick up a con-

venient opening of the dividers, (say

1

0'

=

1

nautical miles). Starting from one of the places, count the number of (say) 1 0' steps of the dividers it takes to (almost) reach the second point. Close

Fig

1

8.

Reading

to latitude scale at

Fig 19.

off latitude

edge of

by using dividers and transferring

chart.

Reading longitude by same technique as

latitude.

43

practical yacht navigator

Single-handed or English dividers: if used like this.

44

a real aid. but not

The correct way

to use single-handed dividers.

equipment the dividers so as to pick up this small remaining piece of the

line,

and by using the

latitude scale

again, find this remaining distance. (Fig 21

.)

At 0200 on a wet, cold night the navigator is

not usually at his best. Anything which will

simplify his

work

or

make

then important. Here off a

is

it

easier or quicker

a small tip,

when

is

laying

course and distance on the chart from

a

Large and small size single-handed dividers, brass with stainless steel points. Also a draftsman's

^t=

compass

OROTJIK DTJ tit- I» P"B1I DELA ALA ROCHXIJUE porrois BRETON

COTJ

UOfM

li^T

Fig 20.

Simple measurement.

A to

B.

is

found on

latitude scale

roughly opposite place measured. Fig 21

.

When

distance exceeds dividers,

it

is

measured

in

steps.

45

practical yacht navigator given position. There are two components to the job: (a) to rule in

the line representing the direction

or bearing of the course,

and

position to measure along this

(b)

from the

line

the required distance.

The line in

first

natural

sequence

is first

to pencil

in

the

compass by other means, and then to

the right direction by using the

rose on the chart or

prick off along this line the required distance,

with dividers or compasses, by using the latitude

Reverse the sequence. Using the compasses,

scale.

open out the compasses

first

to the required

distance by reference to the latitude scale (using) that portion of the scale roughly level with the

two

positions), then get the parallel rule (or other

rule)

on the required direction and cutting the and hold the

first

position, by the usual means,

rule

down

on the

first

firmly.

Then place the compass point

position and describe a tiny arc to

touch the edge of the rule the required distance along the rule. Finally, using the compasses as a pencil, rule in the line between the and the tiny arc marked.

Weems

first

position

protractor

A Weems Zweng

course protractor

Fig 22. is

used by many

American yachtsmen. It has a clear acrylic circular base plate 5^ inches in diameter. Around its circumference is engraved a compass rose in degrees (from 0°N to 359°) and quarter points (the points of a compass being 1 1 ^° apart). The central area of the base plate is engraved with a grid of horizontal and vertical lines used to align the protractor on the chart. Attached to the center of the base plate is a clear acrylic movable arm 17 inches long, which is inscribed with various nautical mile scales. Where the protractor arm meets the base plate, there is also a scale for reading magnetic courses and bearings.

46

Finding a bearing using a

Weems

protractor

equipment

A Weems protractor can be used in the conventional nanner

for finding or plotting the true bearing or

irection of a line

on the

chart.

To

find the true

earing of a line (for example, a course line or line

drawn between two places on the

chart),

Dlace the center of the protractor along the line,

The vertical lines on should coincide with or be Darallel to the meridians on the chart, while the Horizontal lines on the grid should coincide north pointing upwards.

/vith

:he grid of the protractor

or be parallel to the parallels of latitude

/vith

}n the chart. Next

o that

lies

it

move

the arm of the protractor

along the course

line.

:hen easily read the true bearing :uts the

compass

rose.

If

You can

where the arm

the nautical miles

on the chart is the same as one of the scales Dn the arm of the protractor, you can also use he arm to read the distance from the center of he protractor to the end of the bearing line. >cale

[See Fig 22.) Note, too, that the design of a

A/eems protractor makes

it

easy to take reciprocal

Dearings.

A

popular alternative to

Plotter,

the circular

parallel rules.

compass

show magnetic

scale

is

On

the Hurst

clamped on

When

to the square

aligned with meridians and latitudes, the swinging arm then reads off magnetic courses and bearings without the need to convert (deviation where it exists, must be applied).

grid to

variation.

the grid

is

tmmm he

Weems Zweng

course protractor.

47

-

practical yacht navigator

I

J^

Is

~—~

B

ti&'

-7

\V

i

\ \ v--^~A_JSJ\\ \

'

'

'A' ' /

48

'

B'

'

\

'

\

'

\

/ /

V\

B"

/

:

equipment To use on

a

Weems

protractor to lay off (or draw)

from a given position in a given direction, the procedure for finding the bearing of a line is simply reversed. Set the arm at the desired bearing, and place the protractor on the chart so that the arm cuts the point from which the bearing is to be taken. Then adjust the alignment of the base plate so that north points upward and the vertical lines on the grid are parallel to the chart meridians while the horizontal a line

a chart

line to be transferred. Next slide the protractor along the chart, without disturbing the arm, until it

reaches the location where the

new

line

to

is

Again align the protractor grid with the chart meridians and parallels of latitude. The new line can now be drawn in. (See Figs 26 and 27.) be.

another use for a

Still

fix

Weems

protractor

is

to

the ship's position on a chart by horizontal

sextant angles of fixed land objects. This

procedure

explained

is

in detail in

Chapter

9.

lines are parallel to the parallels of latitude.

Now draw in the course line. When you want to read a magnetic

Magnifying glass bearing or plot

a magnetic course, you can use the variation scale on a Weems protractor. First note the variation between true and magnetic north, and then set

the variation scale accordingly. This adjusts the

angle of the arm. The protractor can

now

be used

as described previously.

This will be found useful for verifying small

A Weems

protractor can also be used to transfer from one part of a chart to another. This is done by aligning the protractor grid with the chart meridians and parallels of latitude, and then moving the arm so that it coincides with the

in-built

torch light

Instruments for the yacht The number be as

a line

on the chart. A glass with an is handy for use at night.

figures

Some

many

of instruments to aid navigation can

as the depth of one's pocket allows.

are essential for safe navigation,

many

are

and give additional information, while others are used by keen ocean racers or fun useful aids

things for cruising. Essential are:

Steering

compass

Distance meter

Depth sounder

Those

(or leadline).

falling into the highly desirable

category

are:

Hand bearing compass Direction finding radio

Binoculars

Stopwatch Into a slightly lower category of importance Figs 23, 24,

Triangle it

in

A

is

and 25.

Transferring a line using

two triangles. moved along

held stationary while triangle B is 1 Then the procedure

the direction of arrow

reversed: triangle B

is

.

held stationary while

A

is

in

or

good timekeeper

slid

the direction of arrow 2. Finally, triangle B until the desired position is reached.

along

Deck watch

is

fall

Clock Barometer

is

moved again

Sextant Pelorus

__ 49

practical yacht navigator Lastly, items racer,

considered essential by the ocean

and nice to have but by no means

essential

for cruising are:

Water speed indicator Electronic log

Apparent wind direction indicator Apparent wind speed indicator Efficiency indicator

Sailing performance

(Vmg) computer

Compass A good

magnetic compass

is

an essential part of

every yacht's equipment. There are

many

work on the same principle. A circular card, marked on its circumference, is suspended on a pivot point in a bowl filled with water and alcohol (2 1 ). The bowl is suspended in gimbals. On the inside of the bowl a line the varieties but

all

:

lubberline

—

—

engraved or painted. Fixed to the

is

underside of the compass card are two or more small bar magnets, aligned on the north-south axis of the card so that the freely-suspended

compass

card's north point will always seek to

point to the magnetic north pole.

The compass no matter

how

is

mounted

in

some way so that, compass bowl

the vessel heels, the

(and card) will remain level. The object of the water and alcohol in the bowl is to damp down

Figs 26

and 27.

Transferring a line using a

Weems

protractor

equipment caused by the ship's motion, and to on the pivot by almost floating the

oscillations

reduce

friction

card, alcohol being

added as

anti-freeze.

A

screw plug on one side of the bowl enables it to be topped up with distilled water if necessary. Modern compasses are graduated in degrees, from north, 0°, round to 359°. As the compass must be clearly legible at some distance and sometimes in a poor light, the degree markings and figures must be well separated and bold. The number of markings and figures will depend on the size of the

compass

card.

A

typical yacht

marked every 5°, each 1 0° mark being bolder and showing the number of degrees. The

compass

is

last digit is

omitted to permit

a large figure

being

shown. For example, against the 1 80° mark, 1 8 is shown; against the 20° mark, 2 is shown, and so on. Smaller compasses may be marked only every 10°, while large ones 1 °.

Some compass

may be marked every 2° or show the cardinal

cards also

and intercardinal points (N, NE, E, SE, S etc). (See page 53.) Aboard some yachts, older types of steering compass may be found with different systems of markings. The oldest of these is the points system and since a point is 1 1 g°, it is not convenient for navigation. Just remember that one point is something completely different from 1 ° and if you find a points compass on a boat which you have bought, throw it over the side. There is also a system with limited uses called quadrantal where degrees are marked from south as well as from north and this is equally confusing for use in a steering compass. Some compasses have a transparent dome to the compass bowl, which contains a gimballed ring or "cage" in which the compass card and its magnets are mounted, and which also has a lubberline. The bowl can then be mounted without any further provision of gimbals. The domed bowl heels with the ship, but a cage in which both the compass card and the lubberline are mounted can tilt inside the bowl to remain level at

all

times. This has the additional feature

that the Plexiglass

dome

magnifies the card,

some

distance and water cannot lie on the glass. Some models have the card "dished" which makes the far edge of the card (adjacent to the lubberline) even more

enabling

it

to be read at

easily read.

Another type (the Sestrel- Moore) is designed on top of the coachroof

for fitting at eye-level, e.g. Fig 28.

Some

notation.

One

compasses

are marked only in points an awkward 11^°. but the reason is there are 8 in a 90° segment. Colored sectors here are one point, four points and then eight points.

old

point

is

The compass card has a tunedand one lubberline is side (unlike the more usual forward

or cabin hatch.

down on the

circumferential edge, after

51

practical yacht navigator

The degree markings on the turned-down slewed round 1 80° from those on the edge upper surface which are read against another lubberline on the forward side. The bowl is suspended in gimbals. The compass can be fitted with sight vanes so that the compass bearings of side).

are

consist of a pair of parallel lines, or an arrow.

The

glass can be rotated and

graduated. The "grid"

axis of the graduations.

may it,

or

but

its

vanes on the object and reading the bearing on

cover

flat

Compasses are also which can be mounted on a vertical

surface of the card.

available

bulkhead and again, read on the aft-facing edge.

A plate

Grid Steering

Compass has

engraved or painted with

a

top glass cover

a "grid." This

may

is

if

N-S

distant objects can be taken by aligning the sight

the

may

is

outer edge

is

The compass card

itself

not also have degree markings round

have

not, will axis.

To

rotated

opposite

its

oriented on the north-south

is

a line or lines

marked on

steer a given course the glass till

the required course (say

a lubberline (fixed in line

1

20°)

with the

The vessel is then steered so that the on the glass cover is over and exactly parallel with the N-S line on the compass card (Fig 29.). Some compasses can be used both as a normal compass and as a grid compass. To use such a type as a normal compass, turn the movable outer ring till the 0° mark is exactly opposite the fixed white lubberline on the forward side of the body of the bowl. The course being steered is then read on the compass card against the black (forward) lubberline marked in the bowl, the line on the glass cover being disregarded. To use as a grid compass, turn the movable outer ring till ship's head).

N— S

line

the required course

is

opposite the fixed white

Then steer to cause the arrow painted on the cover glass to lie over the 0° (N) point on the compass card. The N— S axis of the compass card should lie below, or parallel to, the shaft of the arrow on the glass. A grid compass is most useful when steering on a set course for an appreciable length of time. It is much easier on the eye to keep two lines parallel to each other (grid line and compass card), than to keep a lubberline to a required degree-mark. This is particularly so at night. It is lubberline on the bowl.

rather less useful

if

a sailing vessel

hold a steady course (as

Grid steering compass. From left, compass is not set. Fig 29. then grid frame is set to 1 20°. Helmsman brings grid parallel with line on card and yacht begins to head at 1 20°.

52

when

is

not able to

being sailed hard

on the wind, as close to the wind as possible). is then necessary to keep reading the compass course and to decide at intervals what is the average course that has been steered. For this,

It

a

Flush fitted Sestrel Minor compass.

Major compass

binnacle marked at five degree is not shown: when ordered to steer 20 degrees bring "2" to lubberline. 20 on card means 200 degrees. Sestrel

in

intervals. For clarity last digit

53

practical yacht navigator

The Danforth

Tell-Tale overhead compass. Can be mounted above the skipper's or navigator's berth for easy reading between

watches. The compass rolling

is

gimballed to compensate for

and pitching of the boat.

Grid compass compass card

windward.

54

in in

cockpit well. The type with an ordinary addition to the grid is useful when sailing to

equipment normal compass, where one reads the actual course steered against a fixed lubberline is to be preferred. A combined Grid and Steering compass, being capable of use either way, has the best of

Remote control compasses are also availwhich have certain advantages. Here, a master compass drives or controls electronically one or more slaves or reading heads. The able,

both worlds.

Cockpit mounting on Morning Cloud of Danforth White Constellation for

tiller

compass The

steering.

card of this type is highly recommended.

55

Where is

siting a steering

difficult,

as

in

small

compass

tiller

steered yachts a pair of bulkhead reading compasses is practical. Care must be taken about loose magnetic objects inside the cabin.

Closer view of the Homologue. bulkhead steering compass. Numbers under it are angle of heel.

56

equipment advantages are that the master compass (rather bulky) can be sited anywhere in the yacht, where it will be subject to the least movement and clear of any ferrous objects which might influence it, and the reading heads can be quite small and located wherever required, in the most visible or useful position(s). Their disadvantages are that they are expensive, and they depend on a reliable

lying near in

it.

If

the

which happened to have a wire core compass is mounted on the after-face

it,

of the cabin bulkhead, guard against the presence

any ferrous or magnetic object which might be it on the other side, inside the cabin, Compass" notice perhaps on a shelf. A "Warning might be put up on the cabin side of the bulkhead. Wood or fiberglass does not shield from a magnetic of

close to

—

power supply. Compasses are also designed specifically for high speed power craft. They are specially damped

necessary.

up to the motion of this type of vessel. These too are available with or without grid

electric (or oil) light

facilities.

taken that any material used near the compass

(but small) electric

to stand

influence.

Illumination of the steering

Some

(not

marked with luminous

many) paint.

compass

is

are sufficiently If

not, provision for

should be made, care being is

compass needs thought. Ideally, the position should be where it is most easily seen and read by the helmsman in whatever position he may take up. It should be where parallax is least (parallax may occur when edge of compass Siting the

card

is

Again

seen obliquely against the lubberline). the compass should be sited well

ideally,

away from any

which could Chapter 5). Deviation of the compass north from the direction of magnetic north may be caused by: the engine, if within about 4 ft (say 1 \ meters) ferrous material

cause deviation (discussed

the keel,

if

in

of iron

an outboard motor, which has a powerful magnet in

it

a radio loudspeaker, for the

same reason

camera exposure meter and any ferrous objects such as tools, iron bucket, fdod and fuel cans. In this context, objects on the person have been known to upset the compass if the wearer is close to the compass, e.g. jack knife, steel buckle on belt or life harness. once found my compass had developed an error of over 1 0°. After much searching it was found to be due to that most innocent and non-metallic object, a life buoy a

I

Danforth White Corsair steering compass with guards over to prevent damage in cockpit.

practical yacht navigator non-ferrous. The light must be no more than a otherwise glimmer just sufficient and no more the helmsman's night vision will be impaired, and this is important. A small bulb controllable by a

—

—

rheostat

is

1

«

o ,

3

ideal.

J

«

13 «« **"'•*¥

2

2

=€>

30

5

r

3 J

Jr

4

*)

TRl *

Distance measure Distance travelled through the water by three main types of instrument:

is

measured

f

St ^3

21 18

A

(a)

spinner towed on the end of a line

commonly

water, (b)

An

(c)

A

in

the OFF

called the patent log.

01 1

UJUMMATion

impeller protruding from the yacht's hull.

SEHS

~

j

transducer without moving parts.

economy and reliability the Walker patent much to recommend This consists of a registering mechanism or "head" carried on a short For

log has

it.

metal outrigger which can be slotted into either of a pair of

quarter. is

metal plates screwed to the deck on each

An eye on one end

connected to

the mechanism.

a

hook

On

in

(a) Auto pilot control panel (Neco Marine). Course is set on main dial. Rudder, trim and sensitivity controls cope with the

response of the boat to the autopilot.

of a line, the logline,

the head, which drives

the other end of the log-line

a spinner or "rotator"

is

permanently attached.

This is towed through the water. The spinner revolves a set number of revolutions each yard or mile, and the head has dials reading in miles and tenths of a mile. One or more weights are supplied which can be fixed to the logline a few feet

(b)

The

drive unit

which moves the rudder on

control unit.

forward of the spinner to ensure it remains properly immersed while being towed. It is

advisable to "stream the log" (put the

spinner and logline

in the water) till in a reasonable depth of water and clear of the harbor, to guard against bumping the spinner on the bottom, or getting it fouled round a buoy. For the same

remember

"hand the log" (bring it aboard) before entering congested waters. If you hand the line by just hauling it in while it is still attached to the head, you will find that it comes full of twists and aboard like a lot of knitting knots due to the spinner keeping on twisting the reason,

—

58

to

—

n

signals from the

equipment counter over a six-minute period; the number of 1 /1 Oths of a mile clocked up in this time will be the speed the

in

knots (6 min. = 1 /1 Oth hr). Or do three minutes and double the

same over

answer.

Glance time.

If it

at

the spinning logline from time to

starts revolving

yacht's speed

seems

more slowly than the

to warrant, the spinner has

probably gathered some weed. Haul in and clear. The counters can be returned to zero by unlatching the front glass face and turning each of the three pointers back to 0, turning them counterclockwise.

Some parts.

instruments have no external moving The Doppler Speed-log's streamlined

transducer emits a high-frequency signal ahead. (c) The master compass with power pack which detects changes from the automatic course. The repeater compass shows the actual course at the wheelhouse or cockpit.

A

portion of this signal

boundary

layer.

The

is

reflected

back from the

reflected frequency increases

with boat speed increase. The difference between

two frequencies

is converted into speed and and both are displayed on the meter. The EMI Electro magnetic log uses the principle of a magnetic field which is changed by the speed of passage of water past a virtually flushfitted transducer. This also provides both speed and distance run through the water. Impeller-type logs do not have a towed logline. They can be operated either mechanically or electronically. The British "Sumlog" is one which is mechanical. This has a short stalk

the

distance,

line.

Untangling

can be

it

a tedious job. Instead,

unhook the eye on the line from the head as smartly as possible and immediately start paying out back into the water the end just unhooked, while hauling

in

the line working towards the

When the spinner is aboard the whole should be trailing astern, and not twisting round. It can then be brought aboard quite easily, what few turns remain being readily removed.

protruding a couple of inches or so from the well

below water

level.

number

spinner.

which,

line

times per mile sailed through the water. The

If

you do not have

(discussed

later),

by observing the

a

water speed indicator

the ship's speed can be found 1

/1

Oth mile counter. Read this

like

impeller

is

hull,

This carries an impeller

the spinner, rotates a set

connected by means of

of

a rotating

wire to a counter-head which can be mounted

in

the cabin or on cockpit bulkhead, and which records miles and fractions.

The

electronic type of log has an even smaller

impeller

mounted on

a short stalk

below water 59

practical yacht navigator level,

but there

is

no mechanical connection and

the impeller creates electrical impulses which are

sensed and conveyed by wire to the log counter head where the mileage covered is displayed by digits, to two decimal places of a mile. The counter head can be mounted wherever required usually near the chart table. With the electronic type, the impeller can be withdrawn from inside the hull for clearing, should it become

—

fouled. Impeller type logs are less frequently

fouled by

weed

as the impeller

is

usually

more

deeply immersed than the rotator of the patent log and can have a weed deflector built on it.

The

log should be regularly read and recorded, keep track of the ship's position, and to give early warning of a fouled log. Most logs are reasonably accurate if installed according to the maker's instructions. Accuracy should be within 5 per cent, and can be within 1 per cent. Logs tend to over-read when beating to windward, and to under-read when running with a strong wind to

aft.

Depth sounder Rotating neon light meters work on an electronic

impulse which

is

fed by co-axial cable from the

instrument to the transducer, which pointing vertically

downwards,

in a

is

fixed,

suitable place

its operating face on the outside of the underwater hull. This impulse is reflected back from the sea bed, sensed by the same transducer and fed to the instrument. At the instrument the outgoing impulse causes a red neon light, fixed to a revolving arm, to flash, and the returning impulse causes it to flash a second time. As the neon

with

light is revolving, the interval in time between outward and return passage of the impulse is measured by the angular distance between the two flashes. The arm is so set that the first flash occurs when the neon light is passing the zero or

60

Boat speed and depth displays. The yacht is traveling at knots. Depth of water is 1 4 whether meters, fathoms or feet should be known to the navigator!

4^

:

equipment ft

position.

neon

The

circular scale

light revolves

is

round which the

calibrated so that the

yacht's battery,

calibration reached by the returning flash

indicates the depth, at that instant,

below the

transducer.

Most

of this type are calibrated in feet or

fathoms, from

from the one scale to the other (feet or fathoms). When set for fathoms, the arm simply revolves at 1 /6th of the speed as when set for feet. They can

Most

are

if

some can be connected

to the

of the correct voltage.

Prolonged use on the feet setting exhausts a It is economical to set to fathoms when not in shallow water as this dry-cell battery rather quickly.

uses

to 60, with a switch to alter

also be obtained calibrated in meters.

dry-cell operated:

far less current.

These instruments are generally reliable and remarkably accurate. Some owners mount the in the cockpit. As it may not be waterproof a better place is in the cabin, such a place that it can be seen from the

instrument truly in

Recording type echo sounder (Seascribe). which also shows light indication. Note the transducers which will be fitted

neon

to the hull

61

— practical yacht navigator steering position. This protects from spray,

the neon light

more

is

and

readily seen in the shade.

Needle-indicating meters work on the same reflected-impulse principle, but the depth

is

read

on a circular scale with a pointer hand. They also can be switched to show feet or fathoms, and can be had calibrated in meters. These have the advantage of being capable of feeding repeater dials situated away from the instrument, often in the cockpit.

A

Graphic display depth meters These have an inked pen which indicates the depth on a slowly-moving roll of paper, similar to a barograph. By this means a continuous trace is

made

THE PELORUS COMPASS

of the depth traversed. Mainly of value to

fishermen, surveyors and the

like,

these are not

necessary for the cruising yacht. Like sounders, this instrument

will pick

all

echo-

up shoals of

pelorus

compass

commend

Usually

it

is

the steering

consists of a base fitted with a lubberline; a

compass card on a central pivot which can be turned by hand to register any desired "course"

— the position of the

setting being used, feet or fathoms,

bearing read off on the

To operate the

fathoms flash comes up the 25 minute position on a clock face. or

its

dumb compass

pelorus, the base plate

is

fixed (or firmly held) so that the lubberline

indicates the depth without recourse to reading ft

that

card.

flashes relative to the flash at the zero point

the dial; e.g. 25

in

pivot so that a distant object can be "sighted"

it:

the least expensive.

(b) Easily read at night

at

is

readily seen by the frequency of the flashes

when on feet; distinct and when set for fathoms. The echo-sounder has now superseded the

almost continuous separate flashes

leadline because of the speed and frequency with which soundings can be taken with it, and the elimination of the hard work and skill required to use the leadline. The only points in favor of the old leadline are its simplicity and the facility it gives of determining the material on the seabed by

62

when

compass in which the compass card is moved by hand instead of by magnetic forces. It

and

The

used

position; sight vanes pivoting on the central

The neon-type echo-sounder has three characteristics to

(c)

is

so positioned that it is difficult to take bearings of a landmark direct from the steering compass. A pelorus is a dummy

against the lubberline and can be locked

fish.

(a)

compass is

central pivot are

on

a line exactly parallel

and

with

the fore-and-aft line of the yacht. (A convenient place

may be on

with the

aft

the top of the coachroof

side of the pelorus base butted

equipment "arming" the lead with tallow so that particles of is there adhere to the lead. A neon-type echo sounder will give some indication of the composition of the seabed. When over rock, the indicating flash forms a sharp line: when over soft mud the impulse is blurred and the neon light is wider. The transducer should be fitted in accordance with the makers' recommendations. In a sailing yacht consideration should be given to fitting two transducers, one on each side of the keel, so that when the yacht is heeled over steeply when sailing on a tack, the leeward transducer will be sand, shell or whatever

firmly against

any (exactly) athwartships

moulding.) If

the next bearing to be taken

the yacht's head card

is

1

is

that with

35°C, the pelorus compass

unlocked, the card turned

till

1

35°

is

opposite the lubberline, and the card re-locked. The sight vanes are then turned till they are

helmsman 35° by his compass. The object's bearing is then read on the pelorus card under the sight vane's pointer. As both steering compass and pelorus are reading the same heading, the bearing by pelorus will be the same as if taken with the steering compass. As the helmsman is directed to steer on a fresh sighted on the object while the reports he

is

steering

on

1

course (say 1 80°), the pelorus dumb card is unlocked, re-aligned on 180° to its lubberline, and re-locked. When the helmsman reports he

on the new course the sight vane is directed on to the object and the pelorus bearing is taken and recorded. is

"pointing" more or less vertically downwards.

Switches are available which, working under gravity, automatically switch from windward to leeward transducer. If two are decided upon, they must be ordered as a pair as each transducer is matched.

On to

fit

yachts with fiberglass hulls

it

transducers entirely inside the

avoids having the

hull skin

is

possible

hull.

maximum

no skin

fittings,

may be

slightly reduced. Special fitting

but the

This

broken, and there are

operating depth is

necessary to ensure the impulse and reflection are both transmitted through the hull. When fitting a

—

transducer to a power boat particularly a fast planing type care must be taken to fit it in a hull

—

where the water will be least turbulent, as can interfere with correct functioning.

position this

Hand bearing compass There are many occasions when the navigator will wish to find the compass bearing from the yacht of one or more distant objects to determine the yacht's position

in relation

to that object or

objects, such as lighthouse, headland or church

Few steering compasses are positioned to enable that compass to be used for this purpose with any ease. A hand bearing compass, as the tower.

63

practical yacht navigator

A very

weight handbearing compass. Illumination is by The object is viewed through a hole in the edge of the compass which is made of transparent material. (Fig 30). When correctly aligned, the scale on the compass card comes into view immediately below the object being sighted and can be read very accurately. The special feature of this instrument is that the optics are so designed that the compass card is seen with the eye focused at infinity the same as the object. The compass can therefore be held quite close the eye without having to alter the eye's focus between object and scale. A further advantage of this type is that it is small enough to be worn around the neck, or carried in a pocket, when going down through a hatch in rough weather. light

Betalight luminous material.

—

Fig 30.

Betalight

64

View through mini-handbearing compass. At night shows scale.

equipment name

implies,

is

compass, one edge. The prism and lined up by eye with the

a small, easily portable

usually with a prism over

associated backsight are

and in the prism will be seen a edge of the compass card, from which the object's bearing can be read. These compasses usually have either a self-contained torch light with battery in the handle, or glowing luminous material ("Betalight"). When not being used, the handle type compass should always object, (Fig 30.) reflection of the

be secured to a bulkhead.

65

More on Instruments

4.

A

is one of the things a navigator looks on a yacht. Direction finding facilities can give you a bearing on one of the many radio beacons, sited on coasts all over the world. Commercial shipping is increasingly using more sophisticated aids and these simple transmitting radio beacons are primarily of use to fishermen and yachtsmen. Two kinds of aerial can be used to find a bearing. (a) The ferrite rod aerial will give the minimum

radio

after

signal strength

when

aligned parallel with the

direction of the transmitting station, directly

towards or away from the

maximum when line to

(b)

its

axis

is

at right

i.e.

pointing

and the

station,

angles to the

the station.

The loop

aerial will give

strength signal

when

the

minimum

the plane of the loop

is

at

right angles to the direction of the station,

and the maximum when the plane

is

aligned

—

found that the "null" point the which gives the weakest signal is much more clearly identifiable than the position of maximum signal strength. Both types practice

it

is

position of the aerial

—

are therefore operated so as to find the exact

position of

minimum

signal strength.

On

a

good

tuned to a station well within range there will be one position where the signal will be quite

set

66

This

is

the "null" point.

Largely because of their bulk, sets with loop

becoming obsolete on fiberglass or Most loop aerial DF sets and some with ferrite rod aerials have a dial and pointer fitted to the aerial axle, the dial being marked in aerials are

wood

yachts.

degrees to 360°. If the dial is set so that the 0° (N) point lies towards the bow (like a lubberline of a

compass) on the fore-and-aft

aerial

will give

When

line,

and the

rotated to the "null" position, the pointer

is

the relative bearing of the

the relative bearing

is

DF

station.

applied to the

bearing of the ship's head, that

is,

course being steered, the result

will

the

compass

be the

compass bearing of the transmitting station. On some sets the calibrated dial on which the aerial is pivoted can be rotated. The dial can then be turned so that the reading on its edge is set to correspond with the yacht's heading by compass. (The lubberline must of course be accurately positioned, as for a compass). When the radio beacon's signal is tuned to the "null" position by turning the aerial, the compass bearing of the beacon can be read from the dial. The bearing so obtained is a bearing "by ship's compass" and must be converted to a true bearing before being laid off on the chart. See Chapter 5. a lubberline, to

parallel to the line to the station. In

silent.

more instruments Certain

DF

sets are

made with

a ferrite rod

mounted either above or below a small compass. The aerial-and-compass unit is connected to the radio set by its aerial wire. The rod aerial together with its compass can be rotated by hand till the "null" position is found, and the compass bearing of the aerial, and hence aerial

of the transmitting station

found

at

receiving long and

medium wave

transmissions,

so that shipping and general weather forecasts and news can be received. When using celestial navigation frequent radio time signals are essential,

and these too can be received. For good

results,

once, without

reference to the steering compass. This

is an advantage over the set which only provides a

relative bearing, in that the latter requires a very

steady course to be steered while the "null"

is

being found, and two readings are necessary

(compass and

relative bearing)

and

lack of accuracy

One

sort of

DF

with inevitable

risk of error.

set has the ability to find a

beacon almost by itself. This is the Autofix 1 00 by EMI. The operator has only to tune the set to the frequency of a radio beacon when a large pointer on the set automatically turns to point to the transmitting beacon. The pointer is set in a verge ring inscribed 0° to 360°, which can be rotated to correspond with the compass heading of the yacht. The compass bearing of the beacon is then given by the pointer. Most sets having loop or ferrite rod aerials will give identical results whether the pointer on the loop

aerial or

the

ferrite

rod

is

Normally one has

a

AT

pointed

transmitting station, or exactly

which the

but ambiguity can arise

the case of an

in

set

offshore station such as a light vessel. the yacht

when

versa). (Fig 31

station it

.).

is

it.

rough idea of the general

direction of the station to

happen that the

the

AWAY from

is

somewhere

is

It

can

astern of

thought to be ahead

Some

tuned,

(or vice

sets incorporate a device

for resolving this possible ambiguity,

i.e.

will

which end of the rod is pointing to the station and which away from it. Almost all DF radios are also capable of

A

radio direction finder (Sailor). The navigator listens on the ear phones while turning the compass and ferrite rod aerial.

indicate

67

practical yacht navigator

side of the light ship am ? Radio bearing 80° out. For yacht on set course, change of angle gives clue. If bearing opens out. beacon is ahead of the beam; if it reduces, beacon is abaft beam. Fig 31

.

could be

Which

I

1

Radio direction finding loop mounted on a wheel house roof. is essential on steel boats, and it is also generally useful on medium or large motor cruisers. The line of the loop gives a minimum signal at right angles to the beacon. This location

68

more instruments DF

radio receivers should be so sited that the

aerial

a position least subject to radio

is in

and where the aerial-compass will be minimum magnetic influence of objects in the yacht which might cause deviation of the compass. A DF receiver should be distortion,

subject to the

"calibrated" by sailing within sight of a radio

beacon (transmitting station) and taking both radio and visual bearings of the station with the ship heading successively on courses all round the compass. Any radio set capable of picking up the long wave with good power can be used for picking up Consol stations. These are of value only when well offshore. The operation of DF radios is dealt with in Chapter

1

0.

Binoculars It is

surprising

how

often binoculars are used,

buoy

to search for a

or lighthouse or other

landmark, or even to read the

name

of a buoy, or

mistake to buy glasses of too high a power. Magnification x 5 or x 7 is the

of a ship.

It is

maximum

a

The power the more the object viewed will "dance." Magnification x 1 is almost useless, even in a flat calm. The more important feature of

s

to be of practical value at sea.

higher the

For small

craft,

the best

way

of radio direction finding

is

an

connected to a compass. This is a ferrite rod (Brookes and Gatehouse) which gives a minimum signal

aerial

line of

the beacon.

in

the

binoculars

is

the size of the object lens (the

The bigger they are the better will be the light-gathering power, and this determines larger end).

their value

night.

The

when

observing

ideal size

is

in a

poor

light or at

7 x 50 (indicating

magnification of

7,

diameter of object glass

50 mm), 7 x 35

is

also a useful size,

advantage of being smaller and

and has the

lighter

than

7 x 50.

Stop watch is useful for timing lights. The light should be observed and the stop watch used to time it care-

This

69

practical yacht navigator This is accurate and than trying to count. fully.

far

more reassuring

change indicates a probable change in the weather, and if readings are regularly recorded

Clock

A

clock on the cabin bulkhead

One which chimes

is

"ship's bells"

few minutes

obviously useful. is

rather fun,

and

can be a useful reminder of the time to tune in to the next shipping forecast, the time to read the patent log, and to change watches. Eight-day clocks with alarms are useful. (if

set a

a

graph of the barometric pressure can easily be constructed. (Fig 32.). Alternatively, some yachts carry a barograph, a barometer which traces on paper a continuous record of the reading. Hardly necessary on a coastal cruiser, this type is of

fast)

when

particular value

change of an

of as

in tropical

as 3 millibars

little

waters where a

may

give warning

approaching cyclone.

The Sextant Barometer

Essential for long-distance cruising

A

observations are necessary, a sextant can be of

barometer can give additional indications of changes in the weather. On a passage of 24 hours or more it is prudent to make the reading or the barometer one of the routine items to be noted in the logbook at regular intervals. Any marked

great value even

.

1

2

3

4

5

6

7

8

9 10

coastal cruising.

in

A

celestial

sextant

is

designed to measure with great accuracy the angle subtended at the observer between two objects. If the angle between the top of an object and the

B A R

RAPPEL BARO DE LA VEIL LE M-J

when

11

12

13

14

15 16 17

18 19

-

20

21

s

22 23

M

1

1

2

3

P

L

4

5

E

6

BARO DU JOUF

X 7

8

9

10

11

12

13 14

15

16 17 18

19

„ .... situations amicvcloAiQues

20

21

22 23

C

us 1033 1029

1029 1025

1025

1021

1021

1017

1017

1013

1013 -

1009 1005

1001

997

r

1001 :

1

993

993 1

989

.

989

situations dtpresstonnaires

If a barograph is not carried, a graph can be Fig 32. constructed to show the movement of the barometer. This "Baro Simplex" is a 24 hour chart for such use. (It is published

by Editions de

70

la

Mer. Paris.)

more instruments sea level below of the object

is

it

is

measured, then

known

it

is

a

if

the height

moment's work to

from the object. The height of all lighthouses is available, for example. This is a vertical sextant angle (VSA). Similarly, the

find out the distance

horizontal angle between two objects or features can be measured by horizontal sextant angle (HSA). The procedure for obtaining and using VSAs and HSAs is given in Chapter 9. Positions found by these means can be considerably more accurate than those obtained by the more frequently used compass bearings. Even when making modest passages there may well be occasions when a position line or position found by a celestial observation of the sun (or moon, planet or star) will be of value. For this a sextant

is

essential.

Apparent wind direction indicator The movements of an arrow, fixed to the masthead and free to pivot like a weathercock, wind sock or burgee, are transmitted electronically to a

shows the

dial.

A

and number of degrees which the masthead arrow is pointing from the dead-ahead position. Note that this will register pointer

direction

only the direction, relative to the ship's head, of Stopwatch for use on deck, essential this one is sealed in plastic.

for

easy timing of

lights:

the apparent wind, not the true wind. The

instrument

is

of value in helping to steer the

optimum course when close-hauled, at night

when

particularly

the sails cannot readily be

observed, and also for the less experienced

helmsman. The skipper instruct the

helmsman

who knows

his

to steer a course

boat can

which

keeps the apparent wind, say 32° on the port bow, if he knows this is the best angle to the wind in the prevailing conditions. The wind direction indicator

is

a great help

when running down wind

with the wind almost dead astern

— particularly

at

night.

71

— practical yacht navigator

The wind speed

indicator, or

anemometer

mounted on four arms axis, carried at

free to rotate

..

on

a vertical

the masthead and electronically

which translates the revolutions of the cups into wind speed in knots. Knowledge of the wind speed in absolute terms (knots) can reinforce judgement as to when to reef, what sail to carry, and so on. For the skilled racing skipper it can also indicate the optimum connected to

a dial

close-hauled course to the bar story about

steer.

how

it

It

can also support

was "blowing 50

knots.'

.

performance computer

racing

sailing to windward — particularly when — the problem facing the helmsman to

gauge

just

When

is

order to

how

close to the

make good

the

wind

good).

good

A

in

Vmg

to

(Velocity

course too close to the wind

will

made

be

the directional sense but at the cost of

speed through the water; a course too far off the wind will give a high speed through the water but bad in the directional sense. It is the old problem of "pointing" or "footing," and of finding the

optimum to get the yacht fastest to her destination. The performance computer is designed to solve this

problem.

It is

fed (from each of the

appropriate instruments) with wind speed, wind direction (apparent)

and yacht's speed through

the water. The instrument indicates on a

and needle the value of Vmg, and any changes in that value. Fractional alterations of course angle and of the trim of the sails show up as changes in the Vmg, and hence in the yacht's progress towards a windward mark. dial

There are several manufacturers of this type of The Horatio (made by Brookes &

instrument.

Gatehouse Ltd., England) takes matters a step It produces an answer in terms of the

further.

72

is

more

useful than

Vmg

alone as

is,

it

does not change significantly with changes in wind speed, as does Vmg. This enables the course steered and the sail trim to be adjusted

to

give the highest figure without waiting for a period when the wind speed, and hence remain steady. The Horatio has two settings (a)

For a

windward course, the Vmg/Vt

produces the

result

Vmg

setting

described above.

For sailing off the wind, the Vs/Vt setting

is

used, and sheets are trimmed to give the highest reading.

Both settings can also be presented on various between coarse and fine. The latter show a larger movement on the dial for smaller alterations

scales

to steer in

maximum speed

windward, technically called

This

speed of the true wind, that

to the

Vt

(b)

Sailing

Vmg

ratio of

This consists of four small hemispherical cups

of value.

Some ban or

racing organizations and classes have a

restriction

on the type

of electronic

instruments used. At the present time, most racing organizations allow individual instruments but

do not allow them to give

any

sort of

to be linked to a

computed

Vmg computer

position.

North, South, East,

5.

Whenever we frequently

are out of sight of land

when

and quite

within sight of the coast, the

way to tell the heading is by using the compass. The compass is quite the most important instrument on the yacht, so a clear understanding of how to use it is essential. only

As the lubber

line

shows the exact

the yacht's fore-and-aft

line,

direction of

the direction

in

West

same way any bearing picked up from the

chart

be reference to the meridians, which are true (north-south) bearings, must be converted to the corresponding magnetic bearing before being used for steering. This is the application of variation.

Variation Variation

may be

either side of the true direction of

which the yacht is pointing is given by the degree mark on the compass card which is against the lubber line. In a yacht under way and changing direction, one's first impression is that the compass card is swinging and that the lubber line is stationary. But really the compass card remains (relatively) stationary, the

N

pointing to north, and

the lubber line which

it

is

point constantly

4"-

moving round the compass card as the yacht's head moves round. But the north to which the card tries to point is called magnetic north. It is not the same as true north and indeed the whole card is slewed round so that every reading on it will differ from the true direction by the same amount. (Fig 33.). It follows that a magnetic direction, heading or bearing is likely to differ from the corresponding true direction or bearing read from the chart. This difference (or "error"), is

is

called "variation."

To

relate a

on the

compass reading to a true bearing compass reading must be con-

chart, the

verted to the corresponding true bearing. In the

Fig 33.

The yacht's compass seeks

to point to

north (colored arrow). But true north of the chart

difference

is

and there

is

is

magnetic

shown by

the edge

an angular difference. This

variation.

73

practical yacht navigator

Long Island Sound the between 13° west and 14° west. Near Vancouver Island in Canada the variation is as much as 24° east, while near Greenland it is 50° west, because there it is

tremendous effect, so even a foot can throw the yacht off course. One to have a notice in the cabin if the compass

north. For instance, in

seen to have

variation at this time

or so

is

getting very close to the actual north magnetic pole.

So

any reading on the compass to the on the chart the compass reading

to relate

true bearing

must be converted to the corresponding true

(a)

is

position

what the variation is: By looking at the compass rose printed on to find

is

a

it

on the other side

of the bulkheads,

compass is there and that no metal materials must be put in that region of the cabin. There is a little device which can be bought at hardware stores in which a bar of soap

stating that the

is held by pushing a small bit of steel into it and then hanging it near the basin, clean and dry by

means

bearing.

Now

idea

away

of a

magnetic holder.

inside the cabin but less than

might say, for example, "variation 7° west (1 970) decreasing about six minutes annually." Obviously these six minutes must be applied to bring it up to date for the year in which you are. (b) Many nautical almanacs and pilots give the variations at various ports. Some ocean and other small scale charts show variation by means of isogonic lines on them.

other side of the bulkhead

Deviation compass, whether loose gear or the yacht's structure itself causes deviation. When variation has been applied to a true bearing it is known as a magnetic reading: when deviation has been applied on top of this it is known as a compass bearing or course and is written 01 0° C or 1 74° C. On a wood or fiberglass Steel or other magnetic material near the

yacht a well sited compass if

may have no

the engine and iron keel are far

deviation

enough away.

Usually the deviation on fiberglass boats

is

very

more than 2°. Beware however of metal objects which can influence the compass if left carelessly near it. This is old advice but one sees it happen quite small and of the order of not

frequently.

crew

74

knife

An ordinary so-called stainless when near the compass will be

steel

once found one

of

I

the chart. It

I

these installed by the owner's wife on a yacht on which was navigating. The powerful magnet was 1

was

8 inches on the the ship's

steering compass.

Having removed the

compass

it

all

is still

possible influences from

necessary to see

if

there

is

any deviation remaining and this is done by "swinging ship." Bearings are taken with the steering compass of a distant object the magnetic bearing or which is already known or has been found. The yacht heads on each of eight or more equidistant headings all round the compass. Each bearing of the object taken with the compass

compared with the

is

actual magnetic bearing of the

object from the yacht's position, the difference

being the deviation on that heading.

The reason for this becomes apparent when consider the effect, for example, of having a single piece of metal

north and repels

its

which

attracts the

we

compass

south pole, placed, say,

forward of the compass. (Fig 34.) Note the effect the metal will have on the compass needle as the yacht's head is steadied in different directions. Or take the case where a single piece of metal which attracts the

compass N and

repels

its

S pole

placed on the port quarter. (Fig 35.) This

is

is

an

over-simplification of the problem, but will serve to illustrate

how magnetic

influences

in

the yacht

north, south

Fig 34.

A

single piece of magnetic material forward of the

compass deviates the card. The snag is amounts on different points of sailing.

that this

is

for different

Fig 35. Metal (or magnet) on port quarter. Once again deviation changes with the yacht's heading. Note how the piece

of metal

moves round the compass card with change

of ship's

head.

75

:

practical yacht navigator

may

affect the

direction (E or

compass

in

varying amounts and

W) depending on

the direction the

is heading at the time the compass is read. There are three ways of dealing with the problem of deviation 1 Site the compass sufficiently far from any ferrous or magnetic material which could cause deviation, or move the material away. There will then be no deviation.

yacht

.

2.

Place small magnets near the

way

a

yacht's head

is

pointing

in

various directions,

173° magnetic; 173° magnetic; Magnetic;

76

(b) Deviation 5°

W against magnetic N and

(c) Total "error"

10°

circles.

Compass: squares.

E.

True; triangles.

all

round the circle. In practice it is usually sufficient to determine the deviation when heading on each

°

Variation and deviation, where present, affect every 1 5° E variation shows positions for magnetic N and

such

what the professional compass adjuster does. 3. Ascertain what deviations occur when the


W

5 »w

4 3E

181 °C

259 °C

313 °C

(

C

W

(c)

All

True card

Compass Card

readings

W

W

to

N

Whole compass card drawn anticlockwise True card

Compass Card

readings

GREATER

than True readings

than True readings so

so [d)

relative to All

LESS

All

True readings

GREATER than

Compass

readings.

Var n

of True

so

the

317°T

254°T

WEST

Whole compass card drawn clockwise relative to

Here are some examples of applying variation and deviation which are combined: Working from True to Compass:

173°T

True N

Error

Compass drawn

so

larger. (Fig 36.)

True Co.

to E

(b)

we name

EAST

Compass drawn of

name

subtract the smaller from the larger and

answer as the

conversion always test with the

Error (a)

be noted that where names are the same

(both E or

a

jingle.

All

True readings

LESS than Compass readings.

Check these two statements with the two compass roses in Fig 37. It would be nice if we could just call each error "plus" or "minus," instead of E or W. But the sign (plus or minus) to be used depends on whether we are applying the error to compass 77

practical yacht navigator to arrive at true, or to true to get

Compare jingle

is

(c)

and

compass.

(d) above. This

is

why

the

so valuable, and should always be used.

The problem

of

remembering whether to add or is a perennial one

subtract variation or deviation

and gives many people trouble. But really it is problem we are all familiar with, using a watch which is known to be fast or slow we have a "watch error." First, remember that variation and deviation are both "errors of the compass." If small, they can be combined to give a single figure or total error. Consider a watch which is, say 5 minutes slow by time signal. We know that we must add 5 minutes to watch time similar to a

—

to get true time.

If

we know

the true time

.'

>* -f*

Jh

-U

Jit

-^

we 5*

must subtract 5 minutes to get watch time. If our watch is fast, we must reverse the signs in both cases. Applying the same technique to the compass, we can say that an Error WEST means

Compass is FAST or registering HIGH; if EAST the Compass is SLOW or registering LOW.

**« *

-

-

if

~

the

Error

If

Error

WEST:

Compass

Fig 37.

magnetic

reads

The solid line is transferred to the compass rose and shows true and magnetic bearings. True is 292°.

dotted line

is

31 0°. (Variation of

1

8° west.)

HIGH

SUBTRACT from COMPASS for TRUE to TRUE for COMPASS

ADD

Watch

is

ADD

to WATCH for TRUE time SUBTRACT from TRUE time for WATCH

FAST

SUBTRACT from WATCH for TRUE ADD to TRUE time for WATCH time

Mnemonic: Error

If

Error

is

EAST:

Compass

ADD

to

Error

reads

COMPASS

SUBTRACT from

LOW

TRUE TRUE for COMPASS for

78

is

SLOW

WEST, Compass BEST, HIGH (Fast) EAST, Compass LEAST, LOW (Slow)

To swing ship

for compass deviations The following procedure can be used for determining what,

Two Watch

time

if

any, deviations are present.

people are required: a reliable helmsman and an observer to take the bearings. A calm day with

north, south

Fig 38. By going clockwise round the comoass N. NE. E, SE etc the yacht strays from the mark and does not maintain the same bearing to the distant mark. By taking N. S. NE. SW etc in that order the yacht keeps close to the near mark and the bearing to the distant one changes negligibly.

79

practical yacht navigator

good

visibility

can be clearly seen. The yacht is maneuvered, at a minimum steerage speed, near a buoy identifiable on the chart, out of the fairway, and in sight of a landmark at least 5—8 miles away, and also identifiable on the chart. The true bearing of the landmark from the buoy is found from the chart and (by applying local variation) the magnetic bearing is determined. The helmsman is ordered to steer exactly N, 0° by compass, and to call out when he is on course, AND when he is off course. The observer takes the bearing of the landmark by compass while the helmsman is calling "On on on." This compass bearing is noted against yacht's head. This is repeated while the yacht is being steered on each cardinal and intercardinal

— —

heading.

W,

NW.

SE,

the sequence N, S, NE,

in

SW,

E,

This keeps the yacht nearer to the

chosen buoy and reduces parallax.) (Fig 38.) The complete record might appear: Bearing


urs e

I oq

Time fyd

BST

Lee Wake

c°

-E-r*

Way

o

Dev: Var.

Since last

T

It*

w- w-

plot

Stream-

Co.

r

s-

i

Fig 110. Fig 109.

164

Deck

log for

power boat

deck

log.

i

i

i

i

when working-*-

kn Mues Lot / Long.

o

I

i

* Signs operate

VhtTLef. or

Set Rate Vrft.

I

I

ii i

Reverse

i

when working -*-

Navigator's log extracts necessary information from

log

may be

books

should be recorded. The requirement to make these entries ensures that instruments are regularly read and any unusual change is observed. Even a small (but unaccountable) alteration in reading may give early warning of trouble brewing in the power house and enable

dangers are neared, and depending on the he may plot at more frequent intervals. An entry will be necessary at the time he wishes to make the next plot on the chart and on every alteration of course since the last entry, since each new course steered will require its own wake course line to be plotted. (Alternatively, the navigator may decide to calculate a new EP by Traverse Tables instead of by plotting, and for this he will need details of each course steered. See Chapter 17.) The Tidal Stream section entries will depend on circumstances. Streams seldom flow exactly as predicted, and interpolation between springs and neaps may be necessary, but very exact

the engineer/skipper to investigate

calculations are seldom called

yachts

not only of interest but of value to

the navigator. The regular noting of the barometer

can be of help in anticipating the onset of bad weather or a shift in the wind. In a power yacht, the deck log (Fig 1 09.) should also record at reasonably frequent intervals details of the engine(s), such as r.p.m., temperature, oil pressure, ammeter. At perhaps less frequent intervals the state of fuel stocks

A (at

small but useful

midnight) draw a

and below longish

it,

trip

it

tip.

is

across the page

line right

enter the

it.

At the end of each day

new day and

(for tides, nautical

almanac,

On

date.

quite easy to use the

a

wrong date

is

man

men

or

on watch an interest. They can check the speed, and if it drops off, check the trim of the sails (or the engine if under power). Both electronic and towed logs often get fouled by weed and either register slow, or stop.

If

the log

is

read every

The object log,

tidal

and thus to enter the is fast,

or

changing

x time

drift (rate

last entry.

hour's set of the stream since the last

If

the

each

in direction,

wake

course entry can be recorded. There might then be two (or more) stream lines laid off from the

DR

arrived at by reference to the

new

wake

course, to

EP.

Before actually plotting on the chart, in

all

entries

the navigator's log should b3 checked,

from the deck

log, fo' times, log reading,

and

compass Co.

of this separate log (Fig 11 0.)

is

to

record only that information, extracted from the

deck

stream

(a)

The navigator's log

the tidal

stream (set and rate) applying between two log

provide the

half-hour this is soon detected, the log cleared and the recorded mileage corrected.

If

simple matter to determine the average

elapsed) experienced since the

not only

essential for navigation, but gives the

for.

been marked up in pencil with the times each chartlet applies on each day it is usually a atlas has

entries,

etc).

Regular entry of the deck log

visibility,

which the navigator

will

need to plot

the ship's progress and position. The navigator

may decide

to bring the chart

the yacht's

new

up

DR

to date

(i.e.

plot

(b)

from the

(c)

for arithmetical errors. If

tidal atlas (or chart

symbols

if

used).

the deck log records any positive fixes

obtained

— or even good single bearings from EP as

which

a position line

every four hours, or at every change of watch,

at that

time should be plotted and compared with

while on passage. As the destination, or any

the

or PL.

position by

or observations)

fix

is

available, then the

Depending on the navigator's 165

.

practical yacht navigator

confidence in the bearing(s) recorded, so he will decide whether or not to alter his EP. The observer should be encouraged to note in the deck log his own idea of its accuracy (e.g. "good," "rough," "doubtful," "Start Pt L/H ???"). If he is satisfied, the navigator will then abandon the EP and mark a fix and plot forward from there. The column for "Plot Ref." is to enable the navigator to "key" the successive EPs on the chart with the log entries, if he wishes, by letters. Otherwise, the log distance date and time of each EP and fix should be noted on the chart astern of

and close

to,

the EP to which

it

refers.

Note books The navigator

will

be frequently making

calculations of various kinds, fairly

complex,

e.g.

some

simple,

some

heights of tide; conversions

between compass and

true for bearings, courses,

distances, speeds, ETAs, fuel stocks and so on. is

recommended

that

made, and recorded,

all

It

such calculations are

in a

reserved for this purpose.

special note It

is

book

surprising

how

often these will be referred to at a later time for

memory on how they which ones were wrong,

checking, refreshing the

were done and why.

166

or of noting

1 4.

A

Off to Sea

successful passage

commences with thorough

"lanes" which vessels should use while proceeding

preparation long before departure. Preparations

in either direction.

can conveniently be divided

not mandatory, but the majority of merchant ships

into:

(a) Advance preparations which can be made days or weeks in advance. (b) Departure preparations, requiring attention immediately before leaving. (c) Preparations en route, those to be worked out

during the voyage but before landfall.

At the time of writing these are

adhere to them. The zones are marked in purple on National Ocean Survey charts, and on some other charts as well. They should be treated by the yachtsman as a pedestrian does a motorway. If possible, keep well clear: one can expect a large volume of shipping in them. If proceeding in

the

same

or opposite direction,

keep well

clear

of the lane in shallower water (subject to draft).

Advance preparations

If

crossing a separation zone or shipping lane try

scan charts and one essential is a chart covering the whole passage (showing departure point and destination).

to cross at right angles so as to get across as

Port approach charts covering any ports likely

accordingly.

It is

a positive pleasure to

quickly as possible.

Make

sure these are

shown

on the charts to be used, and shape courses

to be entered through force of circumstances are also needed. date,

and

if

Check that them

not, return

all

charts are up-to-

to the chart agent

for corrections, shortly before departure.

Pencil

in

the approximate track from departure

to destination, line,

and study the area along

noting the features as described

Study the

this track

earlier.

sailing directions or pilot covering the

area of the passage,

and any guide book dealing

with the coast and ports en route. Separation

zones are already set up round many headlands and through channels with high shipping density, e.g. in parts of Rhode Island Sound, at the entrance to the Delaware Bay, and others. These prescribe the

Tidal atlas This should be prepared for rapid use in the following manner. Open the a*las at the chartlet for situation at high water. This will be at the center of the series. Across the top or bottom margin pencil in all the days and dates of the planned passage, and under each, note the times of on each day at the port on which the atlas is based. Then work progressively forward and backward through the atlas, changing each pencilled time by one hour (earlier and later) on predecing and succeeding pages. When the stream at any given time and day is requiied, one

HW

167

practical yacht navigator has only to

flick

through the

atlas to the chartlet

LIST

OF DISTANCES AND TENTATIVE COURSES

bearing the time nearest to that required on the appropriate day. At the

same

time, note

whether

the tides will be springs or neaps over the various days.

sufficient to indicate this

It is

on the high water page only. This will show whether the springs or the neaps rates of the stream

will apply, or

enable the rates

at

times

Mibeage

A/C

Total

Varcaton

Oyster Boy

13°

Lloyd Potnt Eaton s Neck

Oil Oil

Stratford Shoal The Race Block Island

016 092

4

4 8'4

4'/?

13'4

22

45

67 89

22

intermediate between springs and neaps to be

LIGHTS LIST

interpolated.

While preparing the

seem tedious work

tidal atlas in this

done

way may

home. It saves further reference to tide tables and the calculation of the interval between a required time and the time of HW on a given day in order to find the correct chartlet, which otherwise will be necessary at a time when one may be working under stress at sea. It is well worth the initial it

is

easily

at

HEIGHT

LIGHT

CHARACTERISTIC

Batons Neck

Ft

W

Stratford ShoaL

FL

\N 10 s.

Old Field Pt

Alb Fl.RiG 3os fl

iv.

rss

FL

&

75s

Little Gull Is

FW

91 2BLostsev iSs

Race Rock

Alt FLMIlR 2os

67 2BZ2&1&18S.

ALt.occ.W.lGpFlRiSs

Stbd. Whistle about ImiLetoPort.

1

Oyster Boy Bell " 9 337° Gony Buoy " 7

0.9

Island

4

26

29 30 37 29 3

1

detailed plan for a coastal passage.

169

practical yacht navigator actual time,

and the leeway according to the

actual conditions being experienced.

colors of such lights. Note these carefully, and

note also the bearing of such transits or leading lights. For example, a chart might be marked:

and Fog Signals. (Fig 1 1 1 and 112) By reference to the track line on the chart, list all navigational lights expected to be seen at

"Steeple of

night. Against each, note

A

List of Lights

(b)

full),

characteristics (in

its

range, height, note also

covered, and color of light

if

note the fog signal of each,

what sectors

are

not white. Also

its

type and

putting

in

brackets.

DF

radio beacons. From a radio from H.O. Pub. No. 1 1 7, Radio Navigational Aids, or from Reed's find and list all radio beacons which will be within radio range of the passage. Bracket together all beacons in the same group (having the same frequency) and note against each its call sign and range. List of

(c)

beacon

(d)

chart,

Port Entry Guide.

Any

port, harbor, or river

which may be entered should be closely studied on a large scale chart to plan in advance a safe line or lines of entry. Look up the port in the pilot or other reference book, and note whether any special advice is given. Port Entry Signals.

Some commercial

ports are

subject to Port Traffic Signal Regulations.

The

type of signals used, and their exact meaning,

Church 21

to right of

in line

°."

1

stranger does not know the names of the churches referred to, and may perhaps only be able to pick out a single church.

given as 21

characteristics (timing and number of blasts). While doing this, also include details of any light which might be seen if one were off course, or had to enter a port of refuge. Indicate these either by insetting, writing in a different color, or

Catherine seen

St.

belfry of Trinity

9° W,

this

1 °.

This

is

true,

so

if

80° M.

transit

is

is

equals 220° M. Take a compass

bearing of the one church seen 1

The

variation

— say

it

bears

Alter course boldly to port, bearing will

increase till it is 220° M. Now observe whether a second church is visible roughly in line with the first. If so, the churches can now be identified. If not, real doubt exists as to whether the church seen is either of those referred to, so stand off and seek another. Do not stand on till the situation clarifies.

Where

leading lights are placed so that

one over the

transit, in line

leading

line,

is

it

in

other, they provide a

important to note the bearing of

may be

this line. This

when

stated

in

the pilot or on the

can be found by laying off the line through the two lights on the chart. Leading lights are by no means always conspicuous and chart.

If

not,

it

sometimes very difficult to identify, particularly holiday resort where they can be lost among neon advertisements and hotel lights. A check with the compass bearing should always be applied when any doubt of identification exists. are

in a

should be noted. Where such regulations exist they apply to

all

vessels, including yachts,

must be complied with.

Failure to

do so

and

will

invoke the wrath of the harbor authorities and possibly a fine at least, and at worst will involve the

risk of a collision

with another vessel, which

probably cannot get out of the way. Study the chart and pilot for any approach transits by day,

and leading

170

lights

by night, including sectors and

Buoyage Where

list

study of a large-scale chart of a port indicates it will be necessary to follow a line of buoys, it is recommended that these are listed, a

preferably by

name

or

number (given on

pilot or other reference

indicating the shape

book), the

and

color,

list

chart, in

clearly

and showing the

compass bearing from each buoy

to the next.

off to sea This

is

particularly useful in

may be some

the buoys

wide estuaries where

when

the next buoy can be seen from the last, the compass bearing will immediately confirm whether the one seen is in fact the correct one. If there

any possibility of the port being entered by night, also list against each buoy its characteristics, and whether fitted with bell is

(or left) light

be steered between

all

List of distances

and courses

turning points.

distance apart. Even

or fog signal.

A

should be prepared, similar to that for the sailing yacht but giving actual courses to be list

steered (instead of only tentative courses). In

addition the mileage at each landmark or turning point should be measured and noted, and the total

elapsed time from

start to

each landmark

computed and noted. Except when in a power boat race, the exact time of departure may

also

Preparations on a power boat Thorough preparations for navigation are just as important for a power yacht as for a sailing craft, possibly even more so in the case of a fast planing power boat. The reason is fairly obvious: (a)

much more quickly, so have to be made

Distances are covered

navigational decisions correspondingly more quickly.

(b) The motion of the yacht may make reading and writing much more difficult, unless speed is drastically reduced. (c)

Identification of

landmarks and buoys

is

more

be in sight for less time, and it may be difficult or impossible to use binoculars. Fixes by hand bearing compass are more difficult

difficult as

and

each

will

less accurate.

From

this

it

the more detailed the advance preparations should be.

Most coastal and open water passages by fast power boats will be completed within a day, and often within a few hours. The speed can be predicted and thus it should be possible to calculate, in advance, the direction

and

rate of

streams to be dealt with during the passage. Unlike the sailing yacht, in normal sea conditions

tidal

the power boat can rely on being able to steer any

— no tacking

till

it

actually happens, so total

is

involved.

It is

therefore possible to prepare accurate courses to

may be

recording predicted clock time.

speed

is in

columns

If

preferable to

the actual

some doubt, one might have two

of total elapsed time:

one

at

maximum

cruising speed, the other at a reduced speed that

might be necessary if sea conditions so dictate. If each column of times is headed with the speed assumed, it is usually easy to interpolate mentally for any intermediate to speed actually sailed. If the yacht's speed is normally controlled by engine revolutions, past experience will enable elapsed times to be calculated and recorded for given r.p.m.s instead of knots.

Engine(s) check

follows that the faster the speed

desired course

be uncertain

elapsed time to each point

list

possibility of the duration of the

If there is any passage approaching (or exceeding) the fuel tank capacity, then it might be prudent to calculate what, under normal conditions, the fuel gauge should register at various points on the passage. If the listed turning-points or landmarks are at

suitable intervals, the predicted state of fuel stock

could be noted against each. Alternatively a separate engine check list should be prepared giving the predicted fuel stock at suitable time intervals, say hourly. The same list can be entered with any routine checks or jobs which should be carried out on a regular schedule, for

171

practical yacht navigator example, lubricate stern bearing, pump header check water flow, temperature, check ammeters, and so on.

destination,

The object of pre-computing fuel stocks is to ensure that warning is available of any undue consumption, to avoid any risk of running out of fuel. Regular and frequent checks of all instruments

that at

tank,

will also give early

on the

trouble,

warning of any possible

"stitch in time" principle.

Factors which are worth consideration are:

What

the rise and fall of the tide at the and the rates of the tidal stream en route? Bear in mind that where the rise and fall is great (e.g. Eastport, Maine) the appearance of the (a)

landscape

is

at

high water

low water, which

is

is

very different from

the scene depicted by

the chart. Tidal streams run strongest at springs,

and when flowing against the wind, the stronger the stream the rougher the seas.

Buoyage

A

list

trip,

each port likely to be entered, similar to slow yachts is even more important for a fast power boat, as there will be list

for

that described for

little

time to consult the chart between buoys.

List of light and fog signals While not essential for short daylight passages, this list will come into its own if for any reason the passage takes longer than expected, or if fog, mist or heavy rain obstructs visibility. Quick knowledge of the identity of a fog signal from a lighthouse, light vessel or buoy may be vital.

Lists in general For use on fast

power

boats,

read under conditions which Bold, clear writing

Check

is

make all lists easy to may be experienced.

important.

lists

Reverting

now

to

all

types of

craft,

an obvious

step to take at the planning stage of a passage

make check

annoying, and serious, if when well on the way, a could be chart, reference book or instrument is found to is

to

lists.

It

is

have been forgotten. Having completed the "early planning" lists, one is in a position to consider whether the proposed passage or trip fits in with the proposed dates available, and if so, the best time to start.

172

or to an

unknown

If

this

is

a first

area of large tides, an

around neap tides is to be preferred to one if this can be arranged. (b) What is the prevailing wind, or most likely direction? If likely to be favorable when outward bound and unfavorable when returning, is there arrival

at springs,

sufficient reserve of time? (c)

Is

there an ocean current en route? e.g. Gulf

Stream, N Portuguese current. These are

on routing If

shown

charts.

dates are suitable, the best time of departure

can be considered. In some cases this may be immaterial. However, intelligent use of the tidal streams can make all the difference to a passage. The timing should be planned so that the maximum advantage is gained from favorable tidal streams, and that foul streams will be met where they will matter least. For example, if the passage is expected to take about 1 8 hours, and is along a coast subject to alternate fair and foul tides, the start would probably be planned for water (high or low as the case might be) before the first favorable tide. One could then expect to have about two favorable and one unfavorable tide. However, the course might lie past a headland where the tide will be

just before slack

strongest, during the period of foul tide.

One

would weigh up the advisability of timing the passage so that two foul but weak tides would be met,

in

order to get the benefit of the strongest

—

— off to sea

fair tide

past the headland. For this purpose a

recommended. Note where the streams run strongest and try to plan times so

tidal atlas

to

have

fair

possible.

as

ahead and

tides at these points or areas.

Departure preparations Weather obtain the latest shipping forecast. Phone the local meteorological office, airport or

—

Coast Guard,

local

you the latest

all

of

latest forecast.

whom

If

will

normally give

available, consult the

synoptic (weather) chart, to see whether

there are any depressions

in

compass bearings, and identify as soon as By day, check for leading marks and look for any objects on shore which are

their

is

the offing.

in transit. Observation of these will enable the approximate rate and direction of the tidal stream to be estimated. Closer inshore the

current

often running counter to the main

Check

by also noting

this

how any

buoys, lobster pots or vessels are behaving.

at

anchor

There is a limit to the preparation of courses to be steered, since one cannot predict precisely at what time the yacht will be at any given place

much Landfall preparations Transfer the EP or last fix from the passage

is

current further out.

will

depend on the wind and sea

chart to the larger scale chart of the destination,

encountered. However, the general strategy can be roughed out. Bear in mind: (a) Landfalls on a well-lit but strange coast are

as soon as this can be done. This will normally be

best

soon

after the landfall

has been made. Check the

new EP or fix by further observations as soon as any are visible. Work out the height of tide for several hours around the ETA. This may be wanted for clearing shoals when you arrive. The height of tide will certainly be necessary if you propose anchoring, and when that moment arrives you may be too busy to work it out. It

is

around the ETA as the

last

few miles often take longer than expected. You will probably switch on your echo sounder when you approach the 1 fathom line, so remember that depths shown must be reduced by the height of tide at the time, for comparison with charted depths.

Examine the large-scale chart and work out in advance a safe line of approach, noting what landmarks are likely to be of use, particularly any transits. These may be shown on the chart, or mentioned in any guide or pilot book being used. If entering by night, check for leading lights, note

well

—

just before

made (b)

in

dawn. The

lights

final

can then

run into port

early daylight.

Landfalls

on

a sparsely

lit

coast or

when

reduced are best made in early daylight to see, and if possible to identify the landmarks. It may be advisable to shape a course

visibility is

so as to close the land a few miles to the right of the destination.

suitable fathom line

advisable to calculate the heights at

several different hours

made

be positively identified, and the

which way

is

When

land

reached,

it

is

is

left

or

seen, or a

then

known

to turn along the coast to reach the

destination.

day can be even when the coast is well-known. If no obvious landmark is visible (such as an identifiable lighthouse or conspicuous building), one hill looks very much like another, and "wishful thinking" is apt to creep in. Even a headland like Cape May, New Jersey, which once seen one would think never forgotten, looks different seen from different angles. When trying to identify hills, study on the chart their heights, contours and relative distances away. Try to identify three (c)

Identification of a coastline by

difficult

173

practical yacht navigator

which make as wide an angle between each other as possible. Lay their bearings on the chart, and if the position lines do not cross or make a reasonably small "cocked hat," they cannot have been correctly identified. When in doubt, stand off and sort things out, never press on if uncertain of the position.

174

15. Coastal

We

Passage

are planning a passage under sail from Oyster

To calculate our estimated time of departure from Oyster Bay, we must work the course backwards from the Race. The distance from the Race to

The charts we intend to use are No. 1 21 3 (new No. 1 2363) of Long Island Sound western part, No. 1212 (new No. 12354) of Long Island Sound eastern part, and No. 1 21 1 (new No. 13205) of Block Island Sound and approaches. From them we can see that our course is out of

that for approximately

Oyster Bay, around Lloyd Point past Eaton's Neck,

intended

past Stratford Shoal opposite Old Field Point,

be flowing with us at a steadily increasing rate, with an average rate of 1 .6 knots. Thus if the

Bay

to Block Island.

eastward down Long Island Sound to the Race, and then across Block Island Sound to Block Island. The total distance traveled is about 95 miles. A look at the tide table shows that the range of tide is about half way between springs and neaps on the proposed day of our trip. This means that the rate of tidal streams will be about average. We do not want to go through the Race during either flood tide or full ebb because of the heavy overfalls there. So we will try to arrive at the

the tide

is still

strongly as

it

Race before slack water, when flowing to the east but not as

would

at

maximum

ebb.

We

find

on this particular day, slack water at the Race is at 0322 and 1 51 9. Since we do not want to pass through the Race during the middle of the

that

night,

our

we

select

1

51 9.

It is

advisable to plan

arrival there a little early in

wind want

is light,

so

we

— or

we

Race about two hours before about 1 300.

to reach the

slack water

case the

tentatively estimate that

Stratford Shoal

is

about 48 miles, and from Bay about 22 miles.

Stratford Shoal to Oyster

Looking

at

the appropriate tidal charts

arrival

time

we

see

3^ hours before our

at

the Race, the tide will

is sailing through the water at 5 knots, we be doing 6.6 knots over the ground. We can now calculate that we will have a fair tide for

boat will

on this particular leg of the course x 3.5 hours). The remaining distance between the Race and

23.1 miles (6.6 knots

29.4 miles (48 miles - 23.1 miles). water we will have 0.8 knots of tide against us. Sailing at 5 knots through the water, our speed over the ground will be 4.2 knots (5 knots — 0.8 knots). Thus, the time it will take to cover the required distance is almost 6 hours (24.9 miles -r 4.2 knots). Between Stratford Shoal and Oyster Bay the tide will again be flowing with us Our speed over the ground will average 5.6 knots, which is less than our speed when approaching the Race because the favorable tide is weaker here. At this rate, the leg between Stratford Shoal and Oyster Bay will take 4 hours (22 miles 4- 5.6 knots). Stratford Shoal

is

In this stretch of

175

practical yacht navigator

When we add

—

these separate times up 3i hours, and 4 hours we find that the passage from Oyster Bay to the Race will take almost 1 3^ hours. This means we must plan a departure from Oyster Bay at about 2330 the previous day if we are to arrive at the Race at our intended time of 1 300 on the day in question. A quick check of the weather forecast tells us that the wind will be a little higher than average but not as light as we had originally made allowances for. So we decide to set our departure

—

nearly 6 hours,

time for midnight.

To draw up our

preliminary sailing plan

we

We

points,

we draw

have to round Lloyd Point and pass close to Eaton's Neck; and we must also pass close to the Stratford Shoal rocks and to Little Gull Island at the Race. Since we want to pass well off these the arc of a circle with a radius

one mile around each one, positioning

We than

to these arcs.

mark our track line tangent The distance to be covered can now

be scaled

with dividers.

lighthouse.

off

Our next step is to draw up a tentative tidal stream plan, such as the one in Fig 1 1 1 We do not know what speed we will make under sail so we do the plan using two speeds: (1 ) the speed we could probably make if there are head winds or light winds (2) the speed we could probably make if sailing .

wind.

off the

first

study the appropriate charts and find whatever danger points (rocks, shoals, races) lie near our course.

of, say,

the center of the circle on the appropriate

We judge that we can

make either 3 knots or 6 knots under these different conditions. Working from our expected departure time of midnight, we calculate the time required to cover each leg (traveling both at 3 knots and at 6 knots). This gives us the times we will arrive at each of the major points along our course. By referring

^

fBlOCK

ISLAND

gulll_VThe__ SOUND

CAJ^°

RAC?~ BLOCK

sTToallt.

ISLAND

LLOYD PI

^^TER

BAY

.

BATON'S NECK 1^^

Fig 112.

rhumb

176

A

line

chart of Long Island Sound showing the course from Oyster Bay to Block Island.

:

.

coastal passage to the appropriate tidal charts

we

can also indicate

the speed and direction of the tidal streams will

encounter. This information

allow us to

will

DECK LOG

we DATE LOG

EST

calculate an accurate course to steer.

Course

Course StNO.ua

f?£ADl*J6

Wind Bar-

Fri day

S

Midnyht

The passage

Sac.

The day of the voyage arrives. The crew is on board and all the gear has been checked against our lists and stowed. We are ready to sail. Casting off the buoy we motor off and enter our departure in the deck log. (Fig 11 3.) The passage down Oyster Bay does not call for navigation because we can determine the courses to be steered by eye and by reference to the buoys which are identified on our large-scale chart of the area. This part of the

trip,

Upon

therefore, involves pilotage.

reaching the No.

1

5 buoy

(Fl

4 sec)

Lloyd Point, the ship's speedometer log zero.

On

the wind

the is

way

out of the harbor

we

from the south, blowing

gives us a comfortable reach.

We

at

is

off

set to

note that 1

knots. This

0045

014

s

0700

3.7 090

074 S

0200

090

09o

S

0142

78.6

090 090

S

0400

19.4

09O O9o

S

8< °K

1

10K /5X

16K 15K

20K

0600 301 090 090 SE

2TK

0630 32.4 090 090 SE

Dropped mooriigs Oyster 1000 Boy under engine.

1000

064-5 33.4

09O oes ESE

0800 40

090 080 ESE

Buoy

** 75

fall

mam

is in

sight slightly to

is poor because the weather is overcast. At 0200 and 0400 we enter up the deck log and from it the navigator's log. By 0630 the wind has increased and headed slightly, so we decide to put the first full reef in the main and to change down to the No. 2 Genoa. By 0645 the wind has headed sufficiently so that the helmsman can no longer steer the desired course. This fact is recorded in the deck log.

port of our course, but visibility

STbd obeam.

999

St ra tford Shoal bears 335° SLight racn -poor v/s. f-iotte.ni.

998 poor

no reef

Tidal stream or current

^

7

A

position line

\fc

77

A

transferred position line

179

practical yacht navigator

through the Race, then we will try to squeeze out through Plum Gut where the tide runs a little longer in our favor. As time goes on, it becomes apparent that we will make the Race quite easily, with an hour to spare before the tide changes. Once through the Race we come onto course 102° heading across Block Island Sound. Until now the tide has been pushing us either forward or backward, but as we progress across Block Island Sound the tide changes and starts to flow against us from a more southwesterly direction. As we close the land, the stream is parallel to the shore, which means that it is pushing us northward. We must therefore alter our course to compensate for this push, so the navigator

works out

the necessary vectors.

At 1705 Block Island

is in

The navigator

sight.

obtains a bearing on a tower located on high

ground. Ten minutes later he takes another bearing, which enables him to accurately work out the tidal set and compensate for it. This area is

known

for

both

its tidal

set

and

its

fog, so

constantly check our bearings until

we

we

are close to

the harbor entrance. From here on we can use our large-scale chart No. 269 to pilot our way through the channel and pick up a mooring.

A

coastal passage for a displacement

power boat assume our yacht has a comfortable 1 2 knots, and we are planning a passage from Miami to Freeport (Grand Bahamas). Not being dependent on the wind we can Let us

cruising speed of

(provided

we

it

is

decide on.

not unduly strong) lay any course

We

should make similar

preparations before departure to those described in

the previous pages, including a

list

of lights

be seen or required, and we should work out a tidal stream plan for the predicted tides during the period of the proposed crossing. likely to

180

Assume we decide to make a night about dawn so as to have the

arriving

lighthouses for our landfall.

First

we

crossing, benefit of

pencil

in

on

the chart the rhumbline or track course required,

from Miami to Freeport. This is 060° T, and the distance is about 90 miles. Disregarding the Gulf Stream, this particular passage would take just under eight hours. (See Fig 1 1 5.) Knowing the Gulf Stream runs strongly, we must allow for it when deciding on the wake course required. If we wished, we could lay off a series of courses to allow for the constantly changing strength, so as to maintain the yacht on the rhumbline. If the course would take us near dangers this might be necessary, and would involve drawing a tidal vector for each successive hourly stream direction and rate, with a series of different courses to be steered. The passage under

open water, and once clear of no dangers until we make our There is therefore no advantage in

discussion

is in

Miami there landfall.

are

making frequent alterations to the course to keep on the rhumbline, and we can calculate a single course which (if the Stream runs as predicted and we maintain a set speed through the water) should bring us to our destination. Using the dividers opened to 12 miles (yacht's proposed speed) mark along the rhumbline 1 2 marks. Departure is planned for 21 30. The latest report has it that the Gulf Stream is flowing at about 3^ knots in mid-stream. As we near Great Isaac Light, the strength of the tide decreases to half a knot and begins to push us into the N.W. Providence Channel. With this information we can lay off the vectors that will enable us to work out a safe course. By checking our wake course and taking bearings on lights in Miami, we can compensate, if necessary, for any change in the rate of the Gulf Stream. Another correction, which we will only

coastal passage be able to ascertain

at sea,

is

that of leeway.

This will depend upon the wind strength and the superstructure of our boat. to steer is now known, but it is necessary to keep a proper deck log and to

The course still

plot the

EP

at regular intervals.

It

may

well be

may be any number of reasons. If a large fishing fleet is encountered it may be necessary to make a wide detour round it; rough seas or reduced visibility may require speed to be reduced, engine trouble may occur, and so on. While it may not be necessary to make frequent plots on the chart, it is still important to have all the data recorded (time, course, distance run by log, et.) so that an EP can be plotted whenever necessary to

alter course, or

the speed

varied, for

necessary.

Before landfall, calculate the approximate height of tide so as to be able to reduce

soundings to chart datum for comparing echo sounder with chart depths. Calculate when Great Isaac lighthouse should be visible. If it does not appear when predicted, watch the echo sounder. Note how the rhumbline crosses the 20 fathom line. Then after the landfall has been made, lose no opportunity to check how the lobster tide is setting by any transits visible this when piloting into pot buoys, etc. Allow for the harbor and guard against being set across course by taking bearings ahead with the hand bearing compass. Watch the echo sounder. Have

—

heights of tide pre-calculated for Freeport.

These will be useful both for reductions to soundings and for deciding where to anchor, this is planned. As the harbor is approached, change to a large-scale chart, and note the buoyage system.

if

181

.

not Lost: Fog!

16. Blinded but

Boating

in

fog

is

an eerie and unnerving

reports from coastal stations state

and even the sea level appears to change as there is no horizon to establish a level. At night the glow of the navigation lights reflected in the fog seems to close one in, and one can even get the experience. All sense of direction

sensation that the yacht

The or less.

It is

lost

sailing downhill.

is

official definition of

condition which reduces

is

fog

an atmospheric

is

visibility to

said to be "mist"

when

1

000 meters

visibility

is

between 1 000 and 2000 meters. There are a number of types of fog due to different causes, but the end effect is moisture in saturated air condensing out into minute droplets which reduce the transmission of sight of land

is

it

light.

Once out

of

very difficult to gauge the

One must be alert to the something suddenly emerging out of

of navigation will

confidently:

is

much

passed,

shorter range than expected. it

is

estimate of the

visibility

reading the log

when

again

when

it

it

a

good

idea to get an

by taking the time or is

close

abeam and

disappears, and (allowing for tidal

stream) thus to calculate the distance. It is

with

it.

have to deal books, routing charts and other sea

better to avoid fog than to Pilot

guides give indications of the prevalence or likelihood of fog at different times of year. Radio

weather and shipping forecasts give reliable warnings of the likelihood of fog, weather

182

that the yacht

"I

am

sure

we

that

is

steered

"we must be

are heading

in

the

The two hazards in fog are the risks of and of running aground. Preparations

collision

dealing with fog should not be deferred

has deteriorated to the

visibility of

buoy

is

grows.

visibility

a

fog

direction" disappear as this confidence

possibility of

If

mean

sudden feelings

near land" or

wrong

visibility distance.

mist or fog at

if

and give the visibility, usually in yards. If in port, a passage may be postponed if fog is present or forecast for any part of the voyage. There is always an element of danger when at sea in fog or mist. As with most aspects of sailing, thorough preparation, in advance, will go far to reduce the inevitable anxiety. The very knowledge present,

in

1 ,1

00 meters

hand the moment

deteriorating. This

one

is

is

official

for

till

fog

of less, but should be put

visibility

shows

signs of

not always easy to detect

if

not sailing within sight of land, buoys or

other vessels, so an eye should be kept on the sharpness of the horizon. Preparation will be more sure if a check list has been prepared in advance. This might read as follows: 1

Obtain

fix

by visual observation

if

possible, or

by DF. Switch on echo sounder, read and record depth and time. 2.

3.

Post lookout(s).

.

.

fog 4.

Hoist radar reflector.

5.

Issue life-jackets to

6.

Prepare flares/Verey light

7.

Sound fog

8.

Prepare anchor for immediate letting go.

9.

Prepare

10. 1 1

arm. This

all

hands.

2.

1

to maintain accurate course

go through these points

Obtain

fix.

position the navigator will have

the yacht runs out of fog.

So

till

is

If

no

possible, as

reliable fix

the fog

lifts,

or

for a considerable

when

by visual observation

well offshore

when

then the EP should be worked up, as accurately as possible, from the last fix or EP. If well within the range of any radio DF

visibility

closes

in,

EP should be confirmed with in mind that some DF which do not operate in clear weather (or

station(s), the

bearings so obtained. Bear stations

only operate infrequently then)

will

the size to

now

as high as possible. This will at least help to

produce some trace on another vessel's radar

last

time the navigator will be working on dead reckoning.

of

Radar reflector. It is almost more important to be seen than to see, so ensure the radar reflector is correctly hoisted and well up. If caught out without a radar reflector aboard, hoist a metal bucket or wet the sails by throwing water on

them

in detail.

This will probably be the

If

silence.

Navigator to lay off safest course, and order.

Let us

way

or skipper.

4.

as ordered. 1

helmsman

crew permits, others should be detailed watch each beam and astern. Order absolute

or dinghy, stock up.

Check engine. Warn helmsman

the quickest and surest

of the

pistol.

signals per rules.

liferaft

is

indicating to the

be

working in fog. 2. Switch on echo sounder. This should be left running throughout fog (if within soundings). The navigator should calculate the height of tide (to a couple of feet or so) and should reduce the depth to CD and should check this with his fix or EP. Depth readings should be taken and recorded (with times and patent log readings) at regular and frequent intervals. The intervals will be governed by the type of coastline (shelving or steep-to) and on the yacht's speed. 3. Lookouts. One man should be posted right in the bows, to have a clear view and to be as far from engine noise as possible. He should be instructed to report everything seen or heard, and to indicate direction by pointing with the whole

display. 5.

Lifejackets.

These should be worn (and

the inflatable type, blown up) by

all

if

hands.

If

of

by

any chance you were involved in a collision, these might make all the difference between being picked up, and not. 6.

Flares/Verey Pistol.

If

sailing at night, these

should be used (white flares) if a vessel's lights are seen on a possible collision course. 7. Fog Signals. Rule 1 5 of the International collision regulations specifies these:

driven or sailing vessel of

40

ft

"A power

or over, to carry a

fog horn sounded by mechanical means, and a bell";

and "A power driven

than 40

or sailing vessel of less

making 'some other efficient sound signal.' " The same rule lays down the sound signals required in fog. These must be known by heart so that not or.lv can you make the correct signal, but that you know, by her ft

to be capable of

what another vessel is doing. For the 40 ft, sounding signals should present no problem. The smaller yacht under 40

signals,

larger yacht over

ft

should carry either: (a) An aerosol-powered pressure horn, (b) (c)

A hand-pump powered A mouth-blown horn.

horn, or

The range of any of these is limited, and will depend on atmospheric conditions, but is 183

I

practical yacht navigator

»

1

1

-A_

;jj^-X4»^,^

«^

^-^-

'jjfl

Fog soon turns simple pilotage into a baffling problem. A marked post provides a clue to channel in an estuary.

single

184

fog

±z

]

Same

scene, but with the fog having

further navigational markers can

now

lifted.

Landmarks and

be seen.

185

practical yacht navigator

Normal view towards shore of an estuary with miles.

visibility several

Fog reduces

about two hundred meters. Shore it and it is even than usual to judge distance.

visibility to

line is just discernible,

more

difficult

but not trees behind

— fog! unlikely to exceed (a) and (b) a mile, and (c) a few hundred yards at best. The aerosol-horn is probably the most practical for the smaller yacht as it is small, light and easily stowed and used. However, one aerosol container will not produce more than 250 to 300 blasts, so it is advisable to

time the frequency of the blasts with these limitations

in

mind.

If

under

sail

(no engine) with

the wind abaft the beam, three blasts every

minute are required by aerosol container

hour, and the yacht

longer than

rule

would

this. In

1

5.

rate, one more than one

At this

last little

may be in fog for much waters crowded with traffic,

placed aboard and secured, or put

in a

handy bag

ready. 1 0. Engine. In a power-driven yacht, the engine should be given a quick check, particularly fuel supply, as it is essential to have full power available if it should be necessary to take rapid avoiding action. As the navigator must know his position continuously, it is important that a steady speed can be maintained. In a yacht under sail, if the wind is sufficient to maintain at least three knots, it may be preferable to continue sailing as the absence of engine noise will enable another ship's, and navigational, fog signals to be heard at

entering a port or estuary frequented by shipping,

much

the signals should be given at the regulation

as

one-minute intervals, but in open waters the intervals should be more spaced out to ensure capacity for sounding on hearing the fog signal

should be started and a steady speed maintained. According to rule 1 6 (a), speed in fog should be of

another vessel. If

anchored, remember to sound

intervals the bell, or

if

at

one minute

not carried, strike a frying

pan, bucket or the suspended kedge anchor

(which "rings" well). Anchor. An anchor or kedge should be ready on deck with some cable or warp veered (flaked 8.

out on deck), so that the yacht can be anchored quickly if necessary. 9.

Prepare dinghy. As the possibility exists of

down by a large vessel in fog, it is prudent to make preparations "just in case." If a self-inflating raft is carried, this should be freed being run

from its holding-down lashings, but NOT inflated. But check that the rip-chord/painter is securely attached to the yacht. It is probably wise to launch a rigid dinghy carried on deck it can be cleared. A packed put back when the fog has inflatable dinghy which is not self-inflating should certainly be fully inflated and either carried right-way-up on deck, or towed aft. Paddles, flares and food and water should be

—

it

greater distances.

If

the wind

often (but not always)

is in

fog

is

very light

— the engine

"moderate, having regard to the existing circumstances and conditions." Rule 1 6 (b) is mandatory for a power-driven vessel (which of course includes a sailing yacht under power). Such a vessel "hearing, apparently forward of her

beam, the fog signal of a vessel the position of which is not ascertained, SHALL, so far as the circumstances of the case admit, STOP HER ENGINES, and then navigate with caution until danger of collision is over." Let us consider the "circumstances." A yacht's auxiliary is apt to be temperamental and may be difficult to re-start when hot. A large vessel stops by going full astern, but her stopping distance may be a mile or more. She has a very wide turning circle. If a yacht meets a large vessel at close quarters, the yacnt's best chance of

avoiding a collision will usually be by alteration of course. She has a very small turning circle (often not much more than her own length) and she will "stop" her forward progress most quickly by going about under full helm and full power. If another vessel's fog horn is first heard

187

practical yacht navigator

Planning a course in intended to stay in the shallow water: distance run between B and C is checked by Fig 11 6.

fog.

It is

log.

188

.

fog!

may be prudent

to slow and thus to give the forward look-out the best chance of gauging the direction of the other vessel. Remember that the other vessel should sound-off

apparently

fairly distant,

the engine

down

every

it

to reduce engine-noise

two minutes. Unless the fog

is

extremely

next, bearing in

mind any cross-current, and

taking care to keep on the out-of-channel side of line. If a buoy is missed and there is shipping about it is prudent to turn into shallow water and anchor rather than to "guess" where the next buoy

the

may

be.

hearing another vessel's fog horn, but to hold

(b)

If

course and speed, with redoubled vigilance. If she comes into sight heading straight for your yacht,

and without offlying rocks, lay a course direct to shoal water (allowing for the approximate height of tide when reading the echo sounder) so as to be out of the reach of most vessels. Then proceed along a fathom line by compass and echo sounder. Better still, lay off a course on the chart which is a straight line for a reasonable distance and one which conforms to the safe soundings decided on. In Fig 1 1 6 it should be possible to detect fairly accurately when the yacht reaches point A, then point B and point C, by noting when the depths increase to those charted, and checking that the distances on the chart correspond to the distance run by

dense,

it

is

advisable not to alter course on

first

AWAY from

her at full throttle and head at 90° from her approximate track. If she about ought to pass ahead, ALSO turn away so as to escape her wash. Only hold your course if you are

turn

SURE

she

Warn

1 1

All

NEVER

pass astern of you.

will

to cross her

attempt

bows.

the

helmsman

sense of direction

is

to maintain course ordered.

lost in fog.

As the

navigator must rely on the course steered and

distance covered to keep track of the yacht's position, accurate steering

navigator must keep

in

is

mind

most important. The his

own

ship's

heading and the most probable heading of vessels met so as to be able to make a quick decision if necessary. If a quick alteration to course is made, new course, time and log reading should be logged at the earliest opportunity and no reliance placed on memory. 1

2.

Navigator's duties. After getting his

fix

or

EP

on the chart and entering it in the log (with time and patent log reading), his next task is to lay off the safest possible course. This will depend on

coasting.

If

along a shelving shore (fathom

lines far apart)

log (corrected for tidal stream).

If

the fog

is

very

dense or there are rocks about, it is clearly more prudent to anchor till visibility lifts. If along a steep-to shore (deep soundings on the chart close to the shore) or with offlying rocks, set a course parallel to, or slightly away from land and warn lookouts to listen for breakers. Watch the echo sounder much more

frequently. (c)

If

well off-shore. Try to estimate the position

Then

course to cross such

circumstances,

of shipping lanes.

enclosed waters, in a buoyed shipping channel or harbor approach, immediately get out of the fairway by steering for the nearest

lanes at a right angle so as to get across and

(a)

\

reasonable to lay a course from one buoy to the

If in

bank.

Watch the echo sounder.

If

the fog

the safest course will be to anchor If

visibility is

in

is

dense,

shoal water.

not less than about a quarter the

distance between channel buoys

it

may be

away from them

lay a

as quickly as possible.

Throughout, the navigator must ensure the deck log is maintained meticulously course steered, time and log reading of every alteration to course, and of fog signals heard to help him gauge shipping lanes. He should plot his EP

—

189

.

practical yacht navigator carefully at suitable intervals

more

frequently.

— the nearer land the

He should pay

particular

attention to tidal streams, bearing

whether the yacht water (but not have the same

is

moving

or

when anchored)

in

mind

stopped

in

that

the

the current will

effect. In fog the wind is often and the sea calm. Streams are likely to conform closely to predictions. If carefully worked up, the positions found by dead reckoning (plus streams) are likely to be most reliable. However, nothing should be left to chance, and EPs should be checked by radio DF and soundings, but when these are not available, trust your EP. If in coastal waters the navigator should make light

a

he has not already done so in the course work) of lighthouses, vessels and buoys, listing their fog signal

list (if

of his normal pre-passage light

characteristics

and type.

aero beacons likely to

be

All radio

come

DF

stations

and

within range should

with times and identification letters. If more than about half their listed range, position so found with caution, particularly

listed,

distant treat a

at night or twilight

when

maximum. Warn

distortion or refraction

hands that the and the distance off of all sound signals in fog can be extremely misleading. Bear this in mind whan deciding on action on hearing a fog is

at a

all

direction

signal.

Maxims

to

remember

in

fog or mist are:

5.

Constant lookout: including astern and abeam. Maintain silence: no avoidable talking. Watch echo sounder (in soundings). Hold a steady compass course and speed. Turn away from danger.

6.

Plot the

1

2. 3.

4.

EP

frequently,

proved wrong. 7. Sound fog signals

in

and

trust the

EP

accordance with

international collision regulations, rule 15.

190

till

Traverse Tables

17.

When we are using a chart EPs we do so by laying off direction

add

and distance

a current line

if

to plot successive a line representing

sailed

through the water,

appropriate, and the end of

new EP. We can read its latitude and longitude from the edges of the chart. If we are making frequent alterations to course steered, as when tacking to windward or sailing on wind

run, or a series of separate runs and/or currents, from our original EP, or a fix or observed position, without the necessity for plotting, or indeed without the use of a chart at all.

the line gives a

shifts,

we

directions

have to plot

a series of runs in different

and distances.

We may

be subject to a

series of tidal streams setting in varying directions

and

rates.

We

can again,

individual "run"

each current

on

line of

a

if

we

wish, lay off each

given course, and lay off

appropriate length and

We

can find the latitude and longitude of the final position reached, or if we wish, any intermediate position. This can be a tedious process, and each separate line provides its individual element of small error. If we are in the middle of an ocean, or making a long semi-coastal passage we shall probably be using a small-chart covering several hundred direction.

miles.

A

run of a score or so of miles, or a current

few hours would be too small to plot accurately and we shall need to calculate (rather than to plot on the chart) the change in position and thus the new position, in terms of its latitude and longitude. The Traverse Tables are a quick means of enabling us to calculate a new EP after a single line for a

The tables In

navigation, positions are described

in

terms of

and longitude. This could be said to

their latitude

be a form of map grid reference: so many degrees and minutes N or S of the equator: so many or E of the Greenwich meridian 0°. The point

W

described

Except

is

at

when

or S, E or

the intersection of the two.

the course happens to be exactly N

W, we

always "traversing" across the

are

chart, diagonally. If

we

sail

from

we

A

to C, (Fig

1 1

7.), a

distance

of,

have made some northing and some easting. The amount of northing will be A— B, and the easting B— C. We have a right-angled triangle. We know the angle "a," the course, and say,

10

miles,

shall

the side A-C, the distance. The traverse tables will tell

us the length of the other

A— B and B— C.

If

one

(N40°W) from

a

known

what

will

sails a

two

sides

course of 320°

position, say

30°N 25°W,

be the position after sailing 50 miles?

amount northward, have increased, and a certain amount westward, so the longitude will have changed to westward. But by how much? This is the sort of problem the traverse table solves. Clearly

one has

sailed a certain

so the N latitude

will

191

practical yacht navigator

know

that,

by definition, one

nautical mile. But

1

longitude does

on the equator.

we

we

NOT

also

1 '

of latitude

know

that

1

=

of

'

equal a nautical mile

— only

obvious from a globe that as move further away from the equator the It is

between two meridians of becomes less and less, till they meet at the poles. So the number of minutes of longitude spanned by a mile depends on the latitude of the position. The Traverse Tables give the answer to distance

N /^

in

miles

longitude

our right-angled triangle in terms of miles both ways. In the diagram, C is so many miles (

=

so Yacht goes

Fig 117.

change

1

miles from

A to C AB is

:

in latitude

traverse tables will

"D. Lat." BC is miles is the "distance."

and longitude. "departure." Course AC is 036 and 1

find

°

minutes of latitude) north of A (A to B), and miles (but not minutes of longitude)

many

east of

A

(B to C). The miles

moved

in a

easterly

or westerly direction are called departure.

Traverse Tables vary

in

format depending upon

the reference book used. But once you understand the basic principles involved, you should be able to find your easily.

If

way around any in

Traverse Table quite

doubt, the reference you are

consulting will always provide specific instructions

with examples for their particular tables. Fig

1 1

8 shows a single page from a set of

Traverse Tables which

we

will

use for purposes

The page covers distances from 1 to 300 miles. Because entries in Traverse Tables are proportional, the scope of a table can be of illustration.

adequately extended by simple multiplication. Note

columns is headed "D Lon" and "Dep/'and underneath "Dist," "D.Lat.," and "Dep." For the moment, disregard the "D Lon Dep" head. The course in our example was 36°, and the distance 1 miles. On the Traverse Table page for 36° at Dist. 1 we find D. Lat. 8.1 and Dep. 5.9. This means that, on this course, the difference in latitude (D. lat.) between A and B will be 8.1 miles (= 8'.1 of lat.) and the change that each block of

—

In Fig

1 1

7,

assume the yacht

is

at position A,

54°N, longitude 3°E and sails 10 miles on course 036° (N36°E). What is the latitude and latitude

longitude of the

final position

C? The traverse ABC.

tables solve the right-angled triangle

But

192

first

we must

consider the units used.

We

in

an easterly direction

will

be 5.9

MILES

of

departure. :

traverse tables Table inly

D

Lon Dist.

Hyp. 1

tat

2 3

4 5

the

6 7

to

8 9 10 11

nd

12 13 14 15 16 17

i

pon indthe to

i

/

36°

tas

Jde

TRAVERSE TABLE

3

18 19 20

Lor i

Dep.

Dist

Adj. 0.8 1.6 2.4 3.2

Ovp. 0.6

Hyp.

4.7 5.3 5.9

12.9 13.8 14.6 15.4 16.2

25.1

32 33 34 35 36 37 38 39 40

25.9 26.7 27.5 28.3

6.5

71

7.1

72 73 74 75 76 77 78 79 80

7.6 8.2 8.8 9.4 10.0 10.6 11.2 11.8

12.1

31

62 63 64 65 66 67 68 69 70

4.1

8.9 9.7 10.5 11.3

17.0 17.8 18.6 19.4 20.2 21.0 21.8 22.7 23.5 24.3

61

1.2 1.8 2.4 2.9 3.5

8.1

22 23 24 25 26 27 28 29 30

21

D

Dep D. Lat.

4.0 4.9 5.7 6.5 7.3

36°

tT

12.3 12.9 13.5

81

82 83 84 85 86 87 88 89 90

14.1

14.7 15.3 15.9 16.5 17.0 17.6

D

Dep D. Lat

Adj.

49.4 50.2 51.0 51.8 52.6 53.4 54.2 55.0 55.8 56.6 57.4 58.2 59.1

59.9 60.7 61.5 62.3 63.1

63.9 64.7 65.5 66.3 67.1

68.0 68.8 69.6 70.4 71.2 72.0 72.8

.

Opp. 35.9 36.4 37.0 37.6 38.2 38.8 39.4 40.0 40.6

D

Dep

D

Dep

Lon Dist.

D. Lat.

Dep.

Lon Dist.

D. Lat.

Dep.

Lon Dist.

D. Lat.

Hyp.

Adj.

Opp.

Hvp.

Adj.

Opp.

Hyp.

Adj.

121

97.9 98.7 99.5 100.3

71.1

181

71.7 72.3 72.9 73.5

182 183 184 185 186 187 188 189 190

146.4 147.2

Dep.

122 123 124 125 126 127 128 129 130

41.1

41.7 42.3 42.9 43.5

101.1

101.9 102.7 103 6 104.4 105.2

44.7 45.3 45.8 46.4 47.0 47.6 48.2 48.8 49.4 50.0 50.5 51.1

51.7 52.3 52.9

74.6 75.2 75.8 76.4

106.0 106.8 107.6 108.4 109.2 110.0 110.8 111.6 112.5 113.3

131

132 133 134 135 136 137 138 139 140

44.1

74.1

141

114.1

142 143 144 145 146 147 148 149 150

114.9 115.7 116.5 117.3

77.0

191

Tib

192 193 194 195 196 197 198 199 200

78.2 78.8 79.4 79.9 80.5 81.1

81.7 82.3 82.9 83.5

201

202 203 204 205 206 207 208 209 210

84.1

84.6 85.2 85.8 86.4 87.0 87.6 88.2

118.1

118.9 119.7 120.5 121.4

Dep Dep.

106 4

241

152.1

107.0 107.6 108.2 108.7 109.3 109.9 110.5

152.9 153.7

111.7

242 243 244 245 246 247 248 249 250

195.0 195 8 196.6 197.4 198.2 199.0 199.8 200.6 201.4 202.3

Opp. 141.7 142.2 142.8 143.4 144.0 144.6 145.2 145.8 146.4 146.9

251

203.1

147.5

252 253 254 255 256 257 258 259 260

203.9 204.7 205.5 206.3

148.1

148.1

148.9 149.7 150.5 151.3

154.5 155.3 156.1

156.9 157.8 158.6 159.4 160.2 161.0 161.8 162.6 163.4 164.2 165.0 165.8 166.7 167.5 168.3 169.1

169.9

111.1

112.3 112.9 113.4 114.0 114.6 115.2 115.8 116.4 117.0 117.6

207.1

148.7 149.3 149.9 150.5

207.9 208.7 209.5 210.3

151.6 152.2 152.8

151.1

118.1

261

118.7 119.3 119.9 120.5

262 263 264 265 266 267 268 269 270

211.2 212.0 212.8 213.6 214.4 215.2 216.0 216.8 217.6 218.4

153.4 154.0 154.6 155.2 155.8 156.4 156.9 157.5

271

219.2

159.3 159.9 160.5

121.1

121.7 122.3 122.8 123.4

158.1

158.7

tions

'and Dep."

42 43 44 45 46 47 48 49 50 51

41.3

head stance

29.9 30.7 31.6 32.4 33.2 34.0 34.8 35.6 36.4 37.2 38.0 38.8 39.6 40.5

41

Note

29.1

52 53 54 55 56 57 58 59 60

Hyp. Dist. D Lon

42.1

18.2 18.8 19.4 20.0 20.6 21.2 21.7 22.3 22.9 23.5

92 93 94 95 96 97 98 99 100

24.1

101

24.7 25.3 25.9 26.5 27.0 27.6 28.2 28.8 29.4

102 103 104 105 106 107 108 109 110

30.0 30.6 31.2 31.7 32.3 32.9 33.5

111

91

c vi°

54

84.1

61.1

84.9 85.8 86.6 87.4 88.2 89.0

61.7 62.3 62.9 63.5

89.8 90.6 91.4 92.2 93.0 93.8 94.7 95.5 96.3

64.1

64.7

Opp.

Adj.

Dep. D. Lat. Dep

D. Lat. I

59.4 60.0 60.5

Dist. D Lon

Adj.

Dep.

Dep

81.7 82.5 83.3

80.1

Hyp.

34.7 35.3

34.1

80.9

56.4 57.0 57.6 58.2 58.8

97.1

46.9 47.7 48.5 Opp.

46.1

53.5 54.1 54.7 55.3 55.8

65.2 65.8 66.4 67.0 67.6 68.2 68.8 69.4 69.9 70.5

112 113 114 115 116 117 118 119 120

42.9 43.7 44.5 45.3

73.6 74.4 75.2 76.0 76.9 77.7 78.5 79.3

152 153 154 155 156 1S7 158 159 160

122.2 123.0 123.8 124.6 125.4 126.2 127.0 127.8 128.6 129.4

161

130.3

162 163 164 165 166 167 168 169 170

131.1

151

131.9 132.7 133.5 134.3 135.1

135.9 136.7 137.5

138.3 172 139.2 173 140.0 174 140.8 175 141.6 176 142.4 177 143 2 178 144.0 179 144.8 180 145.6 Hyp. Opp. 171

Dep.

Dist. Lon

D

88.8 89.3 89 9 90.5 91.7 92.3 92.9 93.5 94.0

212 213 214 215 216 217 218 219 220

94.6 95.2 95.8 96.4 97.0 97.6 98.2 98.7 99.3 99.9

222 223 224 225 226 227 228 229 230

91.1

W

221

100.5

231

101.1

232 233 234 235 236 237 238 239 240

101.7 102.3 102.9 103.5 104.0 104.6 105.2 105.8 Adj. D. Lat.

Dep

^^

211

|

170.7 171.5 172.3 173.1

173.9 174.7 175.6 176.4 177.2 178.0 178.8 179.6 180.4 181.2 182 182.8 183.6 184.5 185.3

124.0 124.6 125.2 125.8 126.4 127.0 127.5 128.1

128.7 129.3 129.9 130.5 131.1

186.1

131.7 132.3 132.8 133.4 134.0 134.6 135.2

186.9 187.7 188.5 189.3

135.8 136.4 137.0 137.5

190.1

138.1

190.9 191.7 192.5 193.4 194.2 Hyp. Opp.

138.7 139.3 139.9 140.5

Dist. Lon

D

141.1 Adj.

Dep. D. Lat. Dep

272 273 274 275 276 277 278 279 280

220.1

220.9 221.7 222.5 223.3 224.1

224.9 225.7 226.5

281

227.3

282 283 284 285 286 287 288 289 290

229.0 229.8 230.6 231.4 232.2 233.0 233.8 234.6

291

292 293 294 295 296 297 298 299 300

228.1

235.4 236.2 237.0 237.9 238.7 239.5 240.3 241.1

241.9 242.7 Hyp. Opp. Dist. Lon

D

^K±

165.2 165.8 166.3 166.9 167.5 168.1

168.7 169.3 169.9 170.5 171.0 171.6 172.2 172.8 173.4 174.0 174.6 175.2 175.7 176.3 Adj.

Dep. D. Lat. Dep

DIP I

161.1

161.6 162.2 162.8 163.4 164.0 164.6

r*

a°

31

Fig 118. A page from a set of Traverse Tables, giving the table for 36° or 54°.

193

practical yacht navigator

— Dep." and use the ITALIC headings "D Lon —

Note Carefully. D. Lat. (difference in

which

are the

same

minutes of latitude

lat.) is

as miles,

Dep. (departure E or

W)

is

BUT not minutes

miles, but

of longitude.

We N

the

S direction, the D.Lat.

or

same as minutes of movement in an E or which is in MILES.

the

movement in

which are and the

°

45°

to

at

In

is

the top, and the

numbered with 89° to 45° at the foot. course angle appears at the foot of a page (e.g. 54°),

"Dist.

then

we must

use the captions

These

of the columns.

— Dep. — D.Lat."

now

(a different

M =

If

at

Dep. 29.1

M =

D. Lon.

we

M

D. Lon.

its

0°10'.0E

D. Lon.

the change

If

sequence from

M

longitude.

in latitude

start in latitude

we

middle,

Mean

use the in

(D. Lat.)

48° and Lat.,

is

are only printed for

1

°

to

89°

all

courses should be converted into quadrantal notation. This simple conversion also ensures

give the D. Lat. and Dep. the correct

EorW) — 039°= Co N 39°

Names

(N orS,

the approximate

that case 49°, for converting the Dep.

Fig

A complete example would look 123a which can be checked with the

Note also that the "summing up" of the figures follows the usual algebraic system are the

W lon.)

same (W and

add;

— when names when names

and S lat.) subtract the smaller and name as the larger, (N).

are opposite (N

S 55° E (180 - 125 = 55) S 44° (224 - 1 80 = 44) N 67° (360 - 293 = 67) We can now "name" the D. Lat. and Dep. the same as the course D. Lat. 21 '.2 N

from the larger

Dep. 19.1 miles

The Deps can be summed up and the

= = =

W W

—

We into

now

must

E.

convert the E or

minutes of longitude

in

W miles (Dep.)

our particular

and

194

use the latitude to determine the page,

we now

disregard the headings "Dist.

a

number

— D.Lat.

of different courses are

be turned up and

listed,

but

it

is

not necessary to

convert each Dep. into D. Lon. separately.

Dep. converted into a

one

total D. Lon.

total (net)

Note also

or a series of tidal streams or current

can be treated

in

saved. The secret

the

same way and much work

lies in a clear,

methodical

tabulation, as in Fig 123b.

Note that

Tables solve this also.

We now

Where

involved, the D. Lat. and departure of each must

that

remembering that the relationship between miles and minutes of longitude depends on the latitude we are in. The same Traverse latitude,

like

Traverse Table extract given.

E

125° 224° 293°

large, e.g.

finish in latitude 50°,

into D. Lon.

As the Tables

e.g.

the

now re-state the work. Run Co. 036° = N 36° E 10M D. Lat. 0°08M N Dep. 5.9 M in Mean Lat. 54° =

the

Dep. 29.1 M.

we

at

can

the

read

D. Lat. 21 .2

(or S)

given as 10'.

then

Co 54° Distance 36

found

(minutes of longitude) 54°N (or S) Dep. 17.0 M = D. Lon. 29'. 0. the Traverse Table page for 54° we should

We

the top headings). e.g.

is

e.g.:

36°N

same pages

are

bottom

the latitude

find that against our Dep. 5.9

Departure,

in

Notice that the Traverse Tables have pages 1

if

36'.

in a

miles

latitude,

W direction

headed

column, In Lat.

now found

have

Dep. " Again,

foot of a page, use italics captions at foot of

this

is

for

conversion of the Departure into

Lat. of 46° has been used as about halfway between 45°20' N and

D. Lon. a

Mean

traverse tables

Old EP (or starting point) M on Co 234° T = S 54°

Run 24

36°05'.0 N

=

D. Lat.

Dep. 19.4 M,

in

Mean

ode)

Lat.

W

24°40'.0

W S

14'.1

36°

=

D. Lon.

24'.0W

!5'

New EP

35°50'.9N

25°04'.0W

Fig 123a.

Last

Course

EP 45°20'.0 N

Distance

1

8°40'.0 W.

D. Lat

N 050° 340° 075° 350° 095° 015°

= N 50° E = N 20° W = N 75° E = N 10°W = S85°E = N 15°E

24 miles 30 miles 42 miles

S

W

Dep.

E

15.4

18.4

28.2

10.3

40.6

10.9

18 miles 12 miles 36 miles

17.7

3.1

12.0

1.0

34.8

9.3

Current setting

241° 249°

= S61°W 2kn x 18 = S69°W H kn x 6

hrs

hrs

= =

M M

36 9

107.0

17.5

31.5

3.2

8.4

21.7

53.3

Last

D. Lat. 85'. 3

Dep. 27.0 E

in

M.

Lat.

Fig 123b.

85'. 3

N

45°20'.0N 1 °25'.3 N

Dep

27.0 E

18°40'.0W

46°

D. Lon.

New EP

N

D. Lat.

EP

80.3

-53.3

-21.7

=

38'. 9 E

46°45'.3 N

18°01'.1

W

195

W

S

practical yacht navigator 46°45'.3 N. (The exact figure o

1

+

45 2 o

Answer: Course 234°

of course

is

°^53 =46°03', but exact

The Tables

T,

are based

Distance 58 miles.

on the solution

of a plane

right-angled triangle. While the answers given are

is seldom necessary). would have been tedious to have plotted all these courses and currents on a chart, and slight inaccuracies would be probable. The use of

interpolation

sufficiently accurate for a relatively small triangle,

It

when

— indeed

it

will

be as

little

and longitude,

latitude

e.g.

What is the true course and distance from a position 36°1 4' N 28°20' to a position

W

35°40' N 29°18' First

W?

position

Second

position

36°14' N 35°40' N

D. Lat.

28°20'

In

Mean

Lat.

D. Lat. 34'. 1

W

29°18'

34' 58'

D. Lon.

36° dep. = and Dep. 46.9

46.9 are

M

found on

Traverse Table for 54°, against distance 58 miles.

S 54°

=

W (names same as D.

234°

196

T.

Lat.

and

are

meridional parts can be used, but as this has

correspond with those actually sailed. The traverse tables can be used for the solution of a number of similar problems, for example, to find the course and distance between two

known

600 miles

and the problem

distances above this figure the table of

accurate as the courses and distances used

positions of

falls off

requires the solution of a spherical triangle. For

traverse tables for this type of problem will give a

more accurate answer

distances above about

involved accuracy

D. Lon.)

practical application to

dealt with here.

yachtsmen

it

is

not

18. Celestial Navigation

In celestial or astro

position

is

navigation the yacht's

established using heavenly bodies

instead of terrestrial objects. identifiable objects

on

When

established by a bearing (or a vertical sextant fix

by bearings,

VSA's of two or more such objects will give the most accurate result. When out of sight of land, various radio methods horizontal sextant angles or

of position finding

may be

available, but accuracy

decreases with distance from the station, and (except with the most sophisticated equipment)

mid-ocean. If any heavenly body and the horizon can be seen anywhere in the world a position line can be established within miles is 1 0—1 5 minutes. Accuracy to within 1 possible under rough conditions, and to within 2 miles under moderate to favorable conditions.

they are valueless

in

By day, the sun, often the moon, and Moon, planets and stars can be used at twilight, and

occasionally a planet can be used.

under very favorable conditions of light can also be used in darkness. The body must of course be visible, either in a clear sky or through gaps in clouds.

No

higher mathematics are involved: simple

straightforward formulae are used which anyone

can soon master. Taking sights with a sextant needs practice but tolerable accuracy should be possible after an hour or so. The rapid sight

now

available (referred to later)

Exactly as with sights from terrestrial objects, a

within sight of

land, a position line

angle) of a single object, or a

reduction tables

simplify the calculations immensely.

body will somewhere on which To obtain an "observed

single observation of a single heavenly

provide only a position is

line,

the observer's position.

position" (so called to distinguish

obtained by

terrestrial objects),

it

it

is

from

a fix

necessary

(Fig 11 9.) either to observe two (or more) heavenly bodies (almost) simultaneously, or to observe one body (usually the sun), then to

proceed

until

materially

taken.

the body's position

moved when

The second

a

in

first

is

make a about 90°). The

position line should

wide angle to the first (ideally direction and distance the yacht has the

the sky has

second observation

observation

was

taken. (Fig

sailed since 1

20.) This

is

precisely analogous to the "running fix."

Some this

is

navigators use the sun exclusively, since

the easiest and most freouently visible.

The

shoot the moon, planets and stars is an advantage, as it enables an observed position to be found at once without having to wait for a second sight after a run of some hours, as must be done if only the sun is used. If three (or more) heavenly bodies are observed (nearly) simultaneously, the position line given by each should theoretically cross all others at a point. As with compass bearings of three or more terrestrial Objects they seldom do so, but form a "cocked ability to

197

—

T=^-

practical yacht navigator hat," the size of

which gives

a

good guide

the accuracy of the sights. (Fig

Ocean passages A large yacht, sail or latest

1

21

as to

.)

power, equipped with the

hyperbolic radio position finding equipment,

could cross an ocean and make a good landfall without taking a celestial observation. Without such equipment, an ocean-going yachtsman must be capable of taking celestial sights. It is interesting to note than many captains of passenger liners insist on their watch-keeping

and on the checked in spite of the ship radio and other devices

officers taking celestial sights daily

ship's position being

using the very latest

which pin-point the position exactly. This is partly to keep the watch-keeping officers "in training," and partly to ensure the radio fixing equipment is working correctly. For these reasons it is fair to say that any yacht however well equipped, should have the means and skill aboard to enable accurate fixes by sextant observations of celestial bodies to be

made,

if

it

is

proposed to make an ocean passage.

Long-distance semi-coastal passages Here we are considering such passages as from Annapolis, Maryland to Edgartown on Martha's Vineyard, from San Francisco to Vancouver, or in Europe from England to Gibraltar. These passages have often been safely made without the use of celestial navigation. Radio beacons can be used at various points (but by no means at all stages of the passage), and careful working up of the position by dead reckoning can be employed. However, the EP can be seriously in error perhaps dangerously so if for any reason a fix by DF beacons or by observations of land objects cannot be established for several days. This could occur if the yacht were obliged to lie a-hull in

—

198

Fig

1 1

9.

Two

Construction Position line

simultaneous sights

line (c) is

is

at right

:

moon and one

star.

actual bearing to celestial body.

angles to

it.

celestial navigation

heavy weather, or had engine trouble, or the radio became unserviceable. If fixes by land objects are being relied upon there is a tendency for the course to be laid perhaps imprudently close inshore. If there is any risk of heavy weather a

yacht

is

50 miles be a

lee

a-hull

safest well off-shore.

may

The

An

offing of

none too great if the coast is liable to shore, bearing in mind that a yacht lying is

drift

downwind

at

1

kn or more.

ability to take celestial sights

encourages

the setting of a course well offshore, with the

knowledge observed

at

visibility of

that the position can probably be

frequent intervals only dependent on the sun or any other heavenly body.

Celestial sights taken

50

or

more miles from the

shore should provide more accurate positions

than any taken from radio beacons or Consolan stations.

Short coastal or sea passages seldom necessary on short up to perhaps 36 hours. Nevertheless, occasions do arise when a celestial observation can be of real value. On Celestial sights are

coastal passages, taking only

Two sun sights, but with a run of 20 miles 240° Fig 1 20. between them. The position (top right) has been transferred double arrowed line to give intersection which is position.

Fig 121 Three simultaneous sights. Each position line obtained from a different star: they intersect to give an observed position. .

is

to

''' 199

practical yacht navigator

DF

bearings with a celestial observation. Head and Round Island are so much in line with yacht's position that she is only known to be in shaded area. But when crossed by position line from morning sun sight, a fix is obtained in red circle Fig

1

22.

The DF

200

Crossing

stations at Mizzen

celestial navigation a trip

across the Bay of Fundy to Halifax,

Scotia,

one may have

a

A

Nova

slow passage and be very glad

traditional sextant costs

and well over

upwards of $300 new, second hand. A

half of this price

much

to be preferred to a

to establish the boat's position well off land.

micrometer sextant

Or to take an example from European waters, the crossing from Land's End, England to Fastnet Rock lighthouse in southern Ireland is about 180 miles. There is a good RDF station ahead (at Mizzen Head) and another nearly astern (Round Island) but DF stations abeam (needed to establish the position along the track line) are too far off to be of value. A celestial observation along this line can be of great help. (Fig 1 22.) admittedly Apart from the occasions

vernier sextant because of the ease of reading the

—

infrequent

value

— where celestial observations are of

when

former, but a

can be

is

good second hand

vernier sextant

cheaper) it just takes a few more moments to read. There is an excellent micrometer sextant on the market made just as accurate (and

is

of specially stabilized plastic which is accurate to well within 2' of arc. Using this, the author has

got position lines to the same degree of accuracy as with traditional sextants, since the limiting factor

is

the stability of the "platform" used

— the

yacht's deck, and the visibility of the horizon, rather than the accuracy of the sextant.

coastal passage making, the

knowledge that such sights can be taken is itself satisfying and rewarding. No skipper or navigator can claim to be fully competent if he is not able to take, and use, celestial observations.

Bubble sextants designed for use on aircraft are offer. Even in the hands of an expert, accuracy miles is unlikely even in a calm sea, to within 1 and they are unusable in seas producing sizeable waves, so are not recommended on yachts.

Accuracy of positions

Except for sights taken for latitude (when the is crossing the observer's meridian) exact time is essential. By exact is meant within about

The accuracy of an observed position will naturally depend first on the experience of the observer, and secondly on the sea conditions and size of the yacht. As a broad guide, the average "week end" yachtsman in a 30 ft sailing yacht in a moderate sea, say, up to Beaufort force 4 or 5, should obtain

a position line to within 5 miles.

A

practised yachtsman should get equal accuracy is clear. These are have taken sun sights from a known position (near a landfall buoy) to within 1 mile in a 30 ft yacht in force 5 while singlehanded. The only essential equipment needed for

up to force 7

if

the sky

conservative figures.

celestial sights (a)

(b)

I

is:

A sextant. A deck watch

or chronometer, or

good

timepiece and radio. (c)

A

nautical

almanac and table book.

on

body

5 seconds.

(It is

not correct that an error

in

time

one second equals one nautical mile). Around the equator, where the sun's altitude moves most rapidly, an error of 5 seconds of time gives a maximum error of about 1 \ miles, and in latitude 50° an error of six seconds gives an error of under a mile. These errors are within f he degree of accuracy with which sights can normally be of

taken at sea. If

a radio capable of picking

up time signals

carried, a deck watch, or an ordinary

is

good pocket

watch can be used provided it has a seconds hand and keeps time to within a few seconds a day. It is, of course, not necessary to keep altering the watch to correspond exactly with the time signal. The error of the watch (minutes and seconds fast or slow of the zone or wrist

201

practical yacht navigator time) should be logged daily or more often, the

and

rate of gain or loss established,

all

passages, interesting and adds a

watch

to

times adjusted by the current error (fast or slow)

zone time. addition to a notebook

2.

to give exact In

for recording

and

signals

books are necessary.

All

commented on

here will

enable sights of the sun, moon, planets and 60 stars of use to the navigator to

The

alternative (a)

combinations

be worked out.

for current year

almanac

or Air

(b)

Almanac

— Nautical

— (Nautical or — Air) either

for current year

Sight Reduction Tables

Air)

(for

H0249 (two volumes cover the world), H0229 (four volumes cover the world upto60°N and S) or

or

Reeds' Nautical Almanac for current year.

(c)

The advantages and disadvantages

of each

alternative are: (a)

Only two books required to cover the

world. The use of haversines and logarithms

(though straightforward) requires more time. Approximate time to work out a sight, 1 0—1 5 minutes. (b)

The quickest and

easiest method. Each

Sight Reduction Table volume covers a band of latitudes,

so the number of books needed depends

upon areas

sailed.

Only the single book is required, but the procedure involves the use of versines and logarithms, and is the slowest with which to work a sight, taking 20 minutes or more. If you want to know whether to study celestial navigation remember: (c)

1

.

The

ability to take celestial

essential for

202

observations

ocean passages, desirable

is

is

for short

good

used.

Celestial Navigation

"black magic" about

almanac

a

a radio

is not difficult; there is no There is less to learn than in coastal navigation. There are many good text books on the subject, and many courses and classes are available. Uniform with this volume, is Ocean Yacht Navigator by the same author.

3.

Navigational Tables or

If

The only other items for celestial work are books as mentioned and a sextant, which will not be costly if one of the plastic type (such as the Ebbco)

are:

Almanac

is

is

capable of picking up time aboard, a good watch can be used.

timepiece.

calculating sextant sights, several alternative

new dimension

open-water sailing. The most expensive item required

it.

-

-«s=

Index

Aero Radiobeacons Anchoring, in fog Apparent wind

35.

138 187 160

indicator

Arc of

visibility

Astro navigation Atlas, tidal stream Autofix,

84.

depths

71

gnomonic

23

harbour plans isogonic

167

projection

lattice

mercator projection

67 72

Anemometer

32.

datum (CD.)

197. 204

RDF.

167 22 96 18 20 20 20. 142

correction of

18 16 19 20 18 17

navigational

non-navigational

Barometer Beacons, radar Beat frequency oscillator

compass

Bearings,

80.

magnetic relative

Beaufort wind scale

buoy

Betalight

Binoculars

&

tables

Bottom, seabed types Bottom, types of

"Bowditch" British

Admiralty charts

Bubble sextant

Buoyage

projections

radiobeacon

5

76. 81

137 47 164 35 64 49. 69 32 35 35 16 17 201 27. 29

Buoys

30 149

23.

radar

Calibration. D.F. sets

buoyage system Catalogue of charts Cardinal

Celestial navigation

Characteristics of lights

Chart datum Charts, abbreviations care of

catalogues coastal co-tidal

204

&

co-range

14 137 27. 29 17 197 23. 34. 129 22. 102. 104 17 33 17 20 20

134 32 19 20

storage of

33.

symbols types of

Check lists Chronometer Circle,

degrees

201

13

in

121, 130

of position

9.70. 174

Clock Clutter, radar

Coastal passage, a refraction.

Cocked

2

20 36 16 172

table for

RDF.

hat

Collision,

avoidance by radar

Compass

adjusting

bearings Cable, distance

20.

scales of

170. 172

list

systems

6.

reading the routing

14.

to lay off

Books

1 1

polar

115

cross-

Bell

ocean

70 149 137. 140 49.

bulkhead reading Danforth White errors of the

grid steering

hand bearing high speed, for lighting

remote control siting the

steering

Compasses, drawing Computer, performance

146 175 136 115. 138 152 76 50. 115 56 57 73

52,54 49.63 56 57 55 51

49.50 36.40 72

Composite

fixes

Consolan. Contours

RDF. 22.

32

Correction of charts Course notes lay off a

shape

133 140 173

82.

a

track-

168 47 86. 90 86

92 86 115 23.85. 115

plotting the

wakeCross-bearings Currents

17. 101.

Currents, tidal

Cyclone

104 70

Eldridge tide and pilot Electra

Decca. RDF. Decimetre

Departure preparations point of

Depths Depth meter Degrees

5.

94 80 74 80 78 78 35 13 49. 134 144

77, 90.

causes of check in emergency finding the

swing ship

for

Diaphone Direction Direction finding radio

Display unit, radar Distance, measurement of meters rising & dipping off

by

VSA&HSA

Diurnal tides

drawing

Doppler log Douglas protractor Drift,

192 173 92 22.96 13

card

surface of tidal stream

Drying heights Duration of tide Dutton's navigation

13

14.43. 58. 59 49. 58

128 120 121, 126 97, 102

Estimated position Explosive, fog signals

103

Factor. Height of tide

15. 22. 111

Fathoms

66 130 119 183 182 35. 183 168. 172 120

Ferrite rod aerial

92. 114. 123. 126.

providing a running in

signals list

of

Four-point bearing

Geographical pole range of Gimbals

Gnomonic

13 light

projection

Graphic display meters Great circle Grid steering

compass

Gulf stream

Gun. fog signal

Hand bearing compass Harbour plans Height of objects on land tide

Homologue compass Horatio Horizontal sextant angle Hurst plotting protractor

Hydrographic Center Hydrographic department Hyperbolic RDF systems

130 50 18 62 12. 18

52.54 23.

85 35

49.63 20 21. 22 96. 101. 173. 180. 181

56 72 121

47 17 17

138

36,40,43,44 59

150 88 94 22.98. 104 102

24. 36.46. 124.

Ice limits

InterScan, radar Interval, tides

Isogonic lines Instruments for chart table yacht

19

146 102 20.74 36 49

16 Knot, unit of speed

Ebbco sextant

73 94 35

compass

Errors of the

Fog. navigation

49. 60. 62

Deviation

Dividers,

21.

153

Equator

Flares

163. 164 49. 201

Deck log book Deck watch Departure (& D.Lon:)

magnetic log

141

22

book

Electrascan

128 94

92.

72 23 59

Efficiency indicator

Fix,

Danger angle, sextant Dead reckoning, position by

125 60.96

station pointer

Echo sounder

15

202

205

173

Landfall preparations Lateral

buoyage system

27. 29

13 142 159 82. 85.92 183 24. 150 22.23. 26. 130 25 24 36

Latitude

Lee bow. Leeway

RDF

20.

to

Life preservers

Light float

house tower vessel Lighting, chart table

compass

57

129 34 21. 32. 168

Lights, characteristics

30. 34.

colour of list

of

Line of soundings

147 163. 176

Log books

59 58 92 13 66

electroscan patent reading the

Longitude aerial.

RDF

C

141

Lowest astronomical Lubber line

tide

Luffing error

Magnetic bearings Magnets, correcting compass Magnifying glass Mercator projection Meridians Meters Micrometer sextant Mile, nautical or sea-

22.96 50.51.73 90 73.81 76

currents

Omega. RDF Parallel rule

Patent log Pelorus Pencils Period of lights Pilotage Pilot

14 13

statute

49.62 37 23. 129. 130.

11

Plan position indicator, radar

95

Plotting the course

114

position Points, of the

compass

18 20

Port approach charts

170

Port entry signals

methods od describing ..

finding

DR & EP a

circle of line of

by sextant

Nautophone Navigational marks Navigators log book

Neap

tides

Night

effect.

RDF

Notation. 360°

14 35 23 164. 165. 177 99. 172 136 13

Note books Null.

RDF

67.

36 137

Sestrel

Quadrantal bearings error.

206

197

51

RDF

136

Racon

149. 151 principles of

Radiobeacons charts

Radio direction finding Radio refraction time signals

Radome. radar Ramark Range, methods

of finding

by radar

Range

of tide

consolan stations Reflector, radar

35.148. 154 145 20. 35.66. 138 16 66.

1

34. et seq

136 201

149 150

Reed's Nautical Almanac

Observed position

167 17 37.81 38.81 46

Weems

194

quadrantal

101

Preparations for passage Projections, chart Protractor. Hurst

16 101

13

114 94 115. 121. 128 114 121. 126. 197

Predictions, of tide

Radar buoys with reflectors National Ocean Survey tables National Oceanic and Atmospheric Administration Nautical mile

51

Polar charts

Position,

168

17.33.84 144

books

201 ;

13 175 58

Passage making

18 13

Minute of arc

36. 40. 41

Parallel of latitude

36.49

15. 22. 111

26 20 19 143

charts

131

Lobes, radar

Loran.

Ocean

12.

Lattice charts.

Loop

Obstructing large vessels

121. 126.128 146. 150. 154

102.105 141

21.33.84.109.202 152. 154.183

1 "

RDF

Refraction.

Relative bearing

14. 134. 150.

136 152

Remote control compass Rhumbline Rising

&

Rule of twelve fix

interval of

111

patterns of

109 97

predictions of

101

range of

102 108 112 102 104

height of

40 42 112 119

roller

and

form for finding height

19

Rule, parallel

Running

duration,

128

Routing charts

97 105 102

curve

55 18

dipping distances

23.84

charts Tide, causes of

22. 96. 105.

rise of

rule-of-twelve Sailing performance

computer

72 20 144

Scale of charts Scanner, radar Seascribe depth meter

Secondary

61

103. 107. 108

ports, tides

24 97 167

Sectors, of lights

Semi-diurnal tides Separation zones Sestrel Luard protractor

38. 91

Moore compass

Sestrel

51.

Transceiver, radar

Transducer Transit

Traverse tables, use of True N. bearings

Uniform buoyage system

128

HSA&VSA

201

Ursa Minor, radar U.S. chart agencies

plastic

201.202

use of

49.70. 197 82.86. 90 85.91. 94

a course, to

book

Ship's log

163

Siren

Variation, applying definition

finding Vector, tide

wind

35

Soundings

21. 96. 131. line of

190

Vernier, sextant

131

Vertical sextant angle

Speed made good indicator, water-

15 60 99 99 123. 125 14 03 et seq 49. 69 59.

wind Spring tides Station pointer

Statute mile

Standard ports, tides Stop watch

1

Sumlog

91 et seq

13.

73.76 26. 29

149 17

77.90 73 74 86. 88. 131

161

126 126

59

Wake

course

Water speed indicator

Wave

guide, radar

Weather forecasts Whistle buoy

Wind

direction indicator

recording

speed indicator

Windward

sailing

85. 94. 95. 131

59.72 144 67. 174 35 71

164 72 155

88 74.78 20 179

drift

for deviation

Symbols, chart navigator's

& books Tack limiting lines Tables

202 156 145 84. 167 169. 172. 190. 195 97 33. 84. 102.

Target, radar Tidal current atlas

allowance causes of

1

91

Speed, unit of

Surface

124. 131

82.86.92. 131. 167 144 59. 60. 96. 98 24. 115

54

201

Ship's head

Swing

terms used Tracing paper, use of Track

danger angle

Sextant, bubble

Shape

tables

for

82. 94. 131

207

Kenneth Wilkes operates a navigational

school in England giving private tuition and correspondence courses from his

chartroom overlooking the Hamble River. Many of his students have subsequently

made

extensive coastal

and

He has been a yacht owner himself for many years and cruised ocean passages.

mainly in the waters of England, France, Ireland and Canada. A qualified Yacht Master (coastal and ocean), he has also been navigator on a large number of ocean races including the Fastnet and been professionally engaged as skipper-navigator by other owners. Prior to engaging in fulltime teaching of

navigation, the author was an

accountant. He has always been associated with the sea, and as a small child he made two round-the-world voyages with his father who commanded a 2,000 ton square rigged ship.

Jacket photograph by Brian

Manby

DAVID McKAY COMPANY, INO 750 Third Avenue York, New York 100 17

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