140 13 26MB
English Pages [214] Year 1978
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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