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BOYS' BOOK
OF
MODEL BOATS
[Illustration: (C)_Jack Sussman_
A TWO-FOOT STEAMBOAT
Making her way across the park pond. Ten miles an hour is a common speed
for a boat of this type]
BOYS' BOOK
OF
MODEL BOATS
BY RAYMOND FRANCIS YATES
WITH NUMEROUS ILLUSTRATIONS
FROM DRAWINGS AND
PHOTOGRAPHS
[Illustration]
NEW YORK
THE CENTURY CO.
Copyright, 1920, by
THE CENTURY CO.
PRINTED IN U. S. A.
TO
LAVERNE YATES
A BUILDER OF MODEL BOATS
PREFACE
EVERY boy likes to build boats. The interest in boats seems to be born
in the race. The little three-year-old chap is instinctively attracted
by a puddle of water in which to sail his "boat," which may take the
form of a piece of shingle or common board. Few men have passed through
their boyhood days without having built boats at some time.
The author was an ardent boat-builder, and he well remembers how he
combed the Children's Department of the local library in search of a
book that would tell him something about boats, and especially for
information regarding the construction of models. He found books on
model airplanes, toys, electricity, radio, and chemistry, but alas!
nothing about model boats. He vowed then that when he became a man he
would write a book on model boats--a book that would contain all the
treasured information he had accumulated during his boat-building
years.
This book is the result of that vow, and the author earnestly hopes that
it will gladden the heart of every boy who builds and sails a boat.
There are probably few happier moments in a boy's life than when he sees
his little model steamer proudly make her way across the park pond, or
his little sail-boat respond to the summer breeze.
The author takes this opportunity to thank his wife, who acted as his
amanuensis in the preparation of this manuscript.
RAYMOND FRANCIS YATES.
CONTENTS
CHAPTER PAGE
I WHY A BOAT FLOATS 3
II THE HULL 12
III HOW TO MAKE SIMPLE BOATS, WITH AND WITHOUT POWER DRIVE 26
IV STEAM AND ELECTRIC PROPULSION 42
V AN ELECTRIC LAUNCH 66
VI A STEAM LAUNCH 75
VII AN ELECTRICALLY DRIVEN LAKE FREIGHTER 91
VIII AN ELECTRIC SUBMARINE-CHASER 98
IX BOAT FITTINGS 107
X THE DESIGN OF MODEL STEAM-ENGINES 126
XI A MODEL FLOATING DRY-DOCK 135
XII OPERATION OF FLASH STEAM POWER PLANTS FOR MODEL BOATS 149
XIII SAILING YACHTS 164
XIV TWO-FOOT SAILING YACHT 184
APPENDIX 207
LIST OF ILLUSTRATIONS
A two-foot steam boat _Frontispiece_
FACING
PAGE
Getting ready for a trip 72
All ready to go 73
A powerful gasolene blow-torch 112
Just after the race 113
A twin-cylinder steam engine for model marine use 168
A cup-winning model sail boat 169
BOYS' BOOK OF MODEL BOATS
BOYS' BOOK OF MODEL BOATS
CHAPTER I
WHY A BOAT FLOATS
BEFORE taking up the construction of any of the model power boats
described in this book, it will be well for the young boat-builder to
become acquainted with such terms as buoyancy, displacement, center of
gravity, etc. Knowledge of these subjects is more or less necessary if
successful boats are to be made. Aside from this, they are terms that
every boy who claims an interest in boats should understand.
"How does a steel boat float?" is a question that many boys ask. The
reason they usually designate a steel boat is probably because steel is
so much heavier than water. But many things heavier than water can be
made to float if they are in the form of a boat. Concrete, for instance,
is now being used in ship construction, and this substance, when
reinforced with steel rods, is very much heavier than water.
Before learning how a boat floats, what is known as "specific gravity"
must be thoroughly understood. Gravity is a force that is continuously
"pulling" everything toward the center of the earth. It is gravity that
gives a body "weight." Some substances are heavier than others; or, to
be more correct, it is said that the specific gravity of one substance
is greater than that of another. It will be well to keep in mind that
specific gravity merely refers to weight. It is simply a scientific
term. The specific gravity of a substance is always expressed by a
figure that tells how much heavier any substance is than water, because
water has been chosen as a standard.
The specific gravity of water is 1. The specific gravity of gold is
19.26, meaning that it is about 19-1/4 times heavier than water. The
specific gravity of a piece of oak is 0.86, which shows that it is not
quite so heavy as water. One cubic foot of water weighs 62.42 pounds.
It will be understood that a cubic foot of gold would weight 19.26 x
62.42, because it is 19.26 times heavier than water. A cubic foot of
oak, however, would weigh only 54 pounds, because it has been found that
it has a specific gravity of only 0.86 which is less than water.
[Illustration: FIG. 1]
A cubic foot of oak (see Fig. 1), with a weight of 54 pounds, will float
when placed in water. The cubic foot of brass (_B_), however, will not
float, because it weights 8.1 times as much as water. For the present,
then, it can be said that a substance lighter than water will float in
water, but that substances heavier than water, such as iron, lead, gold,
silver, etc., will not float. If the cubic foot of oak (_A_) were
placed in water, it would sink to the depth shown at _C_. When the block
sinks into the water, a certain amount of water will be forced away or
"displaced"; that is, the block in sinking occupies a space that was
previously occupied or filled with water. The oak block sinks to within
a short distance of the top because the oak is really just a trifle
lighter than water. If a pine block were placed in the water it would
sink only to the distance shown at _D_, since the weight of pine is less
than oak, or only 34.6 pounds per cubic foot. A pine block will, then,
displace only about 34.6 pounds of water, which leaves nearly half of
the block out of the water. Thus, it will be seen that for a given
volume (size) a cubic foot of wood will sink to a depth corresponding to
its weight. Different kinds of wood have different weights.
If a cubic foot of brass is placed in water, it will sink rapidly to the
bottom, because the brass is much heavier than water. How is it, then,
that an iron or concrete ship will float? If the cubic foot of brass is
rolled or flattened out in a sheet, and formed or pressed into the
shape of a boat hull, as shown in Fig. 2, it will float when placed upon
the surface of the water. Why is it that brass is caused to float in
this way, when it sank so rapidly in the form of a solid square?
[Illustration: FIG.2]
It will be remembered that the pine and oak block were caused to float
because they displaced a greater weight of water than their own weight.
This is just what causes the brass boat-hull to float. If the amount of
water actually displaced by the hull could be weighed, it would be found
that the weight of the water would be greater than the weight of the
hull. It will be understood that the space occupied by the brass
boat-hull is far greater than the space occupied by the block of brass
before it was rolled out and formed into a hull. What is true of brass
holds true of iron, steel, etc. A block of steel will not float, because
the water it displaces does not weigh nearly as much as the block. If
this block, however, were rolled out into a sheet and the sheet formed
into a hollow hull, the hull would float, because it would displace a
volume of water that would more than total the weight of the steel in
the hull.
In the case of the brass boat-hull, it would be found that a greater
portion of the hull would remain out of the water. The hull, then, could
be loaded until the top of it came within a safe distance from the
water. As the load is increased, the hull sinks deeper and deeper. The
capacity of big boats is reckoned in tons. If a boat had a carrying
capacity of ten tons it would sink to what is called its "load
water-line" (L.W.L.) when carrying ten tons. As a load or cargo is
removed from a vessel it rises out of the water.
What if the hull of a boat has a hole in it? If the hole is below the
water-line, water will leak in and in time completely fill the inside of
the hull, causing the boat to sink. Also, if too great a load or cargo
were placed in a boat, it would sink. It must be understood that water
leaking into a boat increases its load, and if it is not stopped it will
cause the boat to sink.
The center of gravity of a boat is a very important matter. First,
attention will be directed to the meaning of "center of gravity." If a
one-foot ruler is made to balance (as shown in Fig. 3) at the six-inch
mark, the point at which it balances will be very close to the center of
gravity. The real center, however, will be in the middle of the wood of
which the rule is composed. It should constantly be kept in mind that
this "center of gravity" is a purely imaginary point.
Look at Fig. 4. If wires are arranged in a wooden frame, as shown, the
point where the wires cross will be the center of gravity if the square
formed by the wooden strips is solid. Every body, no matter what its
shape, has a center of gravity. The center of gravity is really an
imaginary point in a body, at the center of its mass. Oftentimes
engineers are heard saying that the center of gravity of a certain
object is too high or too low. Fig. 5 shows the center of gravity in a
boat. If the center of gravity in a boat is too high (as illustrated in
Fig. 6) the boat is said to be topheavy and unsafe. When a boat is
topheavy or its center of gravity is too high, the boat is liable to
capsize. In fact, some very serious marine accidents have been caused by
this fault.
[Illustration: FIG. 4]
[Illustration: FIG. 5]
[Illustration: FIG. 3]
[Illustration: FIG. 6]
The center of gravity (or center of weight) in a boat should be as low
as possible. A boat with a low center of gravity will be very stable in
the water and difficult to capsize. This is true of model boats just as
much as it is true of large boats. The model boat builder must keep the
weight of his boat as near the bottom as possible. For instance, if a
heavy cabin were built on a frail little hull, the boat would be very
unstable and would probably capsize easily.