t 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.

CHAPTER II

THE HULL

MODEL boat-hulls are generally made by one of two methods. One method i