Boys' Book of Model Boats

become acquainted with such terms as buoyancy, displacement, center of gravity, etc. Knowledge of these subjects is more or less necessa

l 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, fo

ody "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 mer

h 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 1

ere 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 i

crete 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, i

e 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

e 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 ca

l 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

e 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, w

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

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 nea