The Parts of the Model Submarine.—There are only four chief parts to this model, and these are (1) the hull; (2) the ballast tank; (3) the power plant; and (14) the superstructure. All of this is shown in Fig 11.
The hull is of course the body of the boat. The ballast tank is a tin can in the bottom of the hull; when it is filled with water the extra weight makes the boat sink, and when the water is blown out of it by compressed air it makes the boat rise to the surface again.
The power plant includes an electric motor, the batteries to run it, the propeller-shaft and propeller, the pulleys which work the valve that lets the compressed air flow into the ballast tank to blow out the water, and finally the superstructure, which consists of the deck and the conning tower, though in this case the latter is made to hold the compressed air.
The Hull of the Boat.—The first thing to do is to make the hull; and the easiest way to build one that is light, strong, and watertight is to whittle out, or have sawed out, two tapering pieces of wood as shown at A and B in [Fig. 12]. The faces are shown by the dotted lines at C and D in Fig 11.
These are for the nose and tail blocks, as we will call them, and each one is 14½ inches long. The other dimensions, as well as the shapes of these blocks, are also shown in [Fig. 12].
FIG. 11. THE PARTS OF A MODEL SUBMARINE.
Bore four ⅛-inch holes, ¾ inch deep in the faces—that is, the flat ends of each block—at the places shown by the little circles; these are to take in the ends of the brace rods. Next bore a ¼-inch hole lengthwise through the tail block as shown by the dotted lines at B. Bore out this hole with a 1-inch bit to a depth of ¾ inch, to form a stuffing box.