Cut out a rectangular hole ½ inch wide and 2 inches long in the for’ard end of the deck, for the screws and the wires of the switch to pass through. Screw the porcelain block of the switch to a board of the same size, with the tin deck in between them; this insulates the screws of the switch from the tin, which would otherwise short circuit the battery and run it down. Run sealing-wax in and around the edges of both the porcelain and wood blocks to make a watertight joint, for water must not get into the boat.
This done, connect up the batteries and these with the motor, with heavy rubber-covered copper wire, and connect the battery and the motor with the switch with flexible electric-light cord. Set the deck on the hull; and if you are sure everything is in first-class working order, solder it on tight. If, though, you are not quite certain, you can do a temporary job by putting it on with sealing-wax.
Supposing you are young enough to have imagination or old enough to have dim vision, the switch mounted on the deck will look very much like a gun that is just coming through the hatch and getting ready for action.
And Now the Conning Tower.—The conning tower is an airtight vessel—as far as your model goes—having a conical shape.
To make it, scribe two circles, using the same center, on a sheet of heavy tin, making one of them 4 inches in diameter and the other 5 inches in diameter, and cut it out around the larger circle.
Cut a ½-inch hole in the center of the disk. Put the ½-inch length of threaded pipe we told you about under the caption of The Air Control Mechanism in the hole, and solder it fast. Cut the edge of the disk radially with your shears, from its edge to the smaller scribed circle, and then you can bend up the edge all the way round.
Next cut out an arc of tin of the size marked and the shape shown in [Fig. 19]. Make a lap seam and solder it.
Scribe a 3-inch and a 4-inch circle on a piece of tin and cut it out. Cut the edge radially as before, and bend it up all the way round. Cut a ½-inch hole near the edge of the intake air-valve pipe. Solder the two disks to the cone and be sure the ½-inch threaded pipe is inside.
