FIG. 13. THE STRIPS WHICH FORM THE SKIN OF THE HULL.
After you have these strips screwed on, you must solder the lap seams to make them watertight. You can easily do this by using a regular tinner’s soldering copper—a soldering fluid made by dissolving zinc clippings in some dilute muriatic acid—and what is called wire solder.
The cover of the boat, or deck, to give it its nautical name, is a part of the superstructure, and you can cut this out later on.
The Ballast Tank.—The sole purpose of the ballast tank is to add enough weight to the boat to sink it when you want it to sink.
Use heavy sheet tin for the tank. Cut out two strips, each of which is 2 inches wide and 15½ inches long. Make a ½-inch lap seam and solder the ends of this strip together, making one strip 30 inches long. Bend the strip so that each side is 11 inches long and the ends are 3½ inches long; this will bring the ends together, forming another ½-inch lap seam, and this, of course, you must also solder.
FIG. 14. HOW THE BALLAST TANK IS MADE.
Cut out a top and a bottom, each 4 inches wide and 11½ inches long. Cut the corners; bend up the edges ¼ inch all round, and solder the corners. And don’t be afraid to use plenty of solder, for this tank must be strong, and not only watertight but airtight as well.