Page:Popular Science Monthly Volume 91.djvu/313

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�ASH IP has recently been devised which carries a veritable gale pent up, not in an oxskin, such as Homer's Odysseus used to carry away the winds from the isle of Mo\us, but in a cylindrical tank. This boat was designed primarily as a toy, a bicycle pump being used to fill the tank. With one pumping, 16-in. models have a cruising radius of about ioo yd. and run from Yl to 10 minutes, depending upon the rate of escapement of the air.

In the course of experiments with air propulsion it was found that a simple jet of air, allowed to escape from a boat, is very ineffective. Placed in a semi-circular tunnel the jet be- ftrrK

comes doubly effi- cient. Still greater saving of power is made by leading the spent bubbles up in an incline at the stern to the surface, as shown in Fig. I. Thus the lifting power of the bubbles is used in propelling the boat, or it might be said that the boat is continually coasting down a row of bubble rollers.

Making an Air Torpedo

Perhaps the most simple form of an air boat, as a toy or for experimental work, is the torpedo, in which an air chamber forms a greater part of the boat-body. This air chamber, as shown in Fig. 2, is a 2-in. cylinder with semi-spherical ends, into one of which a bicycle tire air-valve is fitted. To this end a stern piece, containing a

���bubble-way, Fig. 3, is soldered. With the air-pipe and nozzle, Fig. 4, in place, and with the tank tested airtight, the torpedo is ready for use. The speed depends en- tirely on the size of the jet aperture. This can best be regulated with a pair of pliers. Since speed is desired, it should be adjusted to exhaust the air supply in 20 to 30 seconds.

How to Make a Submarine Chaser

In the illustration, Fig. 5, there is shown one of the most interesting toys of today, the submarine chaser. It is a V-bottom boat, all metal, war gray, with an automobile-type steering gear that really moves the rudder. It is 16 in. over all, with a 43^-in. beam, and runs from 5 to 12 minutes at a fair speed . Any boy who has a soldering set and tinsnips can build it at small

��Fig. 1. The compressed air is allowed to escape in a semi-circular tunnel at the stern

��expense.

The hull with the

extension of the stern-plate is cut from a single piece of sheet tin, Fig. 6. This metal is bent on the lines A, B, and C to form the keel and sides. With three angle strips to reinforce it, the bow is soldered together as in Fig. 7. The stern-plate is next fitted on. Now it is ready for the tank. This is made of two circular cans, in the larger of which an air- valve is placed before the two are joined, to form a cylinder 8 in. long and 2^ in. in diameter. This is shown in Fig. 8. The ends of the tank are strengthened by a wire

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