Fig. 5
Make the propeller out of a circular piece of stout tin two inches in diameter, cut as in [Fig. 3]. The dark parts are to be cut away. The projections are to be three-quarters of an inch long. Punch a hole one-sixteenth of an inch in the centre, and fix a piece of brass wire one-sixteenth of an inch, two inches long, in the hole, to form an axle for the propeller. Twist each of the fans of the screw out of the plane of the circle about a quarter of an inch, in the manner of the sails of a windmill, as in [Fig. 4]. Now make two little wooden plugs three-quarters of an inch long, and half an inch wide at one end, tapering to a quarter of an inch at the other. Bore a hole through each from end to end one-sixteenth of an inch wide. Take the propeller, and put a glass bead, that will fit easily, on the wire, and push the wire through one of the wooden plugs from the large end; bend the wire into a loop at the small end. Next take another piece of wire, two and a half inches long, and make a similar loop at one end, and put the other end through the other little plug, from the small end, and bend the wire into a handle ([Fig. 5]). Now the only thing we want is the power. This is a strip of strong elastic about three and a half feet long and a quarter of an inch wide; tie the ends together to make a band—a large stout elastic ring will do, or two smaller rings looped together. Fasten a string to the elastic, and pass the string through the tube in the boat, from the stern end; hook the loop on the propeller-wire into the elastic, and push the wooden plug into the tube so that the screw is clear of the rudder; draw the elastic, by the string, through the other end of the tube, and hook the wire in the other plug into it; take off the string and push the plug into its place. You must cut the plug away so that the handle can catch in the teeth cut in the tube. Now the boat is ready for use.
To use it wind up the elastic by the handle at the end of the tube, holding the screw firmly with the other hand. As soon as wound up enough set the rudder and put the boat into the water; release the screw, and the boat will go till the elastic is quite unwound. The distance it will travel will be regulated by the extent to which the elastic is wound up.
II. How to make a small Marine Engine for a Boat four or five ft. long.
By Frank Chasemore.
I have already described the method of making a small boat move through the water by means of an elastic band, which is simply twisted up and then released, but I have no doubt that many readers would like to possess a simple model boat to work by steam.
Such models can now be purchased at all shops where mechanical toys are sold, at prices varying from one shilling, the smallest, eight inches in length, to about twenty pounds, the largest, five feet in length. Although all these boats really go by steam, the application of the power is different in the different sizes.
The small boats are of course the simplest. In these the steam from the boiler is conducted through a short pipe to the sternpost of the boat, where by its pressure on the water in escaping it forces the boat along.
The next class have a further development of the application of steam-power. In the centre of the boat, close behind the boiler, is a fan-wheel, turning on an axle, which in the case of a paddle-boat carries the paddles, and in the case of a screw carries the propeller. The steam is conducted from the boiler through a short pipe to the front of the fan-wheel, which it blows round as it escapes.