One other glider should be mentioned, and that is one with sheet metal planes, Fig. 219. This has advantages and disadvantages. When it strikes hard against some object, the metal is liable to bend, also if it is thrown violently, and should strike someone on the face or hands it might cut. The metal surfaces can be bent into any shape. All corners should be rounded. Some of these gliders can be thrown long distances if properly adjusted.
After working awhile with gliders, we can try model aeroplanes that are suited for the instalment of motors later. Everything must be made as light and strong as possible. All kinds of ribbed surfaces, keels, and light wire braced frameworks, are utilized. Everything that would be used in a self-propelling model, except the propeller and motor.
Make the planes movable so they may be balanced as to pressure, by moving them back and forth, flex more, flex less, tilt more, tilt less, until you get a good glider out of it, then attach your motor and propeller. Some may think best to put motor and propeller on, and do all the experimenting, but it takes time to make a good propeller, and the fewer jams it has the better, so it is better to do some experimenting with the model before the propeller is added. The motor will make practically no difference in the balance, so there would be no advantage of putting it on for experiments in gliding.
We are now ready for some attempts on the self-propelling models.
