CHAPTER IX.
THE STEERING OF THE MODEL.
§ 1. Of all the various sections of model aeroplaning that which is the least satisfactory is the above.
The torque of the propeller naturally exerts a twisting or tilting effect upon the model as a whole, the effect of which is to cause it to fly in (roughly speaking) a circular course, the direction depending on whether the pitch of the screw be a right or left handed one. There are various devices by which the torque may be (approximately) got rid of.
§ 2. In the case of a monoplane, by not placing the rod carrying the rubber motor in the exact centre of the main aerofoil, but slightly to one side, the exact position to be determined by experiment.
In a biplane the same result is obtained by keeping the rod in the centre, but placing the bracket carrying the bearing in which the propeller shaft runs at right angles horizontally to the rod to obtain the same effect.
§ 3. The most obvious solution of the problem is to use two equal propellers (as in the Wright biplane) of equal and opposite pitch, driven by two rubber motors of equal strength.
Theoretically this idea is perfect. In practice it is not so. It is quite possible, of course, to use two rubber motors of an equal number of strands (equality should be first tested by weighing). It should be possible to obtain two propellers of equal and opposite pitch, etc., and it is also possible to give the rubber motors the same number of turns. In practice one is always wound up before the other. This is the first mistake. They should be wound up at the same time, using a double winder made for the purpose.