My aeroplane starts off all right but often begins to rock from side to side like a cradle and then flutters to the ground. How can I prevent this?
A beautiful model built by Stewart Easter
A successful model of 1910 built by E. G. Halpine. Note contrast in plane area
This "rocking" motion is probably caused by a too low center of gravity in your machine. If your planes are set at a dihedral angle, they should be brought nearer to the horizontal. Another plan is to place them lower down. A side gust of wind will start this rocking or vibration, and in order to right itself the machine loses momentum and falls. This difficulty is seldom experienced with horizontal wings, especially if their aspect ratio is high.
I have no trouble in getting my model off the ground, but it seems to rise too fast and fall backward or uses up the power before it really gets under way. Is the trouble with the propeller or the planes, for my motor seems all right?
If your model rises quickly, the planes are probably well designed and built, the motor is effective, and the propeller sufficient for all needs. The trouble is likely to be with the angle of the planes. Perhaps your front plane is elevated too high. The rear plane should be kept horizontal or very nearly so. An aileron at the rear of the main plane will help you to properly adjust same. As a rule, the angle of ascent should be a little more than that of the front plane. If it still acts badly, strengthen your motor and bring your large plane back a trifle.
What is the best place to put the keel?
The greatest stability is usually gained by fixing the keel at the center of gravity. There is great difference of opinion as to whether it should be above or below. Try both ways. What is stability for one aeroplane may mean disaster for another.