The experiment is well worth trying. It would seem that this angle would give increased stability, although if the model were knocked off its course it might increase the resistance considerably. An elaborate test of this form has been made by an aeronaut named Weiss in England, who believes he has gained automatic stability in this way. Mr. Weiss has built and flown a number of aeroplanes, varying in size from one weighing five pounds to one which carried a weight of 140 pounds, and the tests are reported to have been very satisfactory.
What is meant by the phugoid path of a model aeroplane?
The line described by the machine in flight. Every aeroplane left to itself flies in a series of waves swaying more or less up and down from the horizontal. In a aeroplane under the control of an aviator this is largely overcome by manipulating the rudders controlling the vertical motion. Every model aeroplane or soaring machine has a phugoid path peculiar to itself which is affected by the power of its motor, the form of the wings, its ability to right itself, etc. It is obvious of course that if the path of your model aeroplane is irregular the machine must travel more slowly and its distance qualities are therefore reduced.
Is a variable wing surface an advantage and can it be applied to model aeroplanes?
In theory at least there is a great advantage in the variable surface plane. As yet but one aeroplane has been flown in which the pilot may increase or cut down the spread of his wings at will. When such control is possible the aviator may employ the maximum spread of the wings for rising, for instance where it is needed, and then reduce their area when aloft, thus gaining in speed qualities. At the present stage of the development of the model aeroplane a variable wing does not seem practicable, although it is reasonable to suppose that the improvement will come in time. The control would of course have to be automatic, which renders the problem rather complicated.
What is a vortex pack?
Literally a small cyclone or eddy of the air. The term is used by aviators to describe a turbulent section of the atmosphere. It is very common in flying, especially at low altitudes, to run into a very turbulent eddy of air, such as is set in motion by high buildings or deep valleys. They are extremely dangerous since they cause the aeroplane to dip and roll about violently, and call for quick and skilful handling of the aeroplane to keep it from being upset. The term might be used to describe an eddy of air which brings a model aeroplane to grief.
What form of propeller will give the highest efficiency?
It is impossible to lay down a hard and fast rule. Much depends upon the form of the machine. The Voison propellers have been found in actual practice to give only about forty per cent efficiency. This is said to be partially due to the fact that their parts are held together by bolts and projecting nuts which offer considerable skin friction. The Wright propellers are believed to be the most efficient propellers for large machines since their efficiency is about seventy per cent. The accompanying photographs of the standard model aeroplane types in America will show that there is great difference of opinion as to the diameter and pitch of the screws.
What is meant by a variable speed machine?