A Good Example of Careful Designing and Workmanship.
Should you construct a motor-base of this kind with propellers at either end it will be found interesting to experiment by attaching planes of different shapes and sizes. It requires very little surface to keep such a monoplane afloat. Instead of the circular and elliptical plane placed lengthwise, as in the accompanying model, try the effect of larger circles and broader ellipses, placing the latter sideways. This may be varied by using small rectangular planes with the corners rounded off. Sooner or later you will hit upon a shape of plane and a spacing which will give you good, steady flights of surprising length.
It has been suggested that a good motor-base be built with double propellers and the various forms of planes tested out upon it. Let us carry this idea further and, now that we have had some experience in building aëroplane models, construct a quadruple motor-base; that is a motor-base with four strands of rubber bands and four propellers, two forward and two aft. The four would of course have to be very nicely balanced. The two sets of propellers if carefully set up would tend to correct one another, as we have seen in the cylindrical and other double propellers thus giving a very steady flight. The increased speed of such a motor would carry any good model at a much higher rate of speed than any of the present forms.
There is a very simple rule to be remembered in building all biplanes, regarding the spacing of the planes. The distance between the super-imposed planes should always be equal to the width of the planes themselves. A beautiful model ([Plate 23]) is here reproduced, to show how not to space your planes. In all other respects the model is excellent. The planes themselves are beautifully constructed and scientifically curved. It is interesting to note, in this case, that the front and rear sets of planes would be much too far apart were they flat surfaces, but being flexed as they are, their supporting power is greatly increased. By placing them so far apart, a longer and more powerful motor may be used. The rudders, both fore and aft, are adjustable, and appear very effective and shipshape.
The method of tuning up the planes in this model is especially to be recommended. From a post, placed at the center of the planes, wires are run to the corners which holds the frame perfectly taut. For the main frame, or backbone, a metal tube has been used which greatly adds to the appearance of the model. This aluminium tubing may be bought cheaply and will serve admirably for this purpose.
The most popular of all models, among amateur aëronauts in America, at least, is the Wright machine (Plates [24]-[25]). The opinion is ventured that this is due more to the attractiveness of its lines and the pride we all take in its wonderful achievements, than to its actual flying ability as a model. The most perfect of these models will rarely fly more than a hundred feet. They will be found exceedingly difficult to weight and adjust so that they will maintain their course in a disturbed air current.
The planes of these models are usually made separate from the motor base. The shafts of the propellers, with the rubber motors and skids, are built up in a single piece. This plan has the advantage of making the planes adjustable so that they may move backward or forward as desired. The model leaves the ground from a base, much the same as the rail used by the large Wright machines. Some models are even started by the propulsion of a rubber band attached to the frame, which is pulled back and released, like the old-fashioned sling shot.
PLATE VIII.
An Effective Model with Wooden Wings.