Second—Area of the supporting surface required.
Third—Amount of power that will be necessary to secure the desired speed and lifting capacity.
Fourth—Exact dimensions of the main framework and of the auxiliary parts.
Fifth—Size, speed and character of the propeller.
In deciding upon these it will be well to take into consideration the experience of expert aviators regarding these features as given elsewhere. (See Chapter X.)
Estimating the Weights Involved.
In fixing upon the probable approximate weight in advance of construction much, of course, must be assumed. This means that it will be a matter of advance estimating. If a two-passenger machine is to be built we will start by assuming the maximum combined weight of the two people to be 350 pounds. Most of the professional aviators are lighter than this. Taking the medium between the weights of the Curtiss and Wright machines we have a net average of 850 pounds for the framework, motor, propeller, etc. This, with the two passengers, amounts to 1,190 pounds. As the machines quoted are in successful operation it will be reasonable to assume that this will be a safe basis to operate on.
What the Novice Must Avoid.
This does not mean, however, that it will be safe to follow these weights exactly in construction, but that they will serve merely as a basis to start from. Because an expert can turn out a machine, thoroughly equipped, of 850 pounds weight, it does not follow that a novice can do the same thing. The expert's work is the result of years of experience, and he has learned how to construct frames and motor plants of the utmost lightness and strength.
It will be safer for the novice to assume that he can not duplicate the work of such men as Wright and Curtiss without adding materially to the gross weight of the framework and equipment minus passengers.