66 



EXPERIMENTS IN AERODYNAMICS 

 Table XIII. 



This table shows that for an inclination of 2° the velocity of flight which 

 suffices for soaring is 20.0 meters per second, and that the work expended per 

 minute to support the plane (weighing oOO grammes) is 24 kilogrammeters, or 174 

 foot-pounds. The last two columns contain the weight with planes of like form 

 that one horse-power will drive through the air at velocity V. At 2° this is 95 

 kilogrammes, or 209 pounds. This, strictly speaking, holds good only for a system 

 of planes whose weight, inclusive of any actual motor or other attached weight, is 

 500 grammes per square foot of inclined plane surface, and which is made up of 

 30 X 4.8 inch planes. The experiments with the Plane-Dropper show that in 

 horizontal flight at attainable speeds, a system of such planes can be made by 

 placing one above the other at a distance of about 4 inches without any sensible 

 diminution of relative efficiency. Whether these relations of jiower, area, weight, 

 and speed, experimentally established for small planes, will hold good in the 

 same ratios for indefinitely large ones, I am not prepared to say ; but from all 

 the circumstances of experiment, I can entertain no doubt that they do so hold, 

 far enough to afford entire assurance that we can thus transport (with fuel for a 

 considerable journey) weights many times greater than that of a man. 



The preceding investigation, which results in an expression for the varying 

 amounts of work done by an elementary aerodrome driven at the various soaring- 

 speeds corresponding to the various angles given, has been derived for the case in 

 which the direction of propulsion of the aerostat is horizontal and in which its 

 plane makes an angle a with the horizon. In the case of an actual aerodrome, 

 however, it will very probably be found advantageous to propel it in the line of 

 its plane at such an angle (in practice a very small angle) that the resultant 

 forward motion due to this elevation and to the simultaneous action of gravity 

 will be exactly horizontal. If in this case its horizontal velocity be represented 

 by F, the work done per unit of time will be expressed by the product of the 



