D ∝√W.
or in models of similar design the distances flown are proportional to the square roots of the weights. (Derived from data obtained from Clarke's flyers.)
For models from 1 oz. to 24-30 oz. the formula appears to hold very well. For heavier models it appears to give the heavier model rather too great a distance.
Since this was deduced a 1 oz. Clarke model of somewhat similar design but longer rubber motor has flown 750 ft. at least; it is true the design is not, strictly speaking, similar, but not too much reliance must be placed on the above. The record for a 1 oz. model to date is over 300 yards (with the wind, of course), say 750 ft. in calm air.
§ 16. Power and Speed.—The following formula, given by Mr. L. Blin Desbleds, between these is—
W/W0 = 3v0/4v + ¼(v/v0)3.
Where v0 = speed of minimum power
W0 = work done at speed v0.
W = work done at speed v.
Making v = 2v0, i.e. doubling the speed of minimum power, and substituting, we have finally
W = (23/8)W0
i.e. the speed of an aeroplane can be doubled by using a power 23/8 times as great as the original one. The "speed of minimum power" being the speed at which the aeroplane must travel for the minimum expenditure of power.