The following formulae have been devised for ascertaining the resistance and power of skimming boats, but they are equally applicable to the floats of hydroaeroplanes, although all the examples given are of skimming boats varying from 15 to 40ft. in length, the speeds varying from just under 28 knots up to 51 knots.

It will, of course, be readily understood that the power required to overcome the resistance caused by the floats on hydro-aeroplanes is the Effective Horse-Power (E.H.P.), which is the same as the H.P. required to tow a float at any given speed; while the formula for resistance only, does not take speed into account except in the ratio of

In the examples given it will be seen that the variation between R, as ascertained from actual trials by the ordinary ship formula of and r, ascertained by the formula of is very small; while, in the case of E.H.P. from trials, and e.h.p. by the formula the maximum error—if we except example No. 5 (which is a known bad boat)— is only 0.39%, and the average for the other nine examples is 0.2% for the A type, .04% for B, and 0% for C type.