Page:Aerial Flight - Volume 1 - Aerodynamics - Frederick Lanchester - 1906.djvu/395

confined to the determination of $\xi ;$ the instrument may be used quite generally as a comparator of the resistance of planes of various shapes or of different solid forms.

§ 243. Method of Added Surface.—Mica Aerodone. Series C., No. 1, Fig. 154.

Weight (after adjustment of ballast) = .60 gram.

Aerofoil, elliptical, 4${\tfrac {1}{2}}$ in. $\times {\tfrac {3}{4}}$ in.; actual area	=	2.65	sq. in.
Tail plane, area	=	.50	„   „
Back-bone, surface ÷ 2 = equivalent area	=	.48	„   „
Fin area, (without added surface)	=	.14	„   „
		——
Total area, (without added surface)	=	3.77	„   „
		——
Added surface		1.06	„   „

Sept., 1905. Trial of model without added surface.

Launched from 7 ft. Altitude.

	Distance. Ft.	Time.[1] Secs.	Velocity. Ft./Secs.
1 2 3 4 5 6 7	37 40 34 35 37 32 36	3.2 3.2 3.2 3.0 3.2 2.8 3.2	11.55 12.50 10.62 11.66 11.55 11.43 11.25
Total	251	21.8	80.56
Mean	35.8	3.11	11.50

Whence, $\gamma ={\tfrac {7}{35.8}}=$ .1955 or resistance in line of flight = .1955 $\times$ .60 = .1172 grams.

1. Taken by stop watch.

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