Page:Aerial Flight - Volume 1 - Aerodynamics - Frederick Lanchester - 1906.djvu/402

Whence $\tan \gamma ={\frac {13.5}{41}}=.33$ or $\gamma =18{\frac {1}{4}}^{\circ }\sin \gamma =.313.$

Resistance in line of flight
	$=W\sin \gamma =.102\times .313$	$=.032\ {\mbox{lbs.}}$
Aerodynamic resistance
	$=W\ \beta ={\frac {.102}{20}}$	$=.005\ \ {\mbox{„}}$
		—————
∴ Skin resistance	.  .  .	$=.027$

or per sq. ft. $={\frac {.027}{.504}}=.0536$ (pounds) $=1.725$ poundals.

But the normal plane reaction,

$P=.7\times .078\times 32\times 32=55.8$ (poundals)

or

$\xi ={\frac {1.725}{55.8}}=.0309$

It was evident in the course of the above trial that sufficient velocity was not being given to the aerodone, that is to say, its projected velocity was less than its natural velocity and that the necessary velocity could not be given by hand throwing without sacrificing accuracy.^[1] A further series of trials made with a catapult launching device gave data as follows:—

Aerodone launched from 20 feet altitude.

	Distance. Ft.	Time. Secs.	Velocity. Ft./Sec.
1 2 3	66 62 68	1.8 1.8 1.8	36.6 33.2 37.8
4	Model collided with tree and damaged.
	3) 196		107.6
Mean	65	1.8	36

1. Any rotational movement imparted at the moment of projection is most detrimental to the gliding path.

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