458 Capt. J. Hollingworth on a 



Before proceeding to a numerical case it will be advisable 

 to investigate the effect on the result if the wind-pressure on 

 the weight is sufficient to cause it to hang not truly vertical. 



Let the angle at which it hangs be # . 



Equation II. then gives 



(ds\ T 



U/, = o ~ Kv 2 cos 2 0,-w sin O ' 



butT = Wcos# ; 



W cos 0q _ 1 1 +p sin O 



Kr 2 cos 2 O - tv sin 6 ~~ G 2 ' cos 2 6 —p sin # ' 



. n . ds W cos da 1 4- V sin 6 



.'. Ill thlS Case a = — r~~. ^ r-rv. 



dU 1 -f jP sin Dn cos- V —p sin u 



Owing to the irregular shape of the weight it is impossible 

 to calculate the angle O . Experiments with a cylindrical 

 lead weight about 2 inches long and 1J inches diameter 

 weighing If lb. have shown that the angle is 10° to 12°, at 

 a speed of 60 m.p.h. ; with a stream-line weight it would 

 probably be less. The determination of this angle for any 

 given weight is best done in a wind-tunnel, though as one 

 was not available it was actually obtained by hanging the 

 weight by a lead about 2 feet long from the upper plane o£ 

 an aeroplane and observing and photographing the result 

 from the observer's seat. Eddies and vibration tend to make 

 this method inaccurate. 



Returning to equation XI. there is another very im- 

 portant point to be noted, which is that the expression for 

 ds/cW does not contain s explicitly. 



This means that for a given W and p the aerial form is 

 independent of the actual length of aerial employed, so that 

 it is merely necessary to construct one curve for each value 

 of W and p and v, and having got this curve the actual 

 shape of an aerial of any length can be found by measuring 

 up from the bottom point of the curve a length equal to the 

 length of aerial employed. 



A series of numerical determinations will now be given. 

 Two kinds of aerial wire have been considered with two 

 different weights and two air-speeds, making eight cases 

 in all. 



The two wires A and B have constants p respectively : 



For wire A, K='0000129 

 „ „ B, K = -0000043. 



