SOARING MACHINES. 



219 



BA 



Vcrtoc. 



C . 



Race, . 



D. 



Guide . 



£ . 



Divide. 



/'. 



Kite surface 



M . 



Vertex. Nest. 



J '. 



Neck. 



N. 



Bead Air. 



S. 



Discharge. 



Fig. 10. 

 Fig. 10 shows the condition of 

 the air in the neighbourhood of the 

 soaring curve and the following 

 statements may help us to arrive at 

 the exact power developed : — 



1. The hook originates the vortex. 



2. The diameter of the vortex is determined by the radius of 

 the race. 



3. The velocity of rotation is something less than the velocity 

 of the wind or relative wind, and is maintained thereby. If the 

 wind is thirteen miles and the curve advances into the wind at 

 one mile, the relative wind is fourteen miles and the velocity of 

 rotation about 2,600 revolutions per minute. 



4. The air drawn in from the rear of the vortex rises in pressure 

 as the race contracts. 



5. The high pressure air in the race acts on the soaring machine 

 by thrust jon the vortex nest. 



6. The vortex cannot increase in diameter or burst because the 

 vacuum at the centre is of the exact tenuity that balances the 

 centrifugal force of the particles of air forming the vortex. 



7. If the head resistance of the soaring machine is decreased 

 by a lull in the wind, the air in the race expands leaving the 

 vortex slightly to leeward, that is practically increasing the radius 

 of the vortex nest, the vortex then increases in diameter and 



