CHAPTER XIV. 



WATER PERFORMANCE. 



The Condition for Getting Off the Water. When a Model 

 Test has been Made Particularly for the Machine. If the test re- 

 sults are quoted in knots, first convert them to miles per hour 

 by the formula 



V = 1-151 V 



where V is a speed in knots and V is the same speed in miles 

 per hour. 



If the results are given in the form of a table of values of F, 

 the water resistance of the machine in pounds for a series of 

 values of V, the speed in miles per hour, well and good. If, 

 however, the results are given in the form of a table of values^ 

 the water resistance of the model in pounds for a series of values 

 of v, the speed in miles per hour, we must first convert to F and 

 V by the formulae 



and 



where is the linear ratio of dimensions of the machine to the 



model. 



Now the minimum flying speed has been used in making the 

 model tests : let it be V x miles per hour and let the correspond- 

 ing horse-power on the machine performance curve be Pj. 



Now draw up a table in the following form, allowing for as 

 many horizontal lines of figures as test speeds are available : 



