51 



the points on Figure 25. Assuming 

 the load to vary as the square of 

 the speed for these points, a good 

 fit is obtained by the parabola 



L = 3.57 Vp" [7] 



where L is the total load (applied 

 load plus the weight of the float) 

 in pounds and Vp is the speed deter- 

 mined by the horizontal tangent at 

 the hump in knots. Defining a non- 

 dimensional load-carrying or lift 

 coefficient Q by 



C, = 



2.85 



pVH' 















/ 











Displacement 

 Regime 







/ 





















L 



















i 



*• — Experimental 

 Points 













\ 





















t 



' L = 3.57Vp^ 













/ 



















i 





















/ 





















/ 







Planing 

 Regime 











1 









































1 



1 



















/ 



















/ 



/ 



















/ 



















where p is the mass density of the 

 fluid in slugs per cubic 

 foot, 

 V Is the speed in knots, 

 6 is the beam of the float in 

 feet , and 

 2.85 is the factor for convert- 

 ing the square of the veloc- 

 ity in knots to the square 



of the velocity in feet per second, ' 



the float will operate in the planing regime at all values of C^ ^ O.69. 



At speeds above the hump and for the scale of floats likely to be 

 designed on the basis of these data, the observed drag can be expressed by a 

 functional relationship of the type 



) 2 4 6 e 10 



Minimum Speed at which Planing Begins In knots 



Figure 25 - Definition of the 

 Displacement and Planing 

 Regimes for the TMB 

 Planing Float 



^D ~ Q)\Cl. yr j 



[9; 



Here the nondiraensional drag coefficient Q, is defined as 



D 



Cn 



2.85 T.2.2 



[10] 



where D is the drag of the float in pounds and the other variables are as de- 

 fined in the foregoing. 



Equation [9] is represented by the graphs of Figure 26, in which 

 values of C^ are plotted on a basis of Q at constant values of the parameter 



