Propeller -Induced Appendage Forces 



S. .40 



X .10 

 3 .08 



0.157 O- 



Fig. 51 - Blade -rate axial appendage forces as a 

 function of the advance ratio and the spacing for a 

 four-bladed propeller and a symmetrical appendage 



theory by the parameter /3 = 0.05, corresponding to the spacing ratio S/D = 0.02, 

 while /3 = 0.10 -» S/D = 0.063 and (i = 0.20 -^ S/D = 0.107, where this correspond- 

 ence was evaluated at J = 0.6. The relation between the theoretical and experi- 

 mental values can then be examined in terms of these particular distances, lead- 

 ing to the conclusion of good qualitative agreement. 



A significant consequence of the theory is the dependence of the magnitude of 

 a particular force component on the product of the number of blades N and the 

 particular harmonic term m, so that the product Nm determines the nature of the 

 force. The equivalence of the second- harmonic amplitude for a two-bladed pro- 

 peller with the blade-rate term for a four-bladed propeller, as illustrated in 

 Figs. 45 and 46, demonstrates this feature of the theory. This same effect 

 occurs in the interpretation of the behavior of a single-bladed propeller, where 

 examination of appropriate harmonics of the propeller shaft rate provides data 

 for a multibladed propeller. The present theory was evaluated for conditions 

 wherein the thrust coefficient given in Fig. 39 was constant for all the different 



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