By considering the longitudinal distribution of thrust deduction (body 

 only) shown in Figure 21, it may be concluded that virtually all of the 

 interaction force develops on the last 20 percent of the body. Within this 

 region the effect of rake is manifested as a change in propeller induced 

 velocities. The total axial induced velocity on the afterbody is shown in 

 Figure 22. The separate lifting line and lifting surface contributions are 

 displayed in Figure 23, showing corrections for skew and rake to the essen- 

 tial difference. 



The effect of blade thickness is to decelerate the flow ahead of the 

 propeller and hence, reduce the interaction force. In the present example, 

 this effect is more pronounced even for the least raked propeller (4487) 

 because of the relative voturne of each blade compared to the loading. For 

 propellers of equal blade volume, the influence of thickness would diminish 

 with increasing rake. Such is not the case here because, for increased rake, 

 more material is required for equal strength. Thus propeller 4489, while 

 raked the most, also has the largest thickness contribution because of 

 blade volume (for example, it is approximately twice the volume of propeller 

 4487). 



CONCLUSIONS AND RECOMMENDATIONS 

 An improved theory and computer-aided numerical analysis have been 

 developed for predicting the added resistance (thrust deduction) arising 

 from the propeller-hull interaction. The theory is formulated in terms of 

 the diffracted potential flow about the hull in the presence of the 

 propeller-induced velocity field. The propeller representation is derived 

 from lifting-surface theory which includes the effects of blade thickness, 

 skew, rake, and chordwise load distribution. It is shown that these effects 

 may be regarded as corrections to the moderately- loaded lifting-line (sink 

 disk) approximation. 



Important features of the analysis and comparisons with experimental 

 results are illustrated by application to several stern propeller-appended 

 body-of -revolution configurations. Based on these sample calculations, the 

 following conclusions are drawn: 



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