In general, the loads consist of hydrodynamic , centrifugal and 

 gravitational components. However, in this paper, only the hydrodynamic 

 component of blade loading is presented. The results considering total 

 loads showed the same trends as results including only hydrodynamic 

 loads. Centrifugal and gravitational loads were measured to permit the 

 hydrodynamic loads to be determined by subtracting the centrifugal and 

 gravitational loads from the total experimental loads. The centrifugal 

 and gravitational loads were, of course, independent of hull pitching 

 and waves since all conditions were run at the same propeller rotational 

 speed, n. 



B. Centrifugal and Gravitational Loads 



Centrifugal and gravitational loads were determined from air-spin 

 experiments with each flexure over a range of rotational speed n. The 

 centrifugal load, which is a time-average load in a coordinate system 

 rotating with the propeller, should vary as n . The time-average experi- 

 mental data followed this trend. The gravitational load, which is a 

 first harmonic load in a coordinate system rotating with the propeller, 

 should be independent of n. The first harmonic experimental data 

 followed this trend. 



The centrifugal and gravitational loads measured during these ex- 

 periments agreed with the values determined by Boswell et al. (1981) , 

 and the gravitational loads agreed with values deduced from the weights 

 of the blades and associated flexures. Therefore, these results will 

 not be repeated here. 



C. Influence of Dynamometer Boat 



The results of the wake survey with and without the downstream body 

 (dynamometer boat) are presented in Figure 6. Harmonic analysis of 

 these data indicate that the downstream body had only a small effect on 

 the circumferential and radial variations in the flow and only a small 

 effect on the harmonic content of the flow. However, they also indicate 

 that the downstream body reduced the volume mean speed through the pro- 

 peller disk by approximately 12 percent. These results are, of course, 

 without the propeller in place. 



The change in effective speed through the propeller due to the 

 downstream body was deduced from thrust and torque identities between 

 the mean thrust and torque measured during the blade loading experi- 

 ments and mean thrust and torque measured during the corresponding self- 

 propulsion model-experiment. These results, which include the effect of 

 the propeller, indicate that the downstream body reduced the effective 

 speed through the propeller disk by approximately 14 percent; i.e., 

 without the body, (1-w.j.) = 1.00 and (1-wq) = 1.00, whereas, with the 

 body, (1-Wrj,) = 0.86 and (1-Wq) = 0.85. This agrees quite closely with 

 the 12 percent reduction in the volume mean speed due to the downstream 

 body as deduced from the wake surveys at the corresponding conditions. 



10 



