6. Good correlation with the quasi-steady predictions is attributed to the low 

 frequency of the nonuniform wake, and the use of measured mean pressures in the 

 quasi-steady procedure. The general underestimation by the quasi-steady technique 

 was similar to quasi-steady correlations with measured fluctuating blade loads by 



Bo swell and Jessup. ' 



7. Sharp increases in C , at the 0.9 radius of Propeller 4679 are attributed 

 to tip-vortex separation. 



8. Insufficient data were obtained to compute lift coefficients for 

 individual radii. 



9. Calculations of pressure distribution for measured sections showed large 

 deviations from those computed for the design shape, caused by local irregularities 

 on the surface. It is believed that in viscous flow, a more conventional pressure 

 distribution would occur. (See the Appendix) 



RECOMMENDATIONS 

 Work should be done in the near future to complete the effort that has been 

 described. Many of the unresolved questions should be resolved by performing the 

 following: 



1. The experimental results should be compared to the results of the latest 



35 

 propeller lifting surface theories, such as the theory of Kerwin and Lee. This 



will provide a more exact representation of the mean and unsteady pressure distribu- 

 tions than the methods used in this report. 



2. Water- tunnel tests should be conducted on Propellers 4679 and 4718. 

 Cavitation tests would verify the minimum-pressure areas on the blades. Thrust and 

 torque measurements could be used to correlate integrated pressures for the two 

 propellers. Finally, flow visualization techniques should be used to identify 

 possible areas of transition and separation over a range of Reynolds number. 



3. New gage mounting techniques should be developed that minimize the influence 

 of blade loading and maintain a smooth blade surface in the region of pressure 

 measurement on the blade. Also, a technique should be devised so that a greater 

 number of points along the blade chord could be measured. This would permit calcula- 

 tions of integrated load for thrust and torque correlations. 



43 



