428 



tively larger extension on the painted propeller 

 than on the polished propeller. Obviously it is 

 the changes in this aftpart cavitation that cause 

 the changes in propeller characteristics. 



Full scale tests have also been conducted with 

 this propeller design. In Figure 5 the full scale 

 cavitation pattern corresponding to the model tests 

 is shown. This cavitation pattern is very similar 

 to that of the painted model propeller. 



In the author's Figure 29 bubble cavitation 

 is shown very similar to that in tests with the 

 painted propeller at SSPA. The author concludes 



that this cavitation is inconsistent. Based on our 

 experience with full scale cavitation, however, I 

 think that the pattern shown could very well repre- 

 sent a full-scale case. 



The influence of nuclei content and blade 

 roughness on the cavitation pattern is found to be 

 rather similar in the tests at NSMB and SSPA. The 

 main difference is the necessary amount of rough- 

 ness. This difference is possibly due to the dif- 

 ference in Reynolds number, about 10 times as high 

 in the tests at SSPA as in those carried out at 

 NSMB. 



0.8 



T 

 IOKq 



0.6 



0.4 



0.2 



QL- 



QVQs 

 0.4 Painted 



0.8 - 1.0 1.2 

 ADVANCE RATIO 



1.4 J 1.6 



FIGURE 3. 



1.1 a/a =0.4 polished blade." 



FIGURE 1. Propeller characteristics at 6 - u.6. 



FIGURE 4. J = 1.1 a/a 



0.4 painted blade. 



FIGURE 2. 



1.1 a/a 



0.2 polished blade. 



FIGURE 5. 



1.1 5 = 0.65 full scale. 



