Panel Discussion 



Fig. 5 - Pressure distribution on a blade section for 

 different cavitation numbers ""•"• 



as the average power increase in the case of head seas. In that case, the risk of 

 ssc will increase considerably. This type of cavitation has least risk of dam- 

 age due to the cavitation. The chance of psc will remain equal or decrease. 



Data for the behavior of the propeller in quartering seas are still lacking. 

 It might be expected from the data as represented in Fig. 3, that in quartering 

 seas, and as a consequence a power decrease, an increased risk of psc occurs. 

 As a rule, psc must be qualified as very unfavorable from a view point of cavi- 

 tation damage. 



Figure 7 illustrates clearly that propeller and rudder must be considered 

 as a closed system when solving maneuvering problems. The results shown 

 in Fig. 7 refer to a 65,000-t.d.w. tanker. This is a ship type with low SHP/ 

 displacement ratio. Starting from equal speed (2.60 m/sec) and equal rudder 

 angle (20°), the effect of an increase in rpm from 28.8 to 48 on the path of the 

 ship appears already to be considerable; the ship speed only increasing 

 slightly. 



1581 



