Manoeuvrability and Propulsion of Very large Tankers 



A method used frequently for expressing the characteristics of a propeller 

 type is the relationship between Bp, 8, and Vp for optimum propeller diameter. 

 The design coefficient B^ and the speed ratio ^ are defined as 



and 



s = 



ND 



where n is the number of revolutions per minute, the power P is in horsepower, 

 the speed of advance v^ is in knots and the screw diameter D is in feet. The 

 optimum relationship between B , S, and r]^ is given in Fig. 6 for the Ka 3-65, 

 Ka 4-70, and Ka 5-75 screw series in nozzle No. 19a and for the B 4-70 screw 

 series. At the top of the figure the ranges of Bp -values typical for different 

 ship types are indicated. The lightly -loaded screws of fast ships are at the 

 left-hand side, while the heavily loaded propellers of towing vessels are at the 

 right. 



SINGLE SCREW 





TANKERS 



CARGO SHIPS 



0.70 



COASTERS 



TRAWLERS 



TUGS 



Ka 3-65 SCREW SERIES IN NOZZLE 



Ka4-70 N0|9< 



Ka5-75 



B 4-70 



60 70 80 90 100 120 140 160 



Fig. 6 - Comparison of the Ka-screw series 

 in nozzle No. 19A and B4-70 screw series 



245 



