van Manen, Oosterveld and Witte 



and twin-screw installations. In this case of high-powered tankers, the ducted 

 propeller is, according to the experience of the N.S.M.B., superior in propul- 

 sive efficiency compared to all other propellers. 



First, the considerations will be given which have led to the choice of the 

 shape of afterbody and propulsor of the tanker discussed in this paper. Then, 

 the results of resistance and self -propulsion model tests will be presented for 

 each of the conventional and the suggested versions of the tanker. 



Effect of Afterbody on Propulsion 



Investigations into the effect of the afterbody shape on propulsion of a 

 39,000-ton deadweight tanker model carried out at the N.S.M.B. were reported 

 in Refs. 1 and 4. The following variations in afterbody were studied (Fig. 4). 



AFTERBODIES I 



APP 



20 FPP 



AFTERBODY M 



APP 



20 FPP 



Fig. 4 - Body plan and propeller arrangement 

 of afterbodies I, II, III and IV 



• Model I, having an afterbody with moderately U-shaped sections and a 

 rudder shoe. 



242 



