Size, Type, and Speed of Ships in the Future 29 
The 2-percent saving in shaft horsepower obtainable with the cigar-shaped Hogner 
afterbody provided with a complete ring nozzle propeller system becomes highly significant 
when considered together with the 25-percent reduction in propeller diameter obtainable 
over that of a conventional screw, and with the notably reduced vibration and cavitation 
characteristics (Fig. 3 and Table 1). 
Table 1 
Effect of Afterbody Shape on Propulsion 
Results of Resistance and Self-Propulsion Tests on a Model of a 39,000-ton Tanker 
(loaded condition; speed, 16 knots; 16,900 shp) 
Total 
Number resistance 
Afterbody of (percentages— 
Blades afterbody 
I = 100) 
DHP Propul- 
(percentages— sive 
afterbody Coe ffi- 
I = 100) cient 
I (moderately U-shaped) 
II (extremely V-shaped) 
Ill (extremely U-shaped) 
IV (Hogner form) 
V (III + nozzle) 
VII (twin screw) 
VIII (Hogner + nozzle) 
Fig. 3. Tanker model with cigar-shaped afterbody and a propeller 
operating in a nozzle ring 
Another question which must be asked for supertankers is: At which speeds and dead- 
weight tonnages does the submarine tanker, through application of nuclear propulsion, become 
competitive with its surface counterpart. 
646551 O—62——4 
