Uram and Numata 



seas up to about 15 knots. It is interesting that the analysis correctly infers 

 increased heave activity for the Large Bulb Ship. The figure indicates that re- 

 duced motions at high speed can be expected from all the unusual ship forms. 



For particular speed ranges, Mandel investigated the extent of each zone 

 area relative to the entire plot area for a given speed range. Figure 14 was so 

 constructed and gives a more direct comparison of the various ships although 

 the probability of a sea state occurrence is not included. It is seen that the 

 Semi -Submarine is superior in the narrow, low and high speed ranges of 0-20 

 knots and 40 to 50 knots as well as over the entire speed range, 0-50 knots. 



Motions data, mostly in regular seas, for these ships, the pertinent dimen- 

 sions of which are given in Tables 1, 2 and 3, have been obtained at the Davidson 

 Laboratory. Figure 15 shows results for regular 1.0 L head waves. Substantial 

 pitch reductions are realized with both the Large Bulb and Semi-Submerged 

 ships above 10 knots and heave reductions realized above 20 knots. The detun- 

 ing transfers the severe motions to the low speeds, as predicted. Figure 16 

 shows that in 2.0 L waves pitch reductions are obtained above 20 knots but both 

 surface type unusual ship forms encounter more severe heave motions over the 

 speed range than does the destroyer. Results in irregular seas for the Large 

 Bulb Ship, Figure 17, show pitch reductions at high speed but substantial heave 

 increases are incurred. 



SLENDER SHIP 



LARGE BULB 

 SHIP 



SEMI SUBMERGED 

 SHIP 



SEMI SUBMARINE 







W. 



40-50 KNOTS 







m 





CRITICAL ZONE 



: INTERMEDIATE ZONE 



D 



SUB OR SUPER CRITICAL ZONE 



Fig. 14 - Extent of operation zones relative to entire operation range, op- 

 eration range: State 2 to 7 head and following seas, to 50 knots 



732 



