from a number of existing designs are also given in Table 42, and these show that the Series 

 60 parent of 0.70 C g is somewhat U in character to start with, and the V-shaped variation is 

 rather moderate in this respect. The models were fitted with rudder and propeller as previ- 

 ously described, the propeller used being TMB 3376 which was that fitted to the original 

 0.70 Cg parent, Model 4221. It represented a 24-ft diameter propeller on a 600-ft ship (or 

 16 ft on a 400-ft ship). 



Models 4280, 4281, and 4282 were all made in wood, had an LBP of 20 ft, and a smooth 

 enamel finish. They were fitted with a trip wire and run in the deep-water basin which is 51 ft 

 wide and 22 ft deep. Experiments were made at the designed displacement, level trim, and at 

 60 percent of this displacement and a trim of 2.5 percent of LBP by the stern. 



The results of the resistance and propulsion tests are given in Tables 43 through 48 

 and in Figures 62 through 70. 



The change in resistance, as shown in Figures 62 to 65, is relatively small, the U- 

 form being about 2 percent worse and the V-form 3 percent better than the parent at the Troost 

 service speed. On the other hand, the U-form favors the propulsive efficiency, but this is 

 insufficient to offset the superior resistance qualities of the V-stern, with the result that the 

 latter has the lower dhp at all speeds in the full-load condition and over most of the speed 

 range at 60-percent displacement. These changes in resistance and propulsive efficiency 

 are of the kind to be expected as a result of such stern changes. In general, the increase in 

 propulsive efficiency with the U-stern is usually sufficient to more than offset the increase 

 in resistance, although not in this particular case. 



Velocity surveys were also made in the plane of the propeller for all five of the Series 

 60 parents and for th© two stern variations of the 0.70 C g model. This plane was normal to 

 the propeller shaft (and to the baseline) and 0.94 percent of the LBP forward of the after 

 perpendicular. In accordance with the stern arrangement shown in Figure 36, it passed 

 through the 0.7 radius point on the propeller generating line. The velocities were measured 

 at 59 points over a rectangular grid extending from the baseline to a waterline at 0.85 of the 

 load draft and on the port side from the centerline out to a vertical line distant 0.425 of the 

 load draft. They were all made at the full-load displacement and at the Troost^service speed, 

 using a 5-hole spherical pitot tube^ which determines the velocity vector at each point (for 

 details, see Reference 64). 



These velocities have been analysed into longitudinal (fore and aft), vertical and 

 horizontal components V , V ^, and F^, defined as shown in Figure 71. These can be con- 

 verted to Taylor wake fractions 



and 



1 - 



V 



100 



1 - 



V 



100 



1 - 



V 



100 



XI-3 







