The eight new models of any one set were derived from the parents by a straightfor- 

 ward geometrical variation of beam and draft to give the required combinations of — and 77 



values. The lines of the parents for Cg values of 0.60, 0.75, and 0.80 are shown in Figures 

 12, 15, and 16 and those for the new parents of 0.65 and 0.70 C g are shown in Figures 39 

 and 40. Particulars of all 45 models are given in Tables 33 through 37. 



The models were made in wax, 20 ft LBP, as before, but the turbulence stimulation 

 was provided by a trip wire instead of studs; the 0.036-in. diameter wire was placed around 

 a station 5 percent of the length from the forward perpendicular. This change was made for 

 the reasons set out in Appendix A. The model results have been converted to apply to a ship 

 400 ft LBP, using the ATTC 1947 model-ship correlation line with an addition of + 0.0004 

 for ship correlation allowance. The ship figures are given in Apjiendix B as values of C j- 

 and (C) for a standard temperature of 59°F (15°C). 



For the propulsion experiments, the models were fitted with a rudder and keelpiece 

 and the experiments carried out as described in Chapter VIL The propeller diameter was in 

 every case 0.7 of the draft. The propellers for the parent models were specially made for 

 the Series 60 tests, and, as already described, were of the Troost B-type with four blades. 

 As the draft was varied in this geometrical series, so also the propeller diameter had to be 

 changed. To avoid making large numbers of new propellers, and since the principal objective 

 of the propulsion tests was to obtain systematic data on the components of propulsive 

 efficiency, such as wake and thrust-deduction fractions, stock model propellers were used 

 whenever possible. These were chosen to have rake, blade-area ratio, sections, and other 

 features as near to the Troost standard design as possible. Table 38 shows the propeller 

 particulars. 



The propulsion tests were run without bilge keels, and trip wires were used for 

 turbulence stimulation. They were carried out at a propeller loading corresponding to the 

 600-ft ship self-propulsion point with a ship correlation allowance of +0.0004. The data 

 extrapolated to apply to a ship 600 ft LBP are presented in detail in Appendix B. 



vm-2 



