Sec. 57.6 



TOTAL RESISTANCE OF BODY OR SHIP 



317 



for this calculation are Cp = 0.62, B/H = 2.808, 

 and A/(0.010L)' = 123.6, while the value of 

 r„ at the designed speed selected for this example 

 is 0.908. The displacement is assumed here as 

 16,400 tons. 



The linear interpolations described in Sec. 56.3 

 are set down in Table 57. b, adapted from D. W. 

 Taylor's Table VIII-A [S and P, 1943, p. 63]. 

 The characteristic spots drawn in Figs. 56. A and 

 56. B indicate the coordinates of Cp = 0.62 and 

 A/(0.010L)' = 123.6 for both B/H ratios (of 

 2.25 and 3.75, respectively), at a T, of 0.90. The 

 values of Rr/^ for this speed-length quotient 

 were picked from the originals of Figs. 56. A and 

 56. B, drawn to a scale over three times larger 

 than that of the reproductions. Normally it is 

 not possible to determine the values of Rr/A by 

 inspection to more than three significant figures, 

 indicated in Table 57.b for a T, of 0.95. 



The derived value of /? a/A of 4.014 lb per ton 

 is then multiplied by the displacement A of 



16,400 t to give the predicted total /?« of 65,829 

 lb, for the "phantom" TSS ship having the 

 proportions of the ABC ship. 



No allowance is made here for the difference 

 between the salt-water specific gravity of 1.024 

 for all the TSS data and the specific gravity of 

 1.027 for the ABC ship. 



The method of predicting the residuary resist- 

 ance of a given ship from the "phantom" Taylor 

 Standard Series ship having the same proportions 

 is rather different when the Gertler reworked 

 TSS data are employed. These are described in 

 Sec. 56.5 and a sample calculation is set down in 

 Table 57. c. The ship selected is the fifth approxi- 

 mation of the ABC design, hsted in Table 66.e of 

 Sec. 66.11, but the basic data now involve the 

 wetted surface S and the fatness ratio F/(0.10L)^. 

 These are, from Table 66.e, 44,759 ft' and 4.327, 

 respectively. The mass density p is taken as 

 1.9905 slugs per ft^ for "standard" salt water. 



The volumetric coefficient F/L^ of the Gertler 



TABLE 57.b — Residuaby-Resistance Prediction for ABC Ship From Taylor's Rr/A Contours 



The characteristics and proportions listed correspond to those of the fifth approximation in Table 66.e in Sec. 66.11. 

 The method illustrated here is adapted from D. W. Taylor's Table VIII-A in his "The Speed and Power of Ships," 

 1943, page 63. One particular pair of contours required here is reproduced in Figs. 56. A and 56. B. 

 The calculation is made for one speed only, 20.5 kt (the designed speed), at a T, value of 0.908. 



Length on waterline, L = 510 ft 

 Displacement, A = 16,400 t 



A 



(0.0 lOL)' 



B/H - 2.25 

 1.50 



123.6 



Cp = 0.62 



Beam, fi = 73 ft 



Draft, ff = 26 ft 



B 



H 



= 2. 



2.808 - 2.25 

 1.50 



= 0.372 



Difference 2.043 



0.90 0.908 - 0.900 



= 0.16 



0.05 0.05 



Rr/A at a T, of 0.908 = 3.687 + 0.327 = 4.014 lb 

 Rr = 4.014(16,400) = 65,829 lb. 



2.043(0.16) = 0.327 



