where v is the kinematic viscosity of water. Here the Reynolds number R 



n 



is obtained by assuming that the freshwater temperature in two towing 

 tanks was 20 C. Table 4 results are given in Figure 1; the wave resistance 

 computed for the extra large tank was taken to be the same as for unbounded 

 water, already mentioned. In Figure 1, hull wave resistance in the large 

 tank is very close to that for the extra large tank. Thus, the blockage 

 effect on wave resistance is very small for the large tank. Also, the 

 main difference in the total resistance coefficients C measured in the 

 small and large towing tanks is due primarily to the difference in the 

 model wave resistance computed for the two tanks. 



Table 4 gives the speed corrections computed from Equation (9') along 



with the corrected values of (C -C ) . The corrected value of (C -C ) is 



„ 1 w 1 w 



given by (C -C ) (U/ (U+Au) ) . Table 5 gives the frictional resistance co- 



T w A 

 efficients C and C , computed from International Towing Tank Conference 

 r r 



(ITTC) (1957) and American Towing Tank Conference (ATTC) friction formulas. 

 In the present study, it is assumed that the total resistance less the 

 computed theoretical wave resistance is approximately equal to the 



frictional resistance, since the ship hull is thin and smooth, i.e., form 



13 

 drag is assumed to be negligibly small. If we make use of the Granville 



correlation of partial form factor k^ with hull-fineness parameter 

 F = C., /(B/L) (2T/L) for the Wigley parabolic model with F T = 0.5, we find 

 that le = 0.04; i.e., form drag is estimated to be only 4 percent of the 

 frictional drag and a still lower percentage of the total drag. Accord- 

 ingly, speed correction Equation (9') was applied to the resistance 



A 



component C = C - C to correct for blockage effect. Results given in 

 r 1 W 



Table 5 are shown in Figure 2. In Figure 2, the corrected values of 



(C -C ) are lower than the values of C„ given by ITTC and ATTC friction 

 I w r 



formulations, indicating negative hull form drag, which is not acceptable. 

 In other words, if the form drag coefficient and other corrections had 

 been added to the values of ITTC and ATTC friction coefficients, this 

 discrepancy would be even larger. The discrepancy seems to have been 

 caused by computed values of the wave resistance being too large. 



11 



