Sec. 56.6 



OBSERVED SHIP-RESISTANCE DATA 



305 



friction formulation. Unfortunately, the speed 

 range extended only from Froude numbers of 

 0.20 to 0.30, corresponding to T, values of 0.672 

 to 1.007. Takagi's F^ range was from 0.16 to 0.38. 



The thesis data thus derived are in the form of 

 contours of fatness ratio F/(0.10L)^ on a basis of 

 Cr and Cp for eight equidifferent values of Cp , 

 plotted on ten sheets for as many different F„'s. 

 The cross-contours of fatness ratio, when plotted 

 on Cr and F„ , for seven equidifferent values of 

 Cp , appear in Figs. 56. E through 56. K. When 

 thus presented they resemble those for the Gertler 

 reworking of the Taylor Standard Series described 

 in Sec. 56.5. The Desel-Collins data for Cp = 0.72 

 are omitted because this is much too large a Cp 

 value for easy driving of a chubby, fat form. 



Because of the unrelated forms and the rather 

 severe fairing necessary to achieve a regular 

 pattern of data it was not possible in this group 

 of models to indicate the humps and hollows 

 known to occur with change of speed and F^ . For 

 this and other reasons the contours are shown as 

 broken lines. Although lacking the reliability to 

 be expected from tests of a comprehensive 

 systematic series, these data nevertheless furnish 

 an indication of residual resistance to be expected 



Q20 QHI 0.22 Q23 Q24 025 Q26 Q27 028 023 030 



Fig. 56.1 Cr Data for Fat Ships, Cp = 0.66 



0.20 Q2I 0.22 025 OZ^^ O-Zt 0.26 027 023 029 030 



Fig. 56.J Cr Data foh Fat Ships, Cp = 0.68 



in a region where few systematic model tests 

 have been made. 



Among the latter are tests of six fat models, 

 expanded from the Taylor Standard Series, 

 having displacement-length quotients of 300 and 

 400 (fatness ratios of 10.49 and 13.98, respec- 

 tively), Cp values of 0.50, 0.60, and 0.70, and a 

 Bin ratio of 2.25. Test data for these six bare- 

 hull models are given in SNAME RD sheets 

 105 through 110 [ETT, Stevens, Rep. 279, Jan 

 1945]. Comparison of these latter data with the 

 Desel-Collins contours indicates considerably 

 lower — in some cases much lower — Cr values for 

 the Taylor forms. This is due partly to the excel- 

 lence of the TSS parent form and partly to the 

 omission of all appendages on the Taylor models 

 in the Stevens tests. 



No examples are given for Figs. 56. E through 

 56. K because they are used in much the same way 

 as the Gertler data in TMB Report 806. 



H. H. Hagan, in a brief article entitled "The 

 Powering of Ships" [SBSR, 7 Oct 1937, pp. 

 453-455] gives some information to serve as a 



