Sec. 45.12 



FRICTION-RESISTANCE CALCULATIONS 



107 



where L is now the waterline length and the 

 conversion from A to F or V is based upon the 

 volume density of salt water previously mentioned. 

 Supplementing this conversion, a further revision 

 of the contours provides new values of Cs which 

 are somewhat more realistic, especially as every 

 ship has to have plating and most of them carry 

 rudders and other simple appendages. The result 

 is a minor increase of about 0.03 over Taylor's 

 revised values of 1943. The new plots are based 

 largely on data taken from SNAME RD sheets 1 

 through 100, covering modern vessels of many 

 sizes and types and relatively normal form. 



Fig. 45.G gives the new contours of Cs , plotted 

 on Cx and Bx/Hx . As the wetted-surface coeffi- 

 cients for the great majority of ships fall in a small 



area bounded by values of Bx/Hx from 2.0 to 

 3.5 and Cx from 0.9 to 1.05, expanded contours of 

 this area are shown to a consideralily larger scale 

 in Fig. 45.H. A similar plot by M. L. Acevedo 

 [TABLAS, 1943, opp. p. 128] gives values about 

 4 per cent lower than those in Figs. 45.G and 45.H. 

 The new Cs values have been checked repeatedly 

 since their preparation with all available new 

 data, and the agreement has been found to be 

 within limits of engineering accuracy. The new 

 contours are certainly adequate for use in the 

 early stages of a preliminary design. 



However, the Cs contours of Figs. 45.G and 

 45. H are to be used with caution for vessels of 

 abnormal form, such as those of shallow draft, 

 those with broad, flat sterns, with excessive 



'2.0 2.2 2.4 2.6 2.8 , 3.0 3.2 3.4 3.'. 



Beam-Draft Ratio B^/Hy 



Fig. 45.H Enlarged Plot of 0-Diml Wetted-Subfacb Coefficient Cs for Usual Ship Ranges 



