RELATIVE RESISTANCES OF SOME MODELS WITH BLOCK COEFFI- 

 CIENT CONSTANT AND OTHER COEFFICIENTS VARIED. 



By Naval Constructor D. W. Taylor, U. S. N., Vice-President. 



[Read at the twenty-first general meeting of the Society of Naval Architects and Marine Engineers, held in 



New York, December 11 and 12, 1913.] 



Five years ago I had the honor to read before the Society a paper dealing with 

 an experimental investigation into the influence of midship-section shape upon the 

 resistance of vessels. That paper, as was carefully pointed out in it, dealt with shape 

 and not with area, the sectional area curves for the various shapes being identical. 

 Moreover, it dealt with deep water conditions only. 



In this paper I propose to give the results of some investigations where both 

 shape and area vary, and where experiments were made in very shallow as well as 

 deep water. 



When in designing a new vessel we have fixed on dimensions and displacement, 

 the block coefficient is fixed. But with a given block coefficient we may adopt a 

 fine midship section coefficient with resulting full ends, or a full midship section 

 coefficient with resulting fine ends. 



In the experiments I am dealing with there were 20 models tested. There 

 were 4 groups of 5 each, the block coefficients of the group being .56, .60, .64 and 

 .68. The midship section coefficients used with each block coefficient were .86, 

 .92, .98, 1.04 and 1. 10. All models were 20 feet long, of 2,500 pounds displace- 

 ment in fresh water, and 40 cubic feet immersed volume. 



Table I below gives the dimensions and coefficients for the 20 models. The 

 ratio of breadth to draught was 2.4 in every case, and, of course, with variations 

 of block coefficient there were corresponding slight changes in actual breadth and 

 draught as indicated in Table I. 



Table I. 



Dimensions and coefficients of model 20 feet long and 40 cubic feet submerged 

 volume, or 2,500 pounds displacement in fresh zvater. 



