21 



Within any one diagram *" = const. L/B varies as V^ since, from the 

 condition, v is constant it follows that <zi(B/L)^ is constant; the beam of the 

 finer forms is larger than that of the fuller ones. 



The curves V = const." on the two diagrams k and 5 are connected 

 by the relation L/B = *-'^^ 



Although the equation for the hulls is so restricted that it can 

 represent useful ship lines only within a limited range of prisraatics and 

 Proude numbers, and the representation of results is somewhat unfortunate, due 

 to the use of ^, the two diagrams give a useful general idea of resistance 

 properties of ship forms over a wide region of prismatics and speeds. 



A weak point of the investigation lies, however, in the deductions 

 made from Figure 6, reproduced from the paper, which represents a comparison 

 of the wave resistance calculated for the restricted mathematical lines and 

 the residual resistance derived from Taylor's Standard Series. (For some un- 

 known reason, another resistance coefficient 



is used.) Thus the comparison is based on the equality of prismatics alone 

 neglecting the difference between the actual shape or equations of the two 

 series. This coarse approach yields a reasonable approximation within the 

 region of the first and (in a lesser degree) of the second hump; it can, how- 

 ever, become inconsistent for lower Proud e values. Checks Indicate that in 

 this region the calculated resistance of some of Sretensky's ill-chosen forms 

 can be twice or three times as high as the calculated resistance of Taylor's 

 models. Hence some important differences stated are essentially due to dif- 

 ferences in forms used and have nothing to do with discrepancies between the- 

 ory' and facts. 



Glers and Sretensky state: "The use of wave resistance coefficients 

 calculated by theory appears to be inadmissible for drawing quantitative con- 

 clusions in the present state of knowledge." Especially, according to the 

 author, these coefficients cannot be used for obtaining relations dependent 

 upon the variation of one parameter while others are kept constant. 



If these final conclusions — ^arrived at by one of the greatest- author- 

 ities on the subject^were true, the theory of ship wave resistance would be 

 useless from a point of view of naval architecture. We have shown that the 

 conclusions are based on an erroneous procedure and cannot be upheld. More 

 reliable, If less general, comparisons between calculated and measured resist- 

 ances are due to Wlgley and to an extent to the author, who came to much more 

 favorable results. 



