78 



8. The influence on wave resistance of the vertical distribution of the 

 displacement (within a dimensionless shape) can be Investigated with less ef- 

 fort . It leads to the simple rule that the displacement should be arranged 



as deep as possible. Thus, U-shaped sections, from the viewpoint of wave re- 

 sistance, are as a rule suf)erior to V-shaped sections; possible exceptions are 

 mentioned. 



9. The experimental check of theoretical results at low speed-length 

 ratios is seriously hampered by the principle on which Froude's method is 

 based as well as by experimental inconsistencies. No reasonable experimental 

 analysis of the wave resistance of full slow hulls can be made without an 

 additional research on viscous-form drag, especially viscous-pressure drag. 

 However, keeping in mind these restrictions, the following conclusions can be 

 drawn from comparisons between calculated wave resistance and measured re- 

 sidual resistance values 10 to 16. 



10. The trends of the calculated and measured resistance curves gener- 

 ally agree well, but the interference effects (humps and especially hollows) 

 are exaggerated by the theory. 



11. The absolute values of the curves agree reasonably within certain 

 ranges of L/B and <p\ for low L/B ratios and high prismatic coefficients at 

 small Froude numbers the discrepancies are large. Michell's theory clearly 

 overestimates the effects of increasing beam; unfortunately experimental data 

 dealing with the dependence of resistance upon beam and draft are astonish- 

 ingly scarce, so that neither theory nor experiment yields accurate data on 

 resistance effects due to the most elementary changes of a hull. 



12. The relative merits of different forms as established by theory are 

 in many cases supported by experiments. However, theoretical deductions are 

 liable to lead to exaggerations and even to errors when they are based on 

 interference effects which can be affected by viscosity. Theory may fail com- 

 pletely when phenomena are discussed which depend essentially upon viscosity, 

 such as the relative efficiencies of fore and afterbodies, unless some addi- 

 tional corrections are introduced. 



13- The close coincidence between theoretical and experimental deduc- 

 tions on the effect of small changes in shape is stressed as a fact of primary 

 Importance. 



14. Although experiments generally corroborate theoretical results as to 

 the Influence of the vertical distribution of displacement, there are excep- 

 tions where V-sections in the forebody are superior to U-sections at high 

 Froude numbers contrary to calculated results. The actual optimum t values 



