79 



are much lower than following from theory or Taylor's experiments. Thus the 



R V 

 universal validity of Taylor's ^, t.-p;^ charts (Reference 42) must be 



questioned. 



15. The omission of the actual model attitude in the theory causes er- 

 rors at high Froude numbers. 



^6. The application of Michell's theory to ships with a flat bottom, al- 

 though contrary to the conditions for which the integral is valid, still 

 yields useful results . There are theoretical and experimental indications 

 that the concept of dimensionless shape may be overstrained when it is applied 

 to larger values of B/L or B/H. 



17. Shallow-water effects can be investigated by a formula due to Sreten- 

 sky. The basic parameters are a Froude number F, = v/Vgti and the ratio of 

 depth of water to model length h/L; the ratio H/h is less characteristic as 

 long as it is not close to unity. 



18. A further integral valid for the wave resistance of ships moving in 

 a rectangular canal yields information on the permissible model sizes for dif- 

 ferent towing basins. Earlier data based only on the ratio of the cross sec- 

 tion of the models to the cross section of the basins are generally insuffic- 

 ient. Correction factors can be derived for converting model results to full 

 size; besides F, and h/L, the ratios of model length to basin width, L/b, and 

 of basin depth to basin width are characteristic parameters. 



19- The simultaneous treatment of the ship and the propeller leads to 

 important results, on the interaction between the hull and the propeller, in- 

 cluding wave phenomena . 



20. The resistance of wholly submerged bodies, especially bodies of rev- 

 olution, when running close to the surface can be treated on similar lines to 

 those of ships . 



21 . A short synopsis of methods is given which have been proposed by 

 different authors with the intention of improving Michell's theory of wave 

 resistance. The direction of these aims is given by the serious restrictions 

 of Michell's theory: 



a. Assumption of a frictionless liquid. 



b. Assumption of a wedgelike form. 



