34 



Figure 13 - Sectional Area Curves of Models Berlin 1337, 1370 

 Expressed by the Equations (2,3,'+; 0.56;1) (2,4,6; 0.56;1) 



Various attempts have been made, using Michell's integral, to per- 

 form wave-resistance calculations for "actual" ship forms, i.e., forms defined 

 graphically by means of the normal-lines plan. No advantage is gained by such 

 methods,* as it is easier to "mathematize" the ship form and then perform cal- 

 culations. This leads to an easier method of comparing forms and improving 

 their resistance properties, which in the present state of the theory is a 

 much more valuable achievement than the possibility of calculating the re- 

 sistance for an individual form represented graphically. 



To get an idea of what actually can be reached by application of 

 theory we refer to Figure 7 on page 24, discussed earlier, and to Figure 14 

 where the differences between the resistances of two models obtained from ex- 

 periment and theory are compared. The results are impressive. In the light 

 of these and other investigations it is impossible to question the practical 

 value of the present theory. 



3.3.2. Longitudinal Distribution of Displacement 



Outline of a General Procedure; A survey of the resistance proper- 

 ties of ship forms must be based upon sufficiently general equations; the 

 failure by using forms with a single arbitrary parameter has already been dis- 

 cussed. Basic families of ship lines studied earlier admit of sufficient var- 

 iations (see Figures 15 and 16). Although each set contains only two param- 

 eters <d , t , a third one can be introduced by immediately "mixing" two families 

 or by adding an appropriate polynomial. 



*Thls criticism does not apply to a method proposed by Guilloton. 



