48 



with decreasing F, the optimum t values decrease. Also on the aver- 

 age, it depends upon the prismatic and the degree of polynomial used. While 

 very fine ships yield good results with t = up to P = 0.26, full vessels 

 need t values > for P = 0.1 8 and even less. Thus, charts indicating optimum 

 t values must be prepared for several prismatics. 



Absolute values of calculated resistance are not reliable when deal- 

 ing with high <l> and low P; the results due to pronounced interference effects 

 are especially doubtful. Investigations on a pathological model, Pigure 23— 

 whose resistance qualities according to theory should be outstanding — are very 

 significant: Experiments did not agree at all with these deductions up to a 

 Proude number of about 0.19, but for some higher values of P the form was 

 efficient. 



Thus, even a qualitative agreement is sometimes lacking when dealing 

 with full hulls run at speeds below P about 0.19 Por this reason, a more 

 thorough discussion of this most important subject is delayed until further 

 research has been done.^*^ » ®* '^"^ This work must be based on a closer investi- 

 gation of the different parts of wave phenomena constituting the total wave 

 resistance, of wave patterns due to bow and stern angles and curved parts and 

 the mutual interference of the systems mentioned. No decisive attempt has 

 been made so far because of the lack of appropriate tabulated functions. 



The following suggestion may be of interest to the experimentor when 

 Investigating the frictional resistance of plates. It is well known that, at 

 some Proude numbers, wave phenomena can influence results. Havelock has given 

 a first estimate on the subject ^^ using a parabolic form and an arbitrary val- 

 ue for the width of the plate. A closer approximation is reached when the 



/. 



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<l> = 0.68 















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\ \VJ/M,6,8).=2 







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V 

















(3,4,6)t=2— -A\\\ 

 (3,4,6)1 = 1^ — \\\v 





/ 



^ 



>^ 











^^ 



^ 



k 



^ 









V 



^ 



A 



// 





1 







^ 



Y 















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^ 



y 























13 14 15 16 17 IB 19 20 21 



Figure 28a 



