18 WAVE RESISTANCE THEORY AND APPLICATION 
Comparison of Calculated.Wave Resistance with Residuary Resistance 
Derived from Experiments for Model 1846B and Model N43 
The Relation of the Quantity © tothe Resistance is as follows 
5 R = Resistance of Modelin Lbs. 
© =645.8 R/é5v? Where {6 = Displacement of Model in Lbs. 
v = Speed of Model in Ft./Sec. 
9 R = Resistance of Model in Kgs. 
©=78.08 R/873-v2 Where +6 = Displacement of Model in Kgs. 
v = Speed of Modelin Ms/Sec. 
©vw From Calculated Wave 
Resistance in Perfect Fluid 
Resistance Corrected for Effect 
of Viscosity on Wave-Making 
Vf | ZamN 
PRVAS Ss 
a a Ea | 
PURSE ENE AENGEea ew EIEALIS 
a ara | AS 
©pg From Ex: 
ADI 
VALS 
Particulars of Forms 
Equation of 1846 Bis 3-(I-f2)(I-§°)(1+0.257 
Equation of N43 is 3-(I-f 
Both Forms are Symmetrical Fore and Aftand 
the Bowand Stern Endings are Vertical Edges 
©vw From Calculated Wave 
Resistance in Perfect Fluid, | 
Scale of ©,,©Qwand ©yc for Model N43 
Length=16 Ft. Beam=!.5 Ft., Draft=.0 Ft.for Both Forms 
§ ) 2 8 24 
I-§)(1+0.252)+F°UI-F)(1-§7) 
Both Forms have Vertical Sides above the LWL. 
Le Gee ee 
Yh Body Plans of Forms 
Model 
1846B 
Block Coefficient = 0.462 
Prismatic Coefficient = 0.693 
Mid-Section Coefficient = 0.667 
1 Waterplane Coefficient = 0.693 
=z Angle of Entrance on LWL = 12.7° 
} 
Model 1846B 
Sections are Spaced at Intervals of 9.6 Ins. for Both Forms 
0.12 0.14 016 O18 020 022 0.24 026 028 030 032 034 0.36 038 040 042 044 046 048 0.50 052 0.54 0.56 058 0.60 
Fic. 6 
one time thought permissible. Recently Wigley 
and Lunde have worked with forms of fuller mid- 
section and Fig. 6 shows some of their results. 
The original fine form was altered by adding a 
bulge which widened the form amidships as indi- 
cated, and the resistance curves for the two models 
are shown. The comparison is made in a more 
striking manner in Fig. 7, which shows the differ- 
ence between the two models, with calculated and 
observed values. 
The models were tested in different tanks 
(Teddington and Trondheim) and the lack of 
agreement at very high speed is probably a depth 
effect due to the difference in depth of the two 
tanks. As the authors remark, the presence of a 
full mid-section, and therefore of a rather flat 
bottom, does not cause more discrepancies be- 
tween calculation and fact than occur with finer 
mid-sections. 
It is desirable to be able to calculate results for 
non-mathematical forms or for ordinary ship 
models. In essence the object is to replace the 
continuous distribution which represents the ship 
by a finite number of elements; these elements 
must be such that their super-position gives an 
approximation to the form of the model, and the 
elements must be of a simple character so that 
the necessary functions for each element can 
568 
