Studies in Wave Resistance. 585 
D. W. Taylor,* referring to a series of experiments with models of the 
same displacement and of varying, midship section coefficients, states that 
the models with full midship-section coefficients drive a little easier up to 
V—,/L = 1:1 to 1:2, and the models with fine coefficients have a shade the 
best of it at higher speeds. Again, the same author analyses the results of 
another set of experiments thus: “Fig. 67 shows curves of residuary 
resistance for five pairs of 400-foot ships, each pair having the same dis- 
placement and derived from the same parent lines, but differing in midship 
section area or longitudinal coefficient. It is seen that at 21 knots No. 10 
with 0:64 longitudinal coefficient has 23 times the residuary resistance of 
its mate No. 9 with 0:56 longitudinal coefficient. But at 24} knots they 
have the same resistance. Again, No. 4 of 0°64 coefficient at 21 knots has 
nearly twice the residuary resistance of No. 3 of 0:56 coefficient. At 
253 knots they have the same residuary resistance, and at higher speeds 
No. 4 has the best of it, having but 0°9 of the residuary resistance of No. 3 
at 35 knots. 
“These results, which are thoroughly typical, are susceptible of a very 
simple qualitative explanation. A small longitudinal coefficient means large 
area of midship-section and fine ends. A large longitudinal coefficient 
means small area of midship-section and full ends.” e 
It will be noticed that the experimental curves referred to in this extract 
intersect in the neighbourhood of the point V/,/L = 1:2. The curves of 
fig. 2 also intersect near this point. The lines of the models A, Band C 
were chosen to be of suitable form, limited by the necessity for a simple 
mathematical expression which led to integrals that could be evaluated. It 
may be claimed that the curves so obtained agree with experimental data, 
and, further, that they repay detailed study, in that the variations in 
resistance are connected definitely with a precise variation in the form of 
the model. 
* D. W. Taylor, ‘Speed and Power of Ships,’ pp. 96 and 97. 
Hareison anv Sons, Ltd., Printers in Ordinary to His Majesty, St. Martin’s Lane, 
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