ye 
OF FORM OF SHIPS UPON THEIR RESISTANCE: 65 
a large percentage of the residuary resistance, but the resistance due to 
wetted surface would vary but slightly and would be for the usual run of the 
ships somewhere in the neighborhood of 5.2 pounds per ton, making the 
total resistance per ton for a speed length coefficient of 0.8 in the neighbor- 
hood of 7 pounds. We have then a possible gain of 0.4 pounds in 7 pounds, 
or nearly 6 per cent., but bearing in mind that the fine ended features which 
_ helped us as regards residuary resistance would slightly increase the wetted 
surface we may say that by adopting the best combination of water-line 
and sectional area curves we may perhaps gain 5 per cent. over the worst 
likely combination. The conclusions to be drawn from Fig. 42 for the same 
speed and the longitudinal coefficient of 0.64 are practically the same, the 
possible gain being, if anything, somewhat greater. 
Consider now Figs. 41 and 47, Plates 20 and 26, for the speed length coefti- 
cient of 1.1. In Fig. 47, Plate 26, the practicable variation in residuary 
resistance is roughly two pounds, the difference between 8 and 10 pounds, 
orsome 25 percent. At this speed the average frictional resistance in pounds 
per ton for vessels of the type of the models of Series No. 29 would be also 
about 10 pounds to the ton so the gain indicated would be of the order of 
IO per cent. 
From Fig. 47, Plate 26, for the longitudinal coefficient of 0.64 we would 
draw the same conclusion, but it should be pointed out that in practice 
we would seldom, or never, force a vessel-with a displacement length coeffi- 
cient of 129, as shown for Series Nos. 29 and 32, in Table I, up to a speed 
for which the speed length coefficient is 1.1. We would adopt different 
proportions and dimensions so that the residuary resistance would assume 
relatively less importance. For ‘the high speed case also then we would 
hardly be warranted in saying that the possible gain in passing from the 
worst likely combinations of water-line and sectional area curves to the best 
would be more than some 5 per cent. 
It will be found upon studying the contours and lines that while for 
medium speed work lines of the type of Figs. 4 and 7, Plates 4 and 6, are 
excellent, there is material decrease in resistance for high speeds by approach- 
ing the type of Figs. 3 and 6, Plates 4 and 5, or the bulbous bow. 
It is true that Figs. 3 and 6, Plates 4 and 5, indicate also a bulbous 
stern but we have found that the main factor here is the fine water-line 
aft for high speed and not the full ended curve of sectional areas. 
As pointed out already the models of Series Nos. 29 and 32 arenot of high 
speed type and I would not feel warranted in drawing any conclusions from — 
them as to high speed work did not results so far from high speed models 
appear to agree with those from Series Nos. 29 and 32. I think, then, there 
