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DESIGN OF THE SUBMARINE TORPEDO BOAT 65
speeds. The corresponding speed of the new ship would
be in the ratio,
V= 14
/400 *
\800/
15.7 knots
The percentage of the total weight of the submarine
which may be allotted to the power plant is constant with
the displacement and is usually about 33 per cent. Now
it may be seen that to gain this greater speed we have
doubled the displacement and consequently the weight
available for the power plant, but the horse power is more
than doubled, therefore requiring a greater proportion of
this available weight for oil engines than is given in the
smaller boat. This of course leaves a correspondingly less
proportion of the total available weight for electrical equip-
ment, and consequently a reduction of speed and cruising
radius when in a submerged condition.
Effect of Form upon Resistance
The resistance of the ship is greatly affected both by
the form of hull and by the ratio of length to the diameter.
In 1906 Mr. Mason S. Chace conducted a series of experi-
ments in the model basin at Washington, D. C., with a
number of models built on a scale of 1 inch to 1 foot, some
of them 12 feet long. The result of these experiments
V
showed that for the speed length ratio of — = .8 the re-
V
sistance curves are fair, but at a speed of
= i. the curve
shows a marked hump followed by a hollow, and at a speed