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66
THE SUBMARINE TORPEDO BOAT
7
of VL =
1.25 the resistance runs up so rapidly as to put
such speeds out of the question. Submerged, the resistance
curves are free of humps, but are much higher than those
for the floating condition all the way up to a speed of
V
—— = 1.3 when they are nearly coincident.
The resistance
submerged for a speed length ratio of VL = 1. is approxi-
mately 1.15 times the resistance of the surface condition.
In the past it has been common practice to limit the beam
length ratio to about one to ten, but the results of these
experiments show conclusively that to attain the higher
speeds for which we are at present striving, with an eco-
nomical outlay of power, it will be necessary to increase
this ratio to one to twelve, or even greater. This depar-
ture would also tend to give greater steadiness in a sea
way. Constructively this greater beam length ratio need
not cause any worriment. It will be found a very simple
matter to add the necessary longitudinal stiffness by
strengthening the keel and longitudinals, and it is probable
that quite a saving in the hull weights may be made, due
to the decrease in diameter. The metracentric height and
stability could also be increased by a better distribution of
weights.
A still further increase in stability and some decrease
in resistance can be effected by carrying the fullest part
of the ship well forward of the midship section, that is, in
other words, giving it a heavy fore-body with a full en-
trance and a long fine run. This design would of course
carry forward the center of buoyancy. The advantage
of this upon the controllability when submerged and under