Les; -- The German Type XXI submarine of 1944/45 introduced a
combination of streamlining, & powerful electric motors with a snorkel
fitted, which created a true battle submarine. However, the long and
narrow hulls proved unable to cope with the increased in power the
boat had and under certain sea conditions, control could be lost and
the sub would of sunk with the lost of her crew.
Manoeuvrability is very important in sub control systems enable the
boat to be "flown" three -dimensionally, like an aircaft.
The USS Nautilus (SSN 571), the first nuclear powered submarine with
the hull design base on the XXI, could not exceed 23 knots underwater.
In the 1950's there were two more revolutionary developments;
nuclear propulsion and the 'teardrop' hull. The latter was pioneered
by the diesel-electric powered USS Albacore, which with its teardrop
hull- (base on the airship shape), cruciform tail empennage and a single
propeller or screw. This achieved underwater speeds of approx 26 knots.
Second NOISE; A badly finished hull (e.g with poorly designed flood
openings to open sea)) had considererable drag as well as being
noisey. The German Navy knew about this in their U-boat construction,
especially in the development of the type XXI submarines.
Special hull paint can reduce friction, as can releasing polymers all
around the hull. The early class Soviet submarines were coated with a
compliant covering., which combines suction & boundary-layer pressure
equalistation. Some of these methods are now used on the majority
of Western submarine hulls.
Regards; Joe Brennan