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Originally Posted by Albrecht Von Hesse
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Originally Posted by NipplesTheCat
Why do the WWI era subs use 2 shafts with 2 screws instead of a single screw on a single shaft like a modern sub? It seems to me that one larger screw would push a lot harder than those 2 little ones. Was is an issue with the screw breaching the water while the sub was running on the surface?
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Going out on a limb here, as I'm hypothesising:
WWII-era boats were, effectively, surface vessels designed to be able to submerge. As such their design was affected by that paradigm. Multiple screws provide redundancy in case of damage or failure, and for the diesels it enabled recharging batteries and still having propulsion.
Modern submarines are designed, keel-out, as a submerged vessel that, due to necessity, periodically has to come to the surface. And its design reflects that (like having planes on the conning tower rather than the bow). It's designed to maximize thrust and minimize drag, which I think a single-screw design helps. Plus having a single screw cuts in half noise production from cavitation (I understand that military marine screws require a LOT of design and testing to keep cavitation to the strictest minimum).
As I said, I'm only conjecturing here. |
Darn good conjecture! U-boat. Essentially a boat that goes under for short period of time. I makes a U, submerge down go forward suface up...U. Therefore, U-boat. A true submarine is just that, made to be under the water and surface once in a while. Yes, two shafts, one to charge when the clutch is engaged to the generators and one to propel the boat. The schnorkel design created a true German SUBMARINE because it did not have to surface until food or fuel was consumed and drained.