How much shipping did the U-boats have to sink?

How many days in the North Atlantic is Snorkelling possible. I am guessing during the winter its not going to be possible.


Much depends on what type of schnorkel is used, as the Germans coppied the ones from the Dutch, with a seal to prevent water entering through it in waves.
 
Much depends on what type of schnorkel is used, as the Germans coppied the ones from the Dutch, with a seal to prevent water entering through it in waves.

Problem with the snort mast dipping below a wave is you still have two big diesels sucking the subs air.

Must resist temptation to make joke about submariners getting a Seal stuck on their periscope.
 
Problem with the snort mast dipping below a wave is you still have two big diesels sucking the subs air.

Must resist temptation to make joke about submariners getting a Seal stuck on their periscope.

Or even worse, a sealion.
What if, instead of sucking air out of the crew compartment, the engines used a compressed air tank? That way, snorkeling is bearable for the crew. Maybe not a solution for stormy weather, but if the storm is that bad then ASW aircraft might be grounded, so the U-boat can run on the surface.

The other problem is that snorkels couldn't be run above 6 knots because they might break off. This can just be fixed by reinforcing the snorkel. Sure, it will take a few design changes, but that's what engineers are for.

This way, boats can travel shallow at full speed, and switch to electric motors to go deep. As an added bonus, the KM might design a real underwater sub using the snorkel, instead of the primarily surface ships with some dive capabilities of OTL.
 
In the North Atlantic in the winter the U-boats faced a really unpleasant set of options. When the sea states get high, which is quite often, you can't use the snorkel (compressed air for the diesels not really practical as a mechanism to store the air, open valves when snorkel blocked, then recompress air is bulky and complex). If you run on the surface you get battered around severely and potentially a lot of ice. The usual U-boat procedure in that sort of crap conditions was to go deep enough to avoid the worst of the wave effects at low speed to preserve battery and come up only as necessary for air and recharge until conditions were conducive to surface running.

Making a sub with the Albacore design does improve underwater performance, but you lose some surface running stability and lose deck guns both anti-surface and anti-aircraft. I'm not sure this trade off makes sense in the WWII environment and the mission of the U-boats.
 

Deleted member 1487

In the North Atlantic in the winter the U-boats faced a really unpleasant set of options. When the sea states get high, which is quite often, you can't use the snorkel (compressed air for the diesels not really practical as a mechanism to store the air, open valves when snorkel blocked, then recompress air is bulky and complex). If you run on the surface you get battered around severely and potentially a lot of ice. The usual U-boat procedure in that sort of crap conditions was to go deep enough to avoid the worst of the wave effects at low speed to preserve battery and come up only as necessary for air and recharge until conditions were conducive to surface running.

Making a sub with the Albacore design does improve underwater performance, but you lose some surface running stability and lose deck guns both anti-surface and anti-aircraft. I'm not sure this trade off makes sense in the WWII environment and the mission of the U-boats.
By mid-1942 the deck gun and AAA guns are effectively useless on the surface and impede underwater performance.
 
By mid-1942 the deck gun and AAA guns are effectively useless on the surface and impede underwater performance.

Actually the deck guns made very little difference to performance. The RN tried a dissapearing gun, then stopped bothering as the improvement was tiny.
The biggest issue wasnt underwater performance, which was rubbish anyway, it was diving speed.
The problem was, modifying the casing for less resistance for more speed increased the diving time a lot.
 
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