how long could subs stay on patrol?

[lederhosen]

Salute

just a question. I'm playing a type VIIb. I'd like to know just how long could such a sub "Feed" its crew before being forced to return to port?

danke

[Shadowblade]

U-196

Under Kentrat's command she completed the longest patrol made by a submarine during World War II, leaving Kiel on 13 March 1943, and returning to Bordeaux on 23 October 1943, spending 225 days at sea. During that time she sailed all the way around the coast of South Africa and sank two British merchant ships in the Indian Ocean.
but U-196 was Type IXD2 U-boat so she could carry more supplies than your Type VIIB.

[Sailor Steve]

Food was rarely a problem. If a boat was lucky, torpedoes would run out long before supplies did. Without replenishing a Type VII boat was good for about 35 days, but once on station the boat could patrol at a slow speed and extend that by quite a bit. Later in the war there were supply ships available, but the real limiting factor was morale. Sooner or later crew efficiency is going to drop, especially in the cramped quarters of a German u-boat.

[lederhosen]

35 days hmmmm. It just took 23 days to get near Halifax (1/3 speed) perhaps moving faster would be more realistic.

danke for the answer

[Sailor Steve]

No. Faster will use more fuel, and you'll never make it home. Type VIIs weren't meant for voyages of that length. You can make it there and back, but time on station will be minimal.