Hi Gentlemen,
…and how much water was in the regulating cells for the torpedoes at the beginning? (if no torpedo was used) does it carry water for the flooding of the tubes? or where the tubes already flooded?
Well, from my studies of this topic (as no descriptions or manuals are available) I think, that torpedo compensating tanks (
Torpedozelle) initially contained amount of water sufficient to flood tubes with torpedoes within them (that is about 370 litres per tube, that means that
Torpedozelle 1 - aft - contained 370 litres of total 2350 litres volume and
Torpedozelle 2 and 3 contained 740 litres of total 5750 litres each).
I think, that tubes were flooded from compensating tanks because in such case, the weight of boat did not change, and the trim changed only slightly.
When the torpedo was launched, the tube was fully flooded with overboard water (through the muzzle door). After closing the muzzle door, the tube was drained to the torpedo compensating tank (1680 litres of water).
Torpedozellen were also used as the aid to trim the boat, when some of the torpedoes were disposed.
And small interesting fact - aft torpedo compensating tank and one of forward compensating tanks could be used as storage tanks for wash water - they were fitted with piping to the wash water installation.
In middle period of war, forward tank was also used as fuel oil storage tank - to extend the operational range of the boat.
The U458 KTB says, that when the boat stayed in Saint Nazaire between first and second patrol (that means between 27 August - 1 October 1942), one forward torpedo compensating tank was modified to storage fuel. The additional 5,75 m
3 of fuel extended patrol by two days (at 10 knots, both diesels 275 RPM).
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Regards
Maciek