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U-Boat Snorkels

Discussion in 'German U-Boats' started by Jim, Nov 20, 2007.

  1. Jim

    Jim Active Member

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    The snorkel, so long associated with U-boats, was not originally a Ger-man idea. Rather, it was of Dutch origin, having been first experimentally fitted on the Royal Netherlands Navy Submarine 0 21, in February 1940. The fitting was an arrangement of two periscopic pipes, one with a floating ball valve (to preclude the accidental intake of water) was the air inlet, and the second was a valve less exhaust pipe. The end result was the first practical apparatus that allowed a U-boat’s diesels, its main method of propulsion, to be run underwater. With the capture of Holland in May 1940, all records of this research fell into German hands. Yet, rather than capitalize upon this stroke of luck, the Kriegsmarine made no efforts to employ or improve the snorkel until the disastrous spring of 1943 brought the idea back into favour. But now, in-stead of having a new boat designed from the outset for schnorkel use, the Germans was forced to modify existing type VII and IX boats. While these boats did yeoman service between 1943 and 1945, they were constantly limited by the fact that they were not designed for continuous submerged operation.

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    U-889, a type IXC, shows its snorkel in retracted position in the deck casing. The venting that led to the engine compartment was permanently attached to the tower, only the snorkel tube itself raising or lowering. (Below)

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    The snorkel with which these boats were fitted was a simple modification of the original Dutch design. The twin periscopic pipes were replaced by a single rigid tube which could, by pivoting at its base, be lowered into a well in the deck casing. Still fitted with a floating ball cut-off valve, the schnorkel proved tricky in operation. In all but the calmest seas, a seaman had to be detailed to watch the schnorkel, as the diesels had to be shut off whenever the valve closed. If they were allowed to run on for even a few seconds the diesels could pull oxygen out of the boat’s atmosphere, causing severe decompression with accompanying ear and breathing difficulties. Burst eardrums were common. The only way to maintain more or less continuous operation of the diesels was to limit a snorkelling U-boat to 6 kts (1 ½ kts slower than it could move on its electric drive). While the snorkel did offer a U-boat great immunity from Allied anti-submarine measures, it turned it into a slow, blind, largely ineffective weapon. Here the loss of three years of planning and development was most keenly felt. Only now were plans being made to produce, in the type XXI, a boat that could truly take advantage of the potential of the schnorkel. The type XXI went to sea with a vastly improved schnorkel. Being periscopic, it was designed to run higher above the water, giving much better rough water performance. Also, it was fitted with an automatic shut-off switch that solved the diesel run-on problem. With these improvements, the type XXI could schnorkel safely at 12 kts.

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    In the hands of dockyard workers, U-235 (type VIIC) completes modifications. The schnorkel is seen here in raised position. Being out of commission for refit, the U-boat has been re-assigned to the1.U-Flottille, a training unit, and carries that unit’s diablo Insignia on its radar housing. (Below)

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