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Type-XXIX-H stealth U-boat - Covert Shores

Type-XXIX-H stealth U-boat design, 1944
The unbuilt Type-XXIX-H U-Boat design was intended to replace the ubiquitous Type-VIIC U-Boat family. Over 700 VIIs were built and they formed the backbone of the Kriegsmarine throughout the war, but by 1945 they were increasingly dated. So a new mass-service design for the North Atlantic was considered.
Type-XXIX-H stealth U-boat - Covert Shores

Germany had a number of other advanced submarine programs but the famous Type-XXI 'Elektroboote' was too expensive and the advanced Type-XXVI relied on difficult to obtain chemicals to propel it (see ‘Influences’ section below) so the Type-XXIX was conceived as a relatively modest design, albeit incorporating the latest thinking.

Type-XXIX-H stealth U-boat - Covert Shores
Render of 3d model of Type-XXIX-H by CiTrus90

The Type-XXIX concept (Roman numerals for Type-29) was a series of 9 hull concepts. These ranged from 681 tons up to 1,035 tons and had between six and twelve torpedo tubes. Only plans for the -H model seem to have survived the war, and these are the basis of this article.
Type-XXIX-H stealth U-boat - Covert Shores

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Original artwork. CLICK for high-resolution image.

The Type-XXIX-H was the first submarine to incorporate stealthy shaping into the design. Even today only one or two of the latest designs hint at this. The faceted sides and angled sail were similar to the F-117 stealth fighter but instead of deflecting radar waves, it was intended to deflect active sonar pings from enemy warships.
Type-XXIX-H stealth U-boat - Covert Shores
How effective it would have been is difficult to say, and similar forms were not adopted in production submarines in the postwar years although this may have been through lack of awareness, or the shift to passive sonar (against which this has no impact) as the main means of detecting submarines.

Displacement: 715 tons
Length: 52 m
Beam: 6.4 m
Draft: 4.7 m
Speed: 13 knots surfaced, 15.5knots submerged
Operating depth: TBC
Range: 9,000 nm snorkelling at 10 knots, 120 nm submerged on batteries at 6 knots
Propulsion: 1 x 580 hp diesel engine, 1 x 580 hp deisel generator, 1 x 1400 hp electric motor and 1 x 70 hp silent 'creep' engine
Crew: 27
Armament: 6 x 533mm (21") torpedo tubes with a total of 12 torpedoes

The Type-XXIX-H built on previous designs, primarily the Type-XX1 U-boat ('Elektroboote') which is rightly considered the most advanced submarine of World War Two. Up to this point submarines had operated mostly on the surface, especially during long transits. The ‘Elekroboote’ used its snorkel (a Dutch invention!) to remain substantially submerged even when running on its diesel engines – the snorkel provided air for the engines. Another advancement was that all the torpedo tubes were in the bow, and the deck guns used for attacking merchant vessels were removed. This reflected operational lessons and the realities of the Allies’ dominant anti-submarine capabilities.
Type-XXIX-H stealth U-boat - Covert Shores
Pictures from WW2 Weapons

The similarly advanced Type-XXIII coastal U-boats were more numerous than the larger Type-XXI and achieved a good degree of operational success in the final months of the war, scoring five vessels sunk by just six fully operational boats. These were much smaller than the Type-XXIX-H design, with the main comparative limitation being that they only carried two torpedoes versus the XXIX-H’s twelve.
Type-XXIX-H stealth U-boat - Covert Shores

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Some earlier Type-VII U-boats were also fitted with a snorkel which folded into the forward deck casing, and had their deck guns removed, making them much more modern in operational terms but still a relatively dated core design:
Type-XXIX-H stealth U-boat - Covert Shores

German Engineers were also working on a wholly new form of submarine propulsion which promised very high underwater speeds. Instead of using batteries and an electric motor to power the Type-XVII U-boat, they used decomposing hydrogen-peroxide to produce steam, which in turn drove a turbine and drove the propeller. This process did not require a fresh air supply so the motor could be run while the submarine was submerged and is known today as Air-Independent Propulsion (AIP). The man behind this ingenious propulsion system was Professor Hellmuth Walter who first patented the basic idea of AIP in 1925. Gradually his ideas were taken seriously and he was able to build an experimental submarine called V-80 in 1939. This was capable of an incredible 23 knots submerged (some sources say 28 knots) compared to the typical 6-8 knots of regular submarines. The outbreak of war slowed development but eventually an operationally capable boat was produced, the Type- XVII u-boat. However, this revolutionary form of propulsion was never adopted operationally.
Type-XXIX-H stealth U-boat - Covert Shores
Type-XVII u-boat.

Although we cannot be sure, the Type-XXIX-H may have had an influence on the postwar Type-206 submarine which shared many features.
Type-XXIX-H stealth U-boat - Covert Shores

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