A failed breakthrough
U-Boot series XXIX as reconstructed by H. I. Sutton.
It is still difficult to find information about the XXIX series submarines. All links eventually lead to the website of the American naval expert H. I. Sutton and his article from October 7, 2017. Most likely, this is explained by the fact that the Germans did not have time to implement the project "in iron", and of the drawings, only the plans of the XXIX-H variant have been preserved. That is why it is usually used to reconstruct the possible appearance of U-boots of this series (if the very concept of a series can be applied to a concept that was not actually implemented).
By the end of the war, the German "sevens" began to suffer increasing losses from the Allied anti-submarine defense, which had reached the level of an exact science. That is why the projects of "electric robots" of the XXI and XXIII series, boats with a Walter turbine of the XXVI series and other exotic naval wares appeared. The most revolutionary was the XXI series, which had one fundamental drawback - the price. Replacing it with cheaper "babies" of the XXIII series did not work: the displacement (and with it seaworthiness) was too small, and these boats carried few torpedoes. In general, they are suitable for inland seas, but not for ocean-going ones! And not only the Germans, but no one else managed to build reliable serial submarines with a Walter turbine, and the operation of submarines on concentrated hydrogen peroxide was too expensive.
The "Type XXIX" submarine project appeared as a cheap replacement for the XXI project. At the same time, despite the desire to reduce the cost of production and operation, the submarines of this project were an independent type, which had their own, unique features. Nine concepts of the hull of these boats were developed, whose displacement varied from 681 to 1035 tons, and it was the shape of the hull that was the highlight of the project.
It is not known whether this scheme of invisibility from active sonar signals would have worked...
It had a faceted shape. Why? Well, according to the calculations of the German designers, such a shape was supposed to reflect active sonar signals away from the source of the signals. In fact, this is the same principle as the faceted fuselage of the first "stealth", the F-117 fighter-bombers.
Why didn't such a solution become the norm after the war? Perhaps because the XXIX series submarines were never built, and post-war shipbuilding engineers had little information about this rather exotic project (of which, moreover, little remained). Or maybe because covering the light hull of the submarines with a thick rubber coating solved this problem better than using a faceted hull (which most likely did not have the best hydrodynamics). Or maybe because today the main role in detecting a submarine is played by much better passive sonars than during the war...
The submarines of the XXIX-N series were to have the following performance characteristics: length - 52 meters, width - 6,4 meters, draft - 4,7 meters, speed - 13 knots on the surface, 15,5 knots submerged, cruising range - 9000 miles with diesel engines at a speed of 10 knots, 120 miles with electric motors at a speed of 6 knots. Power plant - 1 diesel with a capacity of 580 hp, 1 electric motor with a capacity of 1400 hp, 1 low-noise electric motor "sneaking" with a capacity of 70 hp. The crew of the boat is 27 people. Armament - 6 bow torpedo tubes with a caliber of 533 mm, a supply of torpedoes - 12 pcs. The submarine had a standard snorkel, did not have torpedo tubes in the stern and artillery armament. There was a project to equip the XXIX series submarines with a Walter engine. With a hydrogen peroxide turbine, such a boat, according to calculations, could move underwater at a speed of up to 23 knots.
The boat was controlled by retractable horizontal rudders located above the torpedo tubes and tandem aft vertical rudders with the surface of the aft horizontal rudder located between them. The boat was designed to have one propeller with four blades. But the electronics on the submarine, for the mid-40s of the last century, were very advanced! A FuMO-61 radar and a directional antenna were installed on the wheelhouse. A passive GHG sonar, installed at the bottom of the bow of the hull, was intended to search for underwater targets.
How dangerous would the XXIX series submarines have been if they had been built? It is worth recalling that the small XXIII series submarines managed to achieve certain successes in the last days of the war: they sank four Allied transports without suffering any losses, which was an excellent result for the spring of 1945, when the U-Boot's first trip to sea was often its last. And the XXIX project, unlike the "babies", had 12 torpedoes on board, not two...
Nevertheless, neither these submarines nor even more exotic projects with Walter turbines had a chance to change the course of the war. By the time the "electric robots" of all series went to sea, the war was already completely lost by the Third Reich, and the sinking of another hundred or two transports could not change this fact. But another problem arose: at the end of the war, Germany was catastrophically short of trained crews. One can argue until one drops about the personality of Alexander Marinesko, his attack on the "Wilhelm Gustloff" and how many submarine crews went to the bottom along with this ship. But the fact is that the Reich, living out its last days, no longer had any extra submariners.
There were also problems with submarine bases: Brest, Lorient, La Rochelle and Saint-Nazaire were lost, as were the bases on the Baltic coast. Kiel was constantly bombed from the very beginning of the war, as a result of which the presence of submarines there was unsafe (the submarine U-4708 was sunk right in the bunker by an artificial tsunami caused by a large bomb hitting the harbor), the main base on the North Sea - Heligoland, was abandoned back in 1944, the bunkers in Bremen were not completed, Hamburg and Trondheim remained, functioning until the end of the war, but Hamburg was a construction and repair site, and Trondheim could be based for no more than 16 submarines (there was also a bunker in Bergen, but it was destroyed by the British in 1944 with 5-ton Tallboy bombs).
In general, theoretically, according to Dönitz's calculations, submarine warfare could have helped Germany win in 1939-40, forcing England to sign a compromise peace. But in 1945, this was no longer science fiction, no matter how incredible the submarines German engineers managed to design and build...
German Type 206 U-boats - Possible Descendants of the XXIX Series
P.S. The project of the XXIX series submarines itself may have had a continuation in the form of post-war German submarines of Project 206, built between 1962 and 1968. Two of them are still in service - in the Colombian Navy.
Information