Beaver (submarine)
 Side view of the beaver s with attached torpedoes
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The Biber was a small submarine of the German Navy during the Second World War . Originally he was to receive the designation U-Boot-Klasse XXVII c , which however was not assigned. Its use took place within the small combat units of the navy . The beavers were manufactured from May 1944 to November 1944, with 324 units being produced. Its construction was so flawed that most beaversfailed or had to abort the mission due to a technical defect during their operations. A total of 60 to 70% of the beaver drivers were killed. The successor models should be the Biber II and Biber III . The training of the driving personnel took place in the Reichswald near Lübeck - Schlutup ( code name Blaukoppel ) at the responsible training command 250.
Development history
Prototype development
The beaver was developed according to an idea of the corvette captain Hans Bartels after a copy of the British micro submarine Welman (W-46) got caught in a fishing net during an attack on a floating dock in the port of Bergen in Norway on November 21, 1943 had to show up. As soon as it appeared, it was discovered by a cruising German guard boat and hijacked undamaged. He was transferred to Germany for study and examination that same month. The construction manager of the beaver was Hermann Bunte , director of the Flender works in Lübeck . Before that, Bartels had paved the way for the building contract in initial negotiations on February 4 and 9, 1944. As early as February 23, 1944, the first draft of the Biber prototype , which was named Adam . The construction of the prototypes happened so quickly that Adam could be completed on March 15, 1944 and was ready for the first sea trials on March 29, 1944. The first attempt at diving resulted in Adam , barely being released from the tow ropes, immediately sinking to the bottom of the Lübeck Bay. However, the pilot was able to save himself and Adam was lifted. The first unsuccessful attempt at diving led to a few changes to the specifications of the beaver , which ultimately also convinced Karl Dönitz in subsequent demonstrations . He then ordered four more prototypes and placed the construction contract for an initial 300 boats.
Series production
The series production of the Biber , which amounted to 29,000 Reichsmarks each, began in May 1944 and took place at the Flender works in Lübeck and at the Italian Ansaldo shipyard . While the Flender works also fitted out their boats, the Italian makes were fitted out by the Klöckner-Humboldt-Deutz engine factory in Ulm after their hull was built . To distinguish the two manufacturers, the Flender-Werke boats were given the abbreviation LFW , the Italian KHD, on the inside of the tower .
Armament
Its primary armament consisted of two torpedoes of the type G7 with 53.3 cm in diameter, were mounted in the trough-shaped recesses at the sides of the hull in the running rails. In order to avoid damaging the torpedoes or triggering a detonation in the event of ground contact, the beaver had two massive runners on the underside of its hull, the height of which was slightly higher than that of the torpedoes. Alternatively, mines could be transported instead of torpedoes. The shooting was mostly carried out at a distance of up to 800 m, with the maximum range of the torpedoes of 18.5 knots being 4000 m.
Pressure hull
The actual pressure hull of the beaver consisted of 3 mm thick sheet steel and was divided by several transverse bulkheads. The hull was stabilized with L-shaped frames. The division from bow to stern was as follows: bow compartment - front diving cell - battery compartment - central drive compartment Otto engine and electric motor - stern compartment - rear diving cell. The pilot's headquarters and seat were extremely narrow, so that his head had to find space in the tower structure. In addition, a 1.5 m long periscope , snorkel, 4 compressed air bottles for blowing out the tank, batteries, bilge pump and an oxygen bottle for the pilot's breathing were housed in the control center. Navigation was carried out using a wrist compass and a small nautical chart. The tower and the superstructure were made of aluminum and bolted to the fuselage. The tower opening was only 52 cm above the waterline in the floating state, which meant that in heavy seas with the hatch open (oxygen supply) the beaver easily got overweight from penetrating water. In the worst case, this could lead to "drowning" in the language used at the time.
Range and depth
With around 225 liters of fuel, the range of the Biber overwater was 100 nautical miles (nm) at 6.5 knots or underwater with the electric motor 8.5 nm at 5.3 knots. There was also another 8 nm at a slow speed of 2.5 kn. The beaver also had no trim or control cells. If the boat wanted to dive, the diving cells had to be flooded, but if it were to rise, they had to be blown out. Therefore, no controlled travel in periscope depth was possible. To make matters worse, the beaver was only able to unleash its torpedoes by crossing the water, in order to then move away from the scene or to submerge during attacks.
Its diving depth, which was specified with a maximum of 20 meters, could, however, be exceeded by 50%, which meant that the beaver could dive up to 30 meters. The breathing air in the center was designed for 45 minutes. The breathing apparatus provided an additional 20 hours of oxygen via a so-called hunter's mask , as it was already used by air force pilots . If the pilot wanted to submerge, the following work steps were necessary, which had to be carried out within a few seconds:
- Vent and flood dive cell
- Put down elevator
- Switch off the petrol engine
- Start the electric motor
- Close exhaust and supply air valves
drive
The drive was inevitable, there were no diesel engines available, from a petrol engine from Adam Opel AG that had actually been designed for the Opel Blitz . Due to the dangerous exhaust gases, this was located behind a gas-tight partition directly behind the pilot's seat and developed 23.5 kW (32 HP) at 2400 rpm. The first beavers to be mass-produced suffered from leaky partition walls, which emitted carbon dioxide into the headquarters during long journeys and endangered the pilots seated there. The problem was solved by installing a suction device. The electric motor of the type GL 231 / 7.5 SSW ( Siemens-Schuckertwerke ) was located behind the gasoline engine, producing 9.8 kW (13.3 hp) at 1450 rpm for large and 960 rpm 3.1 kW (4, 25 HP) could mobilize a short trip. The reduction ratio on the shaft was 2.4: 1 and was carried out by means of a gear drive. Overall, however, the beaver's propulsion was too low.
K flotillas
By the end of the war, nine K flotillas had been equipped with beavers. These were given the names:
- K-Flotilla 261 (1st Beaver Flotilla)
- K-Flotilla 262 (2nd Beaver Flotilla)
- K-Flotilla 263 (3rd Beaver Flotilla)
- K-Flotilla 264 (4th Beaver Flotilla)
- K-Flotilla 265 (5th Beaver Flotilla)
- K-Flotilla 266 (6th Beaver Flotilla)
- K-Flotilla 267 (7th Beaver Flotilla)
- K-Flotilla 268 (8th Beaver Flotilla)
- K-Flotilla 269 (9th Beaver Flotilla)
The beaver was used, among other things, in naval warfare during Operation Overlord in the English Channel, in the North Sea and in the winter of 1944/45 off the Dutch coast for coastal defense. Another documented operation was undertaken in January / February 1945 from Emmerich on the Lower Rhine against the bridges over the Waal in Nijmegen , the Netherlands, which had already been captured by US associations . The company was unsuccessful. A beaver recovered from this mission in the Rhine is exhibited together with original photos of the assembly and the “launching” in the Rhine Museum in Emmerich .
Beaver II
Due to the worsening war situation from the perspective of the German Reich, a further development of the beaver was considered. This was created in the Flender works under the name Biber II . Designed as a 2-man mini submarine, this should allow a change of guard, the Biber II should get a stronger outer skin to achieve greater diving depths. At the same time, all of its main dimensions should be increased slightly. Until the end of the war, however, only sketches were made, which were confiscated by the Allies after the war.
Beaver III
The Biber III was designed as a long-range miniature submarine. Its development originated from the Eckernförde torpedo testing facility and from a working group in the development department of the small combat units command. The primary drive should therefore consist of a 48 kW Daimler-Benz diesel engine. The targeted range should be 1,000 nm at a speed of 8 kn. This should also act as a circulation motor for the underwater drive. For this purpose, a new type of oxygen generation system had to be developed. This was necessary because the exhaust gases of the engine were intercepted and cooled in circulation mode in order to then be enriched with oxygen carried in bottles and fed back to the engine as a combustion air mixture. The liquid oxygen system was manufactured by the Griesheim-Elektrogen company in the spring of 1945, but was destroyed again in April 1945 by the approaching allies. The associated mobile oxygen generation system was constructed from December 1944 at the Technical University of Stuttgart by the Research Institute for Automotive Engineering and Vehicle Engines Stuttgart (FKFS; head: Wunibald Kamm ) located there.
Two torpedoes of the new type K-Butt with Ingolin propulsion were used as armament on the side of the hull . On November 14, 1944, the TVA Eckernförde issued the first attempts at towing the reduced model. The original version should have a length of 11.82 m and a width of 2.5 meters. The tow attempts revealed various difficulties with regard to the bow and other parts such as the torpedo suspension. The Biber III project was no longer pursued in the spring of 1945 at the urging of the command of the small combat units against the will of the High Command of the Navy and was finally abandoned. The reasons given were:
- Insufficient experience with recirculation systems that would justify mass production
- too heavy and too big test engines, which also lost noticeable performance in the circulatory system
- other parallel developments that are more promising (e.g. dolphin, etc.)
literature
- Enrico Döring: The beaver drivers. Lone fighter in the submarine war. Verlagbuchhandlung Schnier, Husby 2008, ISBN 978-3-9811361-0-4 ( Edition Seegaard ).
- Lawrence Paterson: Arms of Despair. German combat swimmers and micro-submarines in World War II. 2nd Edition. Ullstein, Berlin 2009, ISBN 978-3-548-26887-3 ( Ullstein 26887 Maritim ).
Web links
- Enrico Döring: The beaver drivers .
Individual evidence
- ↑ Harald Fock: Naval small weapons. Manned torpedoes, small submarines, small speedboats, explosives yesterday - today - tomorrow. Nikol, Hamburg 1996, ISBN 3-930656-34-5 , pp. 67-70.