The VIIC Type U-boot

The bridge atop the conning tower.  Ship’s steering devices and surface torpedo attack controlling devices are visible. Visualisation 3D: Waldemar Góralski

During the World War II nearly 700 submarines of that type, with terrible living and sanitary conditions on board, sunk approximately 9 million BRT of Allied shipping. Human casualties are impossible to count.

History of the Type VIIC U-boat development

In August 1936, U-27, the first of the 10 medium-sized type VII U-boats displacing 500 tons and characterized by the placement of the stern (fifth) torpedo tube on the upper, external deck, was commissioned into the newly created U-Bootwaffe (The “Saltzwedel” Flotilla). It was not a very successful design and already in 1938 a new one was worked out, designated Type VIIB. The stern torpedo tube was mounted inside the pressure hull, the submersion system was improved and the diesels were equipped with superchargers that increased their power. The displacement rose to 517 tons. The modernized type of U-boats that had been commissioned into the “Wegener” Flotilla since 1938 met all the requirements and was highly appraised. Also the first combat experiences after the break out of the World War II confirmed its combat effectiveness. By August 1941, 23 units had been built and commissioned. The U-boat designers, however, were required to introduce yet another alterations to the newly built submarines. These were:
- The change of radio communication equipment, which involved extending the radio room by 60 cm (1 frame) and as a result lengthened the entire hull as well as the conning tower by 30 cm,
- The change of the submersion system by adding starboard and port pressure-tight crash-diving tanks, thus increasing stability (especially in heavy seas) and reducing the time needed to submerge,
- Increase in range by the enlargement of the internal fuel tank no. 1 from 32.5 m³ (type VIIB) to 37.5 m³,
- The replacement of one of the two electric-powered Krupp air compressors (starboard) by the crankless diesel driven Junkers air compressor of higher efficiency thus reducing the battery consumption.
- Due to the high consumption of the engine oil by the diesels, the ship was equipped with an oil purifying plant, so the oil could be reused.
- Protection against corrosion by galvanizing and sacrificial zinc anodes of the mechanisms and levers mounted outside of the pressure hull.
That is how a new version of the U-boat, designated VIIC, was created.

 Visualisation 3D: Waldemar Góralski
On December 2, 1940, the day the first U-boat of that type – U 69 was commissioned, its combat effectiveness was highly appraised. It appeared that a quick victory in the tonnage war depended only on considerable acceleration of the U-boat building programme and their rapid operational deployment. On the Allied side, however, there was a gradual development of the anti-submarine units and weapon systems, which in addition to the breaking of the Enigma code as early as 1943, changed the situation in the Atlantic. It was slowly becoming apparent that the U-boats were falling behind due to the rapid technological development of the enemy. The ugre to build the highest number of units did not allow for their significant modernization and the introduction of the new type of U-boat, the “electroboat” dragged on endlessly. The short-term supplement of the equipment with primitive radar detection device FuMB1 “Biscaya Cross”, “Bold” Asdic decoys and “Aphrodite” radar decoys, brought psychological rather than military advantages. Due to the increased danger of air attacks, in the summer of 1943, the platform behind the conning tower (the so called “Wintergarten”) was extended, so the anti-aircraft armament could be strengthened from a single 20 mm cannon to even two twin mounts and a twin 37 mm mount. Fundamentally, however, all type VIIC U-boats right to the type VIIC/41 U 1308, commissioned on January 17, 1945, were very much the same as the U 69. Approximately 660 units of the  type VIIC and VIIC/41 were built and commissioned. Moreover, there were six type VIID minelayers (1940-1942) and four type VIIF torpedo supply vessels (1941-1943).
In July 1940 the type VIIC had the following characteristics:


1. Torpedoes and mines:
Fourteen 53.3 cm torpedoes, four in forward tubes, one in the stern tube and 9 spare ones; it was possible to carry two TMA or three TMB mines instead of a one torpedo. The following schemes of torpedo/mine armament were provided for U-Boats on the patrol missions:

Scheme    G 7a* G 7e** TMA TMB
1 5 9
2 3 2 21
3 3 2 14
4 2 1 24
5 3 1 16
* steam powered
** electrically powered

2. Artillery
– 8.8 cm SK C/35 mounted in front of the conning tower (the main deck there was widened to 3.8 m),
– 2.0 cm MG C/30 anti-aircraft gun at the back of the conning tower.
Ammunition supply: 8.8 cm – 205 rounds, 2.0 cm – 1500 rounds stored as follows:
– in front of the officers’ quarters: 177 8.8 cm rounds, 1200 2.0 cm rounds,
– under the upper deck: 28 8.8 cm rounds,
– in the conning tower: 20 2.0 cm ammunition cartridges.
Additionally placed in the watertight containers in the control room were:
– two boxes with four explosive charges with fuse,
– two boxes with twelve unarmed explosive charges,
– two boxes with twelve time fuses.

A view of a Type VII A U-boat’s conning tower with an anti-aircraft cannon mounted behind it. Visualisation 3D: Waldemar Góralski