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

3. Small arms
– one MG 34,
– two sub-machine guns with 3000 rounds of ammunition,
– six Mauser 7.65 mm pistols with 860 rounds of ammunition,
– three bayonets,
– one single-barrel and one double-barrel signal pistol with 180 flares and 200 signal rockets.
The small arms ammunition was stored in the officers’ quarters.



The Pressure hull was cylinder-shaped with truncated cones on both ends. It was built with electrically-welded steel plates placed on 82 steel frames. The quality of the weld was examined in the shipyard using X-ray photography. The minimum of 25% of all welds were being examined. The walls of the conning tower, the area were the torpedo tubes were mounted, side diesel exhaust valves and the diesels assembly openings were reinforced. The hull plates were 18.5 mm thick in the cylinder-shaped parts and 16 mm in the conical ones, whereas the reinforcements and the conning tower were 35 mm thick. Two round bulkheads separated the interior of the hull into three sections and three additional ones divided it into six compartments altogether:
Section I:
Compartment 1. – stern torpedo and motor room – the stern torpedo tube, electric motors, transformer, electric motors’ control panels, air compressor, the rudder and stern diving planes engine, torpedo compensation tank, aft trim tank, one compressed air tank and the extra fresh water tank were located there.
Compartment 2. – engine room - two diesel engines with their auxiliary equipment were mounted there. There were also two compressed air tanks used to start the engines, two compressed oxygen tanks, engine oil tanks - auxiliary, header and used oil ones as well as the diesel fuel oil header tank (under the floor plates).
Compartment 3. – non-commissioned officers’ room, which contained the toilet, galley, provisions storage, battery no. 1 circuit breaker, refrigerator, high-pressure compressed air tanks. Below were the fresh and dirty water tanks, internal fuel tank no. 1 and battery room no. 1.
Section II:
Compartment 4. – control room, located there were the main bilge pump, auxiliary bilge and trim pumps, both periscopes’ hoisting mechanisms, rudder and diving planes control mechanisms, electric compass/gyrocompass system, sea water distiller unit, course indicator, fresh water tank, four oxygen tanks. Below was the ballast tank no. 3.
Section III:
Compartment 5. – officers’ and senior non-commissioned officers’ quarters, which contained radio and listening rooms, battery no. 2 circuit breaker, small provisions magazine, toilet and the fresh water tank. Below were internal fuel tank no. 2, watertight ammunition container, wash and dirty water tanks and the battery room no. 2.
Compartment 6. – forward torpedo room with four torpedo tubes, reserve torpedo stowage (2 torpedoes), high-pressure compressed air tanks and three oxygen tanks. Below were reserve torpedo or mine stowage (4 torpedoes), port and starboard torpedo compensation tanks and the forward trim tank.
Conning tower, ellipse-shaped in horizontal cross section to reduce the water resistance when submerged, was placed above the control room. It had a thin metal casing. Inside the tower were the attack periscope with its hydraulic control motor, the rudder control station and torpedo fire control equipment.
The openings in the pressure hull necessary for propeller shafts, pipelines, side valves closing mechanisms, radio wiring and measuring equipment were inspected at the pressure of 15 atm.
Outer hull
In the after section there were the stern watertight compartment and ballast tank no. 1. Both were equipped with vents at the top and had free-flooding holes at the bottom; when submerging the water was allowed by opening the vents.
The fore or bow section contained the forward watertight compartment and ballast tank no. 5. They were also equipped with vents at the top had free-flooding holes at the bottom.
On both sides of the hull were the ballast, compensating and crash-diving tanks. The compensating and crash-diving tanks, just like the pressure hull, were pressure-tight, as they were only partially flooded with the sea water depending on the consumption of the provisions, fresh water and U-boat’s maintenance materials. The crash-diving tanks were flooded when the submarine was on the surface increasing her weight and thus reducing the time needed for submersion. They were blown when the ship was at the periscope depth.
The upper deck (external) was made of metal frames welded to the pressure hull and planks mounted on them. There were gaps between the them that prevented the creation of air bubbles during the dive.
The bridge encased with thin metal sheets houses the ventilation shafts, radio aerial shaft, radio direction-finder, attack periscope, watertight container for ready 2 cm ammunition rounds, and the cooling water tank. When on surface the bridge was the U-boat commander’s post and 2 cm anti-aircraft gun platform.

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

Submersion system