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GORDON WILLIAMSON, illustrated by IAN PALMER
KRIEGSMARINE U-BOATS 1939-45

Internal Description

The 'core' of any submarine is, of course, its pressure hull. In the case of the Type VII this was of circular section, tubular in the centre section, and then tapering slightly towards the bow and stern. The pressure hull was made from welded rolled steel up to 2.2 cm thick. The whole consisted of six sections, plus a bow and stern end cap. Around this pressure hull was built the external casing, an area which was free flooding and was used to accommodate ventilation trunking and for storage.

The two early Type VIIC boats shown here both have the basic conning tower configuration known as 'Turm 0', with a single circular platform for the 2 cm flak gun. Note the heavy staining around the exhaust outlet on the outer boat whilst the inner boat's hull paintwork still appears to be in pristine condition suggesting a newly commissioned boat or recent overhaul. The bollards to which the mooring ropes are attached were retractable when the boat was travelling underwater to reduce drag.

Staring from the bow, the first compartment was the forward torpedo room, into which the four bow torpedo tubes penetrated by some four metres. To the ceiling was attached a hoist used for manoeuvring the torpedoes into the tubes, and the angled torpedo loading hatch. To the rear of the compartment were located three sets of two-tier bunks on each side. Compressed air cylinders were located below the bottom bunk, as were collapsible tables for the use of the junior ratings who occupied this compartment. Under the decking there was storage space for two additional torpedoes and under these, the bow trim tanks.

A type VIID minelayer is identifiable by the raised casing abaft the conning tower.

After passing through the first bulkhead, the next compartment in line was the senior non-commissioned ranks' accommodation, comprising two sets of two-tier bunks each side.

A further bulkhead followed before reaching the officer accommodation. Again, two sets of two-tier bunks were provided but as only three officers were normally carried, one of these was usually stowed. A small table was provided on the port side.

Looking towards the stern from the upper tower flak platform on a late-war Type VIIC. Clearly visible is the four-barrel led 2 cm Flakvierling, a weapon only fitted to a limited number of U-boats.

Then came the commander's bunk. He was the only man on board afforded a modicum of privacy, provided by a simple curtain at the entry to his 'quarters'. Directly across the walkway were located the radio room and sound detector room, giving the operators of these essential pieces of equipment instant access to the commanding officer. Under the decking of this area were stored the forward batteries as well as ammunition for the deck gun.

Reaching the central portion of the boat, the hub of activity was the control room, or Zentral, with a heavy pressurised bulkhead at either end. On the starboard side from the bow end, were located the boat's main helm, the diving planes, the navigator's table and the auxiliary bilge pumps. On the port side were the periscope motor, the main vent controls, the main bilge pump and a drinking water tank. In the centre of the compartment were the periscope tubes, the main optics for the sky, or navigation, periscope being located in the control room.

Above the control room was the conning tower. In it was a tiny space, the commander's attack station. Within this tiny compartment were the optics for the attack periscope, the attack computer, the compass and the exit hatch to the exterior of the conning tower. Under the decking of the Zentral were fitted ballast tanks and fuel bunkers.

Passing through the rear control room bulkhead, the next compartment was the junior non-commissioned ranks' accommodation, consisting of two pairs of twin bunks each side. Towards the rear of this compartment, on one side was the boat's tiny galley and on the other the aft w.c. and food storage pantry. The aft batteries were stored under the deck plates of this area.

The next bulkhead led through to the engine room. Within this small space were located the boat's two diesel engines on their massive founds, with only a narrow passageway in between. A further bulkhead allowed passage into the motor room in which were located the boat's two electric motors, coupled to the same shafts as the diesels. Also contained in this compartment were a compressor for the boat's modest refrigerated storage, the main electrical control panels and the stern torpedo tube, which fired out between the boat's twin rudders. Beneath the deck plating in this area were the stern trim tanks.

External fittings

The U-boat's external decking was covered in wood planking, with a 1 cm gap between planks to allow for drainage. Wood was used co avoid the degree of icing up in winter conditions that would have been encountered with metal decking.

U-995, currently the only complete, restored Type VIIC extant, is mounted on concrete pedestals on the beach at Laboe adjacent to the German Naval Memorial and is open to visitors. This boat features a 'textbook' Turm 4 arrangement with two twin 2 cm flak guns on the upper platform, and a 3.7 cm flak gun on the lower.

A view inside the bow compartment shows just how cramped living conditions were on an operational U-boat. The chains hanging down in the foreground are part of the torpedo hoist.

The area between the outer casing and pressure hull was free flooding, and along the side of the outer casing of any Type VII will be seen numerous draining slots. The exact number and positioning of these varied from manufacturer to manufacturer. In the area between pressure hull and outer casing, in the forward portion of the boat, was located a storage tube for a spare torpedo. On some boats this was replaced by a series of watertight containers for life rafts.

Moving away from the bow, there was an angled torpedo loading hatch leading from the outer deck to the pressure hull. This allowed the torpedo to be taken into the boat nose first, facing the tube into which it would be loaded. Beyond the torpedo loading hatch was a watertight storage container with a small amount of ammunition for the deck gun. This allowed the gun to be brought into action swiftly, while the remainder of the ammunition was brought up through the boat from the ammunition storage under the deck plating on the Zentral.

On outer decking itself at the forward point some early boats still had the serrated net cutter fitted to First World War boats, but by the outbreak of the Second World War most of these had been removed. Retractable bollards were fitted near the bow and stern, with additional pairs, port and starboard approximately mid-way between the bow/stern and the conning tower. A retractable capstan winch and retractable hydrophone array were also mounted on the foredeck.

The conning tower, as has already been discussed, was one of the areas in which considerable differences may be found from boat to boat and at different stages throughout the war. In general, the front and sides of the tower were screened up to a height of some 1.5 m to give the crew some measure of protection against the elements. The rear of the bridge was open, leading onto die aft platform which was surrounded by a safety railing. On the bridge itself were the mounts that supported the periscopes, a pedestal mount for the UZO (Uberwasserzieloptik) torpedo aiming device, a binnacle and, on the starboard wall of the tower, a slot to house the retractable direction-finding loop. Later examples of the Type MI had the snorkel fitting mounted on the port side of the tower.

The diving planes controls in the Zentral of a Type VII U-boat. The large dial just to left of centre is the depth gauge.

The afterdeck was relatively featureless. Apart from the small stern torpedo loading hatch, the space under the rear decking was devoted almost entirely to trunking. The trunking, which passed through the free-flooding area under the afterdeck, led up through the conning tower casing to the rear outer tower wall. Types MIA and MIB had large trunking running up the outside face of the tower, but by the VIIC model this was contained within the tower casing,

A single thick antenna cable ran from the most forward point of the bow to just before the conning tower, where it split, one fork running to a locating point either side of the top of the tower wall. From here, one antenna cable ran down to an anchor point on each side near the stern.

Construction Details

DESCHIMAG, BREMEN

VIIA U-27 to U-32 - 6 boats
(This firm concentrated on the Type IX.)

GERMANIAWERFT, KIEL

VIIA U-33 to U-36 - 4 boats
VIIB U-45 to U-55 - 11 boats
VIIB U-99 to U-102 - 4 boats
VIIC U-69 to U-72 - 4 boats
VIIC U-93 to U-98 - 6 boats
VIIC U-201 to U-212 - 12 boats
VIIC U-221 to U-232 - 12 boats
VIIC U-235 to U-250 - 16 boats
VIIC U-1051 to U-1058 - 8 boats
VIIC U-1063 to U-1065 - 3 boats
Total - 80 boats

BREMER VULCAN, VEGESACK

VIIB U-73 to U-76 - 4 boats

VIIC U-77 to U-82 - 6 boats
VIIC U-132 to U-136 - 6 boats
VIIC U-251 to U-300 - 50 boats
VIIC U-1271 to U-1279 - 9 boats
Total - 74 boats

DANZIGERWERFT, DANZIG

VIIC U-401 to U-430 - 30 boats
VIIC U-1161 to U-1172 - 12 boats
Total - 42 boats

FLENDERWERFT, LUBECK

VIIB U-83 to U-87 - 5 boats
VIIC U-88 to U-92 - 5 boats
VIIC U-301 to U-330 - 30 boats
VIIC U-903 to U-904 2 boats
Total - 42 boats

NORDSEE WERKE, EMDEN

VIIC U-331 to U-350 - 20 boats
VIIC U-1101 to U-1110 - 10 boats
Total - 30 boats

FLENSBURGER SCHIFFSBAU, FLENSBURG

VIIC U-351 to U-370 - 20 boats
VIIC U-1301 to U-1308 - 8 boats
Total - 28 boats

HOWALDTS WERKE, KIEL

VIIC U-371 to U-400 - 30 boats
VIIC U-651 to U-683 - 33 boats
VIIC U-1131 to U-1132 - 2 boats
Total - 65 boats

STULCKEN SOHN, HAMBURG

VIIC U-701 to U-722 - 22 boats
VIIC U-905 to U-908 - 4 boats
Total - 26 boats

SCHICHAUWERFT, DANZIG

VIIC U-431 to U-450 - 20 boats
VIIC U-731 to U-750 - 20 boats
VIIC U-825 to U-828 - 4 boats
VIIC U-1191 to U-1210 - 20 boats
Total - 64 boats

DEUTSCHE WERKE, KIEL

VIIC U-451 to U-458 - 8 boats
VIIC U-465 to U-486 - 22 boats
Total - 30 boats

BLOHM & VOSS, HAMBURG

VIIC U-551 to U-650 - 100 boats
VIIC U-951 toU-1031 - 81 boats
Total - 181 boats

KRIEGSMARINEWERFT, WILHELMSHAVEN

VIIC U-751 to U-779 - 29 boats

ODER WERKE, STETTIN

VIIC U-821 to U-822 - 2 boats

VULCAN, STETTIN

VIIC U-901 - 1 boat

NEPTUNWERFT, ROSTOCK

VIIC U-921 to U-930 - 10 boats

These represent only boats that were actually completed. Others were laid down, but never completed, or were broken up or the order for their manufacture was cancelled.

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