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

The 8.8 cm Deck Gun

The 8.8 cm gun used on U-boats was not directly related to the famous 8.8 or 'Acht-Acht' flak gun which ultimately gained fame as an anti-tank weapon. More correctly entitled the 8.8 cm Schiffskanone C/35, it was a purely naval weapon, developed from earlier weapons of this type used by the Imperial German Navy in the First World War.

The gun was mounted on a low pedestal forward of the conning tower and was traversable through 360°. It could be depressed to -4° and elevated up to +30°. The gun fired a 13.7 kilo shell with a muzzle velocity of 700 metres/sec for a distance of up to 12,350 metres. When submerged, the barrel bore was protected by a waterproof tompion inserted into the muzzle.

It was crewed by three men, the kanonier (gunner), ladeschutze (loader) and richtschutze (gun-layer) supported by numerous other crewmen who would bring the ammunition up on deck from its storage under the floor plates of the Zentral. On the deck just forward and to port of the gun, was a small watertight ammunition locker giving the gun crew sufficient shells to allow the gun to be brought into action immediately whilst the bulk of the ammunition was retrieved from inside the boat. Two folding padded 'U'-shaped supports were provided on both left and right sides of the gun for the gunner and gun-layer to steady themselves against rolling or pitching of the boat. In effect, the gun would be difficult to aim successfully in anything other than calm seas. In rough seas, the crew could strap themselves into position. The gun was controlled and directed, usually by the Second Officer (II Wach Offizier or IIW.O.), from the conning tower.

The 2 cm Flak Gun

Two basic designs of 2 cm flak gun (Flugabwehrkanone) were used. The earlier version, the 2 cm Flak 30, was a single-barrelled weapon, with 360° traverse and capable of -2° depression and +90° elevation. It fired a 0.32 kilo shell with a range up to 12,350 metres. Maximum cyclic rate of fire was 480 rounds per minute, but effective use was around half this rate.

Normally, periscopes would be retracted when not actually in use. Here they have been raised to act as flagpoles for the cord from which the boat's victory pennants are strung. Each pennant has painted on it the tonnage of the vessel sunk. This photo was taken at the end of a very successful cruise for Kapitänleutnant Reinhard Hardegen and U-123, a Type VIIC.

A second, improved model, the 2 cm Flak 38, was a very similar model but had an increased rate of fire at 960 rounds per minute. The second version was also produced in twin-barrelled (Twilling) and four-barrelled (Vierling) versions. It was a direct development of a weapon designed for the army, and simply fitted to a naval pedestal mount (the lafette C/35).

The 3.7 cm Flak Gun

In the second half of the war, many Type VIIs received the 3.7 cm Flak M/42. Also an army weapon adapted for naval use, it fired a 0.73 kilo round up to 15,350 metres at a maximum rate of fire of 50 rounds per minute.

Other Weapons

As well as the main deck armament and flak defence weapons, a limited amount of small arms were kept on board the U-boat for use by boarding parties, guards when the boat was in dock etc. These would include the 9 mm pistol, 9 mm sub-machine gun, 9 mm machine gun and 7.92 mm rifle.

THE TORPEDO

German torpedo nomenclature can be extremely confusing. There were, however, only two principal types of torpedo used on U-boats, but with several variants in detonating devices (the pistol) and in directional control. These two principal types were in fact developments of torpedoes used in the First World War, the G7a and the G7e. By the Second World War, torpedo sizes had been standardised at 54 cm (21 in.) so that all torpedoes, whether launched from surface ships or U-boats, were of the same diameter. The standard length was 7.16 m and some 280 kilos of explosive was contained in the warhead.

Torpedo Types

G7a(TI)

The G7a(TI) was a relatively simple weapon, propelled by steam from the burning of alcohol in air, supplied by a small on-board reservoir. The torpedo was driven by a single propeller. The G7a(TI) had a top speed of some 44 knots and a range of up to 6 kilometres. Its biggest drawback was its visible 'bubble' wake.

G7e(TII)

Broadly similar to the G7a model, the G7e was electrically powered, being driven by a small 100 bhp electric motor. In this case two contra-rotating propellers were fitted. The G7 series left no visible wake, and the G7e(TII) had a range of some 5 kilometres at 30 knots.

View onto the foredeck from the bridge of a Type VII, showing the 8.8 cm deck gun. The 'U'-shaped objects to the right of the gun are leather-covered bracing positions that the gun crew could lean into to steady themselves in rough seas. These could be folded away when not in use. The muzzle was sealed with a plug, whose retaining cord can be seen spiralling around the barrel.

G7e(TIII)

This was a development of the G7e(TII) with greater battery capacity, allowing its effective range to increase to 7.5 kilometres.

Detonators

The pistols used to detonate the torpedo were a source of great trouble to the U-Bootwaffe, with numerous failures to detonate being recorded in the early part of the war. The basic pistol was a dual-function component that could be activated by contact (Abstandzündung) or by the detection of the magnetic field generated by the hull of the ship (Magnetischerzündung).

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