Submarines and their Weapons - Aircraft of World War II

SUBMARINES AND THEIR WEAPONS
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40 hours. Like the bigger, Type XXI boats, they were
streamlined in appearance, with all external fittings
either faired-in or removed.
The Type XXI was a more sophisticated boat than
the Type XXIII; it was 76.7m (251.6ft) long and 6.6m
(21.6ft) abeam, displacing 1620 tonnes (1595 tons) on
the surface. Type XXIs were equipped with six torpedo
tubes, all of them situated in the bow, and a total of
23 torpedoes (they were also to have carried four
30mm anti-aircraft cannon, but never did, a pair of
20mm cannon being substituted). Like the coastal
boats, they were double-decked, the frames being fitted
outside the pressure hulls, which suited the modular,
prefabricated building method by then in use in
Germany. Their powerplants were considerably more
powerful, of course: they had two MAN diesels of
lOOObhp each driving two propeller shafts via two
125()shp electric motors or two 57shp 'creeping 1
motors; on the surface they could make 15.5 knots
and submerged, on main engines, over 17 knots, with
5 knots available from the auxiliary motors.
Almost 700 Type XXIs were scheduled to have
been built by Blohm & Voss in Hamburg, Deschimag
in Bremen, and Schichau in Danzig (Gdansk), but
only 121 were actually commissioned. Many more
were bombed on the slip prior to launching and a substantial
number remained incomplete at the end of the
war. Some of them - and some of the boats already in
commission - were taken to the Soviet Union and
completed there and formed the backbone of the Red
Navy's submarine arm for many years. Indeed, so
greedy were the Soviets for German submarines that
they loaded the hangar decks of the incomplete hull of
the aircraft carrier Graf Zeppelin with U-boat hull
sections and proceeded to tow it the length of the
Baltic to Leningrad, but it hit a mine in the Gulf of
Finland and sank. Only two Type XXI boats ever left
port on operational patrols and neither fired a shot in
anger. The advance in submarine operations which
the Type XXI and Type XXIII represented cannot be
overstated. They altered the world's navies' perceptions
of what could be expected of a submarine, and
every design later produced, up to the modern
'teardrops', reflected that.
Left: The head of an extensible induction mast, or
schnorkel tube. It took considerable ingenuity to produce
a self-regulating valve system which was fast-enough
acting to prevent large quantities of water being sucked
into the submarine. The Dutch were the first to find a
solution to the problem in about 1936.