Type VII U-boats were the workhorses of the German World War II U-boot-waffe. Type VII was based on earlier German submarine designs going back to the World War I Type UB III, designed through the Dutch dummy company Ingenieurskantoor voor Scheepsbouw den Haag (I.v.S) (set up by Germany after World War I in order to maintain and develop German submarine know-how and to circumvent the limitations set by the Treaty of Versailles) and built by shipyards around the world; the Finnish Vetehinen class and Spanish Type E-1. These designs led to the Type VII along with Type I, the latter being built in AG Weser shipyard in Bremen, Germany. The production of Type I was cut down only after two boats, the reasons for this are not certain and range from political decisions to faults of the type. The design of the Type I was however further used in the development of the Type VII and Type IX. Type VII submarines were the most widely used u-boats of the war and were the most produced submarine class in history, with over 700 built. The type had several modifications.

Type VIIA

The Type VIIA boats were designed in 1933 until 1934 as the first of a new generation of attack U-boats. Most were built at Deschimag AG Weser in Bremen with U33-36 built at Germaniawerft at Kiel. They were popular with their crews and much more powerful than the smaller Type II U-boats they replaced, with four bow and one external stern torpedo tubes. Usually carrying 11 torpedoes onboard, they were very agile on the surface and mounted the 88 mm fast-firing deck gun with about 220 rounds.

Ten Type VIIA boats were built between 1935 and 1937. All but two Type VIIA U-boats were sunk during World War II ( and , both scuttled in Kupfermühlen Bay on 4 May 1945).

The boat was powered on the surface by two MAN AG, 6 cylinder, 4-stroke M6V 40/46 diesels giving a total of 2,100 to 2,310 brake-horsepower (1,700 kW) at 470 to 485 rpm. When submerged it was propelled by two BBC GG UB 720/8 electric motors giving a total of 750 hp (560 kW) at a 322 rpm.

List of Type VIIA submarines

There were 10 Type VIIA submarines commissioned.

Type VIIB

The only significant drawback of the VIIA was the limited fuel capacity, so 24 Type VIIB boats were built between 1936 and 1940 with an additional 33 tons of fuel in external saddle tanks which added another 2500 miles (4625 km) of range at 10 knots (19 km/h) surfaced. They were slightly faster than the VIIA, and had two rudders for even greater agility. The torpedo armament was improved as well by moving the aft tube to the inside of the boat. Now an additional aft torpedo could be carried below the deck plating of the aft torpedo room (which also served as the electric motor room) and two watertight compartments under the upper deck could hold two additional torpedoes giving it a total loadout of 14 torpedoes. The only exception was , which lacked a stern tube and carried only 12 torpedoes.
Type VIIB included many of the most famous U-boats of World War II, including (the most successful), Prien's , Kretschmer's , and Schepke's .

On the surface the boat was powered by two supercharged MAN, 6 cylinder, 4-stroke M6V 40/46 diesels (except for U-45 to U-50, U-83, U-85, U-87, U-99, U-100, and U-102 which were powered by two supercharged Germaniawerft 6-cylinder, 4-stroke F46 diesels) giving a total of 2,800 to 3,200 bhp (2,400 kW) at 470 to 490 rpm.

Submerged the boat was powered by two AEG GU 460/8-276 (except in U-45, U-46, U-49, U-51, U-52, U-54, U-73 to U-76, U-99 and U-100 which retained the BBC motor of the VIIA) electric motors giving a total of 750 shp (560 kW) at 295 rpm.

List of Type VIIB submarines

There were 24 Type VIIB submarines commissioned.

Type VIIC

The Type VIIC was the workhorse of the German U-boat force, with 568 commissioned from 1940 to 1945. Boats of this type were built throughout the war. The first VIIC boat commissioned was the in 1940. The Type VIIC was an effective fighting machine and was seen almost everywhere U-boats operated, although their range was not as great as that of the larger Type IX. The VIIC came into service as the "Happy Time" at the beginning of World War II was almost over, and it was this boat that saw the final defeat by the Allied anti-submarine campaign in late 1943 and 1944.

Type VIIC was a slightly modified version of the successful VIIB. They had very similar engines and power, but were larger and heavier which made them slightly slower than the VIIB. Many of these boats were fitted with the Schnorchel in 1944 and 1945.

They had the same torpedo tube arrangement as their predecessors, except for , , , , and , which had only two bow tubes, and for , , , , , and , which had no stern tube.

On the surface the boats (except for , and to which used MAN M6V40/46s) were propelled by two supercharged Germaniawerft, 6 cylinder, 4-stroke M6V 40/46 diesels totaling at 470 to 490 rpm.

For submerged propulsion several different electric motors were used. Early models used the VIIB configuration of two AEG GU 460/8-276 electric motors, totaling with a max rpm of 296, while newer boats used two BBC (Brown Boveri & Co) GG UB 720/8, two GL (Garbe Lahmeyer) RP 137/c electric motors or two SSW (Siemens-Schuckert-Werke) GU 343/38-8 electric motors with the same power output as the AEG motors.

Perhaps the most famous VIIC boat was , featured in the movie Das Boot.

U-flak

The "U-flak" boats were four VIIC boats (, , , and ) modified to be surface escorts for the attack U-boats operating from the French Atlantic bases. They had greatly increased anti-aircraft fire-power.

Conversion began on three others (, , and ) but none was completed, and they were eventually returned to duty as traditional VIIC attack boats.

The modified boats became operational in June 1943 and at first appeared to be successful against the surprised Royal Air Force. Seeing their potential, Dönitz ordered the boats to cross the Bay of Biscay in groups at maximum speed. The effort earned the Germans about two more months of still-limited freedom, until the RAF developed counter-measures. When the RAF began calling in surface hunters to assist the aircraft, the U-flak boats were withdrawn and converted back into fighting vessels.

The concept of the U-flak began the year before, on 31 August 1942, when was seriously damaged by aircraft. Rather than scrap the boat, it was decided to refit her as a heavily-armed anti-aircraft boat intended to stop the losses in the Bay of Biscay inflicted by Allied aircraft.

Two 20 mm quadruple Flakvierling mounts and the experimental 37 mm automatic gun were installed on the U-flaks' decks. A battery of 86 mm line-carrying anti-aircraft rockets was tested, but this idea proved unworkable. At times, two additional single 20 mm guns were also mounted. The submarines' fuel capacities were limited to Bay of Biscay operations only. Only five torpedoes were carried, preloaded in the tubes, to free the space needed for the additional gunners.

In November 1943 – less than six months after the experiment began – all U-flaks were converted back to normal attack boats, fitted with Turm 4. The standard anti-aircraft armament for U-boats was no longer much inferior to U-flaks, and the U-flaks had not been particularly successful. Even with massive anti-aircraft firepower, a U-boat on the surface was still vulnerable to having her pressure hull punctured, so her best bet when encountering aircraft was simply to dive. As well, attacking pilots often radioed in convoy escorts if they found too much resistance from U-flaks. According to German sources only six aircraft had been shot down by U-flaks in six missions (three by U-441, one each by U-256, U-621, and ).

Type VIIC/41

Type VIIC/41 was a slightly modified version of the successful VIIC and had the same armament and engines. The difference was a stronger pressure hull giving them a deeper test depth and lighter machinery to compensate for the added steel in the hull, making them actually slightly lighter than the VIIC. A total of 91 were built; all of them from onwards lacked the fittings to handle mines.

Today one Type VIIC/41 still exists: is on display at Laboe (north of Kiel), the only surviving Type VII in the world.

List of Type VIIC/41 submarines

There were 91 Type VIIC/41 submarines commissioned.

Type VIIC/42

The Type VIIC/42 was designed in 1942 and 1943 to replace the aging Type VIIC. It would have had a much stronger pressure hull, with skin thickness up to 28 mm, and would have dived twice as deep as the previous VIICs. These boats would have been very similar in external appearance to the VIIC/41 but with two periscopes in the tower and would have carried two more torpedoes.

Contracts were signed for 164 boats and a few boats were laid down, but all were cancelled on 30 September 1943 in favor of the new Type XXI, and none was advanced enough in construction to be launched.

It was powered by the same engines as the VIIC.

Type VIID

The type VIID boats, designed in 1939 and 1940, were a longer version of the VIIC with three banks of five vertical tubes just aft of the conning tower, rather like a modern ballistic missile submarine, except that these tubes ejected mines rather than missiles.

On the surface the boat used two supercharged Germaniawerft, 6 cylinder, 4-stroke F46 diesels totalling 3,200 bhp (2,400 kW) at between 470 to 490 rpm. When submerged the boat used two AEG GU 460/8-276 electric motors giving a total of 750 shp (560 kW) at 285 rpm.

These boats did not fare well: only one survived the war; the other five all went down with all hands.

List of Type VIID submarines

There were six Type VIID submarines commissioned

Type VIIF

The Type VIIF boats, designed in 1941, were primarily built as torpedo transports. They were the largest and heaviest type VII boats built. They were armed identically with the other Type VIIs except that they could have up to 39 torpedoes onboard and had no deck guns.

Only four Type VIIFs were built. Two of them, and , were sent to support the Monsun Gruppe in the Far East; and remained in the Atlantic.

It used the same engines as the VIID.

List of Type VIIF submarines

There were four Type VIIF submarines commissioned.

Specifications

See also