It has been many years since I first saw Das Boot. As usual, the characters and incidents are fictitious, but this is not a Hollywood fiction; the types of events portrayed certainly occurred. While I can’t speak for the makers of the film, it gives a gritty German perspective on the one thing that truly scared Winston Churchill – the U-boat peril.
I relied heavily on Wikipedia to provide accurate information on two U-boat types. Many good sources all have copyright material precluding sharing anything.
I posted this in large part because it seems that the true nature of these boats are still not understood.
In comparison to U.S. subs, U-boats were considerably smaller. A plethora of types were planned, some boats were short ranged and used close to British waters; others, far fewer in numbers could operate off the U.S. coast, and the rest operated in the mid Atlantic. One design improvement (such as a single aft torpedo tube) only increased their torpedo capacity to 14 total.
U-Boat type VIIC depth limits: The theoretical crush depth of the Type VIIC was 280 – 375 meters, depending on which figures are used. Design depths from 120 to 150 meters are published. The Germans generally used a safety factor of 2.5 to get design depth and they tested the hull at a safety factor of 1.5.
The maximum safe depth for the VIIC was therefore between 185 and 250 meters. The problem is that most of numbers published do not specify the applicable safety factor, so it is difficult to come up with a precise number for theoretical crush depth. The actual crush depth varied from one boat to another anyway since the quality of the materials and the workmanship varied. SOURCE
Contrast those figures with U.S. Gato class subs depth limits, from WIKI:
The Gato-class were a class of submarines built for the United States Navy and launched in 1941–1943; they were the first mass-production US submarine class of World War II. Together with their near-sisters the andes, their design formed the majority of the United States Navy’s World War II submarine fleet.
The Gato-class design was a near-duplicate of the preceding Tambor and Gar-class boats. The only significant differences were an increase in diving depth from 250 feet (76 m) to 300 feet (91 m), and an extra five feet in length to allow the addition of a watertight bulkhead dividing the one large engine room in two, with two diesel generators in each room. Operational experience with earlier boats led the naval architects and engineers at the Navy’s Bureau of Construction and Repair to believe that they had been unduly conservative in their estimates of hull strength. Without changing the construction or thickness of the pressure hull steel, they decided that the Gato-class boats would be fully capable of routinely operating at 300 feet, a 50-foot (15 m) increase in test depth over the preceding classes.
This will help to understand how deep they might go to escape depth charges:
100 Meters (m) = 328.08399 Feet (ft)
160 Meters (m) = 524.93438 Feet (ft)
220 Meters (m) = 721.78478 Feet (ft)
The larger types, ones that wreaked havoc off U.S. coastal waters early in the war, could carry twenty-two torpedoes; we were woefully unprepared, and hadn’t even a system of protecting ships operating close to the Eastern seaboard. Most were designed for mid Atlantic operations, and until the impact of improved detection methods turned the tide in the latter half of 1942, they were the ones which almost accomplished Donitz’s plan to starve Britain of needed war materials.
Ironically, there were some factors which helped keep the Germans from destroying our efforts outright; Donitz had wanted 300 U-boats to start wartime operation, but had less than 40 immediately available at the outbreak of hostilities. Hitler was not favorable to the Navy; original plans included not starting the war til 1945, and included plans for a Naval fleet which staggers the imagination, had they followed that course.
Seventy-five percent of all German sailors operating U-boats perished by wars end.
Courtesy of Wikipedia –
The VIIA had limited fuel capacity, so 24 Type VIIB boats were built between 1936 and 1940 with an additional 33 tonnes of fuel in external saddle tanks which added another 2,500 nautical miles (4,600 km; 2,900 mi) of range at 10 knots (19 km/h; 12 mph) surfaced. More powerful engines made them slightly faster than the VIIA. They had two rudders for greater agility. The torpedo armament was improved 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 of 14 torpedoes. The only exception was U-83, which lacked a stern tube and carried only 12 torpedoes.
Type VIIBs included many of the most famous U-boats of World War II, including U-48 (the most successful), Prien‘s U-47, Kretschmer‘s U-99, and Schepke‘s U-100.
A note about Prien’s U-47: On October 14th,1939, The HMS Royal Oak was anchored at Scapa Flow. She was a British Battleship, nicknamed “The Mighty Oak”, a veteran of World War I and the mighty pride of Royal Navy. The base at Scapa Flow, was near-ideal anchorage and many considered it impenetrable.
In the darkness of the night, on the 13th of October 1939, German submarine U-47 surfaced in Scapa Flow and crept slowly towards HMS Royal Oak. When the submarine was close enough, the commander of the U-boat, Günther Prien, had given orders to fire torpedoes. The battleship had no chance in this duel and very quickly started to sink. 833 men, including Rear-Admiral Henry Blagrove, died on board HMS Royal Oak.
U-47 had crept out of Scapa Flow unnoticed. VIDEO
Miniature model of a Type VIIC.
The Type VIIC was the workhorse of the German U-boat force, with 568 commissioned from 1940 to 1945. The first VIIC boat commissioned was the U-69 in 1940. The Type VIIC was an effective fighting machine and was seen almost everywhere U-boats operated, although its range of only 8,500 nautical miles was not as great as that of the larger Type IX (11,000 nautical miles), severely limiting the time it could spend in the far reaches of the western and southern Atlantic without refueling from a tender or U-boat tanker. The VIIC came into service toward the end of the “First Happy Time“[Note 6] near the beginning of the war and was still the most numerous type in service when Allied anti-submarine efforts finally defeated the U-boat campaign in late 1943 and 1944.
Type VIIC differed from the VIIB only in the addition of an active sonar and a few minor mechanical improvements, making it 2 feet longer and 8 tons heavier. Speed and range were essentially the same. Many of these boats were fitted with snorkels in 1944 and 1945.
They had the same torpedo tube arrangement as their predecessors, except for U-72, U-78, U-80, U-554, and U-555, which had only two bow tubes, and for U-203, U-331, U-351, U-401, U-431, and U-651, which had no stern tube.