| Class overview | |
|---|---|
| Builders: | Germaniawerft, Kiel |
| Operators: |
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| Preceded by: | German Type U 63 submarine |
| Succeeded by: | German Type UE I submarine |
| Built: | 1913–15 |
| In commission: | 1915–18 |
| Completed: | 5 |
| Lost: | 3 |
| Scrapped: | 2 |
| Preserved: | 0 |
| General characteristics (as U-7 class) | |
| Type: | submarine |
| Displacement: |
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| Length: | 228 ft (69.50 m) (o/a) |
| Beam: | 20 ft 8 in (6.30 m) |
| Draft: | 12 ft 5 in (3.79 m) |
| Propulsion: |
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| Speed: |
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| Range: |
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| Complement: | unknown |
| Armament: |
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| General characteristics (as Type U 66) | |
| Type: | submarine |
| Displacement: |
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| Length: |
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| Beam: |
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| Height: | 7.95 m (26 ft 1 in) |
| Draft: | 3.79 m (12 ft 5 in) |
| Installed power: |
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| Propulsion: | 1 × shaft, 1 × 1.80 m (5 ft 11 in) propeller |
| Speed: |
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| Range: |
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| Test depth: | 50 m (160 ft) |
| Complement: | 4 officers, 32 enlisted men |
| Armament: |
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The Type U 66 was a class of five submarines or U-boats operated by the German Imperial Navy (German: Kaiserliche Marine) during World War I. The class is alternately referred to as the U-66-class or the Type UD. The class was built by Germaniawerft of Kiel to their 506d design as the U-7-class for the Austro-Hungarian Navy. The five boats were sold to the Imperial Germany Navy at the beginning of World War I when it was thought impossible for the submarines to reach the Mediterranean for delivery to Austria-Hungary.
The Austro-Hungarian Navy, after competitively evaluating six submarines of three foreign designs, selected the Germaniwerft 506d or Type UD design over a design from Whitehead & Co. for the U-7 class. The boats, numbered U-7 to U-11, were designed to be 69.50 m (228 ft 0 in) long and displace between 695 and 885 tonnes (684 and 871 long tons) when surfaced and submerged. They were to be armed with five torpedo tubes and a deck gun. For propulsion the design called for twin diesel engines for surface running and twin electric motors for subsurface movement. The Austro-Hungarian Navy ordered the boats in February 1913 and construction began on the first boats in November.
After the outbreak of World War I in August 1914, the Austro-Hungarian Navy became convinced that delivery of the still-unfinished submarines to the Mediterranean via Gibraltar would be impossible. As a result, they sold the five boats to the Imperial German Navy in November 1914. The German Navy assigned the numbers U-66 to U-70 to the five submarines and had them redesigned and reconstructed to their specifications. These changes, which included a larger deck gun, increased the displacement of the U-boats by almost 100 tonnes (98 long tons) surfaced and nearly 50 tonnes (49 long tons) submerged.