Austria-Hungary's U-boat fleet was largely obsolete at the outbreak of World War I, and, over the first two years of the war, the Austro-Hungarian Navy focused its efforts on building a U-boat fleet for local defense within the Adriatic. With boats to fill that need either under construction or purchased from Germany, efforts were focused on building ocean-going submarines for operation in the wider Mediterranean, outside the Adriatic.[1]
To that end, the Austro-Hungarian Navy purchased plans for the Germaniawerft Project 835 design on 11 July 1915 in order to build under license in Austria-Hungary. The plans called for a submarine that displaced 840t surfaced and 1100t submerged. The boats were to be about 241feet long with a beam of 20inchesft8inchesin (ftin) and a draft of 12inchesft11inchesin (ftin). For propulsion, the design featured two shafts, with twin diesel engines of 2300bhp (total) for surface running at up to 16.5knots, and twin electric motors of 1200shp (total) for submerged travel at up to 9knots. The U-50 class boats were designed for a crew of 33 men.
The U-50 design called for six 451NaN1 torpedo tubes—four bow tubes and two stern tubes—and carried a complement of nine torpedoes. The original design specified two 10 cm/35 (3.9 in) deck guns, which were superseded by two 120 mm/35 (4.7 in) deck guns in plans for the third and fourth boats.
On 7 February 1916, Ganz Danubius of Fiume received authorization to build two boats of the class, U-50 and U-51.[2] These first two boats, which comprised one-third of the six ocean-going submarines under construction in 1916,[3] were followed by orders for U-56 and U-57 in September 1918.
Shortages of skilled shipyard workers and materials slowed construction of the boats, and as a result, neither of the first two boats was ever launched, much less completed. The second pair was cancelled before either was laid down. U-50 was 90% complete at war's end, while U-51 was only 60% complete. Both boats had been scrapped in place in 1920.