U-48-class submarine

The U-48 class was a class of four submarines or U-boats planned for the Austro-Hungarian Navy (Kaiserliche und Königliche Kriegsmarine or K.u.K. Kriegsmarine) during World War I. The design of the boats was based on plans purchased from the German firm AG Weser in January 1916. The Navy authorized Cantiere Navale Triestino to begin construction of the submarines in Pola in September 1916. Only two of the planned four boats were laid down, but neither of them was launched or completed. Both incomplete submarines were scrapped after the war ended.

Design
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 submarines for operation in the wider Mediterranean, outside the Adriatic.

In January 1916 Cantiere Navale Triestino (CNT) purchased plans for an 800 t submarine from the German firm AG Weser of Bremen. Austro-Hungarian Navy modifications to the plans resulted in a submarine that displaced 818 t surfaced and 1184 t submerged. The boats were to be 240 ft long with a beam of 21 ft and a draft of 10 ft. For propulsion, the design featured two shafts, with twin diesel engines of 2400 bhp (total) for surface running at up to 16.25 knots, and twin electric motors of 1200 shp (total) for submerged travel at up to 8.5 knots. The U-48 class boats were designed for a crew of 32 men.

The U-48 design called for six 45 cm torpedo tubes—four bow tubes and two stern tubes—and carried a complement of nine torpedoes. The original design specified two 90 mm/35 (3.5 in) deck guns, which were superseded by two 120 mm/35 (4.7 in) deck guns in plans for the third and fourth boats.

Construction
In September 1916, Cantiere Navale Triestino (CNT) received authorization to build two boats of the class, U-48 and U-49, with the proviso that the boats be built in Budapest with final assembly at the Pola Navy Yard. These first two boats, which comprised one-third of the six submarines under construction in 1916, were followed by orders for U-58 and U-59 before the war's end.

Although CNT had secured fully complete plans from Weser, the Austro-Hungarian design modifications delayed the start of construction. Additional changes after construction had begun slowed the boats' progress. Compounding this were shortages of both material and skilled shipyard workers, further slowing construction. As a result, neither of the first two boats was ever launched, much less completed, and the second pair was cancelled before either was laid down. U-48 was 70% complete at the war's end, while U-49 was only 55% complete. Both boats were scrapped in place in 1920.