U-27-class submarine (Austria-Hungary)

Although the U-27 design was based on the German Type UB II submarine, there were some differences between the two designs.[Note 3] The Austro-Hungarian boats were slightly heavier than their German counterparts, by only 1 metric ton (1.1 short tons) while surfaced, but by 9 metric tons (9.9 short tons) while submerged. The UB II boats were shorter by about 3 feet (0.91 m) in length, but nearly identical in beam and draft. Both types of submarines were rated at the same 9 knots (17 km/h) on the surface, but the Austro-Hungarian boats were reported as over 1.5 knots (2.8 km/h) faster underwater even though the electric motors of the two classes had comparable power output. The German boats were more typically more heavily armed than their Austro-Hungarian cousins, and featured two larger torpedo tubes—50 cm (19.7 in) vs. 45 cm (17.7 in)—and many sported a larger deck gun—88 mm (3.5 in) vs. 75 mm (3.0 in).[7]

== Chased, the Austro-Hungarian Navy began the intricate political negotiations to assign the six boats—to be designated U-27 to U-32—between Austrian and Hungarian firms.[4][Note 4] Of the initial order of six boats, two were allocated to the Austrian firm of Cantiere Navale Triestino (CNT) operating out of the Pola Navy Yard,[Note 5] and the balance to the Hungarian firm of Ganz Danubius in Fiume.[4] The Navy ordered the first six boats of the class on 12 October 1915.[8]

The first six boats were all laid down between late 1915 and early 1916.[4] Later in 1916, the seventh boat of the class, U-40, was laid down, after having been presented to the Navy as a gift by the Österreichischen Flottenverein, and an eighth, U-41,[4] as a replacement for U-6,[5] which had been lost in May.[3] The seventh and eighth boats were constructed by CNT at the Pola Navy Yard.[3] Shortages of labor and materials plagued subcontractors and, consequently, the delivery dates for the boats were not met. However, the first six boats had all entered service by the middle of 1917.[4]

The first of the class to be launched was U-27 on 19 October 1916, followed closely behind by U-29 three days later. The final boat launched was U-41 on 11 November 1917.[1] The U-27 class boats were the last domestically built submarines completed for the Austro-Hungarian Navy.[8]

U-27, the lead boat of the class, was built by the Austrian firm of Cantiere Navale Triestino (CNT) at the Pola Navy Yard and launched on 19 October 1916.[1] She was commissioned on 24 February 1917.[11] During the war, she sank the British destroyer Phoenix, damaged the Japanese destroyer Sakaki, and sank or captured 34 other ships totaling 14,386 GRT.[12] U-27 was surrendered at Pola at war's end and handed over to Italy as a war reparation in 1919 and was broken up the following year.[10] Conway's All the World's Fighting Ships, 1906–1921 calls U-27 Austria-Hungary's "most successful submarine".[13]

U-28 was built by CNT at the Pola Navy Yard and launched on 8 January 1917.[1] The boat was commissioned on 26 June 1917.[14] Under the command of Zdenko Hudeček, U-28 sank ten ships totaling 44,743 GRT and damaged another 5,592 GRT.[15] She was surrendered to the Italians at Venice in 1919 and scrapped in 1920.[10]

U-29 was built by the Hungarian firm of Ganz Danubius at Fiume and launched on 21 October 1916.[1] She was commissioned on 21 January 1917,[16] the first of the class to be commissioned. Under commander Leo Prásil, U-29 sank three British steamers (14,784 GRT) and damaged the British protected cruiser Edgar.[17] U-29 was at Cattaro at the end of the war and awarded to France as war reparation in 1920, but foundered while under tow to Bizerta for scrapping.[10]

U-30 was built by Danubius at Fiume, launched on 27 December 1916,[1] and commissioned on 17 February 1917.[18] The boat, under the command of Linienschiffsleutnant Friedrich Fähndrich, sailed from Cattaro on 31 March 1917 and was never heard from again.[19] U-30 sank no ships during her brief career.[20]

U-31 was built by Danubius at Fiume and launched on 28 March 1917.[1] She was commissioned on 24 April 1917.[21] In addition to damaging the British light cruiser Weymouth in October 1918, during the battle of Durazzo. U-31 sank one other ship, an Italian vessel of 4,021 GRT.[22] She was scrapped in Bizerta after she was awarded to France in 1920.[10]

U-32 was built by Danubius at Fiume and launched on 11 May 1917.[1] The boat was commissioned on 29 June 1917.[23] U-32 hit five ships of 6,788 GRT, sinking four and damaging one.[24] At Pola at war's end, the boat was handed over to Italy and scrapped in 1920.[10]

U-40 was ordered after the funds to purchase the boat were presented by the Östereichischen Flottenverein as a gift to the Austro-Hungarian Navy. She was built by CNT at the Pola Navy Yard, launched on 21 April 1917.[1] and commissioned on 4 August 1917.[25] During the war, U-40 sank two ships and damaged two others, hitting a total of 14,979 GRT Commonwealth shipping.[26] The Italian destroyer Ardea claimed to have sunk U-40 in a depth charge attack on 26 April 1918,[27] but the boat was surrendered to Italy at Venice in 1919 and broken up.[10]

U-41 was ordered as a replacement for SM U-6 which had been sunk in May 1916.[5] She was built by CNT at the Pola Navy Yard and launched on 11 November 1917. During construction, U-41 was lengthened about 30 centimetres (12 in) to accommodate the diesel engines on hand that were to have been installed in U-6.[1] U-41 was commissioned on 19 February 1918,[28] the last boat of the class, and the last Austro-Hungarian boat completed and commissioned into the Austro-Hungarian Navy.[5] U-41 sank a single French steamer of 4,604 GRT during her short wartime career,[29] and was at Cattaro at war's end.[10] She was ceded to France in 1920 and towed to Bizerta, where she was scrapped within the year.[10]