The U-27 class was a class

Ship class

A ship class is a group of ships of a similar design. This is distinct from a ship-type, which might reflect a similarity of tonnage or intended use. For example, the is a nuclear aircraft carrier of the Nimitz class....

 of eight submarine

Submarine

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

s or U-boats built for and operated by the Austro-Hungarian Navy

Austro-Hungarian Navy

The Austro-Hungarian Navy was the naval force of Austria-Hungary. Its official name in German was Kaiserliche und Königliche Kriegsmarine , abbreviated as k.u.k. Kriegsmarine....

  during World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

. The class was based upon the German Type UB II

German type UB II submarine

The UB II type submarine was a class of U-boat built during World War I by the Kaiserliche Marine. They were enlarged from the preceding type UB I and were more effective vessels. The boats were a single hull design with a 50 metre maximum diving depth and a 30-45 second diving time...

 design of the German Imperial Navy and was constructed under license in Austria-Hungary.

After the Austro-Hungarian Navy had filled its most urgent needs for submarines after the outbreak of World War I, they selected the German Type UB II design for its next group of submarines in mid 1915. Orders for the first six boats were placed in October 1915 with the Austrian firm of Cantiere Navale Triestino

Cantiere Navale Triestino

CANT was an Italian aviation company which originally specialised in building naval aircraft, formed in 1923 as part of the CNT...

 and the Hungarian firm of Ganz Danubius. Two more boats were ordered in 1916, bringing the class total to eight.

The boats were just over 121 feet (36.9 m) long and were armed with two bow torpedo tubes, a deck gun

Deck gun

A deck gun is a type of artillery cannon mounted on the deck of a ship or submarine.The deck gun was used as a defensive weapon against smaller boats or ships and in certain cases where torpedo use was limited. Typically a crew of three; gunner, loader, and layer, operated the gun, while others...

, and a machine gun

Machine gun

A machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....

. For propulsion they were equipped with twin diesel engine

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

s for surface running and twin electric motor

Electric motor

An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

s for subsurface movement. Although the class was based on the German design, the Austro-Hungarian U-boats were heavier and slightly faster underwater, but less heavily armed than their German counterparts

All eight boats were commissioned into the Austro-Hungarian Navy between 1917 and 1918 and saw active service during the war. and were the most successful in terms of ships sunk and gross register tonnage

Gross Register Tonnage

Gross register tonnage a ship's total internal volume expressed in "register tons", one of which equals to a volume of . It is calculated from the total permanently enclosed capacity of the vessel. The ship's net register tonnage is obtained by reducing the volume of non-revenue-earning spaces i.e...

 sunk, respectively. Two boats sank only one ship each, and a third, , sank no ships. U-30 was also the only boat of the class to be lost during the war. The remaining seven were ceded to France and Italy as war reparations

War reparations

War reparations are payments intended to cover damage or injury during a war. Generally, the term war reparations refers to money or goods changing hands, rather than such property transfers as the annexation of land.- History :...

 and six were scrapped by 1920; the seventh sank while being towed to Bizerta for scrapping.

Background

Austria-Hungary

Austria-Hungary

Austria-Hungary , more formally known as the Kingdoms and Lands Represented in the Imperial Council and the Lands of the Holy Hungarian Crown of Saint Stephen, was a constitutional monarchic union between the crowns of the Austrian Empire and the Kingdom of Hungary in...

's U-boat fleet was largely obsolete at the outbreak of World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

. The Austro-Hungarian Navy

Austro-Hungarian Navy

The Austro-Hungarian Navy was the naval force of Austria-Hungary. Its official name in German was Kaiserliche und Königliche Kriegsmarine , abbreviated as k.u.k. Kriegsmarine....

 satisfied its most urgent needs by purchasing five Type UB I

German type UB I submarine

The Type UB I was a class of small coastal submarines built in Germany at the beginning of the First World War. Twenty boats were constructed, most of which went into service with the German Imperial Navy. Boats of this design were also operated by the Austro-Hungarian Navy and the Bulgarian...

 submarines that comprised the from Germany, by raising and recommissioning the sunken French submarine Curie

French submarine Curie (Q 87)

SM U-14 or U-XIV was a U-boat or submarine of the Austro-Hungarian Navy during the First World War. She was launched in 1912 as the French Curie , but captured and rebuilt for service in the Austro-Hungarian Navy...

 as ,Curie

French submarine Curie (Q 87)

SM U-14 or U-XIV was a U-boat or submarine of the Austro-Hungarian Navy during the First World War. She was launched in 1912 as the French Curie , but captured and rebuilt for service in the Austro-Hungarian Navy...

 had been caught in an anti-submarine net

Anti-submarine net

An anti-submarine net is a device placed across the mouth of a harbour or a strait for protection against submarines.-Examples of anti-submarine nets:*Lake Macquarie anti-submarine boom*Indicator net*Naval operations in the Dardanelles Campaign...

 while trying to enter the harbor at Pola

Pula

Pula is the largest city in Istria County, Croatia, situated at the southern tip of the Istria peninsula, with a population of 62,080 .Like the rest of the region, it is known for its mild climate, smooth sea, and unspoiled nature. The city has a long tradition of winemaking, fishing,...

 on 20 December 1914. See: Gardiner, p. 343. and by building four submarines of the that were based on the 1911 Danish Havmanden class

Havmanden class submarine (1911)

The Havmanden class was a class of six submarines built for the Royal Danish Navy from 1911 to 1914. Also later known as the A class, the boats were designed by the Austro-Hungarian firm Whitehead & Co. of Fiume...

.The plans for the Danish Havmanden class submarines

Havmanden class submarine (1911)

The Havmanden class was a class of six submarines built for the Royal Danish Navy from 1911 to 1914. Also later known as the A class, the boats were designed by the Austro-Hungarian firm Whitehead & Co. of Fiume...

, three of which were built in Austria-Hungary, were seized from Whitehead & Co. in Fiume. See: Gardiner, pp. 344, 354.

After these steps alleviated their most urgent needs, the Austro-Hungarian Navy selected the German Type UB II

German type UB II submarine

The UB II type submarine was a class of U-boat built during World War I by the Kaiserliche Marine. They were enlarged from the preceding type UB I and were more effective vessels. The boats were a single hull design with a 50 metre maximum diving depth and a 30-45 second diving time...

 design for its newest submarines in mid 1915. The Germans were reluctant to allocate any of their wartime resources to Austro-Hungarian construction, but were willing to sell plans for up to six of the UB II boats to be constructed under license in Austria-Hungary. The Navy agreed to the proposal and purchased the plans from AG Weser

AG Weser

Aktien-Gesellschaft Weser was one of the great German shipbuilding companies, located at the Weser River in Bremen. Founded in 1873 it was finally closed in 1983. Altogether, AG Weser built about 1400 ships of different types, including many war ships...

 of Bremen

Bremen

The City Municipality of Bremen is a Hanseatic city in northwestern Germany. A commercial and industrial city with a major port on the river Weser, Bremen is part of the Bremen-Oldenburg metropolitan area . Bremen is the second most populous city in North Germany and tenth in Germany.Bremen is...

.

Design

The U-27-class boats were coastal submarines that displaced 264 metric tons (291 ST) surfaced and 301 metric tons (331.8 ST) submerged. The boats had a single hull

Submarine hull

The term light hull is used to describe the outer hull of a submarine, which houses the pressure hull, providing hydrodynamically efficient shape, but not holding pressure difference...

 with saddle tank

Saddle tank (submarine)

Saddle tanks are a type of ballast tank configuration fitted to mid-era submarines, those of World War II.Saddle tanks are fitted in pairs external to the pressure hull, one on each side, in a similar manner to that of a horse's saddle-bags, the positioning of which they resemble in appearance.-...

s, and were 121 in 1 in (36.91 m) long with a beam

Beam (nautical)

The beam of a ship is its width at the widest point. Generally speaking, the wider the beam of a ship , the more initial stability it has, at expense of reserve stability in the event of a capsize, where more energy is required to right the vessel from its inverted position...

 of 14 in 4 in (4.37 m) and a draft

Draft (hull)

The draft of a ship's hull is the vertical distance between the waterline and the bottom of the hull , with the thickness of the hull included; in the case of not being included the draft outline would be obtained...

 of 12 in 2 in (3.71 m). For propulsion, they featured two shafts, twin diesel engine

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

s of 270 bhp for surface running, and twin electric motor

Electric motor

An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

s of 280 shp for submerged travel. The boats were capable of 9 knots while surfaced and 7.5 knots while submerged. Although there is no specific notation of a range for the U-27 class, the German UB II boats, upon which the class was based, had a range of over 6000 nautical miles (11,112 km) at 5 knots surfaced, and 45 nautical miles (83.3 km) at 4 knots submerged. The U-27 class boats were designed for a crew of 23–24.

The U-27 class boats were armed with two 45 cm (17.7 in) bow torpedo tubes and carried a complement of four torpedoes. They were also equipped with a 75 mm/26 (3.0 in) deck gun

Deck gun

A deck gun is a type of artillery cannon mounted on the deck of a ship or submarine.The deck gun was used as a defensive weapon against smaller boats or ships and in certain cases where torpedo use was limited. Typically a crew of three; gunner, loader, and layer, operated the gun, while others...

 and an 8 mm (0.31496062992126 in) machine gun

Machine gun

A machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....

.

Differences from the Type UB II submarines

Although the U-27 design was based on the German Type UB II submarine, there were some differences between the two designs.The U-27 class was also similar to the Austro-Hungarian Navy's , which consisted of two former German UB II boats purchased in July 1917. The Austro-Hungarian boats were slightly heavier than their German counterparts, by only 1 metric tons (1.1 ST) while surfaced, but by 9 metric tons (9.9 ST) while submerged. The UB II boats were shorter by about 3 foot (0.9144 m) in length, but nearly identical in beam and draft. Both types of submarines were rated at the same 9 knots on the surface, but the Austro-Hungarian boats were reported as over 1.5 knots 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 in).

Construction

With the plans purchased, 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.The Austro-Hungarian Navy

Austro-Hungarian Navy

The Austro-Hungarian Navy was the naval force of Austria-Hungary. Its official name in German was Kaiserliche und Königliche Kriegsmarine , abbreviated as k.u.k. Kriegsmarine....

 was forced to do the same Austrian/Hungarian allocations for builders and subcontractors for the four s. See: Halpern, p. 382. Of the initial order of six boats, two were allocated to the Austrian firm of Cantiere Navale Triestino

Cantiere Navale Triestino

CANT was an Italian aviation company which originally specialised in building naval aircraft, formed in 1923 as part of the CNT...

 (CNT) operating out of the Pola Navy Yard,By this time, the CNT

Cantiere Navale Triestino

CANT was an Italian aviation company which originally specialised in building naval aircraft, formed in 1923 as part of the CNT...

 shipyards at Monfalcone

Monfalcone

Monfalcone is a town and comune of the province of Gorizia , located on the coast of the Gulf of Trieste. Monfalcone means "Mount of Falcon" in Italian....

 had been overrun by the Italian Army

Italian Army

The Italian Army is the ground defence force of the Italian Armed Forces. It is all-volunteer force of active-duty personnel, numbering 108,355 in 2010. Its best-known combat vehicles are the Dardo infantry fighting vehicle, the Centauro tank destroyer and the Ariete tank, and among its aircraft...

. See: Baumgartner and Sieche, as excerpted here (reprinted and translated into English by Sieche). Retrieved 1 December 2008. and the balance to the Hungarian firm of Ganz Danubius in Fiume. The Navy ordered the first six boats of the class on 12 October 1915.

The first six boats were all laid down between late 1915 and early 1916. Later in 1916, the seventh boat of the class, , was laid down, after having been presented to the Navy as a gift by the Österreichischen Flottenverein, and an eighth, , as a replacement for , which had been lost in May. The seventh and eighth boats were constructed by CNT at the Pola Navy Yard. 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.

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

Service career

All the boats of the U-27 class, the most numerous of all the Austro-Hungarian submarine classes, saw active service, and all but one boat had wartime successes; sank no ships during her career, and disappeared after the end of March 1917, the only boat of the class to be lost during the war. and U-41 also had little success, each credited with sinking a single ship. At the other end of the spectrum, U-27, the lead boat of the class, sank the largest number of ships, 33, and sank the greatest amount of tonnage, .

At the end of the war, U-27 and were surrendered at Pola, while U-28 and U-40 were surrendered at Venice. All four of these boats were ceded to Italy as war reparations

War reparations

War reparations are payments intended to cover damage or injury during a war. Generally, the term war reparations refers to money or goods changing hands, rather than such property transfers as the annexation of land.- History :...

 and were scrapped by 1920. U-29, U-31, and U-41 were half of the six submarines at Cattaro,The other three submarines were , , and . See: Gibson and Prendergast, pp. 388–89 and were all awarded to France. The boats were towed from Cattaro to Bizerta, but U-29 foundered en route; U-31, U-41, and the others were scrapped within twelve months of their arrival there.

SM U-27

U-27, the lead boat of the class, was built by the Austrian firm of Cantiere Navale Triestino

Cantiere Navale Triestino

CANT was an Italian aviation company which originally specialised in building naval aircraft, formed in 1923 as part of the CNT...

 (CNT) at the Pola Navy Yard and launched on 19 October 1916. She was commissioned on 24 February 1917. During the war, she sank the British destroyer , damaged the Japanese destroyer Sakaki, and sank or captured 34 other ships totaling . U-27 was surrendered at Pola

Pula

Pula is the largest city in Istria County, Croatia, situated at the southern tip of the Istria peninsula, with a population of 62,080 .Like the rest of the region, it is known for its mild climate, smooth sea, and unspoiled nature. The city has a long tradition of winemaking, fishing,...

 at war's end and handed over to Italy as a war reparation in 1919 and was broken up the following year. Conway's All the World's Fighting Ships, 1906–1921 calls U-27 Austria-Hungary's "most successful submarine".

SM U-28

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

SM U-29

U-29 was built by the Hungarian firm of Ganz Danubius at Fiume and launched on 21 October 1916. She was commissioned on 21 January 1917, the first of the class to be commissioned. Under commander Leo Prásil, U-29 sank three British steamers and damaged the British protected cruiser . 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.

SM U-30

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

SM U-31

U-31 was built by Danubius at Fiume and launched on 28 March 1917. She was commissioned on 24 April 1917. In addition to damaging the British light cruiser in October 1918, during the battle of Durazzo

Battle of Durazzo (1918)

The Second Battle of Durazzo, or the Bombardment of Durazzo was a naval battle fought in the Adriatic Sea during World War I. A large Allied fleet led by the Regia Marina attacked the enemy held naval base at Durazzo, Albania. The fleet destroyed the Austro-Hungarian shore defenses and skirmished...

. U-31 sank one other ship, an Italian vessel of . She was scrapped in Bizerta after she was awarded to France in 1920.

SM U-32

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

SM U-40

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. and commissioned on 4 August 1917. During the war, U-40 sank two ships and damaged two others, hitting a total of Commonwealth shipping. The Italian destroyer Ardea claimed to have sunk U-40 in a depth charge

Depth charge

A depth charge is an anti-submarine warfare weapon intended to destroy or cripple a target submarine by the shock of exploding near it. Most use explosives and a fuze set to go off at a preselected depth in the ocean. Depth charges can be dropped by either surface ships, patrol aircraft, or from...

 attack on 26 April 1918, but the boat was surrendered to Italy at Venice in 1919 and broken up.

SM U-41

U-41 was ordered as a replacement for which had been sunk in May 1916. 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 (11.8 in) to accommodate the diesel engine

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

s on hand that were to have been installed in U-6. U-41 was commissioned on 19 February 1918, the last boat of the class, and the last Austro-Hungarian boat completed and commissioned into the Austro-Hungarian Navy

Austro-Hungarian Navy

The Austro-Hungarian Navy was the naval force of Austria-Hungary. Its official name in German was Kaiserliche und Königliche Kriegsmarine , abbreviated as k.u.k. Kriegsmarine....

. U-41 sank a single French steamer of during her short wartime career, and was at Cattaro at war's end. She was ceded to France in 1920 and towed to Bizerta, where she was scrapped within the year.