3. Wartime oceangoing submarines
3.1. U-51 class
Six boats - U-51 through U-56 - were ordered from Krupp in 1914; they also were called Ms-boats, meaning they were ordered under the war emergency programme. They displaced 715/905 ts and made 17/9 knots, but had only two bow torpedo tubes and a somewhat shorter range of 9.000 nm than the U-43 class (which still was easily twice the range of any contemporary allied submarine). Otherwise, they much resembled the U-31 class, although with an important improvement: They were the first German boats with the aft depth rudders placed immediately behind the screws (they were above the screws on all previous boats); this resulted in better underwater maneuverability and faster crash-dives. All were completed in 1916 with two 88mm guns.
U-51 and U-56 were lost in 1916. The others were rearmed with a single 105mm forward in 1916 or 1917. U-52 landed both 88mm guns at that time; she was lost by accident in 1917.
The other three (U-53, U-54 and U-55) retained the aft 88mm gun and survived the war. U-55 was briefly commissioned by the Japanese as O-3 and used for trials before being scrapped in 1922. The other three were scrapped straight away.
The six boats of this type sank a total of 204 merchant ships, including the Carpathia by U-55 (which had saved the Titanic survivors). They also scored against warships: U-52 sank the French battleship Suffren, the British light cruiser HMS Nottingham, the British sloop HMS Heather and the British submarine C34. U-53 sank an US destroyer and U-54 a British sloop. Wilhelm Werner, one of U-55's skippers, acquired particular notoriety for war crimes; on three separate occasions he ordered the survivors of sunk merchants lined up on his boat's upper deck, had them stripped of their survival vests and crash dived his boat (87 dead prisoners in total). Not surprisingly, this cute fellow joined the NSDAP in 1930 and the SS in 1931, where he eventually attained the rank of Brigadier.
3.2. U-57 class
These six units were the first U-boats ordered from another yard than Krupp or the Imperial Yard, who had built all previous ones. They were built at the AG Weser in Bremen between 1914 and 1916 and turned out very well. They displaced 785/955 tons and had the same gun and torpedo armament as the U-51 type. They made the usual 16,5 knots above water, but only 8,5 knots below the surface, a tendency typical for all later German subs, probably due to an increasing shortage in electric engine production capacity. Range was 11.400 nm at 8 knots, an excellent figure even by the high standards of German subs. The first three were initially fitted with weaker diesels and could make only 14 knots surfaced; for some reason, they also had 4.000 nm less range. Sources are unclear as to whether they were late re-engined.
The last two, U-61 and U-62, were completed with a single 105mm gun instead of the two 88mm pieces of the other four; U-57 received the same armament in 1917. U-57 and U-62 survived the war and were scrapped afterwards; U-61 was lost in 1918.
U-58, U-59 and U-60 replaced their forward 88mm guns with 105mm pieces in 1917 and retained the aft 88mm. U-58 and U-59 were lost soon thereafter, U-60 survived the war and was scrapped.
Six repeat boats - U-99 through U-104 - were ordered in 1916 and commissioned in 1917; they differed only in minor details from U-60 through U-62. As usual, gun armament was more or less subject to availability. U-99 and U-100 were completed with a single 100mm gun. U-99 was lost in this state.
The other four - U-101 through U-104 - had two 88mm guns.
U-101 through U-104 replaced their forward 88mm with a 105mm in 1918, retaining the other two; U-100 was retrofitted in 1918 to the same standard. U-100 and U-101 were the only survivors of this group, were ceded to Britain after the war and scrapped; U-102, U-103 and U-104 were sunk in 1918.
Between them, the twelve U-boats of this class destroyed at least 262 merchantmen, 211 of which were credited to the first six. U-57 also sank a British sloop, U-62 the French armoured cruiser Dupetit-Thouars and U-99 a British destroyer.
3.3. U-63 class
These three vessels, ordered under the war emergency programme, were a Krupp design experiment for a simplified hull better suited to mass production; they were built around available diesels which had been originally ordered by the Russians for Bars-class boats. At 810/925 tons, they were slightly larger than the other 1914 boats; speed was pretty much the same at 16/9 knots, and range exceeded 9.000 nm at 8 knots. All were completed early in 1916 with two 88mm guns.
As usual with early German subs, the forward 88mm was replaced with a 105mm gun in 1917/8 in all three. U-64 was lost in 1918, U-63 and U-65 survived the war and were scrapped afterwards.
Between them, these three submarines sank 163 allied and neutral merchants. U-63 also sank the light cruiser HMS Falmouth and U-64 the French battleship Danton, that being the largest allied warship to be lost to an U-boat torpedo.
3.4. U-81 class
Laid down in 1915 at the Krupp Germania yard in Kiel and all completed during 1916, these six boats (U-81 through U-86) were the mass-production version of the U-63 type with newly built engines; although their flooding arrangements were reworked, giving them a distinctly different look that would become typical for large German submarines of later series, their hulls very much resembled U-63. They were initially designed with rounded stems, all received shark-nose bows before completion, which also became standard for later boats. Range was increased to over 11.000 nm, speed also was slightly better at 17/9 knots. On the minus side, these boats were the last German oceangoing subs with only two bow torpedo tubes. Gun armament varied: U-81 through U-83 were completed with a single 105mm gun; all three retained this armament throughout the war. U-81 and U-83 were lost in 1917; U-82 was ceded to Britain and scrapped after the war.
U-84 through U-86 had two 88mm guns when completed. U-84 and U-85 were lost in 1918 and 1917, respectively, in this guise.
U-86 replaced the forward 88mm gun with a 105mm gun in 1918 and survived the war; she foundered on her way to the breakers in 1919.
Between them these six boats sank 137 merchants; this figure, which is significantly lower than for previous classes, indicates that the job for the U-boats became increasingly harder after 1916. Only U-84 also sank a warship, the sloop HMS Bergamot.
3.5. U-87 class
These six boats (U-87 through U-92) were built by the Imperial Yard at Danzig between 1915 and 1917 and very much resembled the U-43 type, although with an altered CT that more resembled the type preferred by the private yards. Like their predecessors, they had excellent range (over 11.000 nm at 8 knots), but were a tad slower than the Krupp boat (15,5/8,5 knots). From this class onwards, a forward torpedo battery of four tubes became standard for large German U-Boats. U-87 through U-89 were completed with a 105mm gun forward and an 88mm gun aft.
U-90 through U-92 only had the 105mm gun.
None of the class were ever rearmed. U-87 and U-88 were lost in 1917, U-89 and U-92 in 1918. U-90 and U-91 became allied prizes and were broken up. All six together sank 104 merchants and one AMC.
Two improved repeats named U-158 and U-159 were laid down in 1917 on the Imperial Yard at Danzig. They had a considerably lengthened bow with a sharknose shape and a modified CT, resulting in increased displacement (810/1035 tons) and significantly better looks. Armament was six 500mm TTs and one 105mm gun. With a speed of 16/9 knots and a range of nearly 12.500 nm at 8 knots, they would have been excellent performers. Both were virtually complete when the war was over, but none of the pair was commissioned.
3.6. U-93 class
With these boats, Krupp finally adopted the increased forward torpedo battery of four tubes which had been standard for Imperial Yard-built subs since 1913. The increased armament resulted in slightly larger size (840/1.000 ts) and shorter range (about 9.000 nm at 8 knots). Speed was 16,5/8,5 knots, again showing the decrease of average submerged speed of wartime U-boats. With this type, Krupp had reached the end of the tech tree during World War I; it became by far the largest class of oceangoing submarines in the German Navy. A total of 41 were laid down between 1916 and 1918, and another 32 of a stretched, longer-ranged, but otherwise identical variant were on order in 1918, although none of these were begun.
U-93 through U-95 were laid down in 1915; U-96 through U-98 and U-105 through U-114 were laid down in 1916. The first twelve were completed in 1917. Gun fit varied among the units of the class, but apparently was not modified during the war. U-93 through U-95 only had a single 88mm mounted when commissioned. Only U-96 survived the war and was scrapped in Great Britain; U-93 and U-95 were lost in 1918.
U-96 through U-98 had a single 105mm gun forward. All three survived and were ceded to Britain after the war; two were scrapped, one foundered on its way to the breakers.
U-105 through U-110 had a 105mm forward and an 88mm aft. U-106 was lost in 1917, U-109 and U-110 in 1918.
The other three were ceded to the Allies. Britain had U-107 broken up, but France commissioned U-105 as Jean Autric and U-108 as Leon Mignot. Both served till 1935 under French colours without any visible modifications.
All sixteen units were built by Krupp Germania, but the hulls of U-111 through U-114 were subcontracted to the Bremer Vulkan, resulting in a longer buliding period and a slightly different appearance of hull and CT; these did not enter service before 1918. Again, there were variations in gun armament: U-111 and U-113 had a 105mm gun forward and an 88mm gun aft.
U-112 and U-114 had only a 105mm gun. All four survived the war and were broken up afterwards.
A third group of thirteen boats identical to U-111 was ordered in 1917 from the Vulkan Yard in Bremen. The yard proved that they had learned quickly and managed to deliver the first six (U-160 through U-165) to the navy before the war was over. Two more were complete and ready for delivery in 1918, and only the last five (U-168 through U-162) remained uncomplete and were broken up on stocks in 1919. The same goes for another twelve (U-201 through U-212) which were ordered in 1918; the first nine were laid down, but not completed, the last three were not even begun. Among the completed units, U-160 was unique in having two 105mm guns.
All others had only one and looked exactly as U-112 and U-114. Of the U-160 group, only U-165 was lost (to an accident immediately after the armistice); the other five commissioned boats and the two completed, but not delivered ones were ceded to the Allies in 1918. Only the French commissioned their share; U-162 became Jean Roulier and U-166 became Pierre Marast (U-160 also became a French prize, but was cannibalized and never entered service).
The 1918 building programme included further repeat orders of 34 U-boats of a slightly modified type which was 2,45 meters longer and had a range of 11.500 nm. U-229 through U-246 were ordered from Krupp.
U-247 through U-262 were ordered from the Vulkan Yard. None of either group of the 1918 programme was ever laid down.
Between them, the 22 completed submarines of this type sank 146 merchants; only 18 of the type ever went on patrol. U-94 also sank a British sloop and U-106 the destroyer HMS Contest.
3.7. U-115 class
Another newbie to the submarine building business was the Schichau Yard in Danzig, which usually specialized in destroyers. When submarine construction was made top priority after Jutland, Schichau also received orders: Two in 1916 (U-115 and U-116) and 14 under the 1918 programme (U-263 through U-276). At 880/1030 tons, they were the largest variant of the Ms-boat; with a speed of 16/9 kts and a range of 11.500 nm at 8 knots, they easily measured up to the Imperial Yard boats performance-wise. The first two were completed just before the armistice, but not commissioned by the navy. They remained at the Schichau Yard and were broken up. The 14 later units - unlike the 1918 versions of the Krupp and Vulkan boats, they were identical with the 1916 boats and not stretched - were never begun.