U87 class

Germany: Oceanic submersibles: SM U87 to U-92 1916-20.

The U87 class of Project 25 were six oceanic submersibles (Mittle-U Boote) built at Danzig in 1915-17, double-hulled. They were based on the U50, had an improved diving time of 56 seconds, an met sucess in operations, sinking collectively 321,556 tonnes of shipping, so 71 times their own displacement. However all but two were lost: U87 was sunk by ramming by P56 in the Irish Sea in 1917, U88 struck a mine in the Deutsche Bight. U89 was rammed by the cruiser HMS Roxburgh in 1918 in the Atlantic. U92 was sunk by a mine in the North Sea also in 1918.

U-Boat described as SM. U90 but showing a pointed prow.

Development (Project 25):

The Project 25 boats from which we have no plan surviving, was heavily based on the “U50 class” in reality the last of the U43 class by Danzig, introducing a brand new double hull design with new rounded shapes and straight stem. The U87 class was just an improvement over this design. Both the U43/U50 and U87 are considered part of Project 25. They were classed still as “mittle-U”, mid-oceanic submersibles with a range allowing Atlantic cruises. Back in 1913 when the U43 were planned, Danzig looked at Italian Laurenti double-hull designs, believing thay had more advantages compared to classic single hulls with ballasts, like extra reserve buoyancy, better surface stability, better streamlining and better diving time.

The first order for the U43 was signed in July 1913 and last in August 1914. Eight boats were ordered from Danzig, the “mobilization type” (“mob”) to follow until U50, reaching an unprecedented 940 tonnes underwater (878t for the U31 class, 867t for the U27 class). They needed larger trim tanks due also to the new torpedo tubes forward. In 1915, KW Danzig decided to propose the Kaiserliches Marine a repeat of its design with some improvements, notably the diving time, and a stronger deck that would accept two deck guns, including at least one 105mm/43 TK L/45 C/16, and carry more torpedoes, from six to twelve. The new U87 class would be larger overall, for increased fuel capacity and a better range as well.

Construction

The U81 class were all built at Germaniawert shipyard in Kiel, ordered in June 1915 as werk 251 to 256, bulilding them on the following dates:
-SM U87: Werk 31, Laid down on 28 October 1915, launched on 22 May 1916 and commissioned on 26 February 1917.
-SM U88: Werk 32, Laid down on 20 November 1915, launched on 22 June 1916 and commissioned on 7 April 1917
-SM U89: Werk 33, Laid down on 15 December 1915, launched on 6 October 1916, and commissioned on 21 June 1917.
-SM U90: Werk 34, Laid down on 15 December 1915, launched on 6 October 1916, and commissioned on 21 June 1917
-SM U91: Werk 35, Laid down on 1 August 1916, launched on 14 April 1917 and commissioned on 17 September 1917
-SM U92: Werk 36, Laid down on 20 August 1916, launched on 12 May 1917 and commissioned on 22 October 1917.

Design of the U87 class:

Hull and general design

The U87 class displaced 757 t (745 long tons) surfaced and 998 t (982 long tons) submerged, for an overall length of 65.80 m (215 ft 11 in) for the outer hull and 50.07 m (164 ft 3 in) for the pressure hull. In beam they reached 6.20 m (20 ft 4 in) overall for the outer hull, and 4.18 m (13 ft 9 in) for the pressure hull. The total height, from the keel to the portiuco above the CT was 9.35 m (30 ft 8 in). Draught was 3.88 m (12 ft 9 in). Compared to the boast from which they evolved the U50, they displaced more (725/940 t) were longer but no more larger (65 x 6.20m) with the same pressure hull in diameter. Compared to the rival Germaniawerft type 81, they were 4.26 metres (14.0 ft) shorter, with a pressure hull shortened by 48 centimetres (1 ft 7 in), were 1.2 knots (2.2 km/h; 1.4 mph) slower while surfaced and 0.5 knots (0.93 km/h; 0.58 mph) slower submerged but had a better range by 180 nautical miles (330 km; 210 mi) and carried more torpedoes.

Now, there are diverging accounts of the way they look, some sources and photos showed a pointy bow, other shows a straight bow, and basically a slightly scaling up of the U50 design, with , as signalled above a well rounded double hull, as a contrast to previous Germaniawerft boats that had a streight line separation betrween the outer hull and ballasts. Thanks to the work done by the teams that examined SM 90 we known the conning tower was about the same type as for the U50, with the usual open air small helmsman post forward, then the two persicopes, attack and watch, followed by a large open conn protected, and then a lower platform for observation and access.

The pressure hull was divided into 7 main compartments separated all by concave/convexe bulkheads that better resister pressure and that could all be fully enclosed with heavy hatches. Normal access hatches to the deck were three, one forward of the 105mm gun, one in the conn, and on aft of the 88mm gun. There was a small opean air rudder aft, on the same axis as the main underwater rudder for extra agility underwater. The main keel had a central detachable part used as emergency solid ballast.

The outer hull ended with a slope upwards and the ships were often camouflaged, not with complex patterns, but with TB dark grey paint applied to the upper surfaces of the hull and partly on the CT to better blend with the north sea when seen from above. Light grey was kept for all “vertical” surfaces. The crew rose to 36 men, including 4 officers. The CO grade was Kapitänlieutenant (Kptlt.). They U87 boats were all deployed in the III. Flotilla based on Wilhelsmhaven on western side of the Jade Bight, North Sea. The issue in 1917 when they entered active service, was that the British had heavily mined many of the usual deployment channels for German U-Boats, so they had to take the “long road” via the Baltic and round Scotland, then round the British Isles to hunt down merchant traffic, most often their usual hunting ground was the Irish sea.

Power plant of the U81 class

No change there, the boats were rather conservatives, ubut with more power for extra surfaced speed, with two shafts, driving each a 1.66 m (5 ft 5 in) bronze fixed pitch 3-bladed propeller. When surfaced, they were driven by two 2,400 PS (1,765 kW; 2,367 shp) Körting or MAN diesel engines surfaced (versus 2,000 PS on U50) and when underwater, by two Siemens-Schuckert electric engines for 1,200 PS (883 kW; 1,184 shp) just as for U50. Top speed really gained compared to U50 from 15.2 to 16.8 knots (31.1 km/h; 19.3 mph). Underwater it fell slightly from 9.7 knots (18.0 km/h; 11.2 mph) to 9.1 knots (16.9 km/h; 10.5 mph). The longer hull however made for better fuel bunkerage described at 133 tons for 11,380 nautical miles (21,080 km; 13,100 mi) at 8 knots, versus 11,400 nmi (21,100 km; 13,100 mi) for the U50. Diving ability was the same, ca. 50 m or 164 feet.

Armament

The six submarines diverged in armament:
U87, 88 and 89 were completed with a 105mm/43 TK L/45 C/16 deck gun, a 88mm/27 TK L/27 C/08 secondary aft deck gun and four torpedo tubes (500mm), two at the bow bow, and two at the stern for up to 12 torpedoes total. U90 was completed with a 105mm/43 TK L/45 C/16 but no 8,8 cm aft. U91 and U92 had the 105mm/42 Utof L/45 C/16 deck gun.

Torpedo Tubes

U81 and sisters were armed with a 50 cm or 19.7 inches tube fore and aft and four G7 torpedoes (entering service in 1913), or possibly surplus older G/6. The Kerosene powered G/6D was considered too “temperamental” for submarine use indeed. The G/6 was developed from 1908 and entered service in 1911. The Royal Navy was slower on this chapter, only introducing the 21″ (53.3 cm) Marks II, II* and II** for submarine use from 1914 onwards. The four 500 mm (19.7 inches) torpedo tubes could be reloaded from above via the larger hatches going through the outer upper hull.

G7 Torpedo

The G7 was designed in 1910 and entered service in 1913. Originally designed for surface ships, but in 1917 it started to be used on U-boats.
Specs: Weight: 3,009 lbs. (1,365 kg), Overall Length: 276 in (7,020 m).
Explosive Charge: 430 lbs. (195 kg) Hexanide warhead
Range/Speed settings: 4,370 yards (4,000 m)/37 knots and 10,170 yards (9,300 m)/27 knots
Power: Decahydronaphthalene (Decalin) Wet-Heater

10.5 cm SK L/45 naval gun C16 (1916)

As planned from the start, the Germaniawerft U81 clas sboats were designed with a reinforced forward deck to accept a single 105mm deck gun with between 140 and 240 rounds. The crew was planed to manage it, with four officers, and a proper gunnery officer. Built by Meddinghaus, this heavy deck gun was designed specially for deck use, low, with many sensible elements protected from corrosion.

Specs 10.5 cm SK L/45

1,450 kg (3,200 lb), 4.725 m (15 ft 6.0 in), 6.8 mm (0.27 in) wide.
Shell 10.5 cm (4.1 in) 25.5 kg (56 lb) fixed Brass Casing 17.4 kg (38 lb)
Breech: Horizontal sliding-block, MPL C/06: -10° to +30° mount
Rate of fire: 15 RPM
Muzzle velocity 710 m/s (2,300 ft/s)
Effective range 12,700 m (41,700 ft) at 30°

8.8 cm Schnelladekanone Länge 30 naval deck gun

Due to shortage of the above, from U84 onwards, two 88mm 27 calibre TK L/30 C/08 deck guns was installed instead, forward and aft. They were removed and replacec by a single 10.5 cm deck gun only when available later in 1917.

The 8.8 cm SK L/30 gun used the Krupp horizontal sliding block, or “wedge” and the submarine deck version was on either a retractable or fixed pivot mount. The Krupp mount retracted vertically through a hatch, and the Erhardt version folded down onto the ship’s deck. They avoided underwater drag and turbulences. It seems U19 class had the Ubts.L of the second type.
The 8.8 cm SK L/30 was a widely used naval gun on World War I pre-dreadnoughts, cruisers, coastal defence ships, avisos, submarines and torpedo boats in both casemates and turrets as well.
This calibre became so ubiquitous in the German Navy it was still a favourite for WW2 U-Boats as well starting with the Type VII. Read more.

Specs 8.8 cm SK L/30 on Ubts.L mount

Weight: 644 kilograms (1,420 lb)

Overall length: 2.64 meters (8 ft 8 in).
Breech: Krupp horizontal sliding block
Shell: fixed 7 kg (15 lb) cal 88 mm (3.5 in)
Elevation: -10° to +30°
Rate of fire: 15 RPM
Muzzle velocity: 590 m/s (1,900 ft/s)
Maximum firing range: 7,3 km (8,000 yd) at 20° or 10,5 km (11,480 yards) at 30°

10.5 cm SK L/42 Utof deck gun C/16 (1916)

Topic in research, might be an error of denomination.

Author’s rendition of the U87 class

Another rendition of the type showing the double hull, pressure hull, bulkheads, and deployed wireless radio masts.

⚙ U87 type specifications
Displacement	757 tonnes surfaced, 998 tonnes submerged
Dimensions	65.8 x 6.2 x 4.2m (215 ft 14 in x 20 ft 4 in x 13 ft 9 in)
Propulsion	2x 2,367 shp (1765 kW) surfaced, 2x 1,184 shp (883 kw) submerged, see notes
Speed	16.8 knots surfaced, 9.1 knots submerged
Range	11,380 nmi at 8 knots, 56 nmi at 5 knots.
Armament	6x 50 cm torpedo tubes 4 fwd/2 aft (12), 105 mm deck gun, see notes
Max depth	50m (160 ft)
Crew	4 officers, 32 ratings.

Succession:

On one hand there was the type 93 U-Boote standard produced by Germaniawerft and Bremer Vulcan. The U87 were 5.75 metres (18.9 ft) shorter, with a pressure hull 5.98 metres (19.6 ft) shorter as well, 105 tons lighter. They still had a range 2,288 nautical miles (4,237 km; 2,633 mi) longer, but speed was down to 1.2 knots (2.2 km/h; 1.4 mph) slower, surface, same submerged. On the other one, Danzig’s next design was the U115 class. They were much larger at 883/1,233 tonnes.

Career of the U87 class

U87 (1916)

U87, Bundesarchiv CC. Note the camoufage, with dark grey applied to all horizontal surfaces.

U87, the lead boat, was laid down on 28 October 1915, launched on 22 May 1916 and commissioned on 26 February 1917 under command of Kptlt. Rudolf Schneider. She trained from 26 February 1917 until 24 April and entered the III Flotilla at Wilhelmshaven. She made 5 patrols, first under Schneider, then under Kptlt. Freiherr Rudolf von Speth-Schülzburg from 13 October 1917 until her loss in December. In total she sank 22 merchant ships (59,828 GRT) and damaged two. Her first patrol in May-June saw the following: On 23 May she damaged by gunfire the Dutch Bernisse (951t) and the same day snak the Dutch Elve 962t. Three days later she bagged the same day the Russian Lucipara (1,943 GRT) and British Saint Mirren (1,956 GRT). On 30 May she sank the british Bathurst (2,821 GRT) and Hanley (3,331 GRT). On 2 June again she attempted a double kill, the Italian Eliofilo (3,583 GRT) but only damaged the French Mississippi (6,687 GRT).

In her next patrol in July, she sank the following: On 4 July Loch Katrine (151t), probably by gunfire, 4 day later the British Valetta (5,871 GRT), on 10 July the British Seang Choon (5,807 GRT) and a day later the British Kioto (6,182 GRT) then on the 12th the British Castleton (2,395 GRT) and on the 16th the british Tamele (3,932 GRT), three days later the Norwegian Artensis (1,788 GRT) and on the 21th, the british Coniston Water (3738 GRT). Her new patrol was in August: On 19 August the Norwegian Eika II (1,268 GRT), on the 21 st the British Oslo (2,296 GRT) and a day later the Danish Alexander Shukoff (1,652 GRT) than on the 27, two Danish steamers, Anna (1,211 GRT) and Aurora (768 GRT). It iseems her newt two patrols were either for training or without results. Her last patrol was in december: On 13 December she san the British Little Gem (114t) probably by gunfire, on the 24st the british Daybreak (3,238 GRT) and on Xmas day the British Agberi (4,821 GRT), last ship to report her. She was signalled to the nearby sloop HMS Buttercup which spotted and rammed her in the Irish Sea. U87 dived and she depth-charged her for good measure, followed by the P-class sloop P.56. Another DC attack resulted in the usual suspects, air, debris and a pool of fuel oil. U-87 sank with her entire crew of 44.

U88 (1916)

U88 was laid down on 20 November 1915, Launched on 22 June 1916 and commissioned on 7 April 1917. She operated under Kptlt. Walther Schwieger from 23 July 1916 to 5 September 1917 with the III Flotilla, making 4 patrols and sinking 11 merchant ships (33,053 GRT), one auxiliary warship and damaged two merchant ships. On 23 May 1917 she sank the Norwegian Hector (1,146t) and two days later the auxiliary warship HMS Hilary (6,329t). On the 28th she damaged (presumably by gunfire) the 417t Russian steamer “Roma”. A day later she sank the British steamer Ashleaf (5,768t) on bagged two more ships on the 31st: The French Jeanne Cordonnier (2,194 GRT) and Japanese Miyazaki Maru (7,892 GRT).

On 1 June she sank the British Cavina (6,539 GRT) and five days later the Dutch Eemdijk (3,048 GRT). On 7 June she sank the John Bakke from Norway (1,611 GRT). Her next patrol was less successful: On 29 June she sank the Norwegian Escondido (1,066 GRT). On 3 July 1917 the british steamer “Iceland” (1,501 GRT). On 7 July she damaged by gunfire the small British steamer “Coral Leaf” (428 GRT). On 13 July she san the Danish Ceres (1,166 GRT) and on the 16th, the Danish Vesta (1,122 GRT) her last victory. She depared in September for her last mission, never heard again. She was presumably sunk on 5 September 1917 off Terschelling after hitting a mine, with all hands lost.

U89 (1916)

U89 was laid down on 15 December 1915, launched on 6 October 1916, and commissioned on 21 June 1917. She trained under Kptlt. August Mildenberger from 21 June 1917 until entering the III Flotilla and start operations from 6 September 1917. She performed 3 patrolms, sinking 4 ships, damaging one. From 16 January to 12 February 1918 she was under command of Kptlt. Wilhelm Bauck. On her first patrol on 2 October 1917 she sank the Portuguese Trafaria (1,744 GRT) and a day later the British Baron Blantyre (1,844 GRT), then on 6 October the French Victorine (1,241 GRT). In her second patrol on 12 December she damaged the French Reine D’arvor (324 GRT), probably by gunfire. On 21 December she sank the Portuguese Boa Vista (3,667 GRT). Her whereabouts are unknown until Bauk took command, she probably made another patrol in January but on 12 February 1918, she was spotted, rammed and sunk by HMS Roxburgh off Malin Head, sinking with all hands. Her wreck never had been localized.

U90 (1916)

U90 was laid down on 29 December 1915, launched on 12 January 1917 and commissioned on 2 August 1917. She started training under Kptlt. Walter Remy from 2 August 1917 and integrated the III Flotilla 10 September 1917. On 31 July 1918, Remy was replaced by Oblt.z.S. Helmut Patzig, and on 1st sept. August 1918, replaced in turn by Kptlt. Heinrich Jeß under she was surrendered to the allies. She was one of the most successful in class, making 7 patrols and sinking 28 merchant ships (49,348 GRT), two auxiliary warship, damaging a merchant ship and an auxiliary warship.

1st Patrol: On 25 September 1917 she sank by gunfire the small French trawler Union Republicaine (44 GRT). On 27 September she made a triple kill, the French trawler Deux Jeannes (50t), Liberte (49t) and Peuples Freres (41t) like an appetizer. On 30 September she started more serious kills, with the british Drake (2,267 GRT) and Heron (885 GRT) the same day. On 1 October she sank the French Neuilly (2,186 GRT) and on 3 October the French coaster Jeannette (226 GRT).

2nd Patrol: On 20 November she sank the British Robert Morris (146t) and a day later the Aros Castle (4,460 GRT).
3rd patrol: On 22 January 1918 she damaged the British Corton (3,405 GRT) and the same day the Spanish Victor De Chavarri (2,957 GRT). On the 24th she baged the British trawler Charles (78t) and on the 25st the British coaster Normandy (618 GRT). A day later she sank the French sailing ship Union (677 GRT) and on 30 Januarythe Danish Lindeskov (1,254 GRT), then a day later the Russian Martin Gust (248 GRT) and on 1 February 1918 the British Arrino (4,484 GRT).

President Lincoln Sining

4th Patrol. Back in operation in March 1918, on the 16th she sank the British Oilfield (4,000 GRT) and on the 28th the City of Winchester (114t), and on 8 April the Norwegian Superb (489t).
In May she had another patrol (5th), claiming on the 29th the British Begum (4,646 GRT) and Carlton (5,265 GRT) and on the 31st the troopship USS President Lincoln (18,168t) on its way loaded with soldiers to France which caused some turmoil back in the US. Of the 715 people aboard, 26 men were lost with the ship, Lieutenant Edouard Izac was taken aboard U-90 as prisoner. Survivors were rescued from lifeboats late that night by the US destroyers Warrington and Smith, landed in Brest on 2 June.

6th patrol: In August, with clearer skies, and under Oblt.z.S. Helmut Patzig, she bagged the following: On 15 August 1918 USS Montanan (6,659t), and the same day the French J. M. J. (54t) and a day later the USS West Bridge (5,189 t) which survived. On 17 August she sank the British Escrick (4,151 GRT) and US Joseph Cudahy (3,302 GRT). On 24 Augustshe sank the Portuguese Graciosa (2279 GRT). Her 7th and last patrol was in October under Kptlt. Heinrich Jeß saw only two kills, the British Dundalk (794 GRT) on the 14th and Pentwyn (3,587 GRT) on the 16th. Back home, she eventually Surrendered to the entente on 20 November 1918 and foundered in tow in 1919.

U91 (1916)

U91 was laid down on 1 August 1916, launched on 14 April 1917 and commissioned on 17 September 1917. She trained under Kptlt. Alfred von Glasenapp, her only captain, until 13 December 1917 when she integrated the III Flotilla. She was probably the most successful in class, sinking 37 merchant ships sunk (83,302 GRT) and damaging two more.
1st patrol: She started operation the eve of Xmas, on 24 December 1917, badly damaging the British Elmleaf (5,948 GRT), and on the 28th sinking the Robert Eggleton (2,274 GRT). On 2 January 1918 she sank the British Boston City (2,711 GRT) and on the 4th the British Otto (139t) and a day later the Knightsgarth (2,889 GRT). On the 7th she concluded her patrol by sinking, probably by gunfire the British drifter Premier (89 GRT).

In her second patrol in February-March 1918 she sank on the 19th the British Beacon Light (2,768 GRT), on the 22th the Haileybury (2,888 GRT) on the 23th double kill with the Birchleaf (5,873 GRT) assumed sank but she survived, and British Viscount (3,287 GRT). The next day she bagged the Renfrew (3,830 GRT) and ended her patrol again with a small vessel, the British coaster Bessy on 2 March (60t). On her 3rd patrol in April she had her greatest killing spree, with on 20 April the British Florrieston (3,366 GRT), a day later Landonia (2,504 GRT) and Normandiet (1,843 GRT) and a day later the Baron Herries (1,610 GRT). The on 26 April the Ethel (100 GRT) and a day later two, the Gresham (3,774 GRT) and Russian Walpas (312 GRT). Three three on the 28th, the Portuguese Damao (5,668 GRT), British Oronsa (8,075 GRT) and French coaster Raymond (109t).

Her next patrol in july was less successful: She claimed on 1 July the British Westmoor (4,329 GRT), on the 6th the Port Hardy (6,533 GRT), and three days later the Italian Silvia (3,571 GRT). On the 13th she sank the British Badagri (2,956 GRT), Fisherman (136 GRT) and on the 25th, the US Tippecanoe (6,187 GRT). Her lst patrol was in October, relatively successful, but mostly sinking small trawler and drifters: On 1 October the French Therese et Marthe (32t) ad on the 2, Maia (185 GRT), Marie Emmanuel (32t), Ave Maris Stella (22t). On 4 October she bagged the Spanish Mercedes (2,164 GRT) and a day later the British Heathpark (2,205) and Erindring (1,229 GRT). On 8 October the Portguese Cazengo (3,009 GRT) and on 9 October the French coaster Pierre (354 GRT). On 11 October the Norwegian Luksefjell (2,007 GRT) and on 14 October the French Bayard (55t). This was her last kill of the war, she surrendered to France 26 November 1918, and was BU at Brest in July 1921.

U92 (1916)

The last U-Boat in class, she was laid down on 20 August 1916, launched on 12 May 1917 and commissioned on 22 October 1917. She trained under Kptlt. Max Bieler until joining the III Flotilla like her sisters o, 27 December. On 31 May 1918 her was replaced by Kptlt. Günther Ehrlich which operated from 1 June to 9 September 1918, her loss. She made 5 patrols and only sank 5 merchant vessels for 16,000 GRT, damaging two. Her first war patrol started on 1 January 1918 via Heligoland Bight, around Scotland and ending in the northern Bay of Biscay, no sinkings. She was back on 30 January. Her 2nd Patrol started on 24 February, she was sent southwest of Ireland via the Kiel Canal and Baltic Sea to avoid heavy mining in the North Sea. No victories albeit she missed the Skaw, former commerce raider Wolf stranded a prize. She still torpedoed the 7,034-ton steamer British Princess, which was only damaged. She was back to Kiel on 23 March. After a refit, she started her 3rd patrol 24 April, assigned to southwest Ireland via Heligoland, Kiel Canal, Baltic, Denmark, Scotland, Fair Isle. She was back to Wilhelmshaven on 28 May and attacked three times by entente ships and a patrol seaplane, no successes. Kptlt Bieler was relieved of command.

Her 4th Patrol also to the Ireland station started on 29 June under Kptlt. Günther Ehrlich. She was attack her second day in patrol south of Dogger Bank, ambushed by the British submarine E42, which torpedoed her but missed. She attacked a convoy on 9 July and sank two armed steamers, 2814t Ben Lomond southeast of Daunts Rock and 3,550 ton Mars, 74 nmi (137 km; 85 mi) west-north of Bishop Rock. She had a collision. On 10 July, she attacked by gunfore the 339 ton armed schooner Charles Theriault but she survived, towed to port. Next day she bagged the 5,590-ton USS Westover. On 13 July, she sank the 3058-ton Spanish steamer Ramon de Larrinaga ending her cruise On 22 July. For her 5th Patrol she left via Kattegat on 4 September but hit a mine on 9 September in Area B, North Sea Mine Barrage, sank with all hands. Her wreck was rediscovered and explored by late 2007 by the British Maritime and Coastguard Agency ship Anglian Sovereign.