U81 class U-Boote (1916)

Germany: Oceanic submersibles: SM U81 to U-86 1916-20.

The U81 class were a mid-war “medium oceanic” or Germaniawerft “Ms” type displacing 800 tonnes, having slightly better speed and range that former models, excellent accomodations, four torpedo tubes and twelve torpedoes in store and for the first time a 105 mm deck gun from the start. U81 was followed by U82, 83, 84, 85 and U-86, ordered in June 1915 and launched in the summer of 1916, and completed late summer and winter 1916. They were quite successful, venturing deep into the Atlantic and not just on the eastern approache sof the British Isles, and the class alone sank 3.537% of all Allied shipping in the war, 427,247 combined tons (for their own combined tonnage of 4,800 tonnes). They also damaged 89,522 combined tons, captured 3,462 combined tons according to uboat.net.

U86 underway in 1917

Development:

The U81 was the next evolution of the Medium Oceanic type submersible by the specialist of the time, Germaniawerft. They basically derived from the U51 class, with infusion of their U63 design innovations mainly fcocusing on the hull shape and conning tower, each iteraiton being a bit larger. The U51 displaced 715 tonnes standard when launched in 1915, the U63 displaced 810 tonnes, so the U81 jad about the same hull, with some revisions, but a completely renewed internal arrangement. In addition to having had excellent seagoing abilities and handling very well, these new arrangements were considered a landmark in German submarine design and just repeated on the WWII type IX boats as they were designed 20 years later…

They repeated the same torpedo arrangememt as previous U51 clas sboats, two forward, two aft, 500 mm tubes (19.7 inches) but doubled the number of torpedoes, from six overall to twelve thanks to the solutions found internally compared to previous U51/66. For the same reason, they cold fit in more powerful diesels for increased performances and still a reduced diving time. The deck armament was revised and standardized to a 105 mm gun, albeit initially U 81 to U 83 had one 10.5cm gun with 140-240 rounds but U 84, 85 and 86 had two 8.8cm guns instead due to shortages of 105 m deck guns. In 1917, U 84 to U 86 were refitted with a single 10.5cm gun (240 rounds in store) as their earlier sisters.

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 U81: Werk 251, Laid down 31 August 1915, Launched 24 June 1916, Commissioned 22 August 1916 (lost 1 May 1917).
-SM U82: Werk 252, Laid down the same day on 31 August 1915, Launched on 1 July 1916 and commissioned on 16 September 1916.
-SM U83: Werk 253, Laid down on 23 October 1915, Launched on 13 July 1916 and commissioned on 6 September 1916.
-SM U84: Werk 254, Laid down on 25 October 1915, Launched on 22 July 1916 and commissioned on 7 October 1916.
-SM U85: Werk 255, Laid down on 29 November 1915, Launched on 22 August 1916 and commissioned on 23 October 1916.
-SM U86: Werk 256, Laid down on 5 November 1915, Launched on 7 November 1916 and Commissioned on 30 November 1916.

Design of the U81 class:

Hull and general design

Fantastic original 1:50 colored Plans of the U-81 class (click to see it in HD).

This plan is a bonanza of details, showing notably the reworked internals of this groundbreaking design, scanned and uploaded for all to marvel at, by germannavalwarfare.info. This might be the most modern-looking, crisp and well preserved 111 years old plan of any WW1 submarine. Colors have their importance, with the submerged rounded bow in green, the utility structures in blue, hardened open parts (CT and torpedo tubes) in yello, deck in buff, ballasts, as the shape of the forward diving planes in their protective frame, and tail plane. The rounded bow was a definitive feature after the U63, providing better underwater speed to the cost of slightly degraded seaworthiness when surfaced. The bow also had a raised section starting past the reinfirced deck for the 10.5 cm gun. There were protective barriers around the first main sponson and a second one aft, smaller, for an hypothetic 8,8 cm deck gun that was ever mounted.

The U81 class shared the same hull with the U63, albeit slightly heavuer at 808 t (795 long tons) surfaced and 946 t (931 long tons) submerged. It was also 1.6 meter longer at 70.06 m (229 ft 10 in) overall for a pressure hull of 55.55 m (182 ft 3 in) but the same beam at 6.30 m (20 ft 8 in) for a pressure hull of 4.15 m (13 ft 7 in). This went with a same draft essentially at 4.02 m (13 ft 2 in) and relatively similar height of 8.00 m (26 ft 3 in) from the top of the coning tower (periscopes down) to the fixed bilge keel. There were two telkecopic wireless radio masts on starboard, installed on the rounded outer hull, over the ballast.

The plans shows also three periscopes, two main ones in the CT, a watch, larger, and an attack, smaller model. The third was out of the CT forward of the sail, its purpose unclear. Behind it was the usual open helmsman position with a small wheel, and the watch bridge behind the CT. These boats had two anchors in recesses forward, and the compartimentation was classic, with the torpeod room forward followed by the crew quarters, the galley and stored, and the batteries below, in rooms tall enough for a crouched man, and main deck hatch in between. In the center, under the CT and bell was located the command center, and immediately after the diesel rooms, separated by a wall, and the electric engines, then small crew quarters and the aft torpedo room. The hull was composed of two main pressure bulkheaded (concave and convexe) sections fore and aft of the command central. In thoery of it was submerged the crew can escape in either the forward or aft sections and then exit through the tubes or hatches.

Power plant of the U81 class

U86 towed to Bristol in late 1918. Note the shape of stern and outer hull, well rounded.
The U81 were powered by the beefiest machinery so far, composed two MAN 6-cylinder 4 stroke diesels for surface running, totalling 2,400 PS (1,765 kW; 2,367 shp) and two Siemens Schuckert electric motors for a coupled 1,200 PS (883 kW; 1,184 shp) when submerged. This was more than on the previous U63 class (which had in-house Germaniawerft diesels by the way), making for a real increase in performances, as this power was passed on two shafts with 1.70 m (5 ft 7 in) propellers. The top speed when surfaced was now of 16.8 knots (31.1 km/h; 19.3 mph) versus 16.5 knots of the previous U66 and 9.1 knots (16.9 km/h; 10.5 mph) submerged versus 9 knots. Range, surfaced, was also increased based on a large fuel capacity, at 114 tonnes versus 118 tonnes on the U66, at 11,220 nmi (20,780 km; 12,910 mi) at 8 knots (15 km/h; 9.2 mph) surfaced (versus 8,100 nm at 8 kts on the U66) and 56 nmi (104 km; 64 mi) underwater at 5 knots (9.3 km/h; 5.8 mph) (versus 60 at the same for the U66).

Armament

The great novelty of the U81 design was its adoption of twelve torpedo tubes, instead of just six (less the four already preloaded in tubes) making for a magistral difference in combat efficience as they were not constrained to sail back after a few days on busy lanes, or forced to use their deck guns in always dangerous engagements. This was perfectly in line with the new policy of unrestructed submarine warfare. But to achieve this feat, Germaniawerft had their engineers budy with taking the same hull essentially but completely rethinking internal arangements in the pressure hull to free smpace both in the machinery and fore and aft section to have six reserve torpedoes forward (two in tubes) and two at the stern. The loser in these modifications was the crew, confined in even crampiers spaces.

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 (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°

⚙ U81 type specifications
Displacement	808 tonnes surfaced, 946 tonnes submerged
Dimensions	70 x 6.3 x 4m (229 ft 10 in x 20 ft 8 in x 13 ft 2 in)
Propulsion	2367 shp (1765 kW) surfaced, 1184 shp (1765 kw) submerged, see notes
Speed	16.8 knots surfaced, 9.1 knots submerged
Range	11,220 nmi at 8 kn, 51 nmi at 5 knots.
Armament	4x 50 cm torpedo tubes fwd/aft (12), 1x 105 mm decl gun (240)
Mex depth	50m (160 ft)
Crew	4 officers, 31 ratings.

Succession: Germaniawerft’s U93 type

The U93 constituted a brand new Ms type based on the U86 and improved in details. They had the same, slightly large hull, and reached a symbolic 1000 tonnes underwater, had the same powerplant, with slightly degraded speed, more fuel in some of the sub-classes and a return to the U66 range. But more importantly, they were armed like Danzig’s U87 class, with six instead of four 50 cm torpedo tubes, four in the bow instead of two, and a total of 12 torpedoes. But also, that class was several fold larger, as it became a “standard” for Atlantic and British Isles operations with 24 boats ordered, from U93 to U114 for Germaniawerft alone, and they were ordered from Bremer Vulkan in vegesack creating a sub-class. The last of this serie was scrapped incomplete at the end of the war. This was THE oceanic submarine wartime standard. Later designed like Project 43 boats (U115 class) remained incomplete, like the last Germaniwerft design, the U127 class.

Career of the U81 class

U81 (1916)

U81 was laid down on 31 August 1915, launched on 24 June 1916 and commissioned on 22 August 1916. She integrated the IV Flotilla under Kptlt. Raimund Weisbach from 22 August 1916 training and 18 October 1916, then to 1 May 1917 (loss), making 5 patrols for 30 merchant ships sunk (88,483 GRT) 2 damaged for 3,481 GRT but no warship. On 1 December 1916 she sank her first, the Swedish steamer Douglas (1,177 GRT) and 18 days later the 1,397 GRT Norwegian Nystrand. On 2 February 1917 she sanl the 2,090t Norwegian Songdal and a day later the British 8,181 GRt Port Adelaide. On the 4th the Italian Maria (992t) and a day later the British 4,511t Wartenfels. On the 7th the British 1,242 GRT Gravina and the day after, the British 8,253t Mantola, her biggest kill of the week. On the 10th she sank the British 4,227 GRt Netherleen and completed her patrol by bagginf two days later the Swedish 2,577t Hugo Hamilton.

Her next patrol started in early March. On the 10th she sank the same day the Noerwegian 998t steamer Algol and 415t Skreien, both likely by gunfire. On 13 March 1917 she sank the British 2,733t Coronda and a day later the 2,017t Paignton. On the 18th she sank the British 3,061 GRT Pola and 3,112 GRT Trevose and a day after, the 5,900rt packet ship Alnwick Castle and 4,194 GRT Frinton. Next rampage was on 22 March with the Norwegian Attika (2,306 GRT) and on the 25th, three ships the same day the Norwegian C. Sundt (1,105 GRT), Garant (735t) and Laly (1,880 GRT).

Next patrol in April saw the sinking of the British Amulree (1,145 GRT) on the 24th, and on the 25th, three vessels again, one Norwegian, the Glenesk (1,369 GRT) and British Heathfield (1,643), and Invermay (1,471 GRT). On the 27th she bagged the Italian Uranus (3,978 GRT) and a day later, two ships the British Jose De Larrinaga (5,017t) and Terence (4,309t) followed in 30 April by badly damaging the small Danish steamer Elisabeth (217t) by gunfire, surfaced, probably out of torpedoes. Her next patrol was in May. The 1st day, she spotted and damaged the 3,264 GRT Dorie and sank the British 6,458 GRT cargo ship San Urbano. Later she was ambushed by the British hunter submarine HM E54 (of the excellent E class), torpedoed West of Ireland while surfaced probably by night, with 29 dead and 7 survivors.

U82 (1916)

U82 was laid down on 31 August 1915, launched on 1 July 1916 and commissioned on 16 September 1916. She entered the IV Flotilla after training under orders of Kptlt. Hans Adam until 29 April 1918 and Kpt.Lt. Heinrich Middendorf from 30 April to 11 November 1918. She performed 11 patrols, sinking 34 merchant ships for 98,091 GRT, as well as two auxiliary warships, damaged two merchant ships (14,542 GRT) and an auxiliary warship rated for 18,372 GRT. This started in a firsdt patrol on 5 December 1916 by the Danish Dorit (242t) and Ella (879t) and a day later, Christine (196t) and Robert. Four days later, the Gerda (287t). Next patrols she sunk the more substantial French Omnium (8,719 GRT) on the 1st, Danish Viking (761t) on the 3th January and a day later the 1,925t Italian Calabro and on the 5th the Danish 1,028t Ebro and a day later the 1,720t Beaufront. No activity of kills until her next patrol in April, with the Norewegian Marita on the 23th (1,759 GRT) and a day later the British Thistleard (4,136 GRT), and next day the 4,060t Hackensack.

On 4 May she sank the Greek Ellin (4,577 GRT), and in June she sank the 2,917t sloop HMS Zylpha. On 13 June she sankl the Norewegian Storegut (2,557 GRT) and athe nex day the British Ortolan (1,727 GRT), Taplow (2,981 GRT), and two the next on 15 June, the Dutch Albertine Beatrice (1,379 GRT) and British Westonby (3,795 GRT). The next day the British Jessie (2,256 GRT). On the 18th she sank the British Thistledhu (4,026 GRT) and on the 25th Monkstone (3,097 GRT). On the last day, 31st of July 1917 she sank the British Orubian (3,876 GRT) and the auxiliary cruiser HMS Quernmore (7,302 t). Next patrols were in September: On the 19th, the British Saint Ronald (4,387 GRT), and on 15 November, the Dutch De Dollart (243 GRT). In 1918, February, on the 18th she sank the Glencarron (5,117 GRT) and British Philadelphian (5,165 GRT). On 8 April she badly damaged the British Tainui (9,965 GRT) and two days later she sank the Westfield (3,453 GRT).

On 5 June she sank the US Argonaut (4,826 GRT), and on the 7th June, the Norwegian Brisk (1,662 GRT), a day later the British Hunsgrove (3,063 GRT), Saima (1,147 GRT). On 4 September the sank the US Dora (7,037 GRT) and a day later damaged the USS Mount Vernon. On the 12th she sank the Galway Castle (7,988 GRT) and on the 16th the British Madryn (2,244 GRT). She was inactive afterwards in November until the end of the war, and surrendered to the entente on 16 January 1919, attributed to UK and broken up at Blyth in 1919–20.

U83 (1916)

U83 was laid down on 23 October 1915, launched on 13 July 1916 and commissioned on 6 September 1916. Like her sister she joined the IV Flotilla after training with Kapitänleutnant Bruno Hoppe from 31 October 1916 to 17 February 1917 when lost. She only performed two patrols, sinking six merchant ships sunk (6,450 GRT) and damaged an auxiliary warship (3,207 GRT): On 17 December 1916, the Swedish Niord (123 GRT). On 4 February 1917 she sank the French Anna Maria (141 GRT) and the French Coquette (167 GR), and two days later, the British Crown Point (5,218 GRT), and the next day, on 7 February the Russian Diaz (637 GRT), on the 10th the French Paquerette (164t) and aweek later on the 17th she damaged the HMS Farnborough (3,207t) which managed on her side to sink her on the 17th.

U84 (1916)

U84 was laid down on 25 October 1915, launched 22 July 1916, and commissioned on 7 October, she joined after training the IV Flotilla from 3 December 1916 until 26 January 1918 under Kptlt. Walter Roehr. She performed 8 patrols, sinking 28 merchant ships (84,906 GRT) and a 1,290 tons warship, than damaged 7 merchant vessels (42,149 GRT) and took two more as prize (3,462 GRT).
How it unfolded: On 14 December 1916 she captured the Norwegian Aamot (1,362 GRT), and four day later she also captured the Swedish Malcolm (2,100 GRT). On 9 January she damaged the British Alexandrian (4,467 GRT). A day later she sanl the Norwegian Bergenhus (3,606 GRT). On the 12th she sank the British Auchencrag (3,916 GRT) and on the 15th she sank the British Kinpurney (1,944 GRT), and the same day the Danish Omsk (1,574 GRT). On the 20th she sank the Britsh “Bulgarian” (2,515 GRT). On the 20th she sanl the British Neuquen (3,583 GRT). In Feburay she had another round: On the 17th February she sank the French Bayonne (2,589 GRT) and British Romsdalen (2,548 GRT). A day later she bagged four ships in a row: The British Berrima (11,137 GRT), badly damaged, as well as the Hunsworth (2,991 GRT), sinking the Norwegian Juno (2,416 GRT) and the British Valdes (2,233 GRT). On the 21st she sank the Norwegian Dukat (1,408 GRT) and the next day, the Invercauld (1,416 GRT). On 13 April she sank the British Argyll (3,547 GRT) and damaged the Lime Branch (5,379 GRT). On 18 April she sank both the Cragoswald (3,235 GRT) and Rowena (3,017 GRT). On the 19th she sank the Elswick Manor (3,943 GRT) and the next day the Malakand (7,653 GRT).

Next patrol in the summer of 1917 she sank on 1st July 1917 the Spanish Bachi (2,184 GRT), and British Demerara (11,484 GRT) and on 4 July the Goathland (3,044 GRT). On the 7th the Condesa (8,557 GRT) and Norwegian Oxø (831 tonnes). On 12 August she bagged the Norwegian Ursus Minor (623 GRT) and a day later the British sloop HMS Bergamot. Next in the winter, she sank on 24 November the US Actaeon (4,999 GRT). On 1st December she sank the Greek Antonios Stathatos (2,743 GRT), and a day later the Birchgrove (2,821 GRT). On 9 January 1918 she sank the Bayvoe (2,979 GRT), and on the 10th the Cardiff (2,808 GRT). On 11 January she sank the British Mereddio (3,069 GRT). On 12 January she sanl the French Chateau Laffite (1,913 GRT) and on the 17th the British Messidor (3,883 GRT). She was sunk by unknown cause off Penmarch (Britanny, France) on 15 June but originally though to have been rammed and depth charged by PC62 in St George’s Channel.

U85 (1916)

U85 was laid down on 29 November 1915, launched on 22 August 1916 and commissioned on 23 October 1916. She was part of the IV Flotilla after training under Kptlt. Willy Petz from 15 January to 12 March 1917 performing three patrols, sinking four merchant ships (20,225 GRT) and damaging one (7,608 GRT). On 26 January 1917 she sank the Norwegian Dicax (923 GRT). The next rampage was on the 6 and 7th February 1917, sinking the Cliftonian (4,303 GRT), and Explorer (7,608 GRT), California (8,669 GRT) and Vedamore (6,330 GRT). He foundered in the North Sea after 7 March 1917 with 38 dead, all hands lost.

U86 (1916)

U86 underway. Note the pointy prow, a new feature kept for next Germaniawerft designs.
U86 was the last in class, laid down on 5 November 1915, launched on 7 November 1916 and commissioned on 30 November 1916 under Kptlt. Friedrich Crüsemann until 22 June 1917, entering after training the IV Flotilla from 21 February 1917 to 11 November 1918. Her second captain was Alfred Götze from 23 June 1917 to 25 January 1918 and Oblt.z.S. Helmut Patzig until V-Day on 11 November 1918, performing 12 patrols, the longest carrer in class, also the most successful, sinking 31 merchant ships (89,821 GRT) and two auxiliary warships (27,762 GRT), damaging an armed trawler of 163 GRT. On the 23th she sank the 165t Queenborough and on 5 April, three kills, the French Dunkerquoise (127t), Marie Celine (142t) and the Belgian Siberier (2,968 GRT) and the next day 6 April she sank the British Rosalind (6,535 GRT). On the 18th April he sank the Swedish Atalanta (1,091 GRT). On 28 May she sank the British Antinoe (2,396 GRT) and Limerick (6,827 GRT) and a day later the Oswego (5,793 GRT). On 31 May she sank the Greek N. Hadzikyriakos (3,533 GRT). On 2 July she sank the small Swedish Bessie (66t). On 10 August he sank the Norwegian Capella I (3,990 GRT), and on 13 August the British Turakina (9,920 GRT). On 15 December she gunned duel and damaged the small French escort Baron Leopold Davilliers (163t).

On 20 December she sank the British Polvarth (3,146 GRT). On 14 February she sank the trawler Bessie Stephens (119t). On 17 February she sank the British Pinewood (2,219 GRT). On the 19th she sank the trawler Wheatflower (188t) and a day later the British Djerv (1,527 GRT). On the 23th she sank the Norwegian Ulabrand (2,011 GRT). On 30 April she sank the Kafue (6,044 GRT) and the same day the Kempock (255 GRT). On 2 May she sank the Medora (5,135 GRT), on 5 May the Tommi (138 GRT), on 6 May the Leeds City (4,298 GRT). On 11 May she sank the Norwegian San Andres (1,656t) and on the 12th the British Inniscarra (1,412 GRT). On the 16th she sank the British Tartary (4,181 GRT) and on 22 May the Norwegian Meran (656t). Next in June, the 21st, she sank the Norwegian Eglantine (339 GRT) and on the 25th the British Atlantian (9,399 GRT) and two days late the ex-passenger steamer turned Canadian Navy AMC Llandovery Castle (11,423t). Rhe 1st of July in a single day she sank the troopship USS Covington (16,339t) -a former German liner seized in the US- and the British Origen (3,545 GRT). After July 1918 she made no more sorties, possibly restricted to training, until surrendering on 20 November 1918 at Harwich, paraded at Bristol in December with UC-92, for paid visitors to visit her, proceeding to charity. She was then laid up at Portsmouth until scuttled in the English Channel on 30 June 1921. This is the only one in class for which we have photos, shown here.

U86 conducted to Bristol

U86 and UC92 on exhibition in Bristol in Xmas 1918