U5 class (1910)

Germany: SM U5, U6, U7, U8 (1910-1915)

WW1 German U-Boats

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Development

The short-lived U5 class was a simple evolution of the U3 class (two boats launched in 1909). They were conceived as a general improvement, built by Germaniawerft in 1908-1910, unlike the U3, from Danzig NyD. They passed the cape of 500t surfaced, had four instead of two Körting engines and were faster both surfaced and underwater. They also had a longer range and a greater crew, but the armament remained the same. Four were built at Germania, laid down in 1908 and launched, completed in 1910. All were lost in WWI, in 1914-15, including one by a British sub and another by a friendly U-Boat. The next four boats of the U9 class were basically a repeat of the same design by Danzig NyD.

The hulk Acheron used as tender of early German U-Boats. In the photo are present U3 and U5 in Kiel.

Design of Project 13

Hull and general design

(no plans found to far)
These new U-Boats were designed for longer patrols. This led to design larger boats, with a basic displacement of 505 tons above water and 636 tons below water to compare to the U3’s 421/510t, so almost 120t difference. The core specs were for better speed and range. For this, engineers at Germania had to make the pressure hull long and large enough to accommodate twice more engines, albeit the technology remained the same, these were Körting unit running on kerosene (Parrafin). Effort were made to add more batteries as well.

From the U-8 exploratory website, src below

As a result, if the general hull shape remained about the same, with a narrow hull surrounded by generous blisters around the circular pressure hull, topped by flat walkways, it was now longer, 57.30 m (188 ft) overall, while the pressure hull was now 43.10 m (141 ft 5 in). The beam was however unchanged at 5.60 m (18 ft 4 in) for the outer hull and 3.75 m (12 ft 4 in) for the pressure hull. Drought was 3.55 m (11 ft 8 in).

The conning tower design was enlarged considerably, with a hardened tube communicating to the pressure hull at the middle, fairings fore and aft, and a full bridge on top wrapped in canvas when were located the coxswain and his steering wheel forward, and officers in observation behind. There were two periscopes, one for navigation and one for attack, like on the previous design, and two large hatches fore and aft of the surface hull. They also carried a dinghi enclosed below the outer navigation hull. The crew comprised of 28 men in all with four officers, which was three more than the U3 class.

Powerplant

The boats had two shafts and dependong on soources, two or four Körting petroleum engines, with six-cylinder two-stroke and 662kW (900 hp) units installed. Another source states they had these and two eight-cylinder two-stroke petroleum engines as well. The general consensus is that they combined two Körting 6-cylinder and two Körting 8-cylinder two-stroke Kerosene motors rated for 900 PS (660 kW; 890 shp) at 550 rpm surfaced.

For underwater travel, they had a single SSW electric motor rated for 765 kW (1040 hp) at 600 rpm. The longer hull enabled this engine upgrade and thus, granted a top speed of 13.4 knots surfaced (24.8 km/h; 15.4 mph), compared to 11.8 kts for the previous U3 class. The new electric engine also provided a top speed of 10.2 knots underwater (18.9 km/h; 11.7 mph) compared to 9.4 kts. This was also partly due to the more favourable hull length ratio, as the beam was unchanged. Range climbed to 3,300 nm surfaced (6,100 km; 3,800 mi) at 9 knots (17 km/h; 10 mph). While underwater at 5 knots, they were capable 80 nm albeit others sources gives 55 nmi (102 km; 63 mi) at 4.5 knots (8.3 km/h; 5.2 mph). Maximum diving depth was uncharged are roughly 30 meters (98 feet).

Armament

The armament was unchanged, with two torpedo tubes at the bow and stern and two reloads so six torpedoes carried total. Until the end of 1914, they were fitted on deck with 3.7 cm Hotchkiss revolver cannon behind the conning tower. This armament was unchanged since U2. Only the forward tubes were reloadable as there was not enough space to store spare torpedoes aft. The revolver cannon behind the CT was likely replaced by a 5 cm (2.0 in) SK L/40 deck gun in 1915, but some were sunk without it.

Torpedo Tubes

The four 450 mm (17.7 inches) torpedo tubes could be reloaded from above via the larger hatches described above, and these were the 45 cm (17.7″) C/06 of 1907, 1,704 lbs. (773 kg) for 222 in (5.650 m) in lenght, carrying a warhead of 270 lbs. (122.6 kg) TNT to 1,640 yards (1,500 m) at 34.5 knots or 3,380 yards (3,000 m) at 26 knots due to her Brotherhood system. More on navweaps

3.7cm/27 L/30 Hotchkiss Gun

It replaced the 7.9mm/79 machine gun installed on a pintle aft of the CT until 1914. The new Hotchkiss L/30 was installed by late 1914.
It was manufactured under license by the Gruson company, named ‘3.7 cm Revolver Kanone Hotchkiss – Gruson’.
Weight 571 kg, 32.20mm (total tube length), 20 rifled part, 12x grooves 6 degrees angle
Projectile weight: 0.63 kg HE or 0.64 kg shrapnel, mv 494 m/s
Fire rate 32-50 rpm, range 2000 m HE, +18 degrees elevation.

5cm/37 SK L/40 C/92 Gun

Installed on U6 and U8 only in 1915.
Designed in 1892 but produced as the 5 cm SK L/40 (2 inches) first and replaced by the 5 cm Tbts KL/40 in 1913.
It weight 240 kg (530 lb), for 2 m (6 ft 7 in) long, 1.83 m (6 ft) barrel.
It fired a Fixed QF 52 x 333R 1.75 kg (3.9 lb) HE shell at 656 m/s (2,150 ft/s)
The Breech was of the Horizontal sliding-wedge type for a rate of fire of 10 rpm
Elevation was -5° to +20°, traverse 360° with a single gunner, and two loaders.
Maximum firing range was 6.2 km (3.9 mi) at +20°. This was considered a defensive gun only, as the round had little power.

Career of the U3 class

U5 (hull 147) was laid down at Germaniawerft, Kiel in 1908, launched on 8 January 1910 and completed in July 1910 at a price of 2,540,000 Goldmark, under command of Kapt.Lt. Albert Gayer until July 1940. She was sunk on 18 December 1914 under the command of Kptlt. Johannes Lemmer. Whereas she never sank any ship, on two patrols, she was lost in either an accident or a mine encounter off the Belgian coast on 18 December 1914. It was north of Zeebrugge. She sank with no survivors. On 4 September 2023, it was announced that the wreck of U-5 was successfully identified and photographed by a Belgian and Dutch team. On 4 September 2023 divers confirmed her wreck and also that of the German minelayer submarine UC 14 aso sank in 1915 there. Evidence is not clear about a mine detonation but further investigations could led to more clues.

U6 was laid down at yard 148 in Germaniawerft, Kiel on 1908, she was launched on 18 May 1910 and completed in August under command of Alfred Stoß until August 1914. Oberleutnant zur See Wilhelm Friedrich Starke took command in August-September, then Otto Steinbrinck until November, Reinhard Lepsius until 5 January 1915, replaced by Otto Steinbrinck as he fell ill for a few days, then Lepsius until she was sunk on 15 September.
She performed a total of eleven combat missions, sank 13 merchant ships of the Entente and neutral states for a total combined of 4,654 GRT while other sources the states 16 ships for 9,614 GRT and three ships (2,337 GRT) captured as prizes:
On 14 April 1915 the Danish cargo Vestland, 19 July 1915 Swedish Capella, 21 July 1915 Swedish Madonna, 22 July 1915 Swedish Fortuna, 25 July 1915 Norwegian G. P. Harbitz and Sognedalen, 26 July 1915 Danish Elna, Neptunus. 11 September 1915 Norwegian Wansbeck, 12th Norwegian Bien, 13th Norwegian Norte (all verified postwar).
On September 15, 1915, she was still laying in ambush off the Norwegian coast, west of Stavanger but due to cold air, exhaust fumes from her engines, vented by her tall collapsible funnel, were visible from afar. British sub E16 (Commander E. Talbot) spotted her, fired two bow torpedoes from 500 m abeam, one hit her below the CT. She sank slowly enough for the five on deck to survive, but Lieutenant Reinhard Lepsius was in the presure hull when it happened.

U7 was laid down at yard 149 in Germaniawerft, Kiel, laid down on 1909, launched on 28 July 1910 and completed in July 1911 under command of Lieutenant Commander Georg-Günther Freiherr von Forstner from July, 18. U7 made seven combat missions, but score no sinking.
On 20 January 1915, U 7, under command of Lt Cdr Georg König she left Emden heading west and battled heavy seas that day. Meanwhile, U 22 (Lieutenant Commander Bruno Hoppe) left her position off the English coast due to poor weather and returned to Emden. The following day both met within sight of each other, north of Ameland, off the Dutch coast. Poor visibility had Hoppe thinking she was probably a British submarine and he challenged U7 with a prearranged recognition signal, which went unanswered. At the same time, U 7’s commander also believed U 22 to be hostile and tried to move away at greater speed. After another signal still not answered, then a third Hoppe ordered to fire two torpedoes. One hit U 7 at dead center below the conning tower. She sank immediately afterwards but a single crew member was able to leave and was later rescued by U 22, after which captain Hoppe was devastated at discovering the blunder. The particular tragedy was compounded by the fact there was a close personal friendship between the two commanders…

U8 was laid down at Yard 150 in Germaniawerft, Kiel in 1909, launched on 14 April 1911 and completed in June 1911, in service under Kapitänleutnant Wilhelm Friedrich Starke until 31 july 1914, then Kapitänleutnant Konrad Gansser in August 1914 and then Kapitänleutnant Alfred Stoßuntil her loss on 4 march 1915.
U8 performed ten combat patrols, sank five (confirmed) British merchant ships for 15,049 GRT. This was done in two days. On February 23, Chine (2,026 GRT), Oakby (1,976 GRT) and the following day, Harpalion (5,867 GRT), Rio Parana (4,032 GRT) and Western Coast (1,165 GRT).

On 4 March 1915 while sailing west in the English Channel she ran into a newly constructed British net barrier (Dover Barrier) still under construction. She could not pull free and drew the attention of the trawler Robur, who alerted a Royal Navy hunting group. Soon after the Dover Patrol destroyer’s HMS Cossack, Falcon, Fawn, Ghurka, Kangaroo, Leven, Maori, Mohawk, Nubian, Syren, Ure and Viking arrived.

Under gun threat they were forced to surrender but had no answer, Gurkha fired and hit U 8 at around 6 p.m and U8 as she managed do dive, causing a flooding, whereas lighting and engine failure, fire on board constrained Lieutenant Commander Stoß to surface. He ordered to abandon ship, and the destroyers Gurkha and Maori opened fire, sinking her but the crew members were rescued by the British. Not long after on March 4 Stoß and his officers were invited to dinner on the British supply ship Arrogant and asked by the British apparently under the influence of alcohol to sing an anti-English song, to their delight…

Read More/Src

Books

Gröner, Erich; Jung, Dieter; Maass, Martin (1991). U-boats and Mine Warfare Vessels. German Warships 1815–1945. Vol. 2. Conway Maritime Press.
Rössler, Eberhard (1985). The German Submarines and Their Shipyards: Submarine Construction Until the End of the First World War. Bernard & Graefe.
Werner von Langsdorff: U-Boote am Feind. 45 deutsche U-Boot-Fahrer erzählen. Bertelsmann, Gütersloh 1937.
Carl Ludwig Panknin: Unterseeboot „U. 3“. Verlagshaus für Volksliteratur und Kunst, Berlin 1911
Unterseeboot „U. 3“. (Schiffe Menschen Schicksale.
Max Valentiner: U 38. Wikingerfahrten eines deutschen U-Bootes. Ullstein, Berlin 1934.
Einzelnachweise
Bodo Herzog: Deutsche U-Boote 1906–1966. Erlangen: Karl Müller Verlag, 1993
Bodo Herzog: Deutsche U-Boote 1906–1966. Erlangen: Karl Müller Verlag, 1993
Eberhard Möller/Werner Brack: Enzyklopädie deutscher U-Boote Von 1904 bis zur Gegenwart, Motorbuch Verlag, Stuttgart 2002
Ulf Kaack: Die deutschen U-Boote Die komplette Geschichte, GeraMond Verlag GmbH, München 2020
Robert Hutchinson: Kampf unter Wasser – Unterseeboote von 1776 bis heute, Motorbuch Verlag, Stuttgart 2006

Links

on cloudtour.tv/u8
on navypedia.org/
uboat.net u5
uboat.net u6
uboat.net/ u7
uboat.net/ u8
on en.wikipedia.org/ SM_U-5
on denkmalprojekt.org/u06.htm
on vrt.be/
en.wikipedia.org SM_U-5
uboat.net/ commanders
de.wikipedia.org U_5