Bävern-class submarine (1921)

Last time we saw the Hajen class, and the WW1 lineage of the Swedish Navy Subs in this long cycle up to this day. The previous Hajen class were essentially based on the UB-III class miwed with Laurenti-Fiat design features. They were started in 1915-16 but only entered service in 1920. Their successors, the Bävern class, were basically an improvement of this design. But they were laid down only from 1920 at Kockums, Malmö and Karlskrona Navy Yard, launched 1921. They were lenghtened and had more powerful Diesels. They saw service in the interwar and still were operational when WW2 broke out, kept for training after neutrality patrols earlier, but their age started to show and they were all stricken in 1943-44 freeing crews for modern submarines that just entered service. Two were scrapped in 1944 but the lead boat, Bävern, was still mothballed by 1956.

Development

To cut it short (see the previous post introduction to Swedish submarines) we will focus here on the Hajen and derived Bävern. The Hajen were born from the will of the Riksdag to invest in the fleet in this war, including submarines, to better enforce its neutrality. Submarines was a cheap deterrent to counter any unauthorized foray into its waters, and had some favor, despite the will of the Svenskaa Mafinen’s top brass for more coastal battleships and desrtroyers. Around 1916, Swedish naval attachés in Germany received reports from the UB-III being the most produced and arguably most successful Kaiserliches Marine’s submarine in action. The naval staff was impressed by their performance and as a result, Kockums bought a license of this U-boat from AG Weser.

Kockums then started modified the design by removing the rear torpedo tube, shortening the hull and mixing it with elements of the Fiat-Laurenti design a 1912 Kockums design, the Svärdfisken and Tumlaren. The new mixed design was offered to the Navy, who ordered three boats, that were exceptionally quick to be authorzed and voted for fundingby the Riskdag mid-1916. This design entered service as the Hajen class, with three boats, the first of which was completed in 1917 but not commissioned before 1920 due to material shortages and notably their diesels. As no MAN diesels could be obtained, they likely were completed instead with 6-cylinder Hesselman-derived 500 hp diesels ported there to 700 hp. Anyway, they displaced 422 tonnes and were capable of 15.5 knost surfaced.

They were not even operational when in 1918 the Swedish Naval staff requested a repeat design, but improved, to Kockums. The design bureau start to tinker with the design in 1918 and this “improved Hajen” was lenghtened by 3 metres (9.8 ft) in order to place larger fuel tanks and improved endurance. At first it was planned to fit in slightly less powerful engines. The lenghtening was to provide a better hull ratio that would allow an extra speed gain, to the price of agility. Armament was the same and many aspects of the design identical. Once approved they were planned for funding the same year, they were ordered and laid down presumably in late 1918 or early 1919 (dates impossible to find), and all launched in 1921, with only the lead boat Bävern being built at Kockums yard, Malmö, the other two, Ilern and Uttern at the Karlskrona Navy Yard. Some sources states they were manufactured in Sweden still under license from AG Weser, Bremenas a development of the French Laubeuf type.

It is only partially true, the latter was indeed one inspiration for the Spanish engineer Raimondo Lorenzo d’Equevilley-Montjustin (1860–1931) which partenered with Krupp Germaniawerft to pioneer the Firelle and Karp, built for export to Russian but the very first German submarines. They had little to do with Laubeuf’s “Narval”, a grounbreaking submarine but d’Equevilley indeed work with Laubeuf before moving to Krupp. The DNA of Laubeuf’s formula was quite different than the usual Holland and Lake designs that were optimized for underwater performances. Instead Laubeuf designed for the French Navy a “submersible torpedo boat” optimized for surface running. A completely different philosophy that permeated early German U-Boat designs indeed, thus at the (very) distant root of the UB-III.

The Hajen and Bävern class in the 1920s, useful for comparison

Design of the class

Hull and general design

The final Bävern-class design displaced while surfaced, light, 472 tons and when submerged some 650 tons, so way more than the Hajen class. To be exact, 429 tonnes light and surfaced, 472 tonnes loaded and surfaced, 650 tonnes fully loaded underwater. They were also longer at 57.05 metres (187 ft 2 in) overall, but the beam remained close to the previous design at 5.82 metres (19 ft 1 in), for a draught of 3.51 metres (11 ft 6 in). They had a complement of 31. Now, the outlook was very much the repeat of the Hajen, but with a reworked prow, which was quite different from the Hajen: It went up past the deck, still the semi-flattened section former by the upper outer hull, raised towards the bow, then made a downwards slope. All this was supposed to improve their seaworthiness, enabling the prow to be a bit less “wet” and not ploughing as much as the previous design. The boats had two main deck hatches fore and aft and one in the CT, plus two main loading hatches communicating to the pressure hull to reload torpedoes. There might be a small boat stored under the deck as well, described as “a dinghy was carried in the deckhouse”.

The conning tower was however the same, with its peculiar, Swedish shape. It was tall, with an inwards sloped upper wave breaking section. There was a large observation deck. Overall, the Bävern were also much taller. The stern section was the same, rounded and with a double rudder, upper and main underater, a cross-shaped tail with protecting bars around the shafts. They also had a net cutting saw forward and protective cable running to a portico in the CT, a two persicope system one for attack and one for watch.

They also had a taller single wireless telescopic radio mast in the CT with cables anchored aft.
As for their liveries, they were painted dark grey, with the name first letter painted white on the Conning tower. Photos also shows smoothier transitions between the flat deck and outer hull. The Bävern type was a pure double-hull submarine with the pressure hull divided into five pressure-tight compartments. The pressure hull was the same type of tube, with partition bulkheads in several places (forward torpedo section, central command section below CT, engine section, aft torpedo section), the outer ones, to the fore and aft torpedo section had hemispheric bulkheads for better resistance to flooding, intermediates were flat. The pressure hull was conical also fore and aft.

Powerplant

The Bävern class were powered by two diesels (likely German this time), 6-cylinder and likely 1050 bhp each plus two 260 hp electric motors (type unknown) for a total output of 2,100 brake horsepower (1,600 kW) and 520 horsepower (390 kW) total, for two 3-bladed fixed pitch propellers. When surfaced, the Bävern class ran at a top speed of of 15.2 knots (28.2 km/h; 17.5 mph) which was a bit less tnan the Hajen class. They still could to 8.2 knots (15.2 km/h; 9.4 mph) underwater (9 knot for the Hajen). The diesel bunkerage is unknown, but likely superior to the Hajen class. They could reach 3,000 nm at 15 knots surfaced and 54 nm at 6 knots submerged, same as the Hajen. Max diving depht is assumed to be about 30 meters operationally (90 ft). However another sources state (see below) they had a 60m diving depth (180 m) unlike the Hajen II which seems quite optimistic and is perhaps the crush depth limit.

Armament

Armament consisted of four 457 mm (18.0 in) torpedo tubes and a 75 mm (3 inches) deck gun like for the previous design.

75mm/23 Kanon M/16

In some publications, the gun is described as a 57mm/50 K/55 M89B but it’s likely either a typo or the initial spec. It was changed for a 75 mm/23,7cal. kanon M/16.
The 75 mm/23.7 cal. kanon M/16 was a Swedish naval deck gun manufactured by Kongsberg Våpenfabrikk or associated Scandinavian contractors, featuring a barrel length of 23.7 calibers. It was used on the Hajen II-class Submarines and Bävern, fitted as primary deck artillery on Royal Swedish Navy submarines to povide warning shots or engage unarmored targets when surfaced. No specs details.

Torpedoes

The Bävern class had four 45cm bow torpedo tubes and four reloads so 8 total. Either the Torped 14, or its derivative the Torped 27 for submarines in the interwar. Both were thread-steered, with a plate of a thin copper wire through which it was able to provide control signals to the torpedo. However they might be the 45cm UV Stävtub m/93, 3 meters long (453 mm exact diameter) or the m/04 for practice and more likely the m/12 1

Sensors

Hydrophones, no detailed type provided. Perhaps German Atlas type.

⚙ Bävern specifications
Displacement	472 tons surfaced, 650 tons submerged.
Dimensions	57.05 x 5.82 x 3.51 m (187 ft 2 in x 19 ft 1 in x 11 ft 6 in)
Propulsion	2 shafts diesels 2,100 bhp, 2x EM 520 hp.
Speed	15.2 knots surfaced, 8.2 knots submerged
Range	3000 nm/15 kts surfaced, or 54 kts/6 kts submerged
Armament	1x 75mm (3-in) deck gun, 4x 45cm TTs bow (8)
Crew	31

Career of the Bävern class

Bävern was ordered from Kockums, Malmö in 1918, as hull number 129, laid down in 1918, launched on 5 March 1921 and commissioned by June 1921. She sported “B”, then “Bä” on her CT as pennant. Note: Sources are poor on their interwar career. Bävern was decommissioned at least, likely after being sued for training as her sisters, on 6 october 1944. But she was not scrapped like her sisters in 1944 but instead lingered until 1956, possibly used as utility hull for training or storage, and scrapped in 1956. *HSwMS as a prefix is used in British literrature but in Swedish sources it was “HMS” standing for Hans/Hennes Majestäts Skepp. The difference is to avoid confusion with RN vessels.

Illern (pennant I, In) was ordered as hull number 291 at Örlogsvarvet Karlskrona in 1918 likely laid down that year or 1919, launched on 30 June 1921 and completed, commissioned by late 1921. Illern was placed in reserve likely in 1936-37, but reactivated in 1939. Her wartime career is unkown. While passing through the deep channel in Kalmar Sound at Krongrundet lighthouse just north of Kalmar on 12 August 1943, HMS Illern in fog, running surfaced at slow speed, was rammed by the cargo ship Birkaland coming from Gothenburg, near a dredger anchored in the channel.
She had her pressure hull breached by the schock and immediately began to flood. Hanging on the Birkaland bow she was carried by a few hundred meters outside the channel until the cargo ship stopped and backed away from her. After which Illern sank in 12 minutes. Several men on deck were thrown into the sea and one man was thrown onto the dredger. A miracle: All those on board were rescued except the flag submarine engineer, who was among those who fell into the sea during the collision. His dead body was washed ashore two weeks later at Färjestaden on Öland.
She was decommissioned after sinking, stricken.

Uttern (pennant U, Ut) was ordered as hull number 292 at Örlogsvarvet Karlskrona and laid down in 1918, launched on 25 July 1921 and completed, commissioned by late 1921. Her interwar career is unknown. Like her sisters she was likely placed in reserve in 1936-37 and reactivated in 1939, and after one or two neutrality cruises, likely versed to training. She was decommissioned like Bävern on 6 October 1944 and broken up later the same year.

Epilogue

Despite being obsolete, these submarines were all in reserve storage when World War II broke out. They were then put back into service, but outdated, likely made a few neutrality cruises, then versed to instruction, and were scrapped before the war ended for two of them. The Swedish wiki article states they were the first Swedish submarines to “survive submerged for more than 24 minutes” which might be a mistranslation. It is also alleged the pressure hull was of “class 3 and could withstand armor-piercing shells”. If indeed the pressure hull was thick enough to resist pressure it used the same thick steel plating used for armour plating and could offer some resistance, but it is in no way faced-hardened like true armour plating to keep its flexibility, which is very important. So this is nonsense.

In 1925, the Valen class were derived from the Bävern design, but made into mine-laying submarine. They allegedly had the Bävern type hull construction with had largely the same dimensions. The mechanical and electrical equipment was also identical and they retained the torpedo and artillery armament of the Bävern class, but also received 10 mine wells with 20 mines on the sides outside the pressure hull lke the German WW1 UC-III design. In addition, a 25 mm AA machine gun was added. Valen proved to be a successful design and had good performance and was in service during the readiness years until the autumn of 1943.

Read More/Src

Books

Hofsten, Gustaf von; Waernberg Jan, Ohlsson Curt S. (2003). Örlogsfartyg: svenska maskindrivna fartyg under tretungad flagg. Stockholm: Svenskt militärhistoriskt
Klintebo Roderick, red (2004). Det svenska ubåtsvapnet 1904-2004. Forum navales skriftserie, 1650-1837 Stockholm: Literatim.
Granholm, Fredrik (2003). Från Hajen till Södermanland: svenska ubåtar under 100 år. Marinlitteraturföreningen, 0348-2405 Forum navales skriftserie, 1650-1837. Stockholm: Marinlitteraturfören.

Links

web.archive.org/ navypedia.org
vhfk.se/
en.wikipedia.org/ Bavern-class_submarine
sv.wikipedia.org/ Lista subs
hhogman.se/ warships-subs-swe.htm
sv.wikipedia.org Bävern-klass
worldnavalships.com

Videos

Model Kits/3D

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