Hajen class Submersible (1917)

Swedish Submersibles 1916-1946: HSwMS Hajen, Sälen, Valrossen

New Cycle: Swedish WW2 and Cold War submarines. We start with the oldest still in service when WW2 broke out, the Hajen class. They were essentially based on the German Type UB-III U-boat but modified for Swedish service by Kockums, with the stern tube removed, and the prow shortened for better agility. Their career was uneventful, as they entered service at the war’s end and spent a quiet interwar and remained in neutrality patrols in 1939 and training afterwards until decommissioned in 1943, their crews needed on a new generation of submarines.

Development

History of Swedish Subs up to WWI

Sweden got interested in the development of submarines early on, seeing its potential for deterrence of its local waters, even before the dissolution of the Kalmar Union in October 1905: This was the UB N°1 (called Hajen (“Shark”) already) launched in July 1904, a Holland design, also chosen by so many other nations. It was built in Sweden at Motala Verkstad on plans prepared by Carl Richson, which was sent with his team to Electric Boat in the US. It had been preserved to this day. Next was HSwMS Hvalen (186/230t) launched in 1909, then a trio called the Undervattensbåten No 2-class, improved Holland types built in 1908-1910. Next came HSwMS Delfinen in 1914, the two Swärdfisken class (1914) and two Laxen class (1914). Thus as WWI started, Sweden operated nine, soon ten submarines, something not to be skoffed at for any would-be attacker.

The Abborren class, last Holland designs from Carl Richson (1916). Builder’s Model preserved at Karlskrona NyD.

During the war, Sweden also started a new class, the Abborren. They were basically another take on a Holland-derived Laxen, a duo (HSwMS Abborren, Braxen) started at Karlskrona in 1915 and based on the Laxen class. They featured an additional torpedo tube, and more powerful engines. But they were also the last costal submarines based on Richson’s design. Indeed by that point, the Holland class, cutting edge in 1902, were started to be criticized in light of what other Nation’s built. The typical issue of the Holland design was that their underwater agility and general characteristics were excellent, but they were severely lacking seaworthiness, speed and range when surface running. Like all the former Holland-based designs, they served until 1921-1937 before being discarded. None was still around when WW2 broke out.
In 1914, as the war broke out, the Riksdag appropriated funds for additional submarines and in 1915, an order was placed with Kockums Mekaniska Verkstads AB in Malmö for an “improved Svärdfisken”. The design was still undefined by then, apart for its link to the Laurenti design, revised by AG Weser drawings inspired by the UB-III.

A Laurenti-Fiat/UB-III mix

However, the submarine warfare prowesses of Germany since 1914, despite having a limited fleet, much impressed the Swedes, which saw models that had everything the Holland boats lacked, surface seaworthiness, range and speed, and even a better armament and better stability. German designs just looked better suited. Sweden being neutral in WW1 had the choice to purchase boats or plans from any belligerent, but given the needs of their own domestic industries, purchasing plans and building the boats at home, with modifications to suit the Swedish needs, seemed the better option. Thus, in 1916 already, the Svenska Marinen’s naval staff looked at these designs to renew its submarine force and Kockums NyD, which already acquired a licence from Fiat (Laurenti) after the delivery of Hvalen in 1909, sent a delegation to Germany. Under a non-divulgation licensing agreement due to engineering secrecy, AG Weser agreed to cede its modified plans for the UB-III class, by the considered the most advanced of all German designs itself, very much inspired by the Laurenti Design in many aspects. Indeed before that, in the summer 1915, Kockums engineers brought new drawings home from Fiat. Iin the autumn the keels of Hajen, Sälen and Walrossen were laid down. The new design draw enormously on the 1912 Kockums Svärdfisken and Tumlaren (launched 1914) based on the Laurenti design. Hence the naval staff wanted a continuation of this design.

Advanced it was, the UB-III is nowadays considered the progenitor of the whole interwar secret U-Boat lineage (designed at IWS – The Hague) and naturally of both the Type VII of WW2 fame. It was also by far, the most produced model of the Kaiserliches marine, with 200 planned, 91 commissioned before November 1918. It was a well-rounded coastal design, a development of the smaller UC-II which sank more than 1,800 allied ships. However unlike the latter, the UB-III was a brand new design intended no longer for traditional coastal raids but going further, possible to the mid-Atlantic. They were closer to a “medium type” albeit the latter were in general much larger and costier. They were seen as a cheaper “third type”. So what Kockums made was a mix of the Laurenti design with elements of the UB-III. A pizza with Sauerkraut topped with Surströmming (Swedish fermented fish marmelade)…

Still, if the UB-III class was considered an excellent design by Itself, the Swedes wanted less to improve on it than make it more suitable for Swedish needs. The hull for example, shaped to run surfaced in the North sea in winter and North Atlantic, was considered an “overkill” for Baltic conditions. The long clipper bow for example was not required, and given its operative conditions, the stern tube was seen as an unnecessary complication as well. Engineers at Kockums thus started to “clip” the boat fore and aft and keep the rest with minor modifications.
The final design from Kockums was approved by the Swedish admiralty board in mid-1916 and approved exceptionally fast by the Riskdag’s wartime funds. In the meantime, Kockums prepared the laying down of these new boats three boats. The parliament also approved the names of Hajen (sometimes “Hajen II-klass” in Swedish sources as the original Hajen of 1904 was renamed UB N°1 to avoid confusion), Sälen (Seal) and Valrossen (Walrus). Construction started by late 1916. They were launched respectively on 8 November 1917, 31 January and 16 April 1918. But construction was delayed due to issues to procure the right materials and none was delivered until 1920.

Design of the class

Hull and general design

In Swedish sources, the UB-III design nature is toned down as they were considered instead further development of the Italian Fiat-Laurenti design, just significantly larger than its predecessors. Displacement was now 422 tons, the hull featuring sleek lines for better surfaced speeds and larger fuel tanks for extended operational range. Torpedo armament was also doubled to four 45-centimeter bow tubes, and a larger 75 mm deck gun. The final design had a hull displacing 422 tons surfaced and 600 tons submerged for an overall length of 54.00 m (177 ft 2 in), an outer hull beam of 5.21 m (17 ft 1 in) and a draft of 3.51 m (11 ft 6 in). This was compared to 508–555t surfaced/629–684 t submerged and 55.30 x 5.76 x 3.67m for the UB-III. A far cry from the previous Holland-type Abborren (174/310 tons 31 x 3.61 x 3.10 m).
By many aspects, they look like a mixture of the UB-III and Fiat-Laurenti design, especially the straight prow forward with little rise of the deck, a “duck tail” type stern and a specific Swedish conning tower, tall, with a first fairing level wrapped around the conning tower, and an open bridge deck with a sloped wave breaking bulwark. There was a portico to support the protection cables running all the way from the et cutting saw forward to the support aft, two periscopes (attack and watch), and a telescopic mast for wireless radio communication aft of the sail, which also had a small access platform with ladder handles. The boat also had three hatches, two on deck fore and aft, one in the CT. The hull was double, rounded, with a narrow deck and no sponson for the deck gun, an issue that was latter recognized and fixed on next classes. The crew amount to 30 officers and ratings, and they had a small boat placed belly up on deck fittings not to create too much drag underwater.

Powerplant

The Hajen class was powered by two 6-cylinder diesel engines and two electric motors (type unknown, might have been local Hesselman diesels 6 cylinder 500 hp). In total, these produced respectively 2,000 brake horsepower (1,500 kW) and 700 horsepower (520 kW) on two propellers. So that when surfaced, they reached 15.5 knots (28.7 km/h; 17.8 mph) on a displacement of 422 tons. Underwater they were still capable of 9 knots (17 km/h; 10 mph) on a 600 tons displacement submerged. This was also to compare to the previous Abborren which had 920 bhp (690 kW) diesel power for a surfaced speed of 9.5 knots…
Based on their diesel bunkerage (unknown) they were estimated capable of crossing 3,300 nm (6,100 km) at 10 knots surfaced and 54 nm (100 km) at 6 knots underwater.

Armament

The Hajen design had a single 75mm/49 Bofors K/50 M12 on deck forward, and four 450mm bow torpedo tubes with four reloads, eight total. In the early 1930s they were modernized, with the deck gun replaced by a more modern Bofors 57mm/50 K/55 M89B.

75mm/49 Bofors K/50 M12

The Bofors 75 mm m/12 was a Swedish naval gun found also aboard the Sverige-class coast-defense ships and main armament of the Wrangel-class destroyers. It entered service in 1912, was retired around 1938 or beyind.
Specs: Mass 1,010 kg (2,230 lb), Length 3.975 m (13 ft), Barrel length 3.675 m (12 ft 1 in) L/49.
Shell weight 6.5 kg (14 lb) cal. 75 mm (3 in). Muzzle velocity 780 m/s (2,600 ft/s).

45cm Torpedoes

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.

⚙ specifications
Displacement	422 tons/600 tons
Dimensions	54 x 5.21 x 3.51 (177 ft 2 in x 17 ft 1 in x 11 ft 6 in)
Propulsion	2x 6-cyl diesels 1000 hp +2 EM 350 hp: 2000/700 hp
Speed	15.5 kts surfaced, 9 kts underwater
Range	3,300 nm/10 kts and 54 nm/6 kts
Armament	1x 75mm/49 K/50 M12, 4x 450mm TT bow (8)
Sensors	Hydrophones 1930s
Crew	30

Career of the Hajen class

HSwMS Hajen (1917)

Hajen (H), was laid down at Kockums in Malmö in late 1915, launched the first on 8 November 1917, but completed after many delays in May 1920. She was the second under the name “Hajen”. Thus her belonging to the Hajen II class, including her sisters Sälen and Valrossen. Hajen was decommissioned on March 19, 1943 after an uneventful service, used for training from 1939. In 1927, Hajen undertook a long-distance voyage to San Sebastián together with her sister Valrossen, and the more recent Bävern, and Uttern. The abbreviation “HMS” used in Swedish rather than HSwMS found in British literrature, (His/Her Majesty’s Ship) was not used by the Swedish Navy until after 1950. Previously, “HM” (His Majesty’s) was used, followed by the vessel type and name.

HSwMS Sälen (1918)

Sälen, officially HM Submarine Sälen was ordered in 1916 from Kockums Malmö, but only laid down in 1917 launched on 31 January 1918, but not completed before June 1920. HMS Sälen was taken out of service in 1943.

HSwMS Valrossen

Valrossen was the third and last submarine in class, built for the Swedish Navy in what is sometimes called the “Hajen II” class in Swedish sources. She entered the same unit as her sister Hajen and Sälen, leaving Kockums Malmö after a launch 16 April 1918, but completion was delayed due to shortages until August 1920, so two years later. So like her sister she was in service for neutrality patrols in the last months of the war. In 1927, she undertook a long-distance trip to San Sebastián, northern coast of Spain (on the Bay of Biscaye, Basque country) alongside her sisters Hajen, and the next Bävern and Uttern. Valrossen was also active in 1939 for neutrality patrols, but being the oldest with her sisters still active, she was likely used to rather train crews for the next classes in construction, such as the numerous U1 class (launched 1941-44).
Valrossen was decommissioned in 1943, scrapped that same year to provide well-needed high grade steel for new constructions.