Mode class destroyer (1942)

Svenska Marinen HMS Mode, Magne, Munin, Mjölner 1942-70.

The Mode class were four coastal destroyers built in Sweden on Italian Torpedo Boat plans. They were active until 1966-70. The design was based on the preceding Psilander class, Torpedo Boats purchased from Italy before the war, but equipped with Swedish equipment and armament and classed as coastal escorts. They were moderately upgraded postwar, reclassified as frigates to serve for most of the early Cold War, making thirty years of service, with the last retired in 1970.

Development

At the start of World War II, the Swedes had been producing a new type of standard destroyer which design was well matured, the Göteborg class. They were a powerful, but an expensive design however, and some considered an “overkill” for Swedish actual needs. Thus, to meet the demands of a rapidly expanding navy, Sweden looked to Italy to procure ships, four purchased, two each of the Psilander class (ex-Sella class) and two of the Romulus class (Former Spica class Torpedo Boats). The Italians also provided the blueprints for a more modern version of the Sella class, used by the designers at Götaverken in Gothenburg as the basis to develop a new light destroyer. Götaverken also built the first two of that class, but for capacity issues, the second pair was wplit between Öresundsvarvet and Eriksberg.

Mjölner celebrating the end of WW2

Since these ships were needed “for yesterday”, they were designed fast and built fast. The design was ready by mid-1941. HMS Mode for example was laid down in september 1941, launched in April so after just eight months, and completed in next November, so eight months later and sixteen months total or a year and four months, pretty fast to usual Swedish prewar standards of 2.5 years on average. Hence, as these orders were made in April (May for Munin) the last ship was completed on 3 January 1943, still relevant in the context of the time of armed deterrence neutrality.

Despite their small size, originally designed as torpedo boats, they proved perfectly adapted to Swedish needs in shallow waters and maze of islands in the Baltic. They operated as escorts for the remainder of World War II, in the coastal fleet and enforcing neutrality, without loss. Postwar, they escorted ships like the cruiser Gotland on goodwill visits to Belgium, Ireland and France. The class was seen as useful still, provided it could be modenrised, which was done between 1954 and 1955. They were thus re-rated as frigates. One main 105 mm (4.1 in) gun was removed, as the triple 533 mm (21-in) torpedo tube mount for a single Squid depth charge launcher and the remaining 40 mm (1.6 in) Bofors were upgraded. This enabled them to staty active until 1966-68, so about 24 years of service.

Design of the Mode class

Hull and general design

1/100 model at the Museo Storico Navale, Venice, credits stefsap.com

Swedish author Palmsteirna, C. in 1972 in “Swedish Torpedo Boats & Destroyers: Part II” in Warship International Vol. IX described as:

more an expression of standardization, simplicity and simple building methods than carefully planned men of war.

Design proceeded quickly from the the Italian blueprints for the modernized Sella class, and crossing this with reconstructed plans for the Spica class, with Götaverken as master builder. The design work was entirely assigned to Götaverken in Gothenburg, which later produced the final plans, approved in early 1941 by the admiralty, with an acceptance likely by the summer, diet’s approval for funding, after which orders were passed on, and all would bear Thor’s related names, like the 1912 class. The plans were then property of the state, then sent to Öresundsvarvet and Eriksbergsvarvet.

They were small destroyers, only 78 m (255 ft 11 in) long, shorter than the British Hunt class so realy more escort destroyers with a much simplified design that could be produced in large numbers. Their beam was kept narrow too at 26 ft 3 in (8.00 m) for a limited draught of 8 ft 10 in (2.69 m), but a reasonable metacentric heifght overall, so with their tall bridge and structures, combined with Italian light hull constructions, there were concerns over stability. They displacement far less than a Sella class, and even less than a Spica class TB at 750 long tons (760 t) normal and 960 long tons (980 t) full load.

Now for their general outlook, they looked closer to a Spica than a Sella class, with a single funnel, narrow bridge at the end of the forecastle and the way their armament was placed. The forecastle had an elegant transition from the cut to the deck, a clipper bow and generous flare, two anchors, and a bridge was had a rounded, streamline face, on two levels, with the enclosed navigation bridge topped by an open bridge, which wings extended eiter side, unsupported, beyong the beam, making for a distinctive appearance from the prow compared to other Swedish destroyers. A search light platform, fdoubling as lookout post, was supported by the two-part mainmast. There was no aft mast, instead, wireless radio cables were supported by funnel’s struts like on French ships.

The fire control center on Magne

Next, was the aft structure, supportong the raked capped funnel, abaft which were installed two boats under davits and two life rafts for a crew of 100 officers and ratings. Then came the “flying bridge” on which were installed two platforms for the Bofors AA guns, going over the axia single triple torpedo tubes bank and ended with the aft structure, with the superfiring “X” aft gun and “Y” on deck. No superfiring gun forward for obvious stability reasons although one can argue that the bridge was already too tall for stability. It seems however it was calculated well enough for cold war additions, albeit this required sacrifices as well. There were two cranes to reload the toprpedo tubes, mined rails (albeit no mines were ever carried) on the deck, with chutes overhanging the split transom stern, on both sides were placed small 2-depht charge racks on sponsons. Below them there were propeller guard bars. It seems on the model no counter-keels were present.

Powerplant

Machinery was the same for all four ships, two Penhoët A oil-fired 3-drum boilers rated at 16,000 shp (12,000 kW), supplying steam to two de Laval geared steam turbines, for two fixed-picth 3-bladed bronze propellers. Design speed was a modest 30 knots (56 km/h; 35 mph), which was considered adequate for escort work. They carried also 190 tonnes (190 long tons) of fuel oil for a range of 1,260 nautical miles (2,330 km; 1,450 mi) at 20 knots (37 km/h; 23 mph).

Armament

The Mode class sported three 10.5 cm (4 in) K/50 M42 guns from Bofors, installed like for the Spica class, A on the forcastle, X and Y on superfiring positions aft. All these separate mounts were protected by a simple shield instead of a turret. For AA defence they comprised two 40 mm (1.57 in) K/60 M36 in two platform located amidship over the “flying bridge” over the TT banks, and two 20 mm (0.79 in) K/66 M40 on single mounted also from Bofors, located abaft the mainmast at the end of the forecastle, unshielded. The triple torpedo tubes were the same as the rest of the fleet and unlike a Spica class, with 53 cm (21 in) torpedoes.

10.5 cm K/50 M42

These 105 mm Bofors K/50 M/42 were noted as DP guns (dual purpose) but these 10,5 cm kanoner m/42 were derived from the ones designed by Bofors for Coastal Defense ships of the Finnish Väinämöinen class called the model 1932 with a semi-automatic horizontal sliding breech block but same overall length of 50 calibers. There is no data on the M/42 however. In research. This gun fired either the Stgr m/40, 16,5 kg with 1,32kg filler, velocity of 831 m/s. or the Sgr m/40, 16 kg with 1,36kg filler, velocity of 840 m/s.

40mm K/60 m/42 Bofors AA

The first official test was a success on 21 March 1932. In 1933-34 with a watchful eye of the Navy, the model was further refined with 30,000 hours of drawing board work as well as producing all the machine tool necessary to create the masterpiece that was the 40 mm L/60 (In sweden L56, K60) Model 1934. Export success wa simmediate, but strangely the Navy did not adopted it, ordering instead in 1934 was a short-barrel version for submarines, the 40 mm L/43 M1932. Some sources argues that was the model installed on the Psilander class, but it’s doubtful. The model the Navy finally adopted was the 40 mm L/60 Model 1936, the base for the legendary WW2 allies Bofors gun, still in service to this day.

The Bofors 40 mm/60 (1.57″) Model 1936 is the least known variant over the web, so data is scarce. Bore lenght was 88.578 in (2.250 m), full 76.1 in (1.933 m), and as asked by the Svenska Marinen, a rate of fire of 120 rounds per minute per barrel nominal. It slowed down with gravity and elevation and practical if could fell below 80 rpm, especially with a worn out barrel (life 9,600 to 10,000 Rounds). It used an AB 40 mm L/60 HE-T – 2.05 lbs. (0.93 kg) round, complete Bofors 1936 HE – 4.63 lbs. (2.1 kg) with a 17.60 in (44.7 cm) busting charge of 0.150 lbs. (0.068 kg) TNT. It had a Brass cartridge of 40 x 311R, 1.93 lbs. (0.88 kg) filled with 0.661 lbs. (0.300 kg) propellant charge. Muzzle velocity was 2,789 fps (850 mps), bezst range at 42°, 11,019 yards or 10,076 m.

20 mm K/66 M40 Bofors AA

20 × 145 mm R Bofors, in Swedish service 20 mm cartridge m/40, is a rim cartridge (R) developed by Bofors in Karlskoga during the 1930s for their Bofors 20 mm automatic cannon L/70. It was used in the Swedish Armed Forces until the early 1990s in the air defense robot 70 unit.

53 cm Torpedo Tubes

These were 53.3 cm British torpedoes with tubes m/30. It might have been the Torped 61, differing from former steam-driven torpedos by using hydrogen peroxide as oxygen carrier instead of air. This could increase the range from 15 km to about 20 km at the highest speed. More info in research.

Depth Charges & Mines

At the poop as decribed above were two Sjbf “type C” depth charge racks were located, for four m/24 total. It seems also at some point, they carried two depth charge launchers Sjbk m/33 but they don’t appear in the main model. They also carried presumably also hydrophones. The mine rails could support 42 mines, possibly of the Kontaktmina m31 type.

Profile of navypedia, HD one in preparation by the author.

⚙ specifications (1942)
Displacement	750t standard, 960t full load
Dimensions	78 x 8 x 8 ft 10 in (255 ft 11 in x 26 ft 3 in x 8 ft 10 in)
Propulsion	2x De Laval steam turbines, 2x Penhoet boilers, 16K hp.
Speed	30 knots (35 mph; 56 km/h)
Range	1,260 nm (2,330 km) at 20 kts
Armament	3x 150mm/50, 2x 40mm/36 K/60, 2x 20mm/40 K/66, 1×3 533mm TTs
Crew	120

Career of the Mode class

HSwMS Mode (29)

Mode in 1945
Mode (Thor’s son) was laid down by Götaverken in Gothenburg in September 1941, launched on 11 April 1942, delivered to the Navy on 8 October, commissioned on 12 November, and assigned to the Coastal Fleet, sporting the usual grey livery with white bands for and aft of the hull in World War II. She had the initial pennant number 29. In 1947, Mode escorted Gotland with her sister Munin on a trip to France and Britain, stopping at Le Havre, Lyme Bay, Torquay, Glasgow and Oban.

Mode in the 1960s as a frigate

She was modernised in 1953, re-rated as a frigate under the pennant F73. As seen above she lost her aft main gun and triple 533 mm torpedo tubes for a single Squid 305 Squid Mk 4 ASWRL mortar aft (replacing “X” gun mount, with the structure removed) to improve anti-submarine performances. The two 40 mm (1.6 in) guns were updated to the latest cold war model in Swedish use but she and her sisters retained minelaying capability. After an extra decade of useful service, she was decommissioned on 1 July 1970 but used as training ship until stricken, sold for BU and scrapped at Ystad in 1978. It seems there was no discussion about preserving her.

HSwMS Magne (30)

Magne (From Magni, a second son of Thor in Nordic mythology) was built at Götaverken in Gothenburg and was launched on 25 April 1942. She was commissioned in the Swedish Navy on 26 November. She joined the Coastal Fleet under neutrality markings, escorting cruisers from 1942 to 1945 but had no peculiar event or drama in World War II.

In 1953 Magne was reclassified as a frigate and rebuilt in 1953-54 like her other sisters, traditing on 10.5 cm, torpedo tubes for a Squid, and the 40 mm guns m/36 were replaced m/48 plus they gained the new anti-submarine depht charge throwers m/51. They likely also gained a radar, albeit the type is unknown. Magne was decommissioned on 1 January 1966, used as training ship at the machinery school department of Berga. In 1973 she was stricken and sold for scrap to Ystad.

HSwMS Munin (31)

Munin in WW2
Munin (Thor’s favourite Raven) was laid down by Öresundsvarvet in Landskrona by September 1941, launched on 27 May 1942, and commissioned on 3 January 1943, then delivered to the Navy five days later. Like her sisters she was assigned to the Coastal Fleet in World War II, escorting major ships, cruisersand coastal defence ships for their neutrality partrols, without incident, under neurality markings and the the pennant number 31.

Postwar, Munin was part of two goodwill tours to European ports, the first was in 1946, escorting the cruiser Fylgia with her sister Mjölner on a tour of Bergen and Fannefjord, Norway, then Dublin in Ireland, Antwerp in Belgium. The next year she escorted the cruiser Gotland with her sister Mode to France and the United Kingdom, stopping at Le Havre, Lyme Bay, Torquay, Glasgow and Oban.

The frigate Munin (F75) on the cold war
To stay relevant witj the new Soviet submarine threat in the Baltic like her sister she was modernised in 1953 and re-rated as a frigate, pennant F75. She lost a main gun and triple 533 mm (21 in) torpedo tubes for a Squid mortar and had 40 mm (1.6 in) guns upgraded bu she retained minelaying capability. She was eventually decommissioned on 6 December 1968 and was sold for scrap in Gothenburg the next year.

HSwMS Mjölner (32)

Mjölner in WW2
Mjölner (after Thor’s hammer) was laid down by Eriksbergs Mekaniska Verkstad in Gothenburg on September 1941 under pennant number 32. She was launched on 9 April 1942 and commissioned on 12 November 1942, assigned to the Coastal Fleet and escorting various formations or patrolling to ensire no infringement of its waters from their the Kriegsmarine or Soviet Navy, along World War II without notable incident.

In 1946, Mjölner accompanied Fylgia with Munin for a goodwill tour of Norway, stopping at Bergen and Fannefjord, but also she stopped at Dublin in Ireland and Antwerp in Belgium. Like her sisters she was modernised in 1953, re-rated as a frigate (F75). See above for the details. After conversion, she continued her escort and patrol missions ion the Baltic without any incident to report. She was was decommissioned on 1 April 1966, and ubnlike the others first two, not retained for training, but instead stricken, and sold for scrap on 3 November 1969.