Glauco class submarine (1935)

Oceanic Submersibles (1933-37): Glauco, Otario

WW2 Italian Submarines

Balilla class (1927) | Ettore Fieramosca (1929) | Archimede class (1933) | Glauco class (1935) | Pietro Micca (1935) | Calvi class (1935) | Foca class (1937) | Marcello class (1938) | Brin class (1939) | Liuzzi class (1939) | Marconi class (1940) | Cagni class (1940) | Romolo class (1943)

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Mameli class (1926) | Pisani class (1928) | Bandiera class (1929) | Squalo class (1930) | Bragadin class (1929) | Settembrini class (1930) | Argonauta class (1931) | Sirena class (1933) | Argo class (1936) | Perla class (1936) | Adua class (1936) | Acciaio class (1941) | Flutto class (1942)

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CM class (1943) | CC class (Laid down) | CA class (1942) | CB class (1942)

The Glauco class were two medium ocanic submarines ordered by the Portuguese government originlly, but were taken over and completed for the Regia Marina (Royal Italian Navy). They were improved versions of the preceding Squalo class, displacing 1,071 metric tons (1,054 long tons) surfaced, 1,326 metric tons (1,305 long tons) submerged for 73 meters (239 ft 6 in) long and were capable of 17 knots surfaced, 8 knots submerged, for a range of 10,000 nautical miles and armed with two 100 mm deck guns, some AA and eight torpedo tubes, including 4 bow and stern, 14 in reserve. Their engines however proved quite troublesome, cutting short many of their sorties in WW2, both in the Atlantic and Mediterranean. Glauco was eventually depth charged by HMS Wishart, was forced to surface and scuttled. Her sister Otaria survived the war and during the co-belligence was used to train ASW ships.

Glauco Class italian submarine “Otaria” (Sea Lion) 1935-1948 (pinterest).

Development of the Glauco class submarine

In 1930, the Portuguese government adopted a plan to expand and modernize its navy. On of the parts concerned ocean-going, heavily armed submarines that can deter enemy enterprises in far flung colonial possessions. Portugal under then was quite close to British yards but due to cost concerns, sent a request for proposals to Italian shipyards instead, as they were were competitive in price and quality compared to anybody else. In 1931 CRDA shipyard in Monfalcone and its chief engineer Curio Bernardis developed a design based on the latest Squalo-class. The Portuguese government accepted the proposal and ordered two of them straight away, to be named “Delfim” and “Espadarte”.

However the parliament next could not agree to vote their funding and the order was withdrawn. The contract was cancelled leaving the yard in 1932 with two boats just laid down. The construction was taken over by the Italian Navy, the shipyard completed both as “Glauco” and “Otaria”. These were relatively fast submariens for the day, with very good maneuverability while surface and underwater. To boot with their two main guns they were well armed. In fact the Portuguese also ordered a second pair of smaller, coastal submarines, which were also taken over by Italy as the Argo-class. Portugal instead purchased three ships from Great Britain.

Rendition for Atlas

The Glauco-class units were thus started at CRDA shipyard in Monfalcone, laid in 1932 but launched in 1935 so quite late, completed in 1936. Names referred to the mythological son of Poseidon and one of the Naiads, “Glaucos” as well as ther sea lion (Otaria).
These typical Bernardis type had a single hull with bulges as ballast spaces. They had excellent characteristics, strongly built and and manoeuvrabe, achieving a good balance in all aspects. By the time of their completion their package was estimated good enough for the Regia marina to order more of this type in the ftuture years. They became standards.
However rtheir peacetime reputation did not matched the reality in the Spanish Cvil war and their clandestine activities, nor, and even less so in the Second World War. They showed grave definciencly in speed and reliablity and were found slower to dive as expected. Their qualitied only existed on paper and sea trials only.

The speed of 17 knots while surfaced in WW2 was barely adequate for convoy warfare in 1939, just inferior to German U-Boats, but it was in reality rarely reached as in rough seas, it plumitted to less than 10 knots, a speed 1940-41 new merchant ships managed to exceed. Atlantic cruise were plagues by slow speed, heavy weather, and the sortie of October 1940 by Glauco was parred by repeated engine failures, so much so she was reduced at some point to 7.5 knots, against the 9 for good merchant vessels. In the second Atlantic cruise by December 1940 she had another merchant vessel that not only managed to keep her at bay but also fleet. It should be noted that both suvs were unlucky when launching torpedoes. They did not score any hit that was confirmed. Otaria, just like her sister ad even lire, was frequently subject to mechanical failures, including the air conditioning system. However they were stroingly built and during their ever dangerous passage of Gibraltar several times, they were often spotted and depht charges, but proved able to dive well below their maximum design depth of 80 meters in order to regain trim down to 120 meters. Like U-Boats they had safety margins, a tradition in all navies, of crushing depths well below double that of their safe operating depth.

Design of the Glauco class submarine

Hull and general design

The Glauco-class units were large ocean-going, single-hull submarines with a displacement of 1,071 tons (1,054 long tons) surfaced and 1,326 t (1,305 long tons) submerged and a length of 73 m (239 ft 6 in), a beam of 7.2 m (23 ft 7 in) and a draft of 5.12 m (16 ft 10 in). In other sources, they had a declared submerged dispcalement of 1,305 tonnes. The crew consisted of 7 officers and 50 non-commissioned officers and sailors. Thuis was quite an important crew for their moderate size, but the ballasts design maximized the pressure hull’s size. As for the desing in general, they had all the trademarks of the previous Squalo class, but with an elevated sponson forward of the conning tower with the first main gun to deflect waves, the other being on deck behind it. The conning tower and sail were of similar design as previous subs, with an enclosed forward navigation part with windows, an open part behind, while the tall conning tower also contained the two persicopes, one for navigation and another for combat, with graduations and bearing. There was a single Breda heavy machine gun at the first level of the sail and aother further aft, one level lower, ending with the flag pole and main radio antenna.

Powerplant of the Glauco class submarine

The Glauco class were powered while surfaced by two FIAT diesels rated for 3,000 hp. Underwater propulsion comprised two CRDA electric engines rated for 1,200 hp and her twin-screw propulsion system allowed for 17 knots surfaced, 8 knots submerged. Range was 2,825 nautical miles at top speed of 17 knots but 9,760 nautical miles (18,080 km; 11,230 mi) at a economical cruise speed of 8 knots, 110 nautical miles (200 km; 130 mi) at 3 knots when submerged. The fuel tanks contained a total of 59 tons of diesel oil and the hull was rated for a max depth of 90 meters, operating depth around 80 m but more inreality.
The two 1,500-brake-horsepower (1,119 kW) diesel engines were from FIAT, each driving a 3 bladed propeller at the end of the shaft. When submerged the shaft was decoupled and ran through two 600-horsepower (447 kW) electric CRDA (Cantieri Riuniti dell’Adriatico) motors. 17 knots (31 km/h; 20 mph) when surfaces was noted on trials, but in 1940 it could rarely be matched without issues, notably excessive vibrations. 8 knots (15 km/h; 9.2 mph) underwater however was matched.

Armament of the Glauco class submarine

The Glauco class had eight internal 53.3 cm (21 in) torpedo tubes (so all reloadable): Four in the bow, four in the stern. Total capacity was 14 torpedoes included 8 in the tubes and 6 reloads. They were also armed with two 100 mm (3.9 in) deck guns, a noverlty of the the design, placed forward and aft of the sail. Their anti-aircraft armament comprised one of two 13.2 mm (0.52 in) machine guns (see below details).

The artillery armament consisted of two single 100 mm OTO[in other languages] M1931 L/47[3][12] deck guns placed in front and behind the conning tower. The gun’s total weight was 2,177 kg and its length was 4.94 meters; the barrel elevation angle was 45°, the range was 12,600 meters, and the rate of fire was eight shots per minute.[14] The gun fired 26 kg rounds (including a 13.8 kg high-explosive shell and a 5 kg propellant charge) at a muzzle velocity of 840 m/s.[14] Anti-aircraft weapons consisted of two single 13.2 mm L/76 Breda M1931 heavy machine guns.[3][12] The gun’s weight was 47.5 kg, the barrel elevation angle was 85°, and the effective range was 2,000 meters. the weapon was fed from a 30-round magazine (the weight of the cartridge was 0.125 kg with a projectile weight of 0.051 kg), and the practical rate of fire was 400 shots per minute at an initial speed of 790 m/s[15]. The units were also equipped with hydrophones[3].

OTO 100mm/47 modello 1931

Derived from the Škoda 10 cm K1, but with loose liners. A tube, jacket and loose liner with a breech ring that screwed to both the A tube and jacket. Barrel shortened to 4.94 m (16 ft 2 in). Single, hand-worked and unshielded, pedestal-mounts fore and aft of the CT.
Specs:
Shell: 100 millimeters (3.9 in), fixed 13.75 kilograms (30.3 lb) QF 100 x 892R[1]
Breech: Horizontal sliding breech block
Elevation/Traverse: -5° to +45° for 360°
Rate of fire: 8-10 rpm
Muzzle velocity: 880 meters per second (2,900 ft/s)
Max range: 15.2 km (9.4 mi)

AA: 2x 13.2 mm/76 Breda Modello 31

The anti-aircraft defence counted on two twin Breda M1931 13.2 mm L/76 heavy machine guns, placed on rea platform of the conning tower. Each mount weighed 695 kg, but ensired an elevation of -10° to 90°. They fired 125 g unitary rounds, with a muzzle velocity of 790 m/s, maximum range of 6,000 meters and effective range of 2,000 meters. Their rate of fire was 500 rounds/min, so 2000 rounds when both twin mounts fired in concert however.

533 mm torpedoes

Model unknown. When completed it had likely Silurificio Whitehead di Fiume common A140/450 (1921). Capable of 29-32 knots, 6,000-4,000 m range settings, 1,140 Kgs, TNT warhead 140 kg, air tank loaded to 170 atmospheres. It was however quite visible due to the compressed air bubble trail, especially in calm waters.
Later in 1933-36 it was probably given more palatable models, all with wet-heaters:
-W 270/533.4 x 7.2 Veloce: 1,700 kg, 7.2 m WH 270 kg, 3,000-4,000 m/50 knots or 12,000 m/30 knots.
-W 270/533.4 x 7.2 “F”: 1,550 kg, 6.500 m, WH 250 kg, speed 3,000 m/43 knots or 10,000 m/28 knots
-W 250/533.4 x 6.5: 1,550 kg, 7.200 m, WH 270 kg, 4,000 m/48 knots or 12,000 m/30 knots.
-Si 270/533.4 x 7.2 “I”: 1,700 kg, 7.2 m, WH 270 kg, speed 3 km/42 kts or 7 km/32 kts, 9,2km/30 knots, 12km/26 kts
-W 250/533.4 x 6.72: 7.2m, WH 270 kg speed 4km/49 kts or 8km/38 kts.
-Si 270/533.4 x 7.2 “M”: 1,7 ton, 7.2 m, WH 270 kg speed 4km/46 kts, 8km/35 kts or 12km/29 kts.
The standard model carried aboard was allegedly a compressed air-driven mode that was 7.2 meters long, weighed 1,550 kg (260 kg warhead) for a speed of 50 knots at 4,000 meters range or 30 knots at 12,000 meters.

Author’s rendition. Sadly no open source photos exist of these boats.

Career of the Archimede class

Glauco was laid down on 10 October 1932, launched on 5 January 1935 and completed on 20 September 1935. She was assigned to the IV Submarine Group of Taranto and took part in the Spanish Civil War, sent for two clandestine missions carried (December 1936 to August 1937). In the second she had to return hime surfaced after a leak of methyl chloride leaving 27 members of the crew intoxicated. In September 1938 she was back in regular operations, in the Red Sea (Massawa) testing her abilities in tropical waters. She cruise off Somalia from 29 December 1938 to 24 January 1939 with Perla, back to the Mediterranean in October 1939.

It was planned to send her to operate in the Atlantic and it was planned for her to leave in early June. The mission was cancelled as it was necessary to cross the Strait of Gibraltar surfaced by night but this was the new moon. On 26 June 1940 she patrolled west of Cape Carbon (captain c.f. Candido Corvetti) when spotting the British steamer Baron Erskine (3657 TGB), lanching two torpedoes while she was heading towards Gibraltar escorted by a small unit. She missed, surfaced, and trie to sink her by gunfire, hit and damaged her, but she escaped in rough sea.
She made four unsuccessful Mediterranean sorties over 2634 nautical miles surfaced, 351 submerged when ordered to the Atlantic. Her sortie was delayed by a breakdown and she sortied from Naples on 26 September 1940 (captain Giuseppe Mellina) and manage to pass the Strait of Gibraltar undetected on 2 October, at one point deviated from 120 m due to strong currents. The following day while off the Azores, she spotted three destroyers, launched three torpedoes, no hit confirmation. On 7 October she spotted a 18 vessels convoy sailing for the north-northwest and another of 12 ships to the north-east. Her engines breakdowns pervented to chase these off. She was at the time capable of only 7.5 knots. On the 22nd she was back to Bordeaux for repairs and refit.

For having launched the discovery signal 6 hours after sighting, Commander Mellina was harshly criticized by Betasom Commander Admiral Parona, and relieved of duties. On 23 December 1940 now under Lieutenant Luigi Baroni she started a second Atlantic mission bringing her west of Scotland. On 9 January 1941, she spotted and torpedoed a 3900t GRT merchant but missed and surfaced to engage her with artillery, but the merchant was armed and the duel went badly for Glauco. Arms officer s.t.v. Carlo Marenco di Moriondo was wounded and fell into the sea by a wave. The damaged transport, being faster, escaped.
On 27 January, Glauco left for her third Atlantic sortie, this time off Porto. On 14 April she was spotted and hunt down by three submarine chasers taking 130 depth charges. Badly damaged she had to return to Bordeaux for extensive repairs from 22 April 1941.
On 24 June 1941, she left Bordeaux for Naples. Three days later she was spotted by the destroyer HMS Wishart while crossing the Strait of Gibraltar. She was depth charged until damage was just to great to continue, her captain decided to surface and she was battered by artillery, with eight men (an officer, three petty officers and four petty officers and sailors) died. She was scuttled 330 miles west of Cape Spartel and the rest of the crew surrendered and was made POW.

After entering service, she was assigned to the IV Submarine Group, Taranto. In 1936 it was transferred to Naples. Between December 1936 and August 1937 she made a clandestine deployment in the Spanish Civil War, makign two sorties in Spanish waters and Strait of Sicily in search of Republican-flaggd merchant ships and targets of opportunity, especialy warships. On one occasion she managed to sport a Rpublican destroyer, launch a torpedo but missed.
From December 1938 she operated in the Red Sea and Indian Ocean, based in Massawa testing her capabilities in warm seas where water density varied greatly for underwater operations. She was back in Italy since March 1940 when war started for Italy in June.

From 19 June to 5 July 1939 under command of CC Giuseppe Vocaturo (from 16 January 1939) she cruised in the Indian Ocean with the other RM sub Benedetto Brin, but spotted no target. Back to the Mediterranean after a few sorties it was decided to send her to the Atlantic, leaving La Spezia on 23 September 1940 and going through the Strait of Gibraltar. Serious damage forced her to Bordeaux, home of the Atlantic base (Betasom) for repairs.

On 14 October, she left Bordeaux for her second Atlantic deployment and on 17 October she was attacked by a Short Sunderland seaplane, but managed to repel it by AA fire, claiming damage. Between 30 October and 3 November she made several spottings of merchant ships but was unable to attack due to breakdowns and bad weather. On 5 November she launched two torpedoes at a large merchant ship but missed. Four days later she spotted an aircraft carrier and three destroyers, but could not approach due to her speed in severe weather. On 24 January she started a third deployment but had to return after a serious breakdown to Bordeaux on 1 February.
On 6 February she made another sortie and after a week, arrived in her ambush area. However, she spotted none, and was back to base on 1 March.
On 8 May she left Bordeaux under Lieutenant Commander Giuseppe Vocaturo and despite new mechanical problems, managed to torpedo and sink the English steamer Starcross (4662 TGB) on 20 May. Three days later, off the coast of Gironde, she rescued two survivors of the French trawler Notre Dame de Chalet, sunk by a British sub (suspected to be a German patrol trawler). On 25 May Otaria was in refit.
On 7 September 1941 she was back to the Mediterranean, crossing the Strait of Gibraltar and suffering depht charge attacks while there. She was in Naples on the 19th.
On 31 January 1942 she tried to save men trapped in the wreck of the submarine Medusa, sunk by HMS Thorn and on 1 February, under the command of Lieutenant Commander Emilio Berengan she managed to pump air into the wreck until the following day, while weather worsened causing her to lose grip on the seabed and the hoses broke. She was forced to move away and when back on 4 February, survivors were dead.
On 13 June 1942 as the Battle of Pantelleria (It: of Mid-June) she was attacked by a Sunderland, hitting her with machine guns, damaging her.
She was used for four transport missions to Libya with a total of 119 tons of supplies (gasoline, ammunition, provisions).
She was at sea during the Battle of Operation Pedestal (It: mid-August) but never in position to attack.
Worn out at this time it was decided by February 1943 to assigned her to the Submarine School in Pola. She made 101 training missions and after the armistice she surrendered to the Allies in Augusta. She was then in to Malta and on 6 October 1943 returned to Italy, used by the allies for for anti-submarine exercises until V-day in Europe. She continued limited service postwar until decommissioned on 1 February 1948 and sold for BU after 14 combat patrols (6 Atlantic 8 Mediterranean), 4 transport missions, 14,439 miles surfaced, 1,355 submerged.

Read More/Src

Books

Bagnasco, Erminio (1977). Submarines of World War Two. Annapolis, Maryland: Naval Institute Press.
Brescia, Maurizio (2012). Mussolini’s Navy: A Reference Guide to the Regina Marina 1930–45. Annapolis, Maryland: Naval Institute Press
Chesneau, Roger, ed. (1980). Conway’s All the World’s Fighting Ships 1922–1946. Greenwich, UK: Conway Maritime Press
Fraccaroli, Aldo (1968). Italian Warships of World War II. Shepperton, UK: Ian Allan.
Frank, Willard C. Jr. (1989). “Question 12/88”. Warship International. XXVI (1)
Rohwer, Jürgen (2005). Chronology of the War at Sea 1939–1945: The Naval History of World War Two (Third Revised ed.). Annapolis.
Conway’s all the world’s fighting ships 1921-47 p.304
Giorgio Giorgerini, Uomini sul fondo. Storia del sommergibilismo italiano dalle origini a oggi, Mondadori, 2002

Links

https://www.navypedia.org/ships/italy/it_ss_glauco.htm
https://en.wikipedia.org/wiki/Glauco-class_submarine
https://www.worldnavalships.com/glauco_class1.htm
https://uboat.net/allies/warships/class/547.html
https://x.com/MikiAV8BHarrier/status/1834462369272979494

Italian Submarines of World War II

https://it.wikipedia.org/wiki/Classe_Glauco_(sommergibile_1935)
https://pl.wikipedia.org/wiki/Okr%C4%99ty_podwodne_typu_Glauco_(1932)