Argo class (1936)

The Argo-class submarines were two CRDA Montfalcone submarines loosely related to the “600 Series” but ordered originally by Portugal and cancelled while in construction, repurchased by the Italian government. They were capable of 14 knots surfaced but had a generous range, but they were larger than the 600 tonnes series. An excellent design, they were the basis for the WW2 Flutto class. In WW2 Operations, Argo had some success against allied convoys, sinking three ships in 1940 and 1942 for 20,924 GRT. She was refitting at Montfalcone when the armistice was declared, and scuttled. The Germans salvaged but never repaired her. Her sister Velella patrplled as well but was sunk off Salerno, by HMS Shakespeare on 7 September 1943.

ARGO in Cagliari, camouflaged, after a mission return. Erminio Bagnasco and Achille Rastelli, now creatve commons.

Development

The CRDA Yard at Montfalcone was involved previously on others submarines of the 600 series, but on imposed plans. In 1935 it had ideas to proved the Regia Marina it can produce a 600 series design with superior range while keeping the usual surfaced speed. But the real starting point was not a RM order, these were instead a 1931 contract from Portugal, which wanted a model adapted for Atlantic service, while still being small enough to care for coastal waters off Portugal and the Iberian peninsula from the Basque coast to Gibraltar. In 1933, the discussions failed due to cost and contrat issues, officially, or internal arbitrations, but it seems this was due in great part from the tension between Rome and Lisbon over the Italian occupation of Ethiopia in 1935.
The order was rescinded when the two boats were already laid down and well progressed, especially Vellela, close to launch.

CRDA asked the Italian Government to intervene and perhaps saved them from bankupcy, but the Regia Marina followed the design froim the start with great interest anyway. So the two submarines were purchased the same year in 1935, on slip, for the Regia Marina. They thus resumed construction until launched in November 1936, renamed Argo (jason’s ship) and Vellela (“sail”). They would be completed in 1937 on Italian specifications. Specifics of the Portuguese design are no known. Instead, the Portuguese would order three submarines (800/1,029 tonnes) at Vickers, launched in 1934.

CRDA created a design that was originated as a scaled-down variant of Balilla class. It was partially double-hulled. The Italians made some alterations to the original design and they turned out to be a good purchase, as the base design for the successful wartime TRITONE class (1941-1943). They were officially laid down in September 1935, when the Regia Marina took over the project albeit on slip since 1931. Argo was delivered by August 31st, 1937.

The genesis of the ARGO class and later derivates, the three Tritone was not the result of a close collaboration between the Navy and engineers such as Bernardis and Cavallini with the private industry, but completely independent design work from C.R.D.A. Albeiot it was motivated entirely by foreign commission and tailoed specifications, it gave the possibility to the Yard to experiment its own ideas, provided they entered Portuguese specifications. This boat had a double hull boat of the Laurenti design, but with many perks.

Hull and general design

The Argo class were in a singular position, too large to be considered coastal and thus enter the 600 series, but too small to be considered fully oceanic, but they performed well in Atlantic Operations. VBoth the Argo and Tritone class would be later considered by historians as medium submarines. It must be remembered that the original design was a scaled-down Ballila class, a large orcanic submarine, whereas the Portuguese wanted a costal model with limited oceanic capabilities, notably to be deployed if needed in its far flung colonies. So range was paramount, and ended far greater than any of the 600 series. This was the Argo design main selling point.

The Argo class were still small in displacement, at 793 t (780 long tons) surfaced and 1,016 t (1,000 long tons) submerged versus 650-680 tonnes surfaced for a 600-series. They were barely longer however at 63.15 m (207 ft 2 in) overall for the outer hull, but beamier at 6.93 m (22 ft 9 in) but for also a comparable draft at 4.46 m (14 ft 8 in). The remainder of the design was pretty classic, with its bulged ballasts over which a long line of water scoops ran, a semi-rounded clipper prow and wire-cutter, a pair of folding upper diving planes, a main deck gun, sponsoned. She had a flat deck and rounded stern.

The Argo design had a partially enclosed sail, with a covered helmsman position, conning tower behind for two persiscopes, attack and watch, and an open deck cut for a ladder access, with pintles for twin heavy machine guns posts. As usual, a protective anti-net cab ran over the portico above the CT, resting fore and aft on poles. It also acted as wireless communication cables. The crew was 46 officers and enlisted men strong, about the same as a 600 series. Its two crew quarters also had two heads and two galleys, one running on diesel and the other on electric. The former was in the CT but was later removed as impractical. There was a hydrophone, a radio room and gyrocompass. One safety measure was a floating buoy installed above each torpedo room with a telephone system plus colored smoke pot to be located.

The pressure hull was divided into three sections, one at the middle, perfectly cylindrical, two at each ends with concave/convexe bulkheads with the pressure hull ending in semispherical spindly shapes, encasing the torpedo tubes. The pressure hull used steel with low nickel content, 14.5 mm (0.5 inches) thick but tapered down to 14 mm past the two end bulkheads. The sections (Fwd TT comp., Crew quarters and battery hold, control room, NCO quarters and aft battery room, engine room, aft TT room) were riveted to cylindrical beams acting as reinforcement rings every 52-55 cm (20-21 inches), with plating double riveted, layered like brick but overlapping on adjacent plates. The bolts were placed on this double juncture. The outer hull was just 6 mm thick (0.25 in), in which were installed the large fuel and water, trim and oil tanks.

Powerplant

In surface, the Argo class were powered by two 600-750 bhp (559 kW) diesel engines connected to a propeller shaft each. These were FIAT Q 274R and normally ran at 420 rpm for 600 HP, but they could be pushed for short runs at 460 rpm. When submerged, the same propellers were clutched to CRDA 300-horsepower electric motor that could be pushed to 400 hp for short runs (298 kW). They could operate from 45 to 180 volts, their maximum output for 330 RPM. They also could generate direct current to reload the batteries while surfaced. Indeed, the diesels were connected “in line” to the electric motor via a gear joint, and another linked it to the propeller shaft. The electric motor rotated freely when decoupled and surfaced. Underwater this was the diesel engine.

The battery reload was performed as a fixed predetermined speed. These batteries were located in two separare holds under the pressure hull deck, amidship, two times 52 batteries at 750 kg each making for a hard ballast of 78 tons for stability. Capacity was 4,750 amps for one hour, 7,050 amps for three, 9,720 amps for twenty. The Argo class could reach 14 knots (26 km/h; 16 mph) surfaced and 8 knots (15 km/h; 9.2 mph) underwater. Still surfaced, range was exceptional at 10,176 nautical miles (18,846 km; 11,710 mi) at 8 knots (15 km/h; 9.2 mph). For comparison this was almost double 600-series boats.

When submerged, it fell to 100 nmi (190 km; 120 mi) at 3 knots (5.6 km/h; 3.5 mph). To blow ballasts, their primary air compressor was installed in the auxiliary room. They had an HP aior compresssor, a turbo-blower, trimp, bilge and manual pumps as well as an air filtration system to scrub CO2 and oxygen tanks. The semi-compensated rear rudder and forward or diving planes were all electric.

Armament of the Argo class

Cannone da 100/47 Mod. 1931

Placed on the forward deck, on a raised platform or bandstand well integrated into the hull, acting as wave breaker, to avoid sea spray. This 100 mm/47 (3.9″) Modello 1931 benefited from developments and improvements made on the earlier Modello 1928, as manufactured by OTO. It would later evolved into the Modello 1935 and 1938 retofitted on the next Perla, Adua, Argo, Acciaio and Flutto classes. The boats carried either 144 or 152 rounds.

Specs

Gun Length oa: 194.5 in (4.940 m), 8-10 rpm.
Fixed Ammunition (HE) 30.4 lbs. (13.8 kg) 2,756 fps (840 mps)
Range: 35° 13,800 yards (12,600 m), OTO 1932
Weight 4.6 tons (4.7 mt) -5 /+32 or 35°.
To compare the previous Cannone da 100/43 modello 1927 had the following specs:
170 in (4.300 m) long, 8-10 rom. HE shells: 30.4 lbs. (13.8 kg), muzzle Velocity 2,625 fps (800 mps)
Elevation -5/+35°. Range: 30.4 lbs. (13.8 kg) HE Elevation/35° 12,000 yards (11,000 m).

AA: 2×2 Breda Breda Mod. 31

The anti-aircraft defence counted on two twin Breda M1931 13.2 mm L/76 heavy machine guns, placed aft of the conning tower. Each mount weighed 695 kg, but ensured 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. They carried a total of 3,000 rounds. It seems before or during the war, this progressed to two twin mounts for extra AA firepower according to many sources.

12x 533 mm (21 inches) torpedoes

The Sirna class submarines repeated the previous class for the stabndardized torpedo armament, six overall including four in the bow, and two in the stern, all reloadable for the pressure hull, and a reserve of 12 torpedoes including the six already in the tubes.
Models available in 1932:
-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.
They were also given also a pair of hydrophones.

⚙ specifications as built
Displacement	793t surfaced/standard, 1016 tonnes underwater
Dimensions	63.15 x 6.93 x 4.46 (207 x 23 x 15 ft)
Propulsion	2x diesels Fiat 1,500 hp, EM CRDA 800 hp
Speed	14 kts surfaced, 8 knots submerged
Range	10,176 nmi/8 knots surfaced, 100 nmi/3 knots submerged
Max depth	90 m (300 ft)
Armament	100 mm (3.9 in) gun, 4x 13.2 mm AA, 6× 533 mm (21 in) TTs (12)
Crew	46

Career of the Argo class

Argo (AO) was launched 24 November 1936, completed on 31 August 1937. The interwar was spent in training but details are scarce. She was formally assigned to the 42nd Submarine Squadron based in Taranto, but she operated like her sister as a training submarine in the Upper Adriatic until 1938. From 29 January 1939, she was sent to the Red Sea to test her performance in warm seas in case of a wartime deployment there, and was back to the Mediterranean in early March 1940. She then performed two unsuccessful wartime patrols under Lieutenant Alberto Crepas. It was decided to exploit her range and send her to the Strait of Gibraltar on 8 October 1940, for a first Atlantic patrol and a new base, Bordeaux (BETASOM) on 24 October.

Her first BETASOM patrol saw her attacking convoy HG 47. She torpedoed and damaged the destroyer escort HMCS Saguenay on 1 December. 4 days later she sank a freighter (5,066 GRT, 19 survivors from a crew of 55) from the convoy OB 252, her first kill. 1rst Lieutenant Alessandro De Angelis was lost overboard, drowned in heavy seas as she was back to base. Her 2nd and 3rd BETASOM patrols were from 27 February to 28 March and from 19 May to 12 June 1941, both were unsuccessful. It seems they struggled in the Atlantic due to their small size and burned more fuel. It was decided by late 1941 they were too small for Atlantic service and Supermarina send argo on 11 October from Bordeaux, via the Strait of Gibraltar on the 20th.

She reached Cagliari on 24 October 1941 and had a refit. After which she had a first patroll off Cape Ferrat, from 6 to 21 April as well as off Cap Caxime (Algeria) from 22 to 29 May 1942, sustaining damage from aerial attacks (likely Sunderlands). She was back to repairs. She was still deployed to the Balearic Islands from the 15 to 26 October, and off Galite in Tunisia from 29 to 30 October. Her most successful mission was performed under Lieutenant Arcangelo Ghiliberti. She entered Bougie, Tunisia, on 11-12 November 1942, in the aftermath of Operation Torch. There, she managed to spot in the bay and torpedo the anti-aircraft ship HMS Tynwald (2,376t) and later the troopship Awatea (13,482 GRT), already damaged by aerial bombing.

She then patrolled off the North African coast, from 17 December to 8 January 1943 and by February, April and June 1943, no successes. After two patrols off Sicily, in July 1943 she was snt for her major wartime refit at Monfalcone. She was caught there when the armistice of September 8, 1943 was known. Without any time to have her back at sea, the workers and few officers present as well as Captain Lorenzo Stallo were ordered by Rear-Admiral (E) Oreste Bambini to have her scuttled to prevent German troops to capture her, when they arrived in the shipyard two days later on 10 September. She was salvaged but never repaired. Instead she was cannibalized and later scuttled again at Monfalcone on 1 May 1945 to block the yard. Overall she performed 14 combat patrols, 17 transfers over 14.784 miles.

Velella (pennant VL) was launched on 18 December 1936, a month later than her sister, and completed on on 1 September 1937, a day after her sister. After completion, she was assigned to the 42nd Submarine Squadron in Taranto under Lieutenant Pasquale Terra but was used instead in the Upper Adriatic for training, until October 1938. By then under command of Lieutenant Gustavo Lovatelli, she was transferred to Leros, and then to Tobruk and then from 21 December she was sent to Massawa, testing Red Sea conditions.

In March 1940, she was back to the Mediterranean, assigned to the the 14th Submarine Squadron in La Spezia. The start of the war caught her in a mission between Rhodes and Turkey. On 19 June 1940 she had an engine failure and returned to Leros, for fixes, then full repairs at Taranto. She returned in the the eastern Mediterranean but her assignations led to nothing, no spot, no attacks. Given her long range Supermarina decided like her sister to sned them to the Atlantic at BETASOM.

After another refit at La Spezia, Velella sailed on 25 November 1940 via the Strait of Gibraltar on 1 December and reaching Bordeaux on Xmas Day, 25 December. In total she performed four unsuccessful Atlantic patrols and was sent back to the Mediterranean on 24 August 1941. She had another refit at Cagliaria and was sent for training at Pula. In between she was detached to patrol (without success) south of Cape Palos in Spain. By April 1942, she was deployed south of the Balearic Islands. In June, she was sent off the Tunisian coast and by July and August she was sent like her sister, west of the Island of Galite.

In September she was sent south of the Balearic Islands. Back off North Africa in 1943 she scouted off the Gulf of Philippeville and Bay of Bona in November as Operation Torch, expecting to meet allies transports. She was deployed off the north of Cap de Fer in April 1943. She was sent off eastern Sicily in July. Her last patrol was off Salerno, well guarded due to the landings, with frequent allied patrols. It was almost a death sentence. She was sank on 7 September evening, torpedoed by HMS Shakespeare. No survivors.

This part needs development: Velella holds the sad distinction of being the last Italian submarine lost in world war two, against the Allies. The naval command launched the “Zeta Plan” to attack the planned Anglo-American landings expected in Calabria or Campania. Vellela was sent in advance for either of these and left Naples on 7 September 1943 but she was never heard from again. Circumstances of her loss reminder a mystery for some time postwar until researches led to a near-certainty about her fate from British records. Around 8 o’clock, evening on 7 September the S-class submarine HMS Shakespeare was sailing off Punta Licosa when spotting two Italian submarines, Velella and the Benedetto Brin, proceeding on parallel course either side of her.

She attacked Velella because dusk approached and Velella was heading out, clearly visible against dying light. Brin was sailing near the coast and near-invisible. She launched launched six torpedoes and registered four hits by hydrophone. She probably broke in at least two parts and sank immediately after an underwater explosion, also heard from Brin. The entire crew (Commander Patané and 44 petty officers and sailors) went down. She had performed 16 missions, 14 transfers for 19,430 miles. On May 13, 2003, her wreck was located, 8.9 miles from Punta Licosa under 138 meters. In 2025 she was recognized as an “Underwater Military Grave” same status as the submarine Scirè.

Read More/Src

Books

“Sommergibili italiani” di A.Turrini e O.Miozzi – USMM
Giorgio Giorgerini, Uomini sul fondo. Storia del sommergibilismo italiano dalle origini ad oggi, pag. 162
Bagnasco, Erminio (1977). Submarines of World War Two. NIP
Brescia, Maurizio (2012). Mussolini’s Navy: A Reference Guide to the Regina Marina 1930–45. NIP
Chesneau, Roger, ed. (1980). Conway’s All the World’s Fighting Ships 1922–1946. Greenwich, UK: Conway Maritime Press.
Frank, Willard C. Jr. (1989). “Question 12/88”. Warship International. XXVI (1): 95–97.
Rohwer, Jürgen (2005). Chronology of the War at Sea 1939–1945: The Naval History of World War Two (3rd Revised ed.) NIP

Links

regiamarina.net
regiamarina.net CRDA Types
navypedia.org
xmasgrupsom.com
it.wikipedia.org
en.wikipedia.org
worldnavalships.com
velella.it
sommergibili.com
archeologiaindustriale.it
xmasgrupsom.com Vellela

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