The Fluttos were a development of the 600 Series of medium-sized, or seagoing, submarines. They were built to a partial double-hulled Bernardis design, influenced by war-time experience and construction adapted for mass construction. The Fluttos were good sea-boats with improved internal arrangements, hull strength, anti-aircraft armament and diving times. They are regarded as the best medium-displacement submarines built by Italy up to that time. A total of 48 submarines were ordered, in three series (referred to as "Types"). The name Flutto means “wave”, and the Type I vessels were named for marine terms and sea-creatures. The Type II and Type III vessels all bore names of metals.
Type I
The first series of 12 vessels were laid down in 1941; six from CRDA, and three each from OTO and Tosi. Of these 10 were commissioned and saw action; two others were unfinished at the Italian armistice in September 1943 and work on them was abandoned. Of the 10 vessels which became operational, three were sunk by the Allies, and four scuttled at the armistice. These were all raised by the Germans and re-fitted, but all four were sunk in Allied air raids during 1944. Three others were surrendered to the Allies and survived the war. Two vessels, Grongo and Murena, fitted with containers for carrying Maiale manned torpedoes, for operations by the Decima MAS special operations force.
Type II
The second series of 24 were to the same design, though enlarged slightly to resolve trim problems highlighted in the first vessels. These were laid down in 1942, 15 from CRDA, six from OTO and three from Tosi. These constructions were overtaken by Italy's collapse in September 1943, and none had been completed at that time. Most of these hulls fell into German hands, and work was continued on several, but none became operational before Germany's surrender in 1945.
Type III
The third series were a copy of the Type II design, and were due to be started in 1943, but none had been laid down by the time of Italy's surrender in September of that year. All were subsequently cancelled.
Ships
Type I
Cernia: Tosi: Work suspended September 1943 at armistice; laid up 1944
Dentice: Tosi: Work suspended September 1943 at armistice; laid up 1944
Flutto: Launched at CRDA 19.11.42; sunk 11.7.43 by British MTBs
Gorgo: Launched at CRDA 31.1.42; sunk 21.5.43 by US destroyer Nields
Grongo: Launched at OTO 6.5.43; scuttled in September 1943 at armistice. Raised by the Germans as UIT 20; destroyed in air raid in 1944
Marea: Launched at CRDA 10.12.42; surrendered to the Allies in September 1943
Murena: Launched at OTO 11.4.43; scuttled in September 1943 at armistice. Raised by the Germans as UIT 16; destroyed in air raid in 1944
Nautilo: Launched at CRDA 20.3.43; scuttled in September 1943 at armistice. Raised by the Germans as UIT 19; destroyed in air raid in 1944
Sparide: Launched at OTO 21.2.43; scuttled in September 1943 at armistice. Raised by the Germans as UIT 15; destroyed in air raid in 1944
Spigola: Tosi; work suspended in September 1943 at armistice. Broken up in 1948
Gardiner, Robert; Chesneau, Roger, eds. (1980). Conway's All The World's Fighting Ships 1922–1946. London: Conway Maritime Press. ISBN0-85177-146-7.
Dodson, Aidan & Cant, Serena (2020). Spoils of War: The Fate of Enemy Fleets after Two World Wars. Barnsley, UK: Seaforth Publishing. ISBN978-1-5267-4198-1.
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