The ''Perla''-class submarines were the third sub-class of the 600 Series of

coastal submarine A coastal submarine or littoral submarine is a small, maneuverable submarine with shallow draft well suited to navigation of coastal channels and harbors. Although size is not precisely defined, coastal submarines are larger than midget submarine ...

s built for the

Royal Italian Navy The ''Regia Marina'' (; ) was the navy of the Kingdom of Italy (''Regno d'Italia'') from 1861 to 1946. In 1946, with the birth of the Italian Republic (''Repubblica Italiana''), the ''Regia Marina'' changed its name to '' Marina Militare'' (" ...

(''Regia Marina'') during the 1930s and named after gemstones. Of the ten boats built of this class, only three survived World War II.

Design and description

The ''Perla''-class submarines were essentially repeats of the preceding . The modifications that were made compared to the boats of the previous series were mostly of upgrade nature. Among them were enlargement of the false tower at the top, more modern engines, installation of a radiogoniometer that could be controlled from inside the ship. Improvements and the installation of new air conditioning equipment meant a slight increase in displacement, and increase in the fuel stowage also increased the autonomy of these boats compared to the previous series. Their designed full load

displacement Displacement may refer to: Physical sciences Mathematics and Physics * Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...

was surfaced and submerged, but varied somewhat depending on the boat and the builder. The submarines were long, had a

beam Beam may refer to: Streams of particles or energy *Light beam, or beam of light, a directional projection of light energy **Laser beam *Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially localized grou ...

of and a

draft Draft, The Draft, or Draught may refer to: Watercraft dimensions * Draft (hull), the distance from waterline to keel of a vessel * Draft (sail), degree of curvature in a sail * Air draft, distance from waterline to the highest point on a vesse ...

of to .Bagnasco, p. 153 For surface running, the boats were powered by two

diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-ca ...

s, each driving one

propeller shaft A drive shaft, driveshaft, driving shaft, tailshaft (Australian English), propeller shaft (prop shaft), or Cardan shaft (after Girolamo Cardano) is a component for transmitting mechanical power and torque and rotation, usually used to connect ...

with overall power of . When submerged each propeller was driven by a

electric motor An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate for ...

. They could reach on the surface and underwater. On the surface, the ''Perla'' class had a range of at , submerged, they had a range of at .Bagnasco, p. 153 The boats were armed with six internal

torpedo tube A torpedo tube is a cylindrical device for launching torpedoes. There are two main types of torpedo tube: underwater tubes fitted to submarines and some surface ships, and deck-mounted units (also referred to as torpedo launchers) installed aboa ...

s, four in the bow and two in the stern. One reload torpedo was carried for each tube, for a total of twelve. They were also armed with one

deck gun A deck gun is a type of naval artillery mounted on the deck of a submarine. Most submarine deck guns were open, with or without a shield; however, a few larger submarines placed these guns in a turret. The main deck gun was a dual-purpose ...

for combat on the surface. The light anti-aircraft armament consisted of one or two pairs of machine guns.Chesneau, pp. 309–10

Ships

Service

The boats, once commissioned, were assigned to complete the squadrons of "600" submarines from La Spezia (12th and 13th Squadrons) and Messina (34th and 35th Squadrons) and began their training and exercises in metropolitan waters, and underwent endurance training predominantly in the Dodecanese and, to a lesser extent, along the coast of

North Africa North Africa, or Northern Africa is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region, and it is sometimes defined as stretching from the Atlantic shores of Mauritania in ...

. These endurance exercises took place in 1936 and 1937, soon after the initial training was finished. and were "lent" to the Nationalist side during the

Spanish Civil War The Spanish Civil War ( es, Guerra Civil Española)) or The Revolution ( es, La Revolución, link=no) among Nationalists, the Fourth Carlist War ( es, Cuarta Guerra Carlista, link=no) among Carlists, and The Rebellion ( es, La Rebelión, link ...

, under the names of ''Gonzales Lopez'' and ''Aguilar Tablada'' respectively, in the framework of

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...

's aid to Franco's regime. They retained their Italian crews but had a Spanish liaison officer on board. They were returned to the Italian Navy at the end of the conflict. In 1938 and were sent to the Red Sea base of Massawa and returned the following year replaced by , and who in turn returned to Italy before the outbreak of

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

. Between 1938 and 1940 and were for long periods of time deployed outside of Italy, mainly in

Tobruk Tobruk or Tobruck (; grc, Ἀντίπυργος, ''Antipyrgos''; la, Antipyrgus; it, Tobruch; ar, طبرق, Tubruq ''Ṭubruq''; also transliterated as ''Tobruch'' and ''Tubruk'') is a port city on Libya's eastern Mediterranean coast, near ...

. At the outbreak of hostilities, four boats were located at La Spezia, three in Cagliari, two in Augusta and one, , in Massawa. After a disastrous start to the

when

lost ten submarines in the first twenty days, and the

Regia Marina The ''Regia Marina'' (; ) was the navy of the Kingdom of Italy (''Regno d'Italia'') from 1861 to 1946. In 1946, with the birth of the Italian Republic (''Repubblica Italiana''), the ''Regia Marina'' changed its name to ''Marina Militare'' ("M ...

and Regia Aeronautica did not fare much better, Italian command decided to speed up implementation of experimental SLC technology. In July 1940 was modified to carry 4 "Maiale" manned torpedoes in watertight containers on the deck of the submarines. was sunk while conducting tests, before she could be employed against British naval units. underwent conversion to SLC in March 1942 with three SLC units being fitted onto her deck. With a weight of 2.8 tons, these SLC cylinders were able to withstand depths up to 90 meters, about three times more than those installed on . In December 1942, managed to penetrate Algiers harbor, and sank or seriously damaged several merchant ships with a total GRT over 20,000. In common with other Italian submarines the survivors were fitted with smaller conning towers in 1942–43. Overall, the ''Perla'' class submarines proved to be quite successful. They showed good maneuverability, their hull was well designed and strongly built to withstand depth pressure and explosions that exceeded their test values.

Notes

References

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External links