Balilla-class submarine

The "Balilla" class were the first submarines to be built for the Italian navy following the end of World War I. They were large ocean-going cruiser submarines designed to operate in the Indian Ocean based in Italy's East African colonies. The design was double-hulled and based on the German Type UE 2 U-boats, one of which, was supplied to the Italians as a war reparation. A auxiliary diesel engine was installed as an extra generator.
During the war, the boats were stationed in the Mediterranean in 1940 but proved too large to be effective patrol submarines. Their only success was the sinking of the British submarine by on 15 October 1940. After 1941 they were used as transport submarines to supply Italian forces in North Africa. The surviving boats were scrapped after the war.
One submarine, , was built for the Brazilian Navy to a modified design.
Design.
The design of the "Ballila" class consisted of a strong double-hull which gave the ships a maximum diving depth of , though reached in trials. The boats displaced 1,427 tons surfaced and 1874 tons submerged. They were long with a beam of and a draught of . The boats were considered to have poor stability.
The submarines were powered by two Fiat diesels for surface cruising and two Savigliano electric motors for use while submerged driving two shafts. These created and respectively. The second diesel engine was for auxiliary purposes and for recharging the batteries, novel at the time of the boats construction. This gave the ships a speed of surfaced and submerged. However, the initial design called for the ability to reach speeds of surfaced and submerged; the subs never reached these marks. The "Ballila"-class boats had a range of at .
The "Ballila" class was armed with six torpedo tubes with four located in the bow and two in the stern. The submarines carried a load of 16 torpedoes, with two reloads for each bow tube and one reload for each stern tube.
The class was also armed with one 1924 model /27 calibre deck gun that was placed in a shielded mounting in the forward section of the conning tower. In 1934, the class underwent a refit that upgraded the model to a /45 calibre gun. The ships also received two machine guns placed two single mounts.
"Humaytá" sub-class.
"Humaytá" was ordered by the Brazilian navy as a deep-diving submarine. Modifications to the standard "Ballila" design include the placement of the diesel and electric motors further forward, the elimination of the bow planes and a different distribution of the ballast tanks throughout the submarine. The submarine was longer at with a shallower draught, . The vessel displaced 1,390 tons surfaced and 1,884 tons submerged.
The submarine was powered by two Ansaldo diesels with one electric motor creating and respectively. This gave the ship a speed of surfaced and submerged.
"Humaytá" differed in armament too. The submarine was equipped with the six torpedo tubes with four located in the bow and two in the stern. However, the vessel had only a deck gun and carried 16 mines.
Ships.
All ships were built by OTO in Muggiano. "Humaytá" was a modified version of this design built for the Brazilian Navy in 1927. The ship was retired in 1950.