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 .
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==