The Capitan O'Brien class were three submarines built for the Chilean Navy in the late 1920s. Designed and built in the United Kingdom, they were a modified design of the contemporary British s. The lead boat, , was launched on 2 October 1928 and the other two on 15 January 1929. All three submarines entered service in 1929. The three vessels remained in service until being discarded in 1957âÂÂ1958.
The Capitan O'Brien class were three submarines constructed to a modified design based on the British Royal Navy's . The Odin class was the Royal Navy's leading submarine design in the post-World War I era, equipped with strengthened pressure hulls and fuel carried in the ballast tanks to improve rapid diving. They had an extended surface range. The Capitan O'Briens measured long between perpendiculars with a beam of and a draught of . They had a displacement of while surfaced and submerged. The submarines were propelled by two shafts powered by two Vickers diesel engines creating while surfaced and two electric motors creating while submerged. This gave them a maximum speed of when surfaced and while submerged. The builder's photograph of Capitan Simpson gives the dimensions as long overall with a beam of and a draught of with a surface speed of 15 knots and when submerged.
The Capitan O'Briens had a large conning tower that stretched one-third of the deck and mounted the /45 deck gun in a turret. The submarines were also armed with eight torpedo tubes, with six located in the bow and two in the stern. The subs carried 14 torpedoes. Each submarine had a complement of 54 personnel.