O-class Patrol Submarines
Name Pennant Builder Completed Fate
Oberon group
Oberon 21P Chatham RDY 24/8/27 Scrapped 1945
Oxley group
Otway 51P Vickers 9/9/27 Scrapped 1945
Oxley 55P Vickers 1/4/27 Torpedoed by HM s/m Triton in error off Stavanger, 10/9/39*
Odin group
Odin 84P Chatham RDY 21/12/29 Sunk by Italian destroyer Strale in Gulf of Taranto, 13/6/40
Osiris 67P Vickers 25/1/29 Scrapped 1946
Oswald 58P Vickers 1/5/29 Rammed by Italian destroyer Vivaldi off Cape Spartivento, 1/8/40
Otus 92P Vickers 5/7/29 Scuttled off Duran, 1946
Olympus 35P Beardmore 14/6/30 Mined off Malta, 8/5/42
Orpheus 46P Beardmore 23/9/30 Sunk by Italian destroyer Turbine off Tobruk, 19/6/40

* = Apparently, a cloth rag draped over the side of the conning tower cut off the top of the large "O" painted on the side, giving the appearance of a "U" to the periscope of HM s/m Triton.

1:600 HM submarine Oberon. Note the original bull-nosed bow. © Andrew Arthur
1:600 picture of the latter groups. The conning tower was modified, and the bow was longer
and had a ram profile. © Andrew Arthur

These boats were built for operations in the Far East, because of the lapse of an Anglo-Japanese treaty in 1922, it was realised that dditional, modern units would have to be built for service here. They all served in this area until the outbreak of the war.
Compared to the "L" class, they were 40 feet longer, 4 feet more beamier, 2 knots slower, had twice the torpedo armament and a much greater radius of action. The torpedo factor was what stood them apart from the "L" class, the latter were quite capable of reaching and patrolling the Far East, but could not remain fro long, because of limited amounts of reloads for their torpedoes : the "O" class could fire each tube twice.
Each shaft had two electric motors powering it, arranged in tandem, and could be used singly for extended running or all four at once for high speed burst. This arrangement remained standard in the RN ever after. They were also the first RN subs to be fitted with Asdic as standard, a Type 116 set being carried.
An early problem of  the class was fuel seepage from the external tanks which were of riveted construction.
Originally called "O.1", Oberon was very attractive to the RAN, and they ordered two, AO.1 & AO2, to a slightly different design. the main feature was the ram-bow, Oberon having a bull nosed stem. Three similar units were built by Vickers for Chile.
As an economy measure, AO.1 & AO.2 were returned to the RN in 1931, and renamed Oxley
and Otway respectively.
The second, Odin, batch had the ram-bow of the "AO"'s, but a slightly higher surfaced speed. They also had their hydroplanes moved to the top of the hull. Although this meant a slightly slower diving time, they were easier to maintence, were less prone to damage, and could be retraced to lie flush with the hull when not in use, allowing the sub to get very close to a pier.
At the outbreak of war they were dispatched to serve in the Mediterranean for which they were wholly unsuited for, and they were soon returned hime and used in training duties.

  Group   Group
  Oberon Oxley Odin   Oberon Oxley Odin
Surface Displacement 1311 tons 1354 tons 1475 tons Length 82.19 m 83.82 m 86.41 m
Submerged Displacement 1831 ton 1872 tons 2038 tons Beam 8.53 m 8.42 m 9.12 m
Ballast load 510 tons 518 tons 563 tons Draft 4.72 m 4.79 m 4.9 m


Performance & Propulsion
  Oberon Oxley Odin
Range 11400 nm 12300 nm 8500 nm
Dive 91.4 m 91.4 m 91.4 m
Speed 13.75 kts ( 7.5 kts submerged ) 15 kts ( 8.5 kts submerged ) 17.5 kts ( 8.5 kts submerged )
Machinery 2 x Admirality Diesels @ 2950 hp,
2 x Electric motors @ 1350 hp
2 x Vickers Diesels @ 3100 hp,
2 x Electric motors @ 1350 hp
2 x Admirality Diesels @ 4250 hp,
2 x Electric motors @ 1390 hp


Armament & Complement
Complement 6 officers & 47 ratings
  • Torpedo
    • 6 x 21" bow tubes
    • 2 x 21" stern tubes
    • 16 x 21" torpedoes
  • Gun
    • 1 x 1 x 4" DP
    • 2 x 1 x 0.303" MG AA
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