The first submarines to be designed after the First World War. were the O Class - a post-war concept of an Overseas Patrol Submarine. With this class it appears that the Admiralty finally decided that the submarine deserved the dignity of a name: thus, the pioneer of the class was called Oberon.
The L50 Class submarines were chosen as a model for the Oberon design, but the new class had much greater endurance, increased diving depth, improved torpedo armament and increased wireless range. However, a 75 per cent increase in displacement led to a loss of speed, both surface and submerged.
During the building of Oberon, the unforeseen growth in topside fittings had a devastating effect on submerged speed and, although modifications were made after her completion in August 1927, a quoted underwater speed of only 9 knots, attained from two twin-armature motors developing 1300 bhp, is hard to believe.
The two Admiralty-designed six-cylinder diesels in Oberon made at Chatham developed 2700 bhp and gave a quoted surface speed of 13.75 knots. Laid down after the Oberon, Oxley and Otway were built by Vickers for the Royal Australian Navy but had their engines redesigned, an increase in the bore and stroke of the cylinders giving 3000 bhp, which resulted in an increase in surface speed of approximately 1.5 knots.
