volts in parallel, producing submerged power for four main motors of the open shunt wound double-armature type, developing a total of 1600bhp at 300 rev/min for 11/2 hours. Also, an auxiliary drive consisting of a 20hp motor, driving the starboard shaft through a worm drive, could give a slow-running submerged speed of 1.75 knots.
A surface speed in excess if 17 knots was hoped for in the L Class and, even when carrying additional fuel in the external tanks, there is no doubt that this speed was attained. The first boat on trials, L1, actually obtained 17.2 knots and, in 1930, 17.6 knots was given as the design surface speed for the class. Although a designed submerged speed of 11 knots was anticipated in L1, the fitting of a 5ft 6in high fixed bridge screen reduced this to 10.5 knots.
