L9 and its successors were enlarged to accommodate 21-inch (53.3 cm) torpedoes and more fuel. The submarine had a length of 238feet overall, a beam of 23feet and a mean draft of 13feet.[1] They displaced 914LT on the surface and 1089LT submerged. The L-class submarines had a crew of 35 officers and ratings.[2] They had a diving depth of 150feet.
For surface running, the boats were powered by two 12-cylinder Vickers[3] 12000NaN0 diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 600hp electric motor.[1] They could reach 17kn on the surface and underwater. On the surface, the L class had a range of 3800nmi at .[4]
The boats were armed with four 21-inch torpedo tubes in the bow and two 18-inch (45 cm) in broadside mounts. They carried four reload torpedoes for the 21-inch tubes for a grand total of ten torpedoes of all sizes.[5] They were also armed with a 4adj=onNaNadj=on deck gun.[2]
HMS L23 was laid down on 26 July 1917 by Vickers at their Barrow-in-Furness shipyard, launched on 1 July 1919. The boat was then towed to Chatham Royal Dockyard and finished on 31 October 1924. She served on the China Station in the 1920s. HMS L23 survived a heavy depth charge attack by two German destroyers in February 1940. An oil leak occurred, which lead the Germans to believe that the submarine was destroyed. L23 was sold for scrap in May 1946.