British R - class submarine The " R " - class submarines were a class of 12 small British diesel - electric submarine s built for the Royal Navy during World War I , and were forerunners of the modern hunter - killer submarines , in that they were designed specifically to attack and sink enemy submarines , their battery capacity and hull shape being optimized for underwater performance . With a submerged speed of , the class set an underwater speed record not broken until the experimental Japanese Submarine No . 71 of 1938 , which was capable of more than submerged . Description . Ordered in December 1917 , the " R " - class were designed to be faster underwater than on the surface , achieving a submerged speed of versus a surfaced speed of . They were well - streamlined , having no external ballast tanks , casing , or deck gun , and a streamlined spindle - shaped hull of circular cross - section ( not reproduced until the " Los Angeles " - class ) which tapered sharply towards the stern and allowed only for a single screw . The bulbous bow contained five sensitive hydrophones and the lightened conning tower was also well - streamlined . Thirty - five percent of the space inside the pressure hull was occupied by machinery . A single 8 - cylinder 480 hp Diesel engine was installed for surface propulsion , while high underwater speed was given by two large electric motors arranged one behind the other to drive the single propeller shaft , and powered by a 200 - cell battery of the same type fitted to " J " - class submarines . The large battery was , however , sufficient for only about an hour at full power . In addition , the engine took a full day to charge the batteries , using half its power . Charging was therefore undertaken in harbour , using a supply of electricity from the shore or from special battery charging vessels . Despite being designed for maximum underwater performance , the " R " - class submarines were extremely difficult to control submerged , especially at high speeds . Surfaced , they had poor seakeeping and were slow . Minor modifications were made to " R4 " , the only submarine of the class to survive into the 1930s , which made it more manageable on the surface , but reduced its submerged speed to a maximum . Armament . The " R " - class were the first Royal Navy submarines to be fitted with six bow torpedo tubes , number of torpedoes being considered more important than range or size of warhead carried when attacking U - boats . The torpedo tubes were originally the smaller but later changed to . As designed , one spare torpedo was allowed for , but in operation six reloads were carried in place of the senior Ratings ' accommodation . It was originally intended to fit a 4 inch gun on the foredeck , but this was dropped due to the adverse effect it would have had on submerged speed . Construction . " R - 1 " through " R - 4 " were ordered from Chatham , " R - 5 " and " R - 6 " from Devonport ( later changed to Pembroke ) , " R - 7 " and " R - 8 " from Vickers , " R - 9 " and " R - 10 " from Armstrong , and " R - 11 " and " R - 12 " from Cammell Laird . In August 1919 , with World War I over , " R - 5 " and " R - 6 " were cancelled , the rest being completed . To save time , they used " H " - class components . Service . Operating out of Killybegs , Donegal , one of the class reportedly tracked and fired on a U - Boat in October 1918 , firing a full salvo of six torpedoes of which only one hit but did not detonate . All but " R - 4 " and " R - 10 " were sold for scrap in 1923 . The two survivors were relegated to ASW training at Portland , where their high performance led to them ( literally ) running rings around naval trawler s whose performance their crews found deficient . " R - 10 " was sold in 1929 , while " R - 4 " survived as a fast underwater target at Portland until 1934 . * Cancelled while under construction