United States R class submarine

Tied up along the dock from right to left: R-12 (SS-89), R-15 (SS-92), R-13 (SS-90) with R-9 (SS-86) and an unidentified R-boat probably in Pearl Harbor, c. mid 1920s.
Class overview
Name:	R class
Builders:	Fore River Shipyard (R-1 to R-14) Union Iron Works (R-15 to R-20) Lake Torpedo Boat (R-21 to R-27) Electric Boat (4 boats for Peru)
Operators:	United States Navy  Peruvian Navy  Royal Navy
Preceded by:	O class
Succeeded by:	S class
Built:	1917-1919
In commission:	1918-1931, 1940-1945
Completed:	27
Lost:	2
Retired:	25
General characteristics
Type:	Submarine
Displacement:	Group 1: 569 long tons (578 t) surfaced 680 long tons (691 t) submerged Group 2: 510 long tons (518 t) surfaced 583 long tons (592 t) submerged
Length:	Group 1: 186 ft 2 in (56.74 m) Group 2: 175 ft (53 m)
Beam:	Group 1: 18 ft 1 in (5.51 m) Group 2: 16 ft 8 in (5.08 m)
Draft:	Group 1: 14 ft 5 in (4.39 m) Group 2: 13 ft 11 in (4.24 m)
Propulsion:	Group 1: 2 × 600 hp (447 kW) NELSECO diesel engines 2 × 467 hp (348 kW) Electro Dynamic Co. electric motors 2 × 60-cell batteries 2 × shafts Group 2: 2 × 500 hp (373 kW) Busch-Sulzer diesel engines 2 × 400 hp (298 kW) Diehl electric motors 2 × 60-cell batteries 2 × shafts
Speed:	Group 1: 13.5 knots (25.0 km/h; 15.5 mph) surfaced 10 knots (19 km/h; 12 mph) submerged Group 2: 14 knots (26 km/h; 16 mph) surfaced 11 knots (20 km/h; 13 mph) submerged
Test depth:	200 ft (61 m)
Complement:	30 officers and men
Armament:	Group 1: 4 × 21 inch (533 mm) torpedo tubes, 8 torpedoes 1 × 3 inch (76 mm)/50 caliber deck gun Group 2: 4 × 18 inch (450 mm) torpedo tubes, 8 torpedoes 1 × 3 inch (76 mm)/50 caliber deck gun

The R-class submarines were a class of United States Navy submarines active from 1918 until 1945. With the first of the class laid down following the American entry into World War I, they were built rapidly. Although R-15 through R-20 were completed July–October 1918, they did not serve overseas, and the bulk of the class were not completed until after the Armistice.

The Group 1 boats were decommissioned in 1931, but were recommissioned in 1940 to serve as training boats at Submarine Base New London, Connecticut. Three (R-3, R-17, and R-19) were transferred to the United Kingdom's Royal Navy as HMS P.511, HMS P.512, and HMS P.514 in 1941-1942. P.514 was lost on 21 June 1942 in a collision with the Canadian minesweeper HMCS Georgian due to being mistaken for a U-boat. R-12 was lost on 12 June 1943 in an accident off Key West, Florida.

At some point between the wars the US R class were modified for improved rescue ability in the event of sinking. A motor room hatch was added, the motor room being the aftermost compartment. The tapered after casing became a step as a result of this modification.

At least one R-class submarine can be seen briefly in the 1943 movie Crash Dive, filmed at the New London submarine base.

Electric Boat built four R-class boats for the Peruvian Navy (R-1 to R-4). Built after World War I using materials assembled from cancelled S-class submarines, they were refitted in 1935–36 and 1955–56, and renamed Islay, Casma, Pacocha, and Arica in 1957. They were discarded in 1960.