United States R-class submarine

	Tied up along the dock from right to left: USS R-12, USS R-15, USS R-13, with USS R-9, and an unidentified R-boat, probably in Pearl Harbor, c. mid-1920s
Class overview
Name	R class
Builders	Bethlehem Quincy, Quincy, Massachusetts (R-1 to R-14); Bethlehem San Francisco, San Francisco, California (R-15 to R-20); Lake Torpedo Boat Company, Bridgeport, Connecticut (R-21 to R-27); Electric Boat Company (Four 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
Class & type	R-1-class (R-1 to R-20)
Type	Submarine
Displacement	574 long tons (583 t) surfaced; 685 long tons (696 t) submerged;
Length	186 feet 3 inches (56.77 m)
Beam	18 ft 0 in (5.49 m)
Draft	15 ft 6 in (4.72 m)
Installed power	880 brake horsepower (656 kW) diesel; 934 hp (696 kW) electric;
Propulsion	2 × NELSECO 6-EB-14 diesel engines; 2 × Electro-Dynamic Company electric motors; 2 × 60-cell batteries; 2 × Propellers;
Speed	12.5 knots (23.2 km/h; 14.4 mph) surfaced; 9.3 kn (17.2 km/h; 10.7 mph) submerged;
Range	4,700 nautical miles (8,700 km; 5,400 mi) at 6.2 kn (11.5 km/h; 7.1 mph), 7,000 nmi (13,000 km; 8,100 mi) if fuel loaded into the main ballast tanks
Test depth	200 ft (61 m)
Capacity	18,880 US gallons (71,500 L; 15,720 imp gal) fuel
Complement	2 officers ; 27 enlisted;
Armament	4 × 21-inch (533 mm) torpedo tubes (8 torpedoes); 1 × 3-inch (76 mm)/50-caliber deck gun;
General characteristics
Class & type	R-21-class (R-21 to R-27)
Type	Submarine
Displacement	497 long tons (505 t) surfaced; 652 long tons (662 t) submerged;
Length	175 ft (53 m)
Beam	16 ft 7 in (5.05 m)
Draft	13 ft 11 in (4.24 m)
Installed power	500 bhp (373 kW) diesel; 400 hp (298 kW) electric;
Propulsion	2 × Busch-Sulzer diesel engines; 2 × Diehl electric motors; 1 × 120-cell battery; 2 × Propellers;
Speed	14 kn (26 km/h; 16 mph) surfaced; 11.4 kn (21.1 km/h; 13.1 mph) submerged;
Test depth	200 ft (61 m)
Capacity	17,922 US gal (67,840 L; 14,923 imp gal) fuel
Complement	3 officers ; 23 enlisted;
Armament	4 × 21-inch torpedo tubes (8 torpedoes); 1 × 3-inch/50-caliberdeck gun;

The R-class submarines were a class of United States Navy coastal patrol 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. As had been the usual practice in several of the preceding classes, design and construction of the 27 boats of this class was split between the Electric Boat Company and the Lake Torpedo Boat Company. Both designs were built to the same military operational specifications, but differed considerably in design and detail specifics.