Tied up along the dock from right to left:USS R-12,USS R-15,USS R-13, withUSS R-9, and an unidentified R-boat, probably inPearl Harbor,c. mid-1920s
Class overview
Name	R class
Builders	Bethlehem Quincy,Quincy, Massachusetts (R-1 toR-14) Bethlehem San Francisco,San Francisco, California (R-15 toR-20) Lake Torpedo Boat Company,Bridgeport, Connecticut (R-21 toR-27) Electric Boat Company (Four boats forPeru)
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[1][2]
Class & type	R-1-class (R-1 toR-20)
Type	Submarine
Displacement	574long 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	880brake horsepower (656 kW) diesel 934 hp (696 kW) electric
Propulsion	2 ×NELSECO 6-EB-14diesel engines 2 ×Electro-Dynamic Companyelectric motors 2 × 60-cellbatteries 2 ×Propellers
Speed	12.5knots (23.2 km/h; 14.4 mph) surfaced 9.3 kn (17.2 km/h; 10.7 mph) submerged
Range	4,700nautical 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	18,880US gallons (71,500 L; 15,720 imp gal) fuel
Complement	2 officers 27 enlisted
Armament	4 ×21-inch (533 mm)torpedo tubes (8torpedoes) 1 ×3-inch (76 mm)/50-caliberdeck gun
General characteristics[1][3]
Class & type	R-21-class (R-21 toR-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

TheR-class submarines were a class ofUnited States Navycoastal patrol submarines active from 1918 until 1945. With the first of the class laid down following theAmerican entry into World War I, they were built rapidly. AlthoughR-15 throughR-20 were completed July–October 1918, they did not serve overseas, and the bulk of the class were not completed until after theArmistice. 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 theElectric Boat Company and theLake Torpedo Boat Company. Both designs were built to the same military operational specifications, but differed considerably in design and detail specifics.^[4]

BoatsR-1 throughR-20, also referred to as theR-1-class, were designed byElectric Boat and built by the company's subcontractor yardsBethlehem Quincy andBethlehem San Francisco. These single-hull boats were structurally similar to the precedingO-class, but larger and therefore with more powerful machinery to maintain the required speed. Electric Boat departed from their traditional rotating bow cap that acted as the muzzle doors for thetorpedo tubes. All submarines from the R-class forward built by this company would have individual muzzle doors.^[5] For the first time in a US submarine class,21-inch (533 mm) torpedo tubes were fitted, a tube diameter that is still standard worldwide. A more powerful non-retractable3-inch (76 mm)/50-caliberdeck gun replaced the retractable3-inch/23-caliber gun found on previous classes.^[6]

BoatsR-21 toR-27, also referred to as theR-21-class, which were slightly smaller and faster than the Electric Boat design, were designed and built by theLake Torpedo Boat Company.Simon Lake finally gave up on his patented zero-angle (aka "even-keel") diving method with midships-mounteddiving planes, and adopted the Electric Boat style angled diving method using bow and stern mounted diving planes. The Lake-style flat shovel stern with ventrally mountedrudder, diving planes, andpropellers were retained for this class.^[4] There is conflicting information as to what size torpedo tubes were mounted in the Lake boats, with authoritative references by Gardiner^[6] and Friedman^[1] disagreeing as to whether they were equipped with18-inch (450 mm) torpedo tubes or the 21-inch tubes of the Electric Boat design. They were equipped with the same 3-inch/50-caliber deck gun as the Electric Boat design. At least one boat,R-22,^[7] was fitted with an expandedbow buoyancy tank that gave it a humped appearance. This was done to improve surface sea keeping. Unlike the Electric Boat design group, most of which survived to serve inWorld War II, the Lake boats were scrapped in 1930, as part of the Navy's compliance with theLondon Naval Treaty. The Lake company's demise in 1924, and poorly regarded design features, also contributed to this.^[6][4]

Most of the Electric Boat design group spent the 1920s in thePacific, operating out ofSan Diego andHawaii. In 1921, one member of this group,R-14,^[8] was stranded at sea in the Pacific, off Hawaii, when it ran out of fuel during asearch and rescue operation. The boat rigged makeshift sails and sailed 140 nmi (260 km; 160 mi) toHilo, Hawaii.^[9] The Hawaii-based boats returned to the mainland, on 18 January 1931, and were decommissioned to reserve status, at thePhiladelphia Navy Yard, in 1931.

In the aftermath ofS-4's disaster in 1927, all of the EB design boats were modified for greater safety. A motor room escape hatch was added, the motor room being the after most compartment. The tapered after casing became a step as a result of this modification. The boats also received salvage air connections and mating surfaces around topside hatches to allow theMcCann Rescue Chamber to rescue trapped crewmen.^[4]

As the war emergency in Europe became more urgent, most of the boats were recommissioned in 1940, conducting patrols in the Caribbean, or being used as sonar targets atKey West, Florida. They also patrolled betweenSubmarine Base New London, in Connecticut, andBermuda. At least two R-boats unsuccessfully fired torpedoes atGermanU-boats on the Bermuda patrols.

During the war, several R class boats operated out of Key West, being assigned to support theFleet Sonar School. They served primarily as sonar targets for training crews ofdestroyers anddestroyer escorts inanti-submarine warfare. They also conducted patrols in theFlorida Strait, and theYucatán Channel.

Three boats,R-3,R-17, andR-19, were transferred to theUnited Kingdom'sRoyal Navy, as HMSP.511, HMSP.512, and HMSP.514 in 1941-1942.P.514 was lost on 21 June 1942, in a collision with theCanadianminesweeperHMCS Georgian due to being mistaken for a U-boat.R-12 was lost on 12 June 1943, while underway off Key West. While the cause of her loss has never been definitively determined, when her wreck was found by the in 2010, by theLost 52 Project, it was suspected that the old boat suffered from a hull failure in the forward battery compartment.^[10]

Between May and September 1945, the 15 remaining R boats in the US Navy were decommissioned and subsequently scrapped.

Electric Boat built four variants of the R class for thePeruvian Navy (BAPR-1 toR-4). Built after World War I, using materials assembled from cancelled S-class submarines, they wererefitted in 1935–1936 and 1955–1956, and renamedIslay,Casma,Pacocha, andArica in 1957. These were the first submarines built directly by Electric Boat, at their newly established shipyard along theThames River, in Connecticut.^[11] They were discarded in 1960.

In December 2020, the remains ofR-8 were discovered off the coast ofOcean City, Maryland.^[12] The vessel sank there in 1936, after being used for target practice by bomber aircraft.

The 27 submarines of the R class were:

Wikimedia Commons has media related toR-class submarines of the United States.

• NavSource early diesel submarines page
• DiGiulian, Tony Navweaps.com early 3"/50 caliber guns

• Submarine classes
• United States R-class submarines
• World War I submarines of the United States
• World War II submarines of the United States

• Articles with short description
• Short description is different from Wikidata
• Use American English from October 2024
• All Wikipedia articles written in American English
• Use dmy dates from October 2024
• Commons category link is on Wikidata