Rainbow-class submarine

HMS Regent underway
Class overview
Name:	Rainbow class
Operators:	Royal Navy
Preceded by:	Parthian class
Succeeded by:	S class
In commission:	1930–1946
Planned:	6
Completed:	4
Cancelled:	2
Lost:	3
Retired:	1
General characteristics
Type:	Submarine
Displacement:	1,763 long tons (1,791 t) surfaced 2,030 long tons (2,060 t) submerged
Length:	287 ft (87 m)
Beam:	30 ft (9.1 m)
Draught:	16 ft (4.9 m)
Propulsion:	Diesel-electric 2 × Admiralty diesel engines, 4,640 hp (3,460 kW) 2 × electric motors, 1,635 hp (1,219 kW) 2 shafts
Speed:	17.5 knots (20.1 mph; 32.4 km/h) surfaced 8.6 kn (9.9 mph; 15.9 km/h) submerged
Complement:	53
Armament:	8 × 21 inch (533 mm) torpedo tubes (6 bow, 2 stern) with 14 reloads 1 × QF 4.7-inch (120 mm) Mark IX deck gun After 1942 : 2 × 20 mm cannon Equipped to lay mines through torpedo tubes

The Rainbow-class submarine or R class was a quartet of patrol submarines built for the Royal Navy in the early 1930s.

The Rainbow-class submarines were designed as improved versions of the Parthian class and were intended for long-range operations in the Far East. The submarines had a length of 287 feet 2 inches (87.5 m) overall, a beam of 29 feet 10 inches (9.1 m) and a mean draft of 13 feet 10 inches (4.2 m). They displaced 1,772 long tons (1,800 t) on the surface and 2,030 long tons (2,060 t) submerged. The Rainbow-class submarines had a crew of 56 officers and ratings. They had a diving depth of 300 feet (91.4 m).

For surface running, the boats were powered by two 2,200-brake-horsepower (1,641 kW) diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 660-horsepower (492 kW) electric motor. They could reach 17.5 knots (32.4 km/h; 20.1 mph) on the surface and 9 knots (17 km/h; 10 mph) underwater. On the surface, the boats had a range of 7,050 nautical miles (13,060 km; 8,110 mi) at 9.2 knots (17.0 km/h; 10.6 mph) and 62 nmi (115 km; 71 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged.

The boats were armed with six 21-inch torpedo tubes in the bow and two more in the stern. They carried six reload torpedoes for a grand total of fourteen torpedoes. They were also armed with a QF 4.7-inch (120 mm) Mark IX deck gun.

Six boats were planned, but economic considerations resulted in the cancellation of the projected boats HMS Royalist and HMS Rupert.

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