The Rainbow-class submarine or R class was a quartet of patrol submarines built for the Royal Navy in the early 1930s. Design and description 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 overall, a beam of and a mean draft of . They displaced on the surface and submerged. The Rainbow-class submarines had a crew of 56 officers and ratings. They had a diving depth of . For surface running, the boats were powered by two diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a electric motor. They could reach on the surface and underwater. On the surface, the boats had a range of at and at 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. Boats Six boats were planned, but economic considerations resulted in the cancellation of the projected boats HMS Royalist and HMS Rupert. It is often stated that the sank HMS Rainbow. However, the submarine Enrico Toti sank was . Notes References External links Rainbow class at Uboat.net Rainbow class at battleships-cruisers.co.uk Submarine classes