Подводные лодки класса J: История британских дизель-электрических субмарин Первой мировой войны.

1915 class of British submarines
other machines referred to as 'J class'

The J class submarines were seven submarines developed by the Royal Navy prior to the First World War in response to claims that Germany was developing submarines that were fast enough to operate alongside surface fleets. Six were completed during mid 1916, while a seventh entered service at the end of 1917. Although larger and more powerful than previous British submarines, the J class could not keep up with surface vessels, and operated independently during the war. Between them, the submarines sank a U boat, and heavily damaged two battleships, with the loss of to friendly shelling. Following the war, the six surviving submarines were gifted to the Royal Australian Navy (RAN). All six were paid off during the 1920s. Two were scuttled as breakwaters in Port Phillip Bay, and four were scuttled in the ship graveyard off Port Phillip heads.

Shortly before the First World War, incorrect reports reached the British fleet that the Germans were planning a class of fast submarines for operation with the fleet, and British efforts turned toward provision of similar vessels. The driving requirement would be a surface speed that matched the speed of the battlefleet. In order to meet the requirement, the DNC designed a three shaft submarine that was 100 feet (30 m) longer than the E class, with electric motors confined to the two outer shafts and a hull form based on a light cruiser. This resulted in a diesel electric design that was unique within the Royal Navy. The power requirement was per diesel engine. In order to meet this power requirement, Vickers, the pre eminent builder of submarine diesels in First World War Britain, elected to produce a 12 cylinder version of their previously successful per cylinder six and eight cylinder engines for the D and E classes respectively. They retained the bore and stroke of these previous engines and produced 1,200 shaft horsepower at 380 revolutions per minute. These engines eventually went into the J, L and M class submarines. The design featured four bow tubes and two beam tubes for torpedoes; they were the first British submarines to carry four bow tubes. Although designed to reach , the boats could only practically travel at , making them too slow for fleet use. The quest for fleet submarine performance turned toward the subsequent, steam powered K class. The endurance of the J class was considerably greater than previous submarines. Eight boats were originally ordered, although two were later cancelled, while a seventh was later reordered to a slightly modified design. The first six were laid down between March and May 1915, with J7 laid down in August 1916. The six early boats were completed between April and August 1916, and J7 in November 1917.

The first boat, HMS J4 was commissioned at the height of the war on 17 July 1916 and assigned to the 11th Submarine Flotilla at Blyth in Northumberland, where it was soon joined by the others. These large submarines with their high speed and formidable armament were considered prestige commands, and their early commanders included such notables as Nasmith, Boyle, and Horton. The J class submarines took part in activities against German surface vessels and German submarines both off the Tyne and Gibraltar. On 5 November 1916, sighted a group of four German battleships at a range of The boat fired a four torpedo salvo, of which two struck, one hitting , while the other struck ; both enemy battleships were considerably damaged. On 7 July 1917, , sighted a U boat and fired a four torpedo salvo, of which one apparently hit, sinking SM U 99. was sunk in error during 1918 by shelling from the Q ship Cymric off Blyth.

The submarines received an Engineering Heritage National Marker from Engineers Australia as part of its Engineering Heritage Recognition Program.