HMS J7 (later HMAS J7) was a J-class

submarine A submarine (often shortened to sub) is a watercraft capable of independent operation underwater. (It differs from a submersible, which has more limited underwater capability.) The term "submarine" is also sometimes used historically or infor ...

operated by the

Royal Navy The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King of the United Kingdom, King. Although warships were used by Kingdom ...

and the

Royal Australian Navy The Royal Australian Navy (RAN) is the navy, naval branch of the Australian Defence Force (ADF). The professional head of the RAN is Chief of Navy (Australia), Chief of Navy (CN) Vice admiral (Australia), Vice Admiral Mark Hammond (admiral), Ma ...

Design and construction

The J class was designed by the Royal Navy in response to reported German submarines with surface speeds over .Bastock, ''Australia's Ships of War'', p. 86 The submarines had a displacement of 1,210 tons surfaced, but ''J7'' had a lighter submerged displacement than her sister boats, at 1,760 tons. Each submarine was in length overall, with a beam of , and a draught of . The propulsion system was built around three propeller shafts; the J-class were the only triple-screwed submarines ever built by the British. Propulsion came from three 12-cylinder diesel motors when on the surface, and electric motors when submerged. Top speed was on the surface (the fastest submarines in the world at the time of construction), and underwater. Range was at . Armament consisted of six 18 inch (450 mm) torpedo tubes (four forward, one on each beam), plus a 4-inch deck gun. Originally, the gun was mounted on a breastwork fitted forward of the conning tower, but the breastwork was later extended to the bow and merged into the hull for streamlining, and the gun was relocated to a platform fitted to the front of the

conning tower A conning tower is a raised platform on a ship or submarine, often armoured, from which an officer in charge can conn (nautical), conn (conduct or control) the vessel, controlling movements of the ship by giving orders to those responsible for t ...

. The conning tower on ''J7'' was sited further back than her sister boats, as the control room was located behind the machinery spaces. 44 personnel were aboard. ''J7'' was built by HM Dockyard Devonport in

Plymouth Plymouth ( ) is a port city status in the United Kingdom, city and unitary authority in Devon, South West England. It is located on Devon's south coast between the rivers River Plym, Plym and River Tamar, Tamar, about southwest of Exeter and ...

and launched on 12 February 1917.

Operational history

After the war, the

British Admiralty The Admiralty was a Departments of the Government of the United Kingdom, department of the Government of the United Kingdom that was responsible for the command of the Royal Navy. Historically, its titular head was the Lord High Admiral of the ...

decided that the best way to protect the Pacific region was with a force of submarines and cruisers. To this end, they offered the six surviving submarines of the J-class to the

as gifts. ''J1'' and her sisters were commissioned into the RAN in April 1919, and sailed for Australia on 9 April, in the company of the cruisers and , and the tender . The flotilla reached Thursday Island on 29 June, and Sydney on 10 July. Because of the submarines' condition after the long voyage, they were immediately taken out of service for refits. By the time ''J7'' was returned to service in June 1922, the cost of maintaining the boats and deteriorating economic conditions saw the six submarines decommissioned and marked for disposal.

Fate

''J7'' was paid off on 12 July 1922, and was sold on 26 February 1924. The hulk was scuttled in 1930, for use as a

breakwater Breakwater may refer to: * Breakwater (structure), a structure for protecting a beach or harbour Places * Breakwater, Victoria, a suburb of Geelong, Victoria, Australia * Breakwater Island, Antarctica * Breakwater Islands, Nunavut, Canada * ...

at the Sandringham Yacht Club in

Port Phillip Port Phillip (Kulin languages, Kulin: ''Narm-Narm'') or Port Phillip Bay is a horsehead-shaped bay#Types, enclosed bay on the central coast of southern Victoria (Australia), Victoria, Australia. The bay opens into the Bass Strait via a short, ...

. Some years later a stone marina was constructed around the wreck, which was left in situ and visible, being too expensive to remove, where it continues to deteriorate.

Citations

References

External links

Map of Sandringham yacht club marina
{{DEFAULTSORT:J7 British J-class submarines Ships built in Plymouth, Devon 1917 ships World War I submarines of the United Kingdom Scuttled vessels of Australia Royal Navy ship names Shipwrecks of Victoria (state)