Q-ships known as Q-boats, decoy vessels, special service ships, or mystery ships, were armed merchant ships with concealed weaponry, designed to lure submarines into making surface attacks. This gave Q-ships the chance to sink them, they were used by the British Royal Navy and the German Kaiserliche Marine during the First World War and by the RN, the Kriegsmarine and the United States Navy during the Second World War. In the 1670s, HMS Kingfisher was specially designed to counter the attacks of Algerian corsairs or pirates in the Mediterranean by masquerading as a merchantman, hiding her armament behind false bulkheads, she was provided with various means of changing her appearance. During the French Revolutionary Wars, a French brig disguised as a merchantman, with hidden guns and most of her crew below decks, was beaten off by the privateer lugger Vulture out of Jersey. In 1915, during the First Battle of the Atlantic, Britain was in desperate need of a countermeasure against the U-boats that were strangling her sea-lanes.
Convoys, which had proved effective in earlier times, were rejected by the resource-strapped Admiralty and the independent captains. Depth charges of the time were primitive, the only chance of sinking a submarine was by gunfire or by ramming while on the surface; the problem was. A solution to this was the creation of the Q-ship, one of the most guarded secrets of the war, their codename referred to Queenstown, in Ireland. These became known by the Germans as a U-Boot-Falle. A Q-ship in fact carried hidden armaments. A typical Q-ship might resemble a tramp steamer sailing alone in an area where a U-boat was reported to be operating. By seeming to be a suitable target for the U-boat's deck gun, a Q-ship might encourage the U-boat captain to make a surface attack rather than use one of his limited number of torpedoes; the Q-ships' cargoes were light wood or wooden casks, so that if torpedoed they would remain afloat, encouraging the U-boat to surface to sink them with a deck gun. There might be pretence of "abandoning ship" with some crew dressed as civilian mariners taking to a boat.
Once the U-boat was vulnerable, the Q-ship's panels would drop to reveal the deck guns, which would open fire. At the same time, the White Ensign would be raised. With the element of surprise, a U-boat could be overwhelmed; the first Q-ship victory was on 23 June 1915, when the submarine HMS C24, cooperating with the decoy vessel Taranaki, commanded by Lieutenant Frederick Henry Taylor CBE DSC RN, sank U-40 off Eyemouth. The first victory by an unassisted Q-ship came on 24 July 1915 when Prince Charles, commanded by Lieutenant Mark-Wardlaw, DSO, sank U-36; the civilian crew of Prince Charles received a cash award. The following month an smaller converted fishing trawler renamed HM Armed Smack Inverlyon destroyed UB-4 near Great Yarmouth. Inverlyon was an unpowered sailing ship fitted with a small 3 pounder gun; the British crew fired nine rounds from their 3-pounder into UB-4 at close range, sinking her with the loss of all hands despite the attempt of Inverlyon's skipper to rescue one surviving German submariner.
On 19 August 1915, Lieutenant Godfrey Herbert of HMS Baralong sank U-27, preparing to attack a nearby merchant ship, the Nicosian. About a dozen of the U-boat sailors swam towards the merchant ship. Herbert fearing that they might scuttle her, ordered the survivors to be shot in the water and sent a boarding party to kill all who had made it aboard; this became known as the "Baralong Incident". HMS Farnborough sank SM U-68 on 22 March 1916, her commander, Gordon Campbell, was awarded the Victoria Cross. New Zealanders Lieutenant Andrew Dougall Blair and Sub-Lieutenant William Edward Sanders VC, DSO faced three U-boats in the Helgoland while becalmed and without engines or wireless. Forced to return fire early, they managed to avoid two torpedo attacks. Sanders was promoted to lieutenant-commander commanding HMS Prize, he was awarded the Victoria Cross for an action on 30 April 1917 with U-93, damaged. Remembering the early action aboard Q.17, Sanders waited, while his ship sustained heavy shellfire, until the submarine was within 80 yards, whereupon he hoisted the White Ensign and the Prize opened fire.
The submarine appeared to sink and he claimed a victory. However, the badly damaged submarine managed to struggle back to port. With his ship described by the survivors of U-93, Sanders and his crewmen were all killed in action when they attempted a surprise attack on U-43 on 14 August 1917. There may have been as many as 366 Q-ships. After the war, it was concluded that Q-ships were overrated, diverting skilled seamen from other duties without sinking enough U-boats to justify the strategy. In a total of 150 engagements, British Q-ships destroyed 14 U-boats and damaged 60, at a cost of 27 Q-ships lost out of 200. Q-ships were responsible for about 10% of all U-boats sunk, ranking them well below the use of ordinary minefields in effectiveness; the Imperial German Navy commissioned six Q-boats during the Great War for the Baltic Sea into the Handelsschutzflottille. None were successful in destroying enemy submarines; the German Q-ship Schiff K damaged the Russian submarine Gepard of the Bars-class on 27 May 1916.
The famous Möwe and Wolf were merchant raiders. A surviving example of the Q-ships is HMS Saxifrage, a Flower-class sloop of the Anchusa group compl
HMS President (1918)
HMS Saxifrage was launched in 1918 as a Flower-class anti-submarine Q-ship. She was renamed HMS President in 1922 and moored permanently on the Thames as a Royal Navy Reserve drill ship. In 1982 she was sold to private owners, having changed hands twice, now serves as a venue for conferences and functions, serves as the offices for a number of media companies, she is now called HQMS President to distinguish her from HMS President, the Royal Naval Reserve base in St Katharine Docks. She is one of the last three surviving Royal Navy warships of the First World War, she is the sole representative of the first type of purpose built anti-submarine vessels, is the ancestor of World War II convoy escort sloops, which evolved into modern anti-submarine frigates. HMS President was built as an Anchusa-type Flower-class sloop; these were built between 1916 and 1918 as submarine hunters disguised to look like merchant ships, while carrying concealed 4-inch and 12-pounder naval guns. U-boats would dive at the sight of a naval warship, the success of the Q-ships, or'mystery ships' - converted merchantmen with hidden guns - led to the building of these specialised naval vessels for the same purpose.
It was intended that a U-boat captain, unwilling to expend a precious torpedo on a small coastal merchantman, would surface to sink it by gunfire. As the submarine closed for the kill, the Q-ship would reveal her hidden guns and counter attack while the U-boat was at its most vulnerable on the surface. By the time the "warship-Qs" were constructed, the Germans were well aware of this tactic, with the introduction of unrestricted submarine warfare these sloops became active rather than passive submarine chasers. In the case of the warship-Qs the individual builders were asked to use their existing designs for merchantmen, based on the standard Flower type warship hull; this included a dummy merchant ship sternpost rudder, mounted above the waterline over a much more manoeuvrable balanced rudder which allowed the ship to make a fast turn to bring her guns or depth charges to bear on a U-boat, or to ram it before it could escape. The class were given a wide variety of spectacular dazzle camouflage schemes to confuse the primitive range finders of World War I submarines.
Altogether, 120 Flowers were built. Saxifrage was built at the shipyard of Lobnitz & Company, Scotland, as yard number 827 and launched on 29 January 1918, she was named Saxifrage after the flower known as London Pride. HMS Saxifrage escorted convoys in UK waters during 1918, engaged nine U-boats, as recorded in her logbooks held in the National Archives at Kew. In 1922 she was permanently moored on the Thames, renamed President. Other members of the class served as patrol vessels throughout the world during the peacetime years between the wars, but all were disposed of by the Second World War; this allowed the majority of the class names to be revived for the new, smaller Flower-class corvettes, including both Saxifrage and Chrysanthemum. From 1922 she was employed as a Royal Naval Reserve drill ship, as such was moored permanently on the Thames at Blackfriars, her new name was inherited from the Old President of 1829, based in West India Docks from 1862 to 1903 as the first London naval reserve drill ship.
The 1918 President remained in Royal Navy service for a total of seventy years, from 1918 to 1988. She was the last Royal Navy warship to wear Victorian battleship livery of black hull, white superstructure and buff yellow funnel and masts. All naval personnel working at the Admiralty and elsewhere in London were nominally appointed to service in President, they were paid and administered by her staff. MI6/SIS officers who had RN commissions were appointed to President, but paid and administered by the SIS. During the Second World War President was converted to a gunnery training ship, fitted with a large overall "shed" superstructure, her major role was the training of DEMS gunners for defensively equipped merchant ships. Her sister Flower class Q-ship, HMS Chrysanthemum, was moored ahead of her in 1938 to provide additional office and training space. After the war both ships were reconstructed by the Royal Navy with large deckhouses fore and aft, giving an improved drill area and extra offices.
These were dismountable, so they could pass under the London bridges to be periodically maintained in one of the Thames dockyards. In this form, they continued in use as Royal Naval Reserve training ships until 1988, each matching Old President's total of more than seventy years in naval service. Since 1988 the name HMS President has been used for a shore establishment of the Royal Naval Reserve in St Katharine Docks near Tower Bridge. In 1988 the ship was saved by Inter-Action Social Enterprise Trust, run by ED Berman. In President social enterprises included: a base for start-up companies for young people; this period saved her from scrap, preserved her for future generations. She had become a London landmark, marked on street maps, so was permitted to retain her warship title and name "HMS President" with the added suffix "" to distinguish her from the new shore establishment of the same name, her sister ship, Chrysanthemum was hired to Steven Spielberg for the boat chase sequences shot in 1988 in Tilbury Docks for the film Indiana Jones and the Last Crusade.
She was laid up in the River Medway, where the brackish water rusted her hull so badly that she was scrapped in 1995. President was resold in 2001 to David Harper and Cary Thornton purchased in April 2006 by the
HMS Caroline (1914)
HMS Caroline is a decommissioned C-class light cruiser of the Royal Navy that saw combat service in the First World War and served as an administrative centre in the Second World War. Caroline was launched and commissioned in 1914. At the time of her decommissioning in 2011 she was the second-oldest ship in Royal Navy service, after HMS Victory, she served as a static headquarters and training ship for the Royal Naval Reserve, based in Alexandra Dock, Northern Ireland, for the stages of her career. She was converted into a museum ship. From October 2016 she underwent inspection and repairs to her hull at Harland and Wolff and opened to the public on 1st July 2017 at Alexandra Dock in the Titanic Quarter in Belfast. Caroline was the last remaining British First World War light cruiser in service, she is the last survivor of the Battle of Jutland still afloat, she is one of only three surviving Royal Navy warships of the First World War, along with the 1915 Monitor HMS M33, the Flower-class sloop HMS President moored on the Thames at Blackfriars but as from February 2016, in Number 3 Basin, Chatham.
HMS Caroline was built by Cammell Laird of Birkenhead. She was laid down on 28 January 1914, launched on 29 September 1914 and completed in December 1914. Caroline was part of the early sub-set of C-class light cruisers built without geared turbines and subsequent comparisons with vessels of the same class demonstrated the superiority of geared propulsion. Caroline's machinery is still in place today. Caroline was commissioned on 4 December 1914 and served in the North Sea throughout the First World War. Upon commissioning, she joined the Grand Fleet based at Scapa Flow in the Orkney Islands, serving as leader of the 4th Destroyer Flotilla, she was part of the Grand Fleet's 1st Light Cruiser Squadron from February to November 1915. In early 1916 she joined the Grand Fleet's 4th Light Cruiser Squadron and remained with it – fighting as part of it at the Battle of Jutland on 31 May-1 June 1916 under the command of Captain Henry R. Crooke – through the end of the war in November 1918. From 1917 until late 1918, she carried a flying-off platform for the launching of Royal Naval Air Service and Royal Air Force fighters to intercept German airships operating over the North Sea.
Caroline remained in the 4th Light Cruiser Squadron after World War I and in June 1919 went with the rest of the squadron to serve on the East Indies Station. In February 1922 she was placed in reserve, she came out of reserve in February 1924 to become a headquarters and training ship for the Royal Naval Volunteer Reserve's Ulster Division at Belfast, Northern Ireland beginning those duties on 1 April 1924. Harland and Wolff of Belfast removed her weaponry and some of her boilers around 1924, after her arrival in Belfast, her guns were pooled with those of other decommissioned cruisers and used to reinforce the coastal defences of the Treaty Ports From 1939 until 1945, during the Second World War, Caroline served as the Royal Navy's headquarters in Belfast Harbour, used as a home base by many of the warships escorting Atlantic and Arctic convoys, including Captain-class frigates of the 3rd Escort Group. As Belfast developed into a major naval base during the Second World War, its headquarters outgrew the confines of HMS Caroline herself and occupied different establishments in various parts of the city.
Several thousand ratings were wearing Caroline cap tallies. The first such establishment was set up in the Belfast Custom House. Belfast Castle was taken over and included a radio station. There were depth charge pistol and Hedgehog repair workshops associated with HMS Caroline, some of which would have been on the quays beside her berth in Milewater Basin. During the early part of the Second World War when RAF Belfast occupied Sydenham airfield, Fleet Air Arm personnel based there were lodged under HMS Caroline. In 1943, the airfield was commissioned as HMS Gadwall. After the Second World War, the Royal Navy returned Caroline to the Royal Naval Volunteer Reserve, she served as its last afloat training establishment, she underwent a refit at Harland and Wolff in Belfast in 1951. The Royal Naval Reserve Unit decommissioned from the ship in December 2009, moved ashore, recommissioned as the "stone frigate" HMS Hibernia. Caroline herself was decommissioned on 31 March 2011 in a traditional ceremony.
Her ensign was laid up in St Anne's Cathedral in Belfast. Caroline is listed as part of the National Historic Fleet. On her decommissioning, she was placed into the care of the National Museum of the Royal Navy at Portsmouth, though remaining moored in her position in Alexandra Dock in Belfast. Although no longer capable of making way under her own power, Caroline remains afloat and in excellent condition. Buffeting from waves and high winds have caused the ship to come away from her moorings several times. In 2005, during a storm, she ripped several huge bollards out of the jetty concrete, but failed to break free entirely, she was not open to tourists, although entrance was gained during the annual RMS Titanic celebrations. Upon Caroline's decommissioning in 2011, her future was uncertain. Proposals were made to return the ship to her First World War appearance, which among other things would have involved sourcing and installing 6-inch and 4-inch guns of that era and removing the large deckhouse from her midships deck.
One proposal considered was to remain in Belfast as a museum ship within the Titanic Quarter development alongside SS Nomadic. Another was a move to Portsmouth, with many of her original fitt
Length between perpendiculars
Length between perpendiculars is the length of a ship along the waterline from the forward surface of the stem, or main bow perpendicular member, to the after surface of the sternpost, or main stern perpendicular member. When there is no sternpost, the centerline axis of the rudder stock is used as the aft end of the length between perpendiculars. Measuring to the stern post or rudder stock was believed to give a reasonable idea of the ship's carrying capacity, as it excluded the small unusable volume contained in her overhanging ends. On some types of vessels this is, for all practical purposes, a waterline measurement. In a ship with raked stems that length changes as the draught of the ship changes, therefore it is measured from a defined loaded condition. Length overall. Hayler, William B.. American Merchant Seaman's Manual. Cornell Maritime Pr. ISBN 0-87033-549-9. Turpin, Edward A.. Merchant Marine Officers' Handbook. Centreville, MD: Cornell Maritime Press. ISBN 0-87033-056-X. Perpendiculars and Length Between Perpendiculars
Béjaïa Bougie and Bugia, is a Mediterranean port city on the Gulf of Béjaïa in Algeria. Béjaïa is the largest principally Kabyle-speaking city in the Kabylie region of Algeria; the history of Béjaïa explains the diversity of the local population. The town is overlooked by the mountain Yemma Gouraya, whose profile is said to resemble a sleeping woman. Other nearby scenic spots include the Pic des Singes. All three of these geographic features are located in the Gouraya National Park; the Soummam river runs past the town. Under French rule, it was known under various European names, such as Budschaja in German, Bugia in Italian, Bougie in French; the French and Italian versions, due to the town's wax trade acquired the metonymic meaning of "candle". According to Al-Bakri, the bay was first inhabited by Andalusians. Béjaïa stands on the site of the ancient city of Saldae, a minor port in Carthaginian and Roman times, in an area at first inhabited by Numidian Berbers and founded as a colony for old soldiers by emperor Augustus.
It was an important town and a bishopric in the province of Mauretania Caesariensis, Sitifensis. In the fifth century, Saldae became the capital of the short-lived Vandal Kingdom of the Germanic Vandals, which ended in about 533 with the Byzantine conquest, which established an African prefecture and the Exarchate of Carthage. After the 7th-century Muslim conquest, it was refounded as "Béjaïa"; the son of a Pisan merchant, posthumously known as Fibonacci, there learned about Muslim mathematics and Hindu-Arabic numerals. He introduced modern mathematics into medieval Europe. A mathematical-historical analysis of Fibonacci's context and proximity to Béjaïa, an important exporter of wax in his time, has suggested that it was the bee-keepers of Béjaïa and the knowledge of the bee ancestries that inspired the Fibonacci sequence rather than the rabbit reproduction model as presented in his famous book Liber Abaci. According to Muhammad al-Idrisi, the port was, in the XIth century, a market place between Mediterranean merchant ships and caravans coming from the Sahara desert.
Christian merchants settled fundunqs in Bejaïa. The Italian city of Pisa was tied to Béjaïa, where it built one of its two permanent consulates in the African continent. In 1315, Ramon Llull died as a result of being stoned at Béjaïa, where, a few years before, Peter Armengaudius is reputed to have been hanged. After a Spanish occupation, the city was taken by the Ottoman Turks in the Capture of Bougie in 1555. For nearly three centuries, Béjaïa was a stronghold of the Barbary pirates; the city consisted of Arabic-speaking Moors and Jews increased by Jewish refugees from Spain, with the Berber peoples not in the city but occupying the surrounding villages and travelling to the city for the market days. City landmarks include a 16th-century mosque and a fortress built by the Spanish in 1545. A picture of the Orientalist painter Maurice Boitel, who painted in the city for a while, can be found in the museum of Béjaïa, it became a part of colonial Algeria. Most of the time it was the seat of an arrondissement in the Département of Constantine, until Bougie was promoted to département itself in 1957.
During World War II, Operation Torch landed forces in North Africa, including a battalion of the British Royal West Kent Regiment at Béjaïa on November 11, 1942. That same day, at 4:40 PM, a German Luftwaffe air raid struck Béjaïa with thirty Ju 88 bombers and torpedo planes; the transports Awatea and Cathay were sunk and the monitor HMS Roberts was damaged. The following day, the anti-aircraft ship SS Tynwald was torpedoed and sank, while the transport Karanja was bombed and destroyed. After Algerian independence, it became the eponymous capital of Béjaïa Province, covering part of the eastern Berber region Kabylia. With the spread of Christianity, Saldae became a bishopric, its bishop Paschasius was one of the Catholic bishops whom the Arian Vandal king Huneric summoned to Carthage in 484 and exiled. Christianity survived the Arab conquest, the disappearance of the old city of Saldae, the founding of the new city of Béjaïa. A letter from Pope Gregory VII exists, addressed to clero et populo Buzee, in which he writes of the consecration of a bishop named Servandus for Christian North Africa.
No longer a residential bishopric, Saldae is today listed by the Catholic Church as a titular see. and still has incumbents by that title. This titular see was for a long time and concurrently with the city's authentic Roman Latin name Saldae, called Bugia, the Italian language form of Béjaïa. The'modern' form and title, seems out of use, after having had the following incumbents, all of the lowest rank: Miguel Morro, as Auxiliary Bishop of Mallorca Fernando de Vera y Zuñiga, Augustinians, as Auxiliary Bishop of Badajoz.
The Azalea class of twelve minesweeping sloops were built under the Emergency War Programme for the Royal Navy in World War I as part of the larger Flower class, which were referred to as the Cabbage class, or "Herbaceous Borders". The third batch of twelve ships to be ordered, in May 1915, they differed from the preceding Acacia class only in mounting a heavier armament, with either 4.7-inch or 4-inch guns instead of the 12-pounder guns of the earlier class. They were single-screw fleet sweeping vessels with triple hulls at the bows to give extra protection against loss when working. HMS Azalea — built by Barclay Curle & Company, launched 10 September 1915. Sold for breaking up 1 February 1923. HMS Begonia — built by Barclay Curle, launched 26 August 1915. Became Q-Ship from 9 August 1917 as Q10, sunk in collision with German submarine U-151 off Casablanca in Atlantic 2 October 1917. HMS Camellia — built by Bow, McLachlan and Company, launched 25 September 1915. Sold for breaking up 15 January 1923.
HMS Carnation — built by Greenock & Grangemouth Dockyard Company, launched 6 September 1915. Sold for breaking up 14 January 1922. HMS Clematis — built by Greenock & Grangemouth, launched 29 July 1915. Sold for breaking up 5 February 1931. HMS Heliotrope — built by Lobnitz & Company, launched 10 September 1915. Sold for breaking up 7 January 1935. HMS Jessamine — built by Swan Hunter & Wigham Richardson, launched 9 September 1915. Sold for breaking up 21 December 1922. HMS Myrtle — built by Lobnitz and Company, launched 11 October 1915. Mined in Gulf of Finland 16 July 1919. HMS Narcissus — built by Napier & Miller, Old Kilpatrick, launched 22 September 1915. Sold for breaking up 6 September 1922. HMS Peony — built by Archibald McMillan & Son, launched 27 October 1915. Sold out of service 20 August 1919, becoming mercantile Ardena. HMS Snowdrop — built by McMillan, launched 7 October 1915. Sold for breaking up 15 January 1923. HMS Zinnia — built by Swan Hunter, launched 12 August 1915. Sold to Belgian Navy 19 April 1920, retaining same name.
Jane's Fighting Ships of World War I, Janes Publishing, 1919 The Grand Fleet, Warship Design and Development 1906–1922, D. K. Brown, Chatham Publishing, 1999, ISBN 1-86176-099-X "Old Weather – HMS Jessamine". Archived from the original on 2012-02-08. Retrieved 2012-01-22. Transcription of ship's logbooks and weather information
A depth charge is an anti-submarine warfare weapon. It is intended to destroy a submarine by being dropped into the water nearby and detonating, subjecting the target to a powerful and destructive hydraulic shock. Most depth charges use high explosive charges and a fuze set to detonate the charge at a specific depth. Depth charges can be dropped by ships, patrol aircraft, helicopters. Depth charges were developed during World War I, were one of the first effective methods of attacking a submarine underwater, they were used in World War I and World War II. They remained part of the anti-submarine arsenals of many navies during the Cold War. Depth charges have now been replaced by anti-submarine homing torpedoes. A depth charge fitted with a nuclear warhead is known as a "nuclear depth bomb"; these were designed to be dropped from a patrol plane or deployed by an anti-submarine missile from a surface ship, or another submarine, located a safe distance away. All nuclear anti-submarine weapons were withdrawn from service by the United States, the United Kingdom, France and China in or around 1990.
They were replaced by conventional weapons whose accuracy and range had improved as ASW technology improved. The first attempt to fire charges against submerged targets was with aircraft bombs attached to lanyards which triggered them. A similar idea was a 16 lb guncotton charge in a lanyarded can. Two of these lashed together became known as the "depth charge Type A". Problems with the lanyards tangling and failing to function led to the development of a chemical pellet trigger as the "Type B"; these were effective at a distance of around 20 ft. A 1913 Royal Navy Torpedo School report described a device intended for countermining, a "dropping mine". At Admiral John Jellicoe's request, the standard Mark II mine was fitted with a hydrostatic pistol preset for 45 ft firing, to be launched from a stern platform. Weighing 1,150 lb, effective at 100 ft, the "cruiser mine" was a potential hazard to the dropping ship; the design work was carried out by Herbert Taylor at the RN Torpedo and Mine School, HMS Vernon.
The first effective depth charge, the Type D, became available in January 1916. It was a barrel-like casing containing a high explosive. There were two sizes—Type D, with a 300 lb charge for fast ships, Type D* with a 120 lb charge for ships too slow to leave the danger area before the more powerful charge detonated. A hydrostatic pistol actuated by water pressure at a pre-selected depth detonated the charge. Initial depth settings were 40 or 80 ft; because production could not keep up with demand, anti-submarine vessels carried only two depth charges, to be released from a chute at the stern of the ship. The first success was the sinking of U-68 off Kerry, Ireland, on 22 March 1916, by the Q-ship Farnborough. Germany became aware of the depth charge following unsuccessful attacks on U-67 on 15 April 1916, U-69 on 20 April 1916; the only other submarines sunk by depth charge during 1916 were UC-19 and UB-29. Numbers of depth charges carried per ship increased to four in June 1917, to six in August, 30-50 by 1918.
The weight of charges and racks caused ship instability unless heavy guns and torpedo tubes were removed to compensate. Improved pistols allowed greater depth settings in 50-foot increments, from 50 to 200 ft. Slower ships could safely use the Type D at below 100 ft and at 10 kn or more, so the ineffective Type D* was withdrawn. Monthly use of depth charges increased from 100 to 300 per month during 1917 to an average of 1745 per month during the last six months of World War I; the Type D could be detonated as deep as 300 ft by that date. By the war's end, 74,441 depth charges had been issued by the RN, 16,451 fired, scoring 38 kills in all, aiding in 140 more; the United States requested full working drawings of the device in March 1917. Having received them, Commander Fullinwider of the U. S. Bureau of Naval Ordnance and U. S. Navy engineer Minkler made some modifications and patented it in the U. S, it has been argued. The Royal Navy Type D depth charge was designated the "Mark VII" in 1939. Initial sinking speed was 7 ft/s with a terminal velocity of 9.9 ft/s at a depth of 250 ft if rolled off the stern, or upon water contact from a depth charge thrower.
Cast iron weights of 150 lb were attached to the Mark VII at the end of 1940 to increase sinking velocity to 16.8 ft/s. New hydrostatic pistols increased the maximum detonation depth to 900 ft; the Mark VII's 290 lb amatol charge was estimated to be capable of splitting a 7⁄8 inch submarine pressure hull at a distance of 20 ft, forcing the submarine to surface at twice that. The change of explosive to Torpex at the end of 1942 was estimated to increase those distances to 26 and 52 ft; the British Mark X depth charge weighed 3,000 pounds and was launched from 21-inch torpedo tubes of older destroyers to achieve a sinking velocity of 21 ft/s. The launching ship needed to clear the area at 11 knots to avoid damage, the charge was used. Only 32 were fired, they were known to be troublesome; the teardrop-shaped United States Mark 9 depth charge entered service in the spring of 1943. The charge was 200 lb of Torpex with a sinking speed of 14.4 ft/s and depth settings of up to 600 ft. Versions increased depth to 1,000 ft and sinking