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Type of United States Navy drydocks From Wikipedia, the free encyclopedia
An auxiliary floating drydock is a type of US Navy auxiliary floating dry dock. Floating dry docks are able to submerge underwater and to be placed under a ship in need of repair below the water line. Water is then pumped out of the floating dry dock, raising the ship out of the water. The ship becomes blocked on the deck of the floating dry dock for repair. Most floating dry docks have no engine and are towed by tugboats to their destinations. Floating dry docks come in different sizes to accommodate varying ship sizes, while large floating dry docks come in sections and can be combined to increase their size and lift power. Ballast pontoon tanks are flooded with water to submerge or pumped dry to raise the ship.[1][2]
This article needs to be updated. The reason given is: which type designations are still in use by the US Navy and which, if any, vessels are still in service. (April 2024) |
At the start of World War II, the US Navy had only three steel auxiliary floating dry docks:
To reduce travel time for repair work, over 150 auxiliary floating dry docks of different sizes were built during World War II between 1942 and 1945. These newly built floating dry docks had a lift capacity of 400 to 100,000 tons. Without these forward repair bases, ships would have had to return to the US for repairs. Between 1 October 1944 and 17 October 1945, 7,000 ships were repaired in auxiliary floating dry docks. After World War II some auxiliary floating dry docks were sold for private use and others were scrapped. In addition to auxiliary floating dry docks, timber floating dry docks were built for use in World War II. Timber floating dry docks had a lift capacity of 400 to 20,000 tons. They were not towed across the open ocean and were not given a US Navy class.[4][2]
During wartime, ships in continuous use need repair both from wear and from war damage such as from naval mines, kamikaze attacks, dive bombs and torpedoes. Rudders and propellers are best serviced on dry docks. Without remote on-location dry docks, months could be lost if a ship returned to a home port for repair. Most auxiliary floating drydocks had provisions for the repair crew, including bunk beds, meals, and laundry. Most had power stations, ballast pumps, repair shops, machine shops, and mess halls to be self-sustaining. Some auxiliary floating drydocks also had provisions for the ship under repair, but when possible, the crew of the damaged ship remained on ship while repairs were done. Many had cranes able to lift tons of material and parts to remove damaged parts and to install new parts.[5][2]
Most auxiliary floating drydocks had only anti-aircraft guns for defense, as space would not allow for large guns. Typical armaments included 40 mm and 20 mm machine guns. Japanese pilots sometimes mistook empty auxiliary floating drydocks for aircraft carriers.[6][2]
Auxiliary Floating Docks, Big (AFDB), also known as Advance Base Sectional Docks (ABSD), came in sections, 93 ft (28 m) long and 3,850 tons each. Each section had a 165-foot (50 m) beam, a 75-foot (23 m) molded depth, and 10,000 tons of lifting capacity. Sections could be put together to lift larger ships. AFDB were needed to repair battleships, aircraft carriers, cruisers, and large auxiliary ships. The AFDB-1 Artisan had 10 sections (A to J) for a total lift of 100,000 tons, and was 1,000 ft (300 m) long with all 10 sections installed. AFDB-1 to 7 were built between 1943 and 1945 and towed to remote navy bases. An AFDB would have a crew of 600 to 1,000 men, a fresh-water distilling plant and was otherwise self-sustaining. They had a rail traveling 15-ton capacity crane with an 85-foot (26 m) radius and two or more support barges. To pump water from the tanks, there were two 24-inch (61 cm) discharge pumps on each section, each pump rated 15,000 US gallons (57,000 L) per minute. For electricity, there were two 350-kw diesel AC generators on each section, producing 440 volts 3-phase 60-cycle power. AFDBs had steam plants to run the pumps. Each section could store 65,000 US gallons (250,000 L) of fuel oil to supply the ships under repair. Crew lived in barracks ships, called APL, that docked next to the AFDB.[4][7][2][8]
Post WW2
AFDM are from 6,800 to 8,000 tons and are from 528 to 622 ft (161 to 190 m) long. An AFDM has a crew of 140 to 200 men. An AFDM had a lift capacity 18,000 tons and was armed with two 40 mm and four 20 mm guns. It also had two 7+1⁄2-ton cranes with 16 ballast tank compartments. AFDMs were built in three pieces, a long center section and two shorter sections, one at each end.[4][17][2][18] All AFDM also had Yard Floating Docks (YFD) class numbers.
Auxiliary repair dock Mobile (ARDM) are 5,200 tons and 489 feet (149 m) long. ARDs had a ship form hull and lifting capacity of 3,500 tons. ARDMs were used to repair destroyers, submarines, and small auxiliaries. ARDMs had a crew of 130 to 160 men.[4][2]
Post WW2
Auxiliary Floating Docks, Light (AFDL), also known as Auxiliary Floating Docks (AFD), were 288 ft (88 m) long, had a beam of 64 ft (20 m), and draft of 3 ft 3 in (0.99 m) empty and 31 ft 4 in (9.55 m) flooded to load a ship. A normal crew was 60 men. AFDL displacement was 1,200 tons and could lift 1,900 tons. AFDL were built as one piece, open at both ends. AFDL were used to repair small craft, PT boats and small submarines. All AFD were reclassified AFDL after the war in 1946.[4][29][30]
Auxiliary Repair Docks were built by Pacific Bridge Company in Alameda, California. ARD are 483 ft (147 m) long, have a beam of 71 ft (22 m), a draft of 5 ft (1.5 m), and a displacement of 4,800 tons. The crew complement is 6 officers and 125 enlisted. ARD have an armament of two single Oerlikon 20 mm cannons, a bow and are sea worthy. They are self-sustaining with rudders to help in tow moving and have two cranes with a five-ton capacity. ARD also have a stowage barge for extra space. They were used to repair destroyers and submarines. Class 2 could repair Landing Ship, Tank (LST). The stern of the ship is open to allow a ship in need of repair to enter.[4][2][59]
Auxiliary Repair Dock, Concrete were mobile dry docks made of concrete, due to the shortage of steel during World War II. ARDC had a 2,800 ton lifting capacity. ARDC were 389 ft (119 m) long, 84 ft (26 m) wide, and 40 ft (12 m) deep. ARDC has a crew of five officers and 84 enlisted men. Each had a 5-ton crane, with a 42 ft (13 m) reach. Eight were built at Wilmington, North Carolina, and five at San Pedro in Los Angeles, California.[93][94][95][2]
Yard Floating Dock (YFD) was used for many types of floating docks, mostly used for harbor or shipyard use. YFDs normally had little-to-no crew space and were serviced from shore. Some auxiliary Repair Docks were converted to YFDs. Types of YFDs were: 400-ton concrete docks, 1,000-ton, 3,000-ton and 5,000-ton wood docks; sectional wood docks from 7,000 to 20,000 tons lifting capacity and a three-piece self docking steel sectional docks with 14,000 to 18,000 tons lifting capacity. All Medium Auxiliary Floating Dry Docks were converted to YFDs after World War II.[102][103][2]
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