Liberty ship

SS John W. Brown, one of two surviving operational Liberty ships
Class overview
Name:	Liberty ship
Builders:	18 shipyards in the USA
Planned:	2,751
Completed:	2,710
Preserved:	2
General characteristics
Class and type:	Cargo ship
Displacement:	14,245 tons[1]
Length:	135 m (441 ft 6 in)
Beam:	17.3 m (56 ft 10.75 in)
Draft:	8.5 m (27 ft 9.25 in)
Propulsion:	Two oil-fired boilers, triple-expansion steam engine, single screw, 2,500 horsepower (1,864 kW)
Speed:	11 to 11.5 knots (20 to 21 km/h)
Range:	23,000 miles (37,000 km)
Capacity:	10,856 metric tons deadweight (DWT)[1]
Complement:	41 men
Armament:	Stern-mounted 4-in (102 mm) deck gun for use against surfaced submarines, variety of anti-aircraft guns

Liberty ships were cargo ships built in the United States during World War II. Though British in conception, they were adapted by the U.S. as they were cheap and quick to build, and came to symbolize U.S. wartime industrial output. Based on vessels ordered by Britain to replace ships torpedoed by German U-boats, they were purchased for the U.S. fleet and for lend-lease provision to Britain. Eighteen American shipyards built 2,751 Liberties between 1941 and 1945, easily the largest number of ships produced to a single design.

The production of these vessels mirrored, on a much larger scale, the manufacture of the Hog Islander ship and similar standardized types during World War I. The immense effort to build Liberty ships, the sheer number of ships built, and the fact that some of the ships survived far longer than the original design life of five years, make them the subject of much study.

History

In 1936, the American Merchant Marine Act was passed to subsidize the annual construction of 50 commercial merchant vessels to be used in wartime by the United States Navy as naval auxiliaries. The number was doubled in 1939 and again in 1940 to 200 ships a year. Ship types included a tanker and three types of merchant vessel, all to be powered by steam turbines. Limited industrial capacity, especially for turbine construction, meant that relatively few of these ships were built.

In 1940, the British government ordered 60 tramp steamships from American yards to replace war losses and boost the merchant fleet. These Ocean class ships were simple but fairly large (for the time) with a single steam, 2,500 horsepower (1,864 kW) reciprocating engine of obsolete but reliable design. Britain specified coal fired plants because it had plenty of coal mines but no indigenous oil fields. The predecessor designs, including the Northeast Coast, Open Shelter Deck Steamer, were based on a simple ship originally produced in Sunderland by J.L. Thompson & Sons (see Silver Line) from 1879, and widely manufactured up to the SS Dorrington Court, which was built in 1938. The order specified an 18-inch (457 mm) increase in draught to boost displacement by 800 tons to 10,100 tons. The accommodation, bridge and main engine of these vessels were located amidships, with a long tunnel to connect the main engine shaft to its aft extension to the propeller. The first Ocean-class ship, Ocean Vanguard, was launched on 16 August 1941.

The design was modified by the United States Maritime Commission to conform to American construction practices and to make it even quicker and cheaper to build. The U.S. version was designated 'EC2-S-C1': 'EC' for Emergency Cargo, '2' for a ship between 400 and 450 feet (140 m) long (Load Waterline Length), 'S' for steam engines, and 'C1' for design C1. The new design replaced much riveting, which accounted for one-third of the labor costs, with welding, and featured oil-fired boilers. The order was given to a conglomerate of West Coast engineering and construction companies known as the Six Companies, headed by Henry J. Kaiser, and was also adopted as the Merchant Marine Act design.

On 27 March 1941, the number of lend-lease ships was increased to 200 by the Defense Aid Supplemental Appropriations Act, and increased again in April to 306, of which 117 would be Liberty ships.

The ships were constructed of sections that were welded together. This is similar to the technique used by Palmer's at Jarrow but substitutes welding for riveting. Riveted ships took several months to construct. The work force was newly trained—no one previously built welded ships. As America entered the war, the shipbuilding yards employed women to replace men who were enlisting in the armed forces.

Any group which raised war bonds worth $2 million could propose a name. Most were named for deceased people. The only living namesake was Francis J. O'Gara, the purser of the SS Jean Nicolet, who was thought to have been killed in a submarine attack but in fact survived the war in a Japanese prisoner of war camp. Other exceptions to the naming rule were the SS Stage Door Canteen, named for the USO club in New York, and the SS U.S.O., named after the organization itself.^[2]

Another notable Liberty ship was SS Stephen Hopkins, which sank the German commerce raider Stier in a ship-to-ship gun battle in 1942 and became the first American ship to sink a German surface combatant.

SS Richard Montgomery is also notable, though in a less positive way; the wreck of the ship lies off the coast of Kent with 1,500 tons of explosives still on board, enough to match a small nuclear weapon should they ever go off. One Liberty ship that did explode was the SS E. A. Bryan which detonated with the power of 2,000 tons of TNT in July 1944 as it was being loaded, killing 320 sailors and civilians in what was called the Port Chicago disaster.

Six Liberty ships were converted at Point Clear, Alabama, by the United States Army Air Forces into floating aircraft repair depots, operated by the Army Transport Service, starting in April 1944. The secret project, dubbed "Project Ivory Soap", provided mobile depot support for B-29 Superfortress and P-51 Mustangs based on Guam, Iwo Jima, and Okinawa beginning in December 1944. The six ARU(F)s (Aircraft Repair Unit, Floating), however, were also fitted with landing platforms to accommodate four R-4 helicopters, creating the first seagoing helicopter-equipped ships, and provided medical evacuation of combat casualties in both the Philippines and Okinawa.^[3]

The last Liberty ship constructed was the SS Albert M. Boe, launched on 26 September 1945 and delivered on 30 October 1945. She was named after the chief engineer of a United States Army freighter who had stayed below decks to shut down his engines after a 13 April 1945 explosion, an act that won him a posthumous Merchant Marine Distinguished Service Medal.^[4]