Liberty ship
Liberty ships are a class of cargo ship built in the United States during World War II under the Emergency Shipbuilding Program. Although British in concept, the design was adopted by the United States for its simple, low-cost construction. Mass-produced on an unprecedented scale, the Liberty ship came to symbolize U.S. wartime industrial output.
The class was developed to meet British orders for transports to replace ships that had been lost. Eighteen American shipyards built 2,710 Liberty ships between 1941 and 1945, easily the largest number of ships ever produced to a single design.
The Liberty ship was effectively superseded by the Victory ship, a somewhat larger, materially faster, more modern-powered vessel of generally similar design. A total of 531 Victory ships were built between 1944 and 1946.
Liberty ship production mirrored the manufacture of "Hog Islander" and similar standardized ship types during World War I. The immensity of the effort, the number of ships built, the role of female workers in their construction, and the survival of some far longer than their original five-year design life combine to make them the subject of much continued interest.
History
Design
In 1936, the American Merchant Marine Act was passed to subsidize the annual construction of 50 commercial merchant vessels which could be used in wartime by the United States Navy as naval auxiliaries, crewed by U.S. Merchant Mariners. The number was doubled in 1939 and again in 1940 to 200 ships a year. Ship types included two tankers and three types of merchant vessel, all to be powered by steam turbines. Limited industrial capacity, especially for reduction gears, meant that relatively few of these designs of ships were built.However, in 1940, the British government ordered 60 Ocean-class freighters from American yards to replace war losses and boost the merchant fleet. These were simple but fairly large with a single compound steam engine of outdated but reliable design. Britain specified coal-fired plants, because it then had extensive coal mines and no significant domestic oil production.
The predecessor designs, which included the "Northeast Coast, Open Shelter Deck Steamer", were based on a simple ship originally produced in Sunderland by J.L. Thompson & Sons based on a 1939 design for a simple tramp steamer, which was cheap to build and cheap to run. Examples include SS Dorington Court built in 1939. The order specified an increase in draft to boost displacement by to. The accommodation, bridge, and main engine were located amidships, with a tunnel connecting the main engine shaft to the propeller via a long aft extension. The first Ocean-class ship, SS Ocean Vanguard, was launched on 16 August 1941.
File:Liberty ship 140-ton VTE engine.jpg|thumb|upright|140-ton vertical triple expansion steam engine of the type used to power World War II Liberty ships, assembled for testing before delivery
The design was modified by the United States Maritime Commission, in part to increase conformity to American construction practices, but more importantly to make it even quicker and cheaper to build. The US version was designated 'EC2-S-C1': 'EC' for Emergency Cargo, '2' for a ship between long, '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 had oil-fired boilers. It was adopted as a Merchant Marine Act design, and production awarded to a conglomerate of West Coast engineering and construction companies headed by Henry J. Kaiser known as the Six Companies. Liberty ships were designed to carry of cargo, usually one type per ship, but, during wartime, generally carried loads far exceeding this.
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.
Variants
The basic EC2-S-C1 cargo design was modified during construction into three major variants with the same basic dimensions and slight variance in tonnage. One variant, with basically the same features but different type numbers, had four rather than five holds served by large hatches and kingpost with large capacity booms. Those four hold ships were designated for transport of tanks and boxed aircraft.In the detailed Federal Register publication of the post war prices of Maritime Commission types the Liberty variants are noted as:
; EC2-S-AW1
;Z-EC2-S-C2
;Z-ET1-S-C3
;Z-EC2-S-C5
In preparation for the Normandy landings and afterward to support the rapid expansion of logistical transport ashore a modification was made to make standard Liberty vessels more suitable for mass transport of vehicles and in records are seen as "MT" for Motor Transport vessels. As MTs four holds were loaded with vehicles while the fifth was modified to house the drivers and assistants.
The modifications into troop transports also were not given special type designations.
Propulsion
By 1941, the steam turbine was the preferred marine steam engine because of its greater efficiency compared to earlier reciprocating compound steam engines. Steam turbine engines however, required very precise manufacturing techniques to machine their complicated double helical reduction gears, and the companies capable of producing them were already committed to the large construction program for warships. Therefore, a vertical triple expansion steam engine, of obsolete design, was selected to power Liberty ships because it was cheaper and easier to build in the numbers required for the Liberty ship program, and because more companies could manufacture it. Eighteen different companies eventually built the engine. It had the additional advantage of ruggedness, simplicity and familiarity to seamen. Parts manufactured by one company were interchangeable with those made by another, and the openness of its design made most of its moving parts easy to see, access, and oil. The engine— long and tall—was designed to operate at 76 rpm and propel a Liberty ship at about.Construction
The ships were constructed of sections that were welded together. This is similar to the technique used by Palmer's at Jarrow, northeast England, but substituted welding for riveting. Riveted ships took several months to construct. The work force was newly trained as the yards responsible had not previously built welded ships. As America entered the war, the shipbuilding yards employed women, to replace men who were enlisting in the armed forces.File:Liberty ship construction 03 keel plates.jpg|Day 2 : Laying of the keel plates
File:Liberty ship construction 07 bulkheads.jpg|Day 6 : Bulkheads and girders below the second deck are in place.
File:Liberty ship construction 09 lower decks.jpg|Day 10 : Lower deck being completed and the upper deck amidship erected
File:Liberty ship construction 10 upper decks.jpg|Day 14 : Upper deck erected and mast houses and the after-deck house in place
File:Liberty ship construction 11 prepared for launch.jpg|Day 24 : Ship ready for launching
The ships initially had a poor public image owing to their appearance. In a speech announcing the emergency shipbuilding program President Franklin D. Roosevelt had referred to the ship as "a dreadful looking object", and Time called it an "Ugly Duckling". 27 September 1941 was dubbed Liberty Fleet Day to try to assuage public opinion, since the first 14 "Emergency" vessels were launched that day. The first of these was, launched by President Roosevelt. In remarks at the launch ceremony FDR cited Patrick Henry's 1775 speech that finished "Give me liberty or give me death!". Roosevelt said that this new class of ship would bring liberty to Europe, which gave rise to the name Liberty ship.
The first ships required about 230 days to build, but the median production time per ship dropped to 39 days by 1943. The record was set by, which was launched 4 days and 15 hours after the keel had been laid, although this publicity stunt was not repeated: in fact much fitting-out and other work remained to be done after the Peary was launched. The ships were made assembly-line style, from prefabricated sections. In 1943 three Liberty ships were completed daily. They were usually named after famous Americans, starting with the signatories of the Declaration of Independence. Newsreel footage of the launching of the ship named for American author Jack London can be seen in the film Jack London. 17 of the Liberty ships were named in honor of outstanding African-Americans. The first, in honor of Booker T. Washington, was christened by Marian Anderson in 1942, and the, recognizing the only woman on the list, was christened on 3 June 1944.
Any group that raised war bonds worth $2 million could propose a name. Most bore the names of deceased people. The only living namesake was Francis J. O'Gara, the purser of, who was thought to have been killed in a submarine attack, but in fact survived the war in a Japanese prisoner of war camp; see USS Outpost. Not named after people were:, named after the USO club in New York; and, named after the United Service Organizations.
Another notable Liberty ship was, which sank the German commerce raider in a ship-to-ship gun battle in 1942 and became the first American ship to sink a German surface combatant.
File:Liberty Ship scaler HD-SN-99-02466.JPG|thumb|right|Eastine Cowner, a former waitress, at work on the Liberty ship at the Kaiser shipyards, Richmond, California, in 1943. One of a series taken by E. F. Joseph on behalf of the Office of War Information, documenting the work of African-Americans in the war effort
The wreck of lies off the coast of Kent with of explosives still on board, enough to match a very small yield nuclear weapon should they ever go off. detonated with the energy of in July 1944 as it was being loaded, killing 320 sailors and civilians in what was called the Port Chicago disaster. Another Liberty ship that exploded was the rechristened, which caused the Texas City Disaster on 16 April 1947, killing at least 581 people.
Six Liberty ships were converted at Point Clear, Alabama, by the United States Army Air Force, 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 bombers and P-51 Mustang fighters based on Guam, Iwo Jima, and Okinawa beginning in December 1944. The six ARUs, however, were also fitted with landing platforms to accommodate four Sikorsky R-4 helicopters, where they provided medical evacuation of combat casualties in both the Philippine Islands and Okinawa.
The last new-build Liberty ship constructed was, 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. In 1950, a "new" liberty ship was constructed by Industriale Maritime SpA, Genoa, Italy by using the bow section of and the stern section of, both of which had been wrecked. The new ship was named, and served until scrapped in 1962.
Several designs of mass-produced petroleum tanker were also produced, the most numerous being the T2 tanker series, with about 490 built between 1942 and the end of 1945.