Liberty ship

Liberty ships are a class of cargo ship that were built in the United States during World War II under the Emergency Shipbuilding Program. The idea for the ships came from Britain, but the United States used the design because it was simple and cheap to build. The ships were mass-produced in very large numbers. Because of this, Liberty ships became a symbol of American industry during the war.

The class was developed to meet British orders for transport ships to replace ships that had been sunk. Eighteen American shipyards built 2,710 Liberty ships between 1941 and 1945. This was an average of about three ships every two days. This was the largest number of ships ever built using one single design.[source?]

Later, the Liberty ship was replaced by the Victory ship. Victory ships were a little larger, much faster, and had more modern engines, but they were similar in design. A total of 531 Victory ships were built between 1944 and 1946.

History

Design

Profile plan of a Liberty ship
A colored diagram of compartments on a ship
A colored diagram of compartments on a Liberty ship, from the right side, front to the right
  Machinery spaces
  Command and control
  Liquid stores
  Dry cargo
  Engine room
  Misc
  Dry stores
  Habitation

In 1936, the American Merchant Marine Act was passed. It helped pay for the building of 50 merchant ships each year. These ships could be used by the United States Navy during wartime as support ships. They were crewed by the U.S. Merchant Mariners. In 1939, the number was doubled. In 1940, it was increased again to 200 ships per year. The ship types included two tankers and three kinds of cargo ships. All of them were planned to use steam turbines. Because American industry could not make enough reduction gears, only a small number of these ships were actually built.

In 1940, the British government ordered 60 Ocean-class freighters from American shipyards. These ships were meant to replace ships lost in the war and to strengthen Britain’s merchant fleet. The ships were simple but large for their time. They used a single 2,500 horsepower (1,900 kW) compound steam engine. The engine design was old but very reliable. Britain asked for coal-fired engines because it had many coal mines but little oil production.

The earlier ship designs included the "Northeast Coast, Open Shelter Deck Steamer". These were based on a simple ship first built in Sunderland by J.L. Thompson & Sons. The design came from a 1939 tramp steamer that was cheap to build and operate (see Silver Line). One example was SS Dorington Court, built in 1939. The order required an 18-inch (0.46 m) deeper draft to increase carrying capacity by 800 long tons (810 t), for a total of 10,100 long tons (10,300 t). Crew spaces, the bridge, and the main engine were placed in the middle of the ship. A tunnel connected the engine to the propeller at the back. The first Ocean-class ship, SS Ocean Vanguard, was launched on 16 August 1941.

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 later changed by the United States Maritime Commission. This was done partly to match American building methods, but mainly to make the ships faster and cheaper to build. The American version was named “EC2-S-C1”. “EC” meant Emergency Cargo, “2” meant the ship was between 400 and 450 feet (120 and 140 m) long, “S” meant steam-powered, and “C1” was the design number. The new design replaced much of the riveting with welding, which greatly reduced labor costs. Oil-fired boilers were also used. The design was approved under the Merchant Marine Act, and construction was given to a group of West Coast companies led by Henry J. Kaiser. This group was known as the Six Companies. Liberty ships were designed to carry 10,000 long tons (10,200 t) of cargo, usually one type per ship. During the war, they often carried more than this amount.

On 27 March 1941, the number of lend-lease ships was increased to 200 by the Defense Aid Supplemental Appropriations Act. In April, the number was raised again to 306 ships. Of these, 117 were Liberty ships.

References

  1. ↑ Wardlow, Chester (1999). The Technical Services – The Transportation Corps: Responsibilities, Organization, and Operations. United States Army in World War II. Washington, D.C.: Center of Military History, United States Army. p. 156. LCCN 99490905.
  2. ↑ Flippen, J. B. (April 2018). Speaker Jim Wright. Austin, Texas: University of Texas Press. p. 60. ISBN 9781477315149. Archived from the original on 17 June 2022. Retrieved 29 November 2021. mass-produced during the war, the Liberty Ship had become a symbol of the miracle of American production
  3. ↑ "Liberty Ships built by the United States Maritime Commission in World War II". usmm.org. American Merchant Marine at War. Archived from the original on 9 May 2008. Retrieved 28 November 2021. (2,710 ships were completed, as one burned at the dock.)
  4. ↑ Jaffee, Capt. Walter W., The Lane Victory: The Last Victory Ship in War and in Peace, 2nd ed., p. 14, The Glencannon Press, Palo Alto, CA, 1997.
  5. ↑ "MARAD, Victory Ship, U.S. Maritime Commission design type VC2-S-AP2". Archived from the original on 2 July 2025. Retrieved 2 July 2025.
  6. ↑ National Geographic, 2017. "Nazi Megastructures: Hitler's War Trains"
  7. ↑ During WW II, Nazi Germany made a similar choice when it mass-produced coal-powered steam locomotives called Kriegslokomotives. Even though newer engine technology existed, Germany lacked oil but had large coal supplies, especially in the Ruhr region.
  8. ↑ "Dorington Court (1939)". Archived from the original on 1 July 2015. Retrieved 28 June 2015.
  9. ↑ "Capacity of One Liberty Ship". Usmm.org. Retrieved 11 March 2022.

Sources

Further reading

Other websites