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LST Class, Allied Landing Ships


Naval Historical Center #97857

Schematic diagram of LST

ONI 226


Specifications:


Tonnage 2400 tons loaded for landing operations
Dimensions 327' by 50' by 13'
99.7m by 15.2m by 4.0m
Maximum speed      11 knots
Complement 119
Armament 13 0.50 machine guns
6 20mm Oerlikon AA guns
Cruising speed
8 knots
Machinery
2-shaft diesel (1800 shp)
Range
12,000 nautical miles
Capacity 20 medium tanks or 750 tons cargo
Modifications
Beginning in late 1943, LSTs began shipping additional antiaircraft armament. This typically brought the antiaircraft battery up to 3 to 5 40mm Bofors AA guns, 11 to 18 20mm guns, 4 to 18 machine guns, and one 3"/50 AA gun.

By the end of the war, 8 40mm guns was standard armament.


The Landing Ship, Tank, or LST, was designed to land up to twenty tanks on a beach.  It did so by dropping a ramp onto the beach through a set of bow doors after the ship was deliberately grounded. The design dated to November 1941, when a British delegation to the United States asked for 200 ships and 400 craft capable of bringing tanks ashore. The former became the LST and the latter the LCT.

An important design requirement for the LST was that it be an ocean-going vessel, capable of crossing the Atlantic. This could not be achieved with the shallow draft required for landing operations, but the problem was solved by adding two submarine-style ballast tanks. When these were filled, the LST had sufficient draft for ocean passage. The tanks could be quickly pumped out when the ship approached the landing beach, reducing the draft for the grounding operation. However, even when ballasted down, the LST had poor seakeeping. The flat-bottomed hull required for landing operations limited the ship's speed and handling, and the LST experienced severe pounding in heavy seas. This occasionally caused the deck to develop cracks. The combination of shallow draft and broad beam also meant the ships had a very quick roll that was very uncomfortable for the crews and required cargo to be tightly secured.

Other elements of the design included a pair of skegs resembling those of the new fast battleships. This created a tunnel into which the propellers and rudders were placed, protecting them during grounding and from fouling by the stern anchor chain. Vehicles on the tank deck were expected to start their engines before the bow doors opened, and this required a forest of portable ventilation ducts that could be connected to the vehicle exhausts. Trucks could be carried on the main deck but had to be lowered via an elevator to the tank deck in order to exit through the bow. Later models replaced the elevator with a hinged ramp that was more complicated but hastened disembarkation. Starting with the Sicily invasion in August 1943, LSTs were equipped with davits so that they could carry six LCTs in place of trucks on the main deck.

LSTs had rather light point defenses and were quite slow, so that some wags claimed that “LST” stood for “Large Slow Target.” In light of experience gained at New Georgia, LSTs in the South Pacific shipped many additional antiaircraft guns by the time of the Bougainville landings. The ships were also equipped with barrage balloons, but these were discarded in 1944 because they were too visible to enemy search aircraft.  Many crews improvised additional antiaircraft defenses using scrounged weapons, ranging from Army 37mm antiaircraft guns and machine guns to additional 40mm guns. However, the ships had good survivability, both because their broad beam gave them a large reserve of stability and because their hulls were quite strong. A total of 37 LSTs were lost to enemy attack during the war, a small number considering that they were very lucrative targets.

South Pacific LSTs were rarely used for their designed purpose of bringing vehicles ashore. Instead, they were used to land large quantities of supplies. At first, cargo was stacked to the rear of a few preloaded trucks. The trucks would discharge their cargo, then come back to be loaded with more, while additional cargo was manhandled onto the beach. This allowed about four times as much cargo to be carried as would have been the case if all the cargo had been preloaded onto trucks, but the unloading process was slow, taking about eight hours. The process was improved by loading the cargo into trailers that could be hauled ashore by tractors. About 33 trailers could be packed into an LST with little loss of cargo capacity, and unloading was much faster: An LST so loaded could discharge about 750 tons of cargo in about two hours.

LSTs were designed for a beach slope of 1 in 50. On this ideal beach, an LST would ground evenly along her entire length and her ramp would come down on dry ground. On shallower beaches, the ramp would drop into the water, and the gap had to be bridged with interlocking pontoon units. On deeper beaches, the LST did not ground properly and was liable to yaw dangerously in the surf. In either case, the uneven grounding put considerable strain on the hull. Because few beaches were ideal, an LST was too badly worn out for further use in landing operations after about ten landings. The Navy judged that it was more cost-effective to build new LSTs than to refurbish the old ones or to try to strengthen the design. The old, worn-out LSTs were used for every imaginable purpose, including repair ships, floating barracks, floating depots, and hospital barges. Some were even fitted with a flight deck capable of operating a handful of light reconnaissance aircraft — a dubious concept at best.

A number of LSTs were modified by converting part of the troop deck into a small surgical suite. LST-464 was converted into a dedicated hospital ship, with a surgical suite, X-ray room, laboratory, and isolation ward. She began service off New Guinea with 7 Fleet and served with great distinction in the second Philippines campaign.

LSTs were considered a sufficient priority early in the war that, on 28 May 1942, a number of Maritime Commission shipyards were instructed to begin mass production of the ships (as standard type S3-M2-K2). Some 75 LSTs were produced by Maritime Commission shipyards, including 15 at a new yard near Oakland (Richmond #3a, later redesignated Richmond #4) and 30 at Vancouver, which had previously completed just two Liberty Ships.The priority given to construction of LSTs significantly delayed the destroyer escort program.


Units arriving in the Pacific:

2/42

1

11/42 5
12/42      10
1/43 9
2/43 10
3/43 12
4/43 12
5/43 17
6/43 7
7/43 8
8/43 15
9/43 21
10/43 13
11/43 5
3/44 3
4/44 22
5/44 65
6/44 39
7/44 44
8/44 41
9/44 42
10/44 34
11/44 39
12/44 27
1/45 43
2/45 13
3/45 1
4/45 1
Total 559

Photo Gallery


Profile of LST

U.S. Navy

Forward hull of beached LST

U.S. Navy

Stern hull of beached LST

U.S. Navy

Doors of beached LST

U.S. Navy

Doors of beached LST

U.S. Navy


References

Cowdrey (1994)

Friedman (2002)

Leighton and Coakley (1955)

Morison (1950)

NavSource.Org (accessed 2009-10-1)


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