Unrep MSC to amphib

Sunday, July 06, 2008

Sunday Ship History: Tank Landing Ships (I)


It's not often that a ship design can be traced to a specific event, but you can come pretty close by looking at the the history of Tank Landing Ships, more well known by their acronym, LSTs. While small landing craft had been around for some time, in the early 1940's there were no sea-going vessels capable of loading and unloading vehicles from and to the beach...until Dunkirk caused some serious thinking:
The British evacuation from Dunkirk in 1940 demonstrated to the Admiralty that the Allies needed relatively large, ocean-going ships capable of shore -to-shore delivery of tanks and other vehicles in amphibious assaults upon the continent of Europe. As an interim measure, three medium-sized tankers, built to pass over the restrictive bars of Lake Maracaibo, Venezuela, were selected for conversion because of their shallow draft. Bow doors and ramps were added to these ships which became the first tank landing ships (LST's). They later proved their worth during the invasion of Algeria in 1942, but their bluff bows made for inadequate speed and pointed up the need for an all-new design incorporating a sleeker hull.
The "Maracaibo" class LSTs had a distinctive look - a very tanker look with a forward bridge (see the before and after photos immediately below from this site).
Following the Royal Navy experiments, discussions with the Americans led to a design being developed:
...John Niedermair of the Bureau of Ships sketched out an awkwardlooking ship that proved to be the basic design for the more than 1,000 LST's which would be built during World War II. To meet the conflicting requirements of deep draft for ocea n travel and shallow draft for beaching, the ship was designed with a large ballast system that could be filled for ocean passage and pumped out for beaching operations.
***
The preliminary plans initially called for an LST 280 feet in length; but, in January 1942, the Bureau of Ships discarded these d rawings in favor of specifications for a ship 290 feet long. Within a month, final working plans were developed which further stretched the overall length to 328 feet and called for a 50-foot beam and minimum draft of three feet 9 l/2 inches. This scheme distributed the ship's weight over a greater area enabling her to ride higher in the water when in landing trim. The LST could carry a 2,100-ton load of tanks and vehicles. The larger dimensions also permitted the designers to increase the width of the bo w door opening and ramp from 12 to 14 feet and thus accommodate most Allied vehicles. Provisions were made for the satisfactory ventilation of the tank space while the tank motors were running, and an elevator was provided to lower vehicles from the maind eck to the tank deck for disembarking. By January 1942, the first scale model of the LST had been built and was undergoing tests at the David Taylor Model Basin in Washington, D.C.

In three separate acts dated 6 February 1942, 26 May 1943, an d 17 December 1943, Congress provided the authority for the construction of LST's along with a host of other auxiliaries, destroyer escorts, and assorted landing craft. The enormous building program quickly gathered momentum. Such a high priority was assi gned to the construction of LST's that the keel of an aircraft carrier, previously laid in the dock, was hastily removed to make place for several LST's to be built in her stead. The keel of the first LST was laid down on 10 June 1942 at Newport News, Va. ; and the first standardized LST's were floated out of their building dock in October. Twenty-three were in commission by the end of 1942.
The basic design of the LST was not complicated - as set out here:
After consideration and calculations for buoyancy, stability, and payload requirements, the final drawings resulted in a 328-foot length, a 50-foot beam, a flat-bottom, a sloping keel, giving a 7-1/2-foot maximum draft (forward), and a 14-foot maximum draft (aft), with about a 16-foot freeboard. The tank deck dimensions were 230-feet long, 30-feet wide, and 12-feet high. John Neidermair insisted upon 3/8” plating for the hull (shell plating), rather than the planned original 1/4”, and the plating under the bow was 1” thick. The firm of Gibbs and Cox, New York, completed the actual design details, and became the contractor charged with the procurement of materials/equipment, and they selected the Dravo Corporation as the first contractor.

John C. Neidermair insisted the design should contain no more shapes and sizes of plates than you have fingers on your hand -- five of each. The LST required 30,000 parts, including such items as steering gear, stern anchor gear, armament, snaking winch, appliances, refrigeration plant, ladders, doors, pumps, engines, stanchions, main generator and power distribution switching gear.
***
The LST was designed to ground evenly (from bow to stern) on a beach with a slope of about one-foot for every fifty-feet (the design gradient). Each propeller (screw) is protected by a skeg which extends forward from it and provides a sturdy “runner” beneath its blades. The twin rudders are mounted directly behind the screws, and thus achieve maximum effectiveness as a result of the propeller discharge. The propellers were spaced almost 40-feet apart and set up clear of the base line of the hull. The sea chests, or intakes for sea water, were located on the sides of the hull.
These ships were powered by two diesel engines and could do about 12 knots. The design was modified as experience grew with these ships as might be expected. Over half of the 1,000 ship LST class were built in shipyards located on rivers well inland from the sea. Modifications to the LSTs included providing hinged masts to allow them to pass under bridges as they headed to the sea. In addition to the hinged mast, some bridges along the routes were modified as set out here:
The need for LST's was urgent, and the program enjoyed a high priority throughout the war. Since most shipbuilding activities were located in coastal yards and were largely used for construction of large, deep-draft ships, new construction facilities were established along inland waterways. In some instances, heavyindustry plants such as steel fabrication yards were converted for LST construction. This posed the problem of getting the completed ships from the inland building yards to deep water. The chief obstacles w ere bridges. The Navy successfully undertook the modification of bridges and, through a "Ferry Command" of Navy crews, transported the newly constructed ships to coastal ports for fitting out. The success of these "cornfield" shipyards of the Middle West was a revelation to the long-established shipbuilders on the coasts. Their contribution to the LST building program was enormous. Of the 1,051 LST's built during World War II, 670 were constructed by five major inland builders.

By 1943, the construction time for an LST had been reduced to four months; and, by the end of the war, it had been cut to two months. Considerable effort was expended to hold the ship's design constant; but, by mid-1943, operating experience led to the incorporation of certain changes in the new ships. These modifications included: the replacing of the elevator by a ramp from the main deck to the tank deck, an increase in armament, and the addition of a distilling plant to make potable water. The main deck was strengthened to accommodate a fully-equipped landing craft, tank (LCT).
See also photos of LST 512 folding her mast and storing it (photos from LST Homeport which has a substantial collection).


Given their number and capacity, it probably isn't surprising that some LSTs were converted to other uses:
The LST proved to be a remarkably versatile ship. A number of them were converted to become landing craft repair ships (ARL). In this design, the bow ramp and doors were removed, and the bow was sealed. Derricks, booms, a nd winches were added to haul damaged landing craft on board for repairs, and blacksmith, machine, and electrical workshops were provided on the main deck and tank deck.

Another successful conversion was the LST "Mother Ship." Thisv ersion of the standard LST hull had two Quonset huts erected on the main deck to accommodate 40 officers. Bunks on the tank deck berthed an additional 196 men. A bake shop and 16 refrigeration boxes for fresh provisions augmented the facilities normally p rovided the crew. Four extra distilling units were added, and the ballast tanks were converted for storage of fresh water.

Thirty-eight LST's were converted to serve as small hospital ships. They supplemented the many standard LST's which removed casualties from the beach following the landing of their cargo of tanks and vehicles. For example, on D day, LST's brought 41,035 wounded men back across the English Channel from the Normandy beaches. Other LST's, provided with extra cranes and handling gear, were used exclusively for replenishing ammunition. They possessed a special advantage in this role, as their size permitted two or three LST's to go simultaneously alongside an anchored battleship or cruiser to accomplish replenishment more rapidly than standard ammunition ships. In the latter stages of World War II, some LST's were even fitted with flight decks from which small observation planes were sent up during amphibious operations. (see here).*
LSTs saw action in WWII in both the Atlantic and Pacific, with landings in France, Italy, the Philippines, Iwo Jima and Okinawa.





While LSTs suffered mine hits, Kamikaze attacks and other horrors of war, one particular event deserves special attention - an ammunition handling accident at West Loch, Pearl Harbor, as described here and here:
Elements of the Saipan landing Force entered Pearl Harbor May 20th, 1944, after practicing for the Saipan Landings off Maui. Twenty-one LSTs (Landing Ship Tanks) proceeded to West Loch and tied up side by side in five rows across the channel from the Naval Ammunition Depot. They were floating bombs crammed with munitions, vehicles and other supplies of the 2nd and 4th Marine divisions, Sea Bees and Army units. More ships were at Pearl Harbor at that time than any other period during WW II.

Sunday morning May 21st, 1944, some of the men went ashore on liberty while others performed shipboard duties or had taken their vehicles and guns ashore for servicing after the salt water dousing they received in rough seas during the invasion rehearsal off Maui. LST 353 was berthed second from the end in the first row and a little after 1500 hours erupted into a huge explosion hurling men, vehicles, pieces of bodies and steel high into the air. Suddenly other LST’s frantically moved away as the fires and explosions spread to other ships.

Six LSTs were destroyed, 163 men killed and 396 injured, the numbers would have been much larger if all personnel had been on duty. This was the second worst disaster in Pearl Harbor during World War II since the Japanese Attack on Pearl Harbor December 7, 1941.

A Naval Court of Inquiry concluded the probable cause for the explosion was a defective fuse or carelessness while loading mortar ammunition onto a truck parked on the ship’s elevator.

This could have been a disastrous for the Saipan invasion forces; however replacement men, ships, and equipment were found and the LSTs sailed out of Pearl Harbor on May 25,1944, (only one day late) and that day was made up enroute. The Saipan Invasion was carried out as originally scheduled and became a major supply depot and large airbase for B 29 long-range bombers through the rest of WW II.
See also here.

Workhorses.

Large Slow Targets.

Manned by Navy and Coast Guard crews.

And absolutely vital.


Following the WWII, large numbers of LSTs were decommissioned, mothballed, sunk or transferred to foreign navies. Completing the circle, converted LSTs were used as oilfield support vessels in Venezuela.


In Part II, their "second life" will be visited.


However, if any one knows any more about the following picture and caption, I'd like to hear from you...
Picture of 40 man army tent the Hickman County Hoisted when the engines failed.1968.
*UPDATE: More on the mini aircraft carrier LSTs:
In the latter stages of World War II, some LST's were even fitted with flight decks from which small observation planes were sent up during amphibious operations. These LSTs were converted to mini-aircraft carriers and actually launched fixed wing reconnaissance aircraft from their modified decks. They were used as floating platforms from which small spotter planes were launched and recovered by Brodie Gear, which may very roughly be compared to a giant slingshot.

Many missions that required liaison aircraft were not possible, even with the excellent short field takeoff and landing ability of the L-4, without taking some extraordinary measures. To provide artillery observation during amphibious assaults, the Army employed two unorthodox methods. The first was to convert a Landing Ship Tank (LST), into a mini-aircraft carrier with a plywood runway approximately 60 meters (197 ft) long and 5 meters (16 ft 5 in) wide, which could support no more than ten light planes. These vessels saw extensive service supporting amphibious landings in the Mediterranean and the invasion of the Philippines. However, the conversion of the LSTs into a liaison plane carrier took considerable time and effort and the large scale of amphibious operations frequently required the use of all available LSTs. Thus, a more exotic, but simpler system came into use.



Navy Lieutenant James Brodie, on assignment to the Office of Strategic Services (OSS), forerunner of the Central Intelligence Agency (CIA), developed a system in which an L-4 or an L-5, with a hook mounted above the cockpit, could catch a trapeze bar suspended off the side of an LST or Liberty ship. The trapeze rolled along a wire suspended between two gantries that hung over the sides of the ship, and allowed the aircraft to come to a smooth stop. A similar rig allowed the aircraft to launch by reaching flying speed while suspended and then disengaging the hook. The advantage of this system was that it did not preclude the use of the ship for standard operations. The Brodie system only saw operational service during the invasion of Okinawa. Brodie also developed a land-based version for use in the Far Eastern theaters in situations where there was insufficient time or capability to construct a suitable airstrip, but the opportunity never arose to use this system.
More on the Brodie System here from when the adjacent photos came, except for the photo of LST 325 which came from here. More photos of LST air ops here.

No comments:

Post a Comment