Design

On 4 November 1941, John C. Neidermair, a designer with the Bureau of Ships, submitted his first drawing of the LST. Mr. Neidermair had a long and illustrious career with the Bureau of Ships, having a part in the design of over 8,000 ships. It was to be 280 feet long and 45.4 feet wide. 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.

The LSTs actually took more man-hours to build than the Liberty and Victory (cargo) ships, which were almost 5 times larger; about 10,600 tons deadweight to the LST’s 2,180 tons. Some compromises in construction difficulty/cost/time constraints were made. Using a flat-plate design to form the turn at the bilge would have added 16-25% more water resistance, and adversely affected the 10-knot speed desired. The decision was a curved bilge. Constructing a curved (cambered) main deck would have drained water more readily, but added to the construction time and cost. The decision was to build a flat main deck.

The first LSTs were designed with an elevator to carry equipment between the tank deck and the main deck. This was a time-consuming process which the “LST-511 class” improved upon by replacing the elevator with a ramp that was hinged at the main deck for this purpose. It permitted vehicles to be driven from the main deck to the leading edge of the tank deck, across the bow ramp to the beach or causeway. Some other modifications, with the “LST-542 class”, included the installation of the (Conn) navigation bridge [3rd level above the main deck] atop the Captain’s sea cabin, the installation of a water distillation plant with a capacity of 4,000 gallons per day, removal of the tank deck ventilator tubes from the center section of the main deck, strengthening the main deck to carry an LCT (Landing Craft, Tank), and an upgrade in armor/armament. These modifications were not major structural changes, and 1,055 LSTs were built on this “platform” before the next class--USS Terrebonne Parish (LST-1156) was launched in August 1952.

The ship could carry 1,060 tons of diesel fuel in ballast tanks. Draft forward could be as little as 1-1/2-feet when unloaded and unballasted. The LSTs were actually loaded for ocean passage to as much as 1,600 tons on the tank deck, and 300 tons on the main deck, and resulted in 33.3 tons per inch of immersion. The draft forward with a 1,900-ton payload was about 8-feet. For beaching, the designed load was 500 tons, and the actual load was an average of 700 tons.

The design was excellent in many ways. The hull was double-bottomed, and water-tight compartments lined the entire sides of the ship, offering some protection to the engine room spaces. The double-bottom compartments contained salt-water, diesel fuel, and fresh water, in a grouped arrangement order progressing from the bow to the stern.

Production of the “LST-1 Class” was begun late in l942 and continued through 1943. The “LST-511 Class” was built in 1944, with the “LST-542 Class” being built in 1944 and l945.

Production costs averaged $1.6 million per ship for the LST-542 class, versus $1.4 million for the LST-1 and LST-511 classes.

Hull	All-welded steel 3/8” thick
Length	327’ 9”
Beam	50-feet
Displacement empty / full	1,650 / 3640 (LST 1) 4080 (LST 511)
Design draft forward / aft	6’ 8-1/2” 13’ 0-3/8” [Displacement @ D.D. 3,590 tons]
Empty draft forward / aft	1'6" / 10'6"
Full load draft forward / aft	8' / 14'6"
Beaching trim forward / aft	3' to 6' / 10' to 13'
Freeboard	16'6"
Engines	2 (GM V-12 Diesel - 12-567A)
Screws	2
screw horsepower	1,700

American Bridge, Ambridge, PA- LST 137-141, 261-295, 653-681, 754-771, 829-849, 1081-1095

Chicago Bridge & Iron, Seneca, IL -LST 132-136, 197-231, 511-522, 600-652, 772-774, 850-860, 1115-1152

Dravo Corp., Pittsburgh, PA - LST 1-5, 7-15,17-20, 22-24, 26-60, 730-753, 775-796, 884-905, 1038-1059

Jeffersonville Boat, Jeffersonville, IN -LST 61-84, 117-121, 181, 501-510, 523-530, 682-729,797-805, 861-873, 1096-1100

Missouri Valley Bridge & Iron, Evansville, IN -LST 122-131, 157-180, 237-247, 491-500, 531-599, 806-828, 874-883, 1101-1114