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T2 AO-36 Kennebec / T2-A AO-41 Mattaponi
T2-SE-A1 AO-49 Suamico / AO-65 Pecos
T2-SE-A2 AO-80 Escambia / AO-111 Mission Buenaventura / AW-3 Pasig

The T2 tanker was a quantum leap in technology. The Liberty ship, along with the smaller shallow draft FS ship (Freight Supply), the T-2 Tanker, and the later war Victory class ship, were key to the maritime supply effort for Allied forces during World War II. The 16,000 dead-weight ton (dwt) capacity of the T-2 tanker was the yardstick for determining required depths for major U.S. deepwater ports in the 1940s. Since then, shipyards have been turning out even larger commercial cargo vessels. Some of the newer crude oil tankers, for example, have a capacity of more than 300,000 dwt, and even larger vessels will soon ply the world's sea lanes.

The design of the T2 tanker derived initially from Socony-Vacuum Company's SS Mobilfuel and SS Mobilube. Six of these ships were built by the Bethlehem Steel Sparrows Point Shipyard in Baltimore, MD. These ships were 501.5 feet long overall, with a beam of 68 feet. They displaced about 21,100 tons, with 9,900 tons gross, and 15,850 deadweight tons. In US Naval service they were the AO-36 Kennebec class.

Five T2-A type tankers were laid down in 1940 by Sun Shipbuilding and Drydock Co., Chester, PA for the Keystone Tankship Corporation. They were taken over by the US Navy in 1942, and completed as Navy oilers. Mattaponi (AO-41), built under Maritime Commission contract, was laid down originally as Kalkay (M.C. hull No. 149) by Sun Shipbuilding on 09 September 1941; launched as Mattaponi. These ships were 526 feet long overall, with a beam of 68 feet. They displaced about 22,500 tons, with 10,600 tons gross and 16,300 deadweight tons. Machinery consisted of geared steam turbines driving a single shaft at 12,000 shaft horsepower. This provided a maximum rated speed of 16.5 knots.

The US Maritime Commission's type T2-SE-A1 was the most common variety of the T2 style tanker, with a total of 481 built between 1942 and 1945. This commercial design was initially built by Sun Shipbuilding Company for Standard Oil Company of New Jersey. When the war required expanded production, this design was also built by Alabama Drydock & Shipbuilding Company of Mobile, AL, Kaiser Company's Swan Island Yard at Portland, OR, Marinship Corporation at Sausalito, CA, and Sun Shipbuilding & Drydock Company of Chester, PA. The average production time from laying of the keel to completion for sea trials was about 70 days. This included 55 day on the building ways and another 15 days in the fitting out dock. The record was held by Marinship Corporation, completing S.S. Huntington Hills in just 33 days; 28 days on the way and 5 days of fitting out.

The T2-SE-A1 ships were 523.5 feet long overall, with a beam of 68 feet. They displaced about 21,880 tons abeam, with a gross rated tonnage of 10,448 tons and 16,613 deadweight tons. Propulsion consisted of a turbo-electric drive, with a steam turbine generator driving a propulsion motor which turned the propeller. This eliminated the need for a large main reduction gear, which would have required time and machinery to produce. With the outbreak of the War, such machinery was busy making gear sets for warships. The propulsion system delivered 6,000 shaft horsepower, with a maximum power of 7,240 horsepower gave maximum speed of 15 knots with a cruising range of about 12,600 miles. The propulsion plant was produced by the General Electric Company, Lynn MA; the Elliott Company, Jeanette, PA; and the Westinghouse Electric and Manufacturing Company of Pittsburgh, PA.

The T2-SE-A1 tankers were not the first ships to have turbo-electric propulsion. During World War I several commercial ships and some warships were propelled by turbo-electric plants. In 1938, some tankers built for the Atlantic Refining Company of Philadelphia, PA by Sun Shipbuilding Company had turbo-electric plants. SS J.W. Van Dyke and six sister ships had 6,040 SHP General Electric equipment that gave them a maxiumum speed of about 13.5 knots.

The T2-SE-A1 had a total of 9 sets of tanks, with a total cargo was about 5,930,000 gallons [141,000 barrels]. A small dry cargo space of about 15,200 cubic feet was located forward of Tank Number 1. Two pumprooms were located forward and aft. The main pumproom was aft, with six pumps, while the forward pumproom had two lower capacity pumps.

USNS Suamico (T-AO-49) was used for point-to-point transportation of fuel, and did not have the underway-replenishment gear used by fleet oilers. Escambia and Mission Buenaventura T2-SE-A2 version of the T-2 and the T2-SE-A3 version of the T2 were generally similar, though their 10,000 SHP propulsion machinery, developed a top speed of 16 knots.

AO-101 Cohocton appears to be the only T2-SE-A3 to enter US Navy service. Concho, laid down as T2-SE-A3, was completed as the T2-SE-A AO-102 Mission Santa Ana (II), Conecuh, laid down as T2-SE-A3, was completed as the T2-SE-A2 AO-103 Mission Los Angeles (II), and Contocook, laid down as a T2-SE-A3, was completed as the T2-SE-A2 AO-123 Mission San Francisco (II).

The second Pasig was laid down as Mission San Xavier (MC hull 1826) by the Marinship Corp., Sausalito, Calif., 18 May 1944; renamed Pasig (AO-91), 3 July 1944; launched 15 July 1944; redesignated AW-3, on 28 August 1944; acquired by the Navy from the Maritime Commission 21 October 1944; and commissioned 11 December 1944. Following shakedown off California, Pasig sailed, 3 March 1945, to begin her mission of distilling and supplying fresh water to units of the Allied navies in the western Pacific. She arrived at Ulithi 23 March and immediately commenced supplying water to landing craft, preparing for the Okinawa campaign, merchant vessels, and various harbor craft. With no natural water supply at Ulithi, Pasig refilled periodically from tankers from the Philippines, or made trips to the closest natural source. Recommissioned 15 March 1951, Pasig reported to MSTSWestPac at Yokosuka in April. For 37 continuous months her 120,000 gallon/day distilling plant provided fresh water, for human and machine consumption, to units of the United Nations forces operating in Korean and Japanese waters. USS Abatan, a 22,350-ton (full load displacement) Pasig class water distilling ship, was built at Sausalito, California, as a Maritime Commission T2-SE-A2 tanker. In the expectation that she would become a Navy oiler, she received the hull number AO-92 in July 1944, but was redesignated AW-4 about a month later and completed for water supply purposes.

In the early 1940s the Coast Guard developed an intact GM criterion using Liberty Ship and T-2 tanker type vessels as the data base. This criterion has remained in effect and is referred to as the weather criterion (now in 46 CFR 170.170). The vessels in the data base had limited superstructure and carried their deadweight inside the buoyant envelope. Consequently, the center of the buoyant envelope was near the center of gravity (much like a submarine or an OBO). This provided a large range of stability and lots of righting energy, even with fairly small GM. Also, the vessels in the data base were much larger than T-boats and much smaller than car carriers.

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Page last modified: 22-07-2011 17:42:57 ZULU