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The Second Group of National Defense Tankers

On 9 February 1940, the maritime commission announced that it had reached agreement with the Socony-Vacuum Oil Company to construct six additional high-speed national defense tankers.1 Socony-Vacuum had wanted to participate in the maritime commission's program earlier, but had found the commission's twin-screw design unsuited for its operations on the Beaumont Canal in Texas. A ship the size of Cimarron was simply too large to successfully navigate within the restricted waters of the canal. Twin screws were a further liability being more easily damaged than a single, centrally mounted screw and added significantly to the machinery cost of the vessel. An acceptable compromise was reached when Socony agreed to adapt the design of its newest tankers so that they could be modified to obtain a speed of 161/2 knots.2 These new tankers, the Mobilfuel and Mobilube, were proving to be very successful in service. They had been ordered from Bethlehem Steel, Sparrows Point, on 18 February 1938 and were built to a design developed by N. J. Pluymert, a naval architect who headed the company's construction repair division.3 The first of the pair, the Mobilfuel, was launched one year later on 25 February 1939 with the Mobilube following on 29 April. Both ships were 500 feet, 71/2 inches long overall with a 68-foot beam, displaced 21,450 tons, and had a cargo capacity of 16,400 deadweight tons.4 Each was a single-screw vessel equipped with a 4,000 s.h.p. turbine designed for a sea speed of 131/2 knots.5

Invited to observe the trials conducted for Mobilube, representatives of the maritime commission were impressed with her design, which proved to be very economical to operate.6 After the trials were completed, it was agreed that the technical staff of Socony-Vacuum would modify the design to meet the navy's requirements while retaining the same features that had been responsible for the low operating costs of the tankers already delivered. As per the contracts awarded earlier for the first twelve high-speed tankers, the maritime commission agreed to pay


for any national defense features incorporated in the design of the new ships with Socony-Vacuum meeting the higher operating costs.

The biggest change involved the propulsion system, which had to be redesigned in order to raise the sea speed from 131/2 knots to the 161/2 knots required by the navy. Under Pluymert's direction, Socony successfully squeezed a 12,000 s.h.p. unit into the same space used by the 4,000 s.h.p. turbine in the original design.7 The problem of increasing the steam-generating capacity was cleverly solved by flaring the boilers so that the upper portion was wider than the base, thus taking advantage of the total space available without increasing the deck space required for the new boilers. Other changes made to the original design included the addition of gun foundations, magazine spaces, and added crew spaces.

In an effort to enhance the speed characteristics of the proposed vessel, the maritime commission conducted model tests to improve the design of the underwater hull.8 Based on this work, the commission's staff of naval architects developed a new lines plan that would have included a semibulbous bow had it been adopted.9 Although the revised design was less than 500 feet along the waterline, it was still designated as a T3-type tanker in the title block.10 Since this design had the same dimensions as the Mobilfuel and the Mobilube--500 feet overall (o.a.), 487 feet between perpendiculars (b.p.), and a 68-foot beam--it is clear that at this juncture the commission considered the Socony/Bethlehem design a single-screw variant of the original T3-S2-A1 design concept for high-speed tankers, hence the use of the T3 designation. This rather incongruous assignment of type number would form the foundation for a great deal of the future confusion concerning the various design types built by the maritime commission and the actual differences in their physical characteristics. In future contracts, the T3 designation would be used to signify the Bethlehem design (T3-S1-A1) and would be unrelated to size.

Socony-Vacuum awarded construction contracts to Bethlehem Steel for the first four ships on 1 November 1939.11 Orders for an additional two ships were placed on 10 January 1940 for a combined total of six vessels, all to be duplicates of the Mobilfuel and the Mobilube. After completing successful negotiations with the maritime commission, the contracts for all six vessels were amended to include the increased speed and additional defense features that were to be subsidized by the government.

Orders for a total of eighteen high-speed tankers had now been placed on behalf of the maritime commission. Six more were needed to fulfill the navy's goal to have twenty-four such tankers available. The commission continued to seek additional participants for its highspeed tanker program and was close to concluding a second agreement with the Keystone Tankship Corporation. After signing the contracts


for the Socony-Vacuum vessels, the maritime commission announced that it was requesting bids for the construction of six more tankers similar in design to the six just ordered for Socony-Vacuum. Potential builders were requested to submit bids on two different types: the T2 of 161/2 knots and the T2A of 131/2 knots.12 The difference in costs would be used to justify cost subsidy to be paid by the government for the added speed. Bids were to be submitted no later than 19 March 1940.

The lowest bid for the 161/2 knot type was received from the Sun Shipbuilding and Dry Dock Company.13 Lower still was the alternate bid submitted by Sun for building the requested ships to their own design. These were offered at a price $40,000 per vessel less than the base bid, even though the proposed ships would be 121/2 feet longer (b.p.) than the design based on the Socony-Vacuum type requested by the maritime commission.14 On the basis of this bid, Sun was subsequently awarded contracts to build five national defense tankers for the Keystone Tankship Corporation. The first two ships were ordered on 20 April 1940.15 This was followed in June with orders for three additional vessels of the same type. As was the case with the Socony-Vacuum deal, the maritime commission would pay the cost differential for the increased speed.

The tankers ordered by Keystone were similar in design to a series of three ships (Sun hull numbers 208, 209, and 210) ordered by Standard Oil of New Jersey in February, but were provided with larger power plants to meet the higher speed requirements of the navy. The passage of time has obscured the genesis of Sun's design for these 500-foot (b.p.) ships, but it appears likely that they too evolved from the T2 plans prepared by the Joint Board for the Standardization of Merchant Vessels.16

The Kennebec (AO-36) Class

The first of the Socony-Vacuum tankers was launched on 19 April 1941.17 Christened SS Corsicana, she was named after Corsicana, Texas, the town where the first refinery in Texas was built. Delivered on 18 August 1941, the Corsicana immediately entered service with the Socony-Vacuum Oil Company. Of the six fast tankers ordered by Socony-Vacuum, only the Corsicana and her sister ship the Caddo had been completed by 7 December 1941. Both were immediately taken over by the navy at the outbreak of war. Commissioned as the USS Kennebec (AO-36) on 4 February 1942, the Corsicana became the lead ship of her class. The Caddo was also commissioned that date as the Merrimack (AO-37). The four remaining ships were also acquired by the navy. The first three--Winooski (AO-38), Kankakee (AO-39), and Lackawanna (AO-40)--were acquired immediately upon completion and commissioned soon after. Catawba, the last of the class, was not acquired until August. She was commissioned on


Kennebec, first of the Socony tankers acquired by the navy, leaves Norfolk Navy Yard 24 July 1944. Note the radar antenna on the mast and the raised gun platforms on the aft deck house with their new 40 mm guns. These changes became commonplace for all oilers in the last two years of the war. (National Archives)
Kennebec, first of the Socony tankers acquired by the navy, leaves Norfolk Navy Yard 24 July 1944. Note the radar antenna on the mast and the raised gun platforms on the aft deck house with their new 40 mm guns. These changes became commonplace for all oilers in the last two years of the war. (National Archives)

16 September 1942 as the second Neosho (AO-48), replacing her namesake sunk at the battle of the Coral Sea in May (see chapter 17).

The Kennebec was driven by a single screw powered by a cross-compound, double reduction geared steam turbine manufactured by Westinghouse. The turbine was designed to deliver a maximum of 12,000 s.h.p. when supplied with steam at 375 psi and 700 degrees Fahrenheit. For backing power, an astern turbine was incorporated in the low-pressure casing. Steam was supplied by two Foster Wheeler "P" type marine boilers at 450 psi and 725 degrees Fahrenheit. These had been specially designed to fit into the limited space available. Each boiler had a normal capacity of 52,500 lbs/hr and a maximum capacity of 58,000 lbs/hr. Table 11 summarizes the Kennebec's characteristics.

As a bulk oil carrier, the Corsicana was originally designed to carry approximately 129,000 barrels of crude oil distributed in eight center and sixteen wing tanks. A number of these tanks were modified during her conversion to a fleet oiler so that she could carry and dispense gasoline, diesel fuel, and lube oil in bulk. This was typical for all tankers that were acquired by the navy. Loading and unloading of the main cargo was still accomplished via three main cargo pumps located in the forward pump room, although auxiliary pumps were probably installed for the other fluids handled, especially gasoline, which would have required special provisions. Each of the main pumps was


Principal Dimensions of Kennebec (ex-Corsicana)

Length, overall 501' 71/2"
Length, between perpendiculars 487' 6"
Beam, molded   68' 0"
Depth, molded to upper deck at side   37' 0"
Draft, molded design   29' 81/2"
Total displacement 21,000 tons
Total deadweight capacity 15,850 tons
Tank capacity, barrels 129,000 (42s)
Shaft horsepower, max. (@ 105 rpm) 12,000
Speed at 80% of max. power (@ 97 rpm) 161/2 knots

driven by a 200 hp electric motor connected to the pump by a jack shaft running through the bulkhead separating the motor room from the pump room. The pumps, which were manufactured by the De Laval Steam Turbine Company, had a capacity of 1,900 gpm, sufficient to load or unload the vessel in about sixteen hours. Three rotary-type stripping pumps were also supplied: two motor driven and one steam turbine driven, each having a 400 gpm capacity.

Mattaponi, leaving Norfolk on 23 November 1942, was the first of five national defense tankers ordered by the Keystone Tankship Company to be commissioned by the navy.
Mattaponi, leaving Norfolk on 23 November 1942, was the first of five national defense tankers ordered by the Keystone Tankship Company to be commissioned by the navy. Note the characteristic "clipper bow," which distinguishes them from the T2s that followed and the addition of radar, which was being fitted to auxiliaries at this early stage of the war. (National Archives)



Length, overall 520' 0"
Length, between perpendiculars 500' 0"
Beam, molded   68' 0"
Depth, molded to upper deck at side   37' 0"
Draft, molded design   29' 111/2"
Total displacement 21,800 tons
Total deadweight capacity 16,400 tons
Cargo capacity, barrels[1] 131,500 (42s)
Shaft horsepower, max. (@ 105 rpm) 12,000
Speed at 80% of max. power (@ 97 rpm) 161/2 knots

[1] Total cargo including diesel oil, lubricating oil, and gasoline.

The Mattaponi (AO-41) Class

None of the national defense tankers built by Sun were completed prior to the outbreak of war. The Aekay was the first to be finished. She was delivered to the Keystone Tankship Corporation in February 1941 and immediately pressed into service. Had she not been on a voyage to the Far East, the Aekay would have been the first of her class to be acquired by the U.S. Navy.18 Instead this honor went to the Kalkay, the second Keystone tanker to be completed by Sun. Tankers were urgently needed by the navy and she was acquired immediately upon completion in March. Renamed the Mattaponi she was commissioned on 11 May 1942, becoming AO-41. Mattaponi was followed by the Tappahannock (AO-43; ex-Jorkay), Monongahela (AO-42; ex-Ellkay), Neches (AO-47; ex-Aekay), and finally Patuxent (AO-44; ex-Emmkay), the last of the Keystone tankers to be transferred to the navy.

Except for the addition of the national defense features and a moderate increase in power, the Mattaponi and her sister ships were identical to the Sun-built tankers the Esso Trenton and the Esso Albany designed by the Standard Oil Company.19 These had been delivered in the previous year and had proven to be extremely successful. Although de signed for a service speed of 151/2 knots, the Esso Albany had attained a speed of 17.03 knots during her trials at approximately 85 percent of the rated capacity of the 9,000 s.h.p. General Electric turbine with which she was equipped.20

The Mattaponi was very similar in design to the Kennebec. The arrangement of both vessels was based on previously accepted commercial designs for single-screw bulk oil carriers, modified to provide the 161/2-knot sea speed desired by the navy (see table 12). The Mattaponi was slightly larger, however, having been built to a somewhat newer design standard. Mattaponi's larger hull provided the extra space needed to mount the larger boilers that were required to provide sufficient steam for the more powerful (12,000 s.h.p.) turbine. This was a decided advantage over the Kennebec design since it eliminated the need to fabricate specialized boilers.


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