Drew's Fighting Ships: T2 Tanker

The T2 superfamily of tankers and fleet oilers were part of the Pitt administration’s second building program. Like other designs of the program, the name reflects this, T indicating tanker, and 2 indicating the second program. The superfamily includes several prototype and demonstrator vessels, four classes of civilian tankers (many members of which eventually saw military use), two classes of Navy tankers, and one class of fleet oilers. All of these vessels were based on a common design, and most included a now infamous weakness between frames 72 and 201. Poorly understood metallurgy, coupled in some cases with rushed, inferior construction technique, exacerbated this weakness, as well as obfuscating its nature. Many T2 did live full, productive lives, but enough of them failed, and enough of the failures were spectacular, that the opposition seized upon the class to discredit Pitt and force him from office. Today, the T2 is most important for its engineering and design lessons.

Design and Evolution:
The T2 was envisioned as a vessel that could build up Britain’s merchant fleet, then shrinking and wearing out under wartime austerity measures, while violating neither the letter nor the spirit of those measures. The design was fully compatible with Naval facilities of the time, could keep up with convoy vessels, and allowed for easy conversion to Navy service. Partial government subsidy encouraged civilian operators to participate in the building program, and enabled many cash-strapped operators to afford to replace obsolete and worn-out vessels, with the proviso that the Navy could purchase the ship at book value on 30-days’ notice.

The initially-approved design met all of these needs, producing, after a few prototypes, the Syracuse class of T2s starting in 2732. Syracuse class vessels featured 9 cargo bays; bay 1, at the bow, held two tanks, separated by a midline bulkhead, each carrying about 80,000 gallons. The remaining bays held a center tank of about just under 400,000 gallons and two wing tanks, each of 160,000 gallons, giving a combined capacity of a little under six million gallons of fluids.

The stern was dominated by a two-by-two arrangement of 1 GW thrust engines at the corners (often Kingfisher Astro series, though roughly-equivalent Rolls-Royce and Viscount engines were also used), with twin 0.5 MW Kingfisher Director engines on a rotating nose ring for pitch, yaw, and roll. Bays, wiring, and magazines for two 14 GW plasma-arc cannon per side were fitted, though the cannon themselves were not. (Cannon would be supplied by the Navy if the tankers were appropriated. Some civilian operators installed dummy cannon as a measure of protection, or less-powerful real cannon; and some appropriated vessels retained their Navy-issue cannon on their return to civilian life.) Twin 70 GW reactors powered the whole.

Builders laid 173 keels of this class, of which 144 saw completion. Three were destroyed on the stocks by enemy action, sixteen were cancelled mid-production, and the remaining ten were appropriated by the Navy prior to their completion, being converted into various prototypes and experimental vessels. The class came to an end as a casualty of the emerging design for what would become the Gravelines class of supercarriers, which required greater quantities of coolants and lubricants than the earlier New Orleans and Trafalgar classes.

A hurried redesign increased cargo capacity by close to 16% by cutting back frames 72 through 201 and disrupting the beam belt in the same area. An external “bilge keel” was added to compensate for the disrupted beam belt, a visible feature absent in the Syracuse class and the most obvious external feature (i.e. feature in absentia) of that class.

Of the ten incomplete Syracuse vessels purchased by the Navy, seven were built as prototypes of the evolving T2a design (the other three saw such extensive alteration as Special Projects experimental vessels that they are frequently excluded from the class). The last of these, Chapel Hill, had all of the main features seen in the T2a group, and some scholars consider Chapel Hill to be the class leader. The Navy, however, named the class for the first vessel ordered to the design, the Mount Pleasant.

Mount Pleasant class tankers differed from their predecessors primarily through their increased cargo volume, but other changes were also made, including dividing the crew’s berthing area into several smaller compartments for better gender harmony, and rearranging the bulkheads of the officers’ quarters. The class is also the parent class to the Navy’s Ticonderoga tankers. These vessels received cannon during fitting out at their builders’, featuring either Armstrong pattern cannon before about 2745, or Blomefield pattern cannon after. Since the Navy did not appropriate any Mount Pleasant class tankers before the middle of 2746, Armstrong pattern cannon are almost exclusive to the Ticonderoga class of T2s. Ticonderoga class craft were also equipped with 2500 gpm cargo pumps, rather than the 2000 gpm pumps seen on their civilian-built sisters, or the 3500 gpm pumps of the later Wichita class of fleet oilers. Builders completed 372 Mount Pleasant craft, plus another 77 Ticonderoga vessels for the Navy.

The New Hyde Park class of T2s were built, through Lend-Lease, in American yards. In many respects they were identical to the British Mount Pleasant class, with the important distinction that all structural (and many other) members were built to SAE dimensions. These dimensions gave the New Hyde Park craft a curb weight about 2% less than that of the Mount Pleasant craft, and about 3% greater efficiency, as the engines were the same for both classes. The Navy’s Melbourne tankers were also American-built and SAE-dimensioned, being related to the New Hyde Park civilian tankers much as the Ticonderoga tankers were related to the Mount Pleasants. Production numbers for these classes were 198 New Hyde Parks, and 42 Melbournes.

Thus far, the power plant and engines of the original Syracuse design had met the modest needs of a tanker, but by 2750 the T2s often found themselves as the slowest vessels of the convoy, and a re-engining and redesign was in order. Five Ticonderoga class vessels were refitted with 1.5 GW engines, but this was really more than the installed power plant could handle, and none of the conversions were deemed successful. After a catastrophic fire on board one of these vessels, thought to be related to an overtaxed reactor, the remaining four vessels were decommissioned and scrapped. Eleven incomplete Mount Pleasant tankers were appropriated before the installation of their power plants. Experiments with these vessels yielded the T2b series, fitted with synergy-linked twin reactors (then a new technology) each capable of putting out 75 GW independently, or 165 GW together. Four 1.2 GW engines (typically Curtis Industrie Shakespeares), still in a two-by-two at-the-corners plan, provided about 15% extra thrust over the T2 and T2a designs, enabling the vessels to keep pace with their convoys. The Manchester was the first T2 to be ordered and built with the new power plant and engines, and so became the class leader. Manchesters were identical, in other respects, to the Mount Pleasant class vessels they superseded. 98 were built.

The final member of the T2 superfamily is the Wichita class of fleet oilers. Intrest in using a T2 design as a fleet oiler had originally risen in 2736, when Curtis’s buyout of Julio-Novak threatened continued availability of J-N’s Red Ball oilers. Under heavy pressure (the government threatened to block the acquisition), Curtis agreed to continue producing the Red Ball, renaming it the JN-3, but increasing dissatisfaction with Curtis’s product led the Navy to revisit the idea of a T2 oiler in 2741, and again in 2743. Several prototypes were made by converting existing T2s, but none proved satisfactory and the government struck a ten-year contract with Wang instead.

In 2752, this contract was coming to an end, and the Pitt administration pressed the Navy for an in-house design. Electronic Transport Controls’ Source Four Engines were selected, rated at the same 1.2 GW as Curtis’s Shakespeare engines, but delivering 30% more thrust (drawbar). This was enough to enable the prototype vessels to easily keep up with the main battle fleets of the time, and the substitution of 3500 gpm cargo pumps and a second, larger hangar area (added at the expense of a sick bay, and by shrinking the avionics bay - functions assumed by the capital ships of the battle fleet in any case) produced a vessel capable of replenishment under weigh operations. The first vessel in which all of these features appeared, Wichita, became the class leader (not the first vessel ordered to these specifications from the ground up, in breaking with past T2 tradition). In total, the Navy launched 45 Wichita oilers.

Problems, and Retirement:
All members of the T2 superfamily, with the exception of the Syracuse class, had in common a structural discontinuity at frame 72, and again at frame 201. External bracing (the so-called “bilge keel”) was intended to compensate for this, but T2 tankers suffered structural failures at a higher rate than many other vessels of the time. Rushed, substandard construction was blamed at the time, and did have a role in some incidents (e.g. the Yarm-on-Tees), but others occurred on vessels built in careful, well-respected yards where the standard of work was high. Various additional theories were put forth, including the sulphur content of the steel used, and “built-in stresses,” but none of the proposals led to successful amelioration of the problem. Computer analysis completed in the early 2800s, based on improved understanding of the physical stresses of a craft in space, showed that the “bilge keel” bracing failed to adequately address the loss of structural integrity caused by the interruption of the beam belt when the liquid storage tanks were expanded, and this is now the accepted reason for most failures.

Regardless of the reason, by 2755 the T2 had earned a reputation as a poorly-built craft, prone to catastrophic structural failure, and various inspection and repair programs were initiated. Some of these helped, to a degree; but others perversely exacerbated the problem by focussing stresses on already weak areas of the hull. Orders for the design fell off. The last T2 launch (Owston Ferry, a Wichita class oiler) occurred in May of the following year.

Of all five classes together, approximately 1,000 T2 craft were built and launched over the program’s 24 years. The Navy divested itself of all of its T2 by 2762, though many continued with the Transport Board and civilian operators for many years after than time.