WARTIME EMERGENCY DESIGNS

By 1940 it was obvious that the standard design ships, while excellent, were being produced in numbers too small for the expected wartime demand for ships. Adding tankers to the US Maritime Commission mix made things worse because tanker construction further limited the capacity available to build increased numbers of standard design freighters. In addition, standard design freighters had to compete for resources with the rapidly expanding US Navy’s shipbuilding requirements as well as tankers. Reduction gears, required to transform the rotations of fast-spinning steam turbines to the much slower marine propeller speeds were in particularly short supply. Building new factories to manufacture reduction gears took years, however. Even if the gears were available, steam turbines – likewise built to extremely tight tolerances – were also scarce, as were marine diesels. The solution was two-fold: build new shipyards and build ships that did not require reduction gear, or steam turbines.

The answer lay in a British ship design being built in the United States. In 1940 Britain contracted with Todd Shipyards to build 60 Ocean-class freighters. These ships were 416ft long, had a beam of 57ft, and could carry 7,174 tons of cargo. They had a top speed of 11kn. The design was based on the Sunderland Tramp, a ship class dating back to 1879. The major difference between the Oceans and their 19th-century ancestors was that the Oceans were oil-fired and welded rather than riveted. Both ship classes were powered by triple-expansion steam engines.

The US Maritime Commission had previously disassociated itself from this project, judging the Oceans to be too slow. Freighters were needed and needed quickly, however, and the Oceans fit that requirement. They could be built quickly, and triple expansion engines solved the propulsion bottleneck. The Commission briefly considered using an Emergency Fleet Corporation design from World War I, the similarly sized Los Angeles class, but the design had several weaknesses, including the need to update it from riveted to welded construction. Ultimately, the Commission decided to modify the Ocean-class design for their emergency ship.

The US Maritime Commission took the Ocean-class plans and redrafted them to US standards. Water-tube boilers replaced the Scotch coal-fired boilers of the Oceans. The ships’ double-bottoms were used to store fuel oil, and two deep tanks were added to the Hold 1 for water ballast. The amidships deckhouse was enlarged so the entire crew could be housed there. Steel decks and hatch covers replaced wood. Finally, a standardized engine design was used, with interchangeable parts, allowing any parts from one engine manufacturing plant to be used in an engine made by any other plant. The engine produced 2,500hp, and drove the Oceans at a maximum speed of 11kn.

The design had a gross register tonnage (GRT) of 7,176 tons, but a DWT of 10,414 tons, and displaced 14,245 tons. The difference was due to the purpose of each measurement. GRT measured the internal volume of the ship, with 100cu ft equaling one register ton. DWT was the total weight – cargo, fuel, passengers, crew, and supplies – a ship could carry. Displacement measures the total weight of the ship, including the structure. DWT and displacement were measured in long tons, 2,240lb to the ton.

The result was called the Liberty ship. The US Maritime Commission classified it as an EC2-S design: “EC” stood for Emergency Cargo, “2” meant the waterline length was between 400 and 450ft (it was 416ft with an overall length of 441.5ft), and “S” indicated it was a single-screw steamship.

What made them “emergency” ships were design factors undesirable in vessels intended for commercial profitability. Their triple-expansion engines were obsolete in 1941, and the ships were slower and less fuel-efficient than their steam-turbine counterparts. They were also optimized for fast construction rather than hydrodynamic efficiency. They had a minimum of curves, reducing the number of bends required to shape the plates to the hull form. The EC2 design had a longer parallel mid-body than similar sized C2 designs. The hull bottom was flat, curved 90 degrees where it met the sides. These design features meant the Liberty ship could be built faster than any other comparably sized vessel.

SS STEPHEN HOPKINS

Stephen Hopkins was an EC2 S-C1 Liberty ship ordered by the US Maritime Commission. It was named for Stephen Hopkins, a signatory of the Declaration of Independence in 1776. Built by Kaiser, it was laid down on January 2, 1942, and launched on April 14, 1942, at the Permanente Metals Corporation Shipyard No. 2 in Richmond, California. Upon completion in May 1942, the US Maritime Commission turned the ship over to the Luckenbach Steamship Company to operate under charter for the War Shipping Administration.

On its maiden voyage it traveled to the South Pacific carrying a mixed cargo for various US Army posts there before making its way to Cape Town, South Africa. It departed Cape Town on September 19, sailing independently to Paramaribo, Dutch Guiana (now Surinam), where it was to pick up a load of bauxite. It never arrived. On September 27, 1942, just over a week out of Cape Town, it encountered the German raider Stier and supply ship Tannenfels. After a fierce engagement, in which it crippled Stier, Stephen Hopkins sank.