ON THE WATERFRONT: Doxford’s mystery craft

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As Britain entered the Great War on August 4, 1914, William Doxford and Sons’ prominence in shipbuilding and engineering was an asset to the nation.

Besides the company’s contribution to the war effort in terms of merchant and naval tonnage, some of its innovations are less well known.

In 1916, a mysterious craft was completed at Pallion shipyard. Resembling a submarine or even a giant torpedo, it was not a secret weapon but an experimental floating marine storage tank for oil.

Bearing the identification number C95, the origins of the 100-ton gross vessel dated back to October, 1913, when Doxford’s applied to patent an invention for “improvements in or relating to marine storage tanks for oil.”

Previously, rectangular floating tanks had been utilised, these being superseded by cylindrical vessels. Doxford’s recognised that such tanks were vulnerable to attack during wartime and set about designing an improved version which would be safe from land or aerial bombardment.

Experiments were carried out on various designs, one being a cylindrical vessel with hemispherical ends and internal dividing bulkheads. Doxford’s suggested that a convenient size would be 150 feet in length by 30 feet in diameter. This could carry some 2,400 tons deadweight of liquid fuel and be submerged in any reasonable depth of water by use of ballasting compartments.

Another idea, aimed at reducing the visible surface area above water, was to sink one end of the tank to the sea or riverbed.

Doxford’s also designed a 450-foot barge with a beam of 50 feet nine inches to carry 20,000 tons of oil. Although intended to remain afloat in a harbour, it would always float around its loaded draft due to water being pumped into tanks.

It is thought that these floating storage facilities remained on the drawing board until C95 was launched in 1916. By then, it appears that plans for full submersibility had been abandoned.

Instead, the prototype C95 unit was introduced; this having the capability of being towed around harbour areas to supply ships with fuel bunkers.

A system allowing automatic balanced pressure in each oil compartment was installed, with the vessel’s upper space being used for buoyancy, pumping apparatus and other gear.

A feature of the design kept the craft floating at a constant draft and trim, this being achieved by the intake of seawater while simultaneously pumping out fuel (and vice-versa).

During the war, C95 was in continuous use for naval experiments. Close attention was paid to the effectiveness of internal arrangements designed to prevent water from contaminating fuel.

Although C95’s fate is unknown, it is said that it remained at Doxford’s for many years - perhaps as a yard oil storage tank.