Turret deck ship

A turret deck ship is a type of merchant ship with an unusual hull, designed and built in the late 19th and early 20th centuries. The hulls of turret deck vessels were rounded and stepped inward above their waterlines. This gave some advantages in strength and allowed them to pay lower canal tolls under tonnage measurement rules then in effect. The type ceased to be built after those rules changed.

Turret deck ships were inspired by the visit of the US whaleback vessel Charles W. Wetmore to Liverpool in 1891. Like others of the type, Wetmore had a hull in the form of a flattened cigar, with a continuous curve above the waterline to where the sides met amidships. The superstructure atop the hull was in round or oval "turrets", so named because of their resemblance to gunhouses on contemporary warships.

In 1893 William Doxford and Sons Ltd. ("Doxford") of Sunderland, England built one whaleback under license from the type's designer, but had already built its first turret deck ship to a design by Arthur Havers, the concern's chief draughtsman. Havers toned down the more radical features of the whaleback. His design retained conventional bows and sterns instead of the upswept conoid "snout" of the whaleback. Instead of a rounded hull, the hull of a turret vessel was stepped inward above the waterline, but the horizontal and vertical surfaces of the hull met in curves rather than by right angles as in conventional ships. Finally, the design joined the rounded turrets of whalebacks into one long and narrow rectangular structure (also called a "turret") of about half the beam, and used that space as part of the hold.

The design was patented and Doxford's first ship, Turret, was notable due to its abnormally long and wide hatches in the turret and self trimming due to the rounded shape in the upper hold and lower turret and thus ideal for grain.Turret was designed for tonnage of 4,700 DWT at a load line draft of 20 feet 3 inches (6.2 m) at 2,850 GRT. With engines aft the design was seen as ideal for the bulk oil trade meeting the latest Suez Canal regulations in which coal bunkers would be separated from oil cargo by a double bulkhead filled with water. It was noted that the vessel had an unusually high righting angle which was obtained whether full or lightly loaded. In particular the design was seen as a solution to the problem of strength and economical cost. On well deck ships the lack of a continuous line of the deck, one the turret ship design solved with a continuous line and solid structure up to the top of the turret, resulted in weakness with classification societies taking notice by requiring increased strengthening in construction. The long, wide hatches were seen as making the design especially suitable for carrying heavy or bulky machinery. That feature later resulted in cargoes such as 75 feet (22.9 m) long, 8 feet (2.4 m) wide girders and a 110-ton gun being easily loaded.

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