A turret deck ship is a type of merchant ship with an unusual hull

Hull (watercraft)

A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...

, designed and built in the late 19th and early 20th centuries.

The hulls of turret deck vessels were rounded and stepped inward above their waterline

Waterline

The term "waterline" generally refers to the line where the hull of a ship meets the water surface. It is also the name of a special marking, also known as the national Load Line or Plimsoll Line, to be positioned amidships, that indicates the draft of the ship and the legal limit to which a ship...

s. This gave some advantages in strength and allowed them to pay lower canal

Canal

Canals are man-made channels for water. There are two types of canal:#Waterways: navigable transportation canals used for carrying ships and boats shipping goods and conveying people, further subdivided into two kinds:...

 tolls under the tonnage

Tonnage

Tonnage is a measure of the size or cargo carrying capacity of a ship. The term derives from the taxation paid on tuns or casks of wine, and was later used in reference to the weight of a ship's cargo; however, in modern maritime usage, "tonnage" specifically refers to a calculation of the volume...

 measurement rules then in effect. The type ceased to be built after those rules changed.

Development

Turret deck ships were inspired by the visit of the U.S.

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 whaleback

Whaleback

A cargo steamship of unique design, with a hull that continuously curved above the waterline from vertical to horizontal leaving, when fully loaded, only the rounded portion of the hull above the waterline, was unofficially called a "whaleback". With sides curved in towards the ends, it had a...

 vessel to Liverpool

Liverpool

Liverpool is a city and metropolitan borough of Merseyside, England, along the eastern side of the Mersey Estuary. It was founded as a borough in 1207 and was granted city status in 1880...

 in 1891. Like others of her 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

Gun turret

A gun turret is a weapon mount that protects the crew or mechanism of a projectile-firing weapon and at the same time lets the weapon be aimed and fired in many directions.The turret is also a rotating weapon platform...

 on contemporary warships.

In 1893 William Doxford and Sons Ltd.

William Doxford & Sons

William Doxford & Sons Ltd, often referred to simply as Doxford, was a British shipbuilding company.-History:The Company was established by William Doxford in 1840. From 1870 it was based in Pallion, Sunderland, on the River Wear in Northeast England. The Company was managed by William Doxford's...

 ("Doxford") of Sunderland, England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

 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 bow

Bow (ship)

The bow is a nautical term that refers to the forward part of the hull of a ship or boat, the point that is most forward when the vessel is underway. Both of the adjectives fore and forward mean towards the bow...

s and stern

Stern

The stern is the rear or aft-most part of a ship or boat, technically defined as the area built up over the sternpost, extending upwards from the counter rail to the taffrail. The stern lies opposite of the bow, the foremost part of a ship. Originally, the term only referred to the aft port section...

s 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

Hold (ship)

thumb|right|120px|View of the hold of a container shipA ship's hold is a space for carrying cargo. Cargo in holds may be either packaged in crates, bales, etc., or unpackaged . Access to holds is by a large hatch at the top...

.

Description and design

In side profile, turret deck ships resembled other merchant vessels with flush deck

Flush deck

In naval architecture, a flush deck refers to when the upper deck of a vessel extends unbroken from stem to stern. There is no raised forecastle or lowered quarterdeck. Ships of this type may be referred to as "flush deckers", although this is often taken as referring to a series of United States...

s or with small forecastle

Forecastle

Forecastle refers to the upper deck of a sailing ship forward of the foremast, or the forward part of a ship with the sailors' living quarters...

s and poop deck

Poop deck

In naval architecture, a poop deck is a deck that forms the roof of a cabin built in the rear, or "aft", part of the superstructure of a ship.The name originates from the French word for stern, la poupe, from Latin puppis...

s. In cross-section the differences between turret deck vessels and more conventional ships are apparent. There was no gunwale

Gunwale

The gunwale is a nautical term describing the top edge of the side of a boat.Wale is the same word as the skin injury, a wheal, which, too, forms a ridge. Originally the gunwale was the "Gun ridge" on a sailing warship. This represented the strengthening wale or structural band added to the design...

; the vertical side of a turret ship curves inward above the load line to a horizontal plane. This flat area was known as the harbour deck. Further inboard, this "deck" arced to the vertical again by a reverse curve. That vertical plane then joined the weather deck atop the turret at a right angle. Structurally these elements were part of the hull, not of the superstructure

Superstructure

A superstructure is an upward extension of an existing structure above a baseline. This term is applied to various kinds of physical structures such as buildings, bridges, or ships...

, and the cargo holds of the ship extended up to the true weather deck atop the turret.

This design, and that of its near relative trunk deck ship

Trunk deck ship

A trunk deck ship is a type of merchant ship with a hull that was stepped inward in order to obtain more favourable treatment under canal toll rules then in effect. As those tolls were set by net tonnage, a measure of volume, and as the tonnage rules did not account for all of the cargo space of...

s, were said to maximize strength, allowing larger vessels and reduced the amount of steel needed for construction. In reality, it is more likely that the geometry inhibited the development of cracks in the sheer strake

Strake

A strake is part of the shell of the hull of a boat or ship which, in conjunction with the other strakes, keeps the sea out and the vessel afloat...

 but vessels to this design were not any lighter than conventional vessels due to their unique geometry. In operation their hull form promoted self-trimming of homogenous cargo and inhibited shifting. The design also called for a cellular double bottom, which was the probable reason for claims of the type's exceptional hull strength, but it also raised the centre of gravity of the cargo. A higher centre of gravity increased the roll period and reduced the violence of rolls. But loading heavy cargo too high, and failing to properly ballast the bottom tanks, raised the centre of gravity and led to instability. This led to accidents, a Board of Trade

Board of Trade

The Board of Trade is a committee of the Privy Council of the United Kingdom, originating as a committee of inquiry in the 17th century and evolving gradually into a government department with a diverse range of functions...

 investigation, and cautions from Doxford on proper loading. The design also was inconvenient, as the narrowness of the turret made for smaller cargo hatches and restricted habitation spaces in the superstructure atop the turret.

Turret deck ships had a low net tonnage

Tonnage

Tonnage is a measure of the size or cargo carrying capacity of a ship. The term derives from the taxation paid on tuns or casks of wine, and was later used in reference to the weight of a ship's cargo; however, in modern maritime usage, "tonnage" specifically refers to a calculation of the volume...

 (an approximate measure of cargo space) in comparison to their deadweight

Tonnage

Tonnage is a measure of the size or cargo carrying capacity of a ship. The term derives from the taxation paid on tuns or casks of wine, and was later used in reference to the weight of a ship's cargo; however, in modern maritime usage, "tonnage" specifically refers to a calculation of the volume...

 capacity (weight of cargo) allowing them to operate at a lower fee structure than a conventional hull. Net tonnage is a computation of volume, and the method of measurement used at the Suez Canal

Suez Canal

The Suez Canal , also known by the nickname "The Highway to India", is an artificial sea-level waterway in Egypt, connecting the Mediterranean Sea and the Red Sea. Opened in November 1869 after 10 years of construction work, it allows water transportation between Europe and Asia without navigation...

 to determine tolls was based on a measure of net tonnage which excluded some of the cargo spaces of these unconventional hulls. Turret and trunk deck ships therefore paid less in tolls than conventional ships of the same capacity.

In 1911 the toll measure changed at Suez to account for all cargo spaces, and contemporaneous refinements in the design of ships of more conventional hull form eliminated the structural advantages of turret deck ships. Construction of the type therefore ceased.

History of use

Over 180 ships of the type had been built before the design was abandoned, 176 of them by William Doxford and Sons. They were used in both line voyage

Freight liner (ship)

A freight liner is a cargo ship sailing on a regular schedule, as opposed to a tramp ship.The fee is listed in a liner tariff by owner or freight conference and unchanged in a rather long time....

 and tramp

Tramp steamer

A ship engaged in the tramp trade is one which does not have a fixed schedule or published ports of call. As opposed to freight liners, tramp ships trade on the spot market with no fixed schedule or itinerary/ports-of-call...

 service until retired, wrecked, or lost in the First or Second World War. The Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

-based Clan Line

Clan Line

The Clan Line was a passenger and cargo shipping company that operated in one incarnation or another from the late nineteenth century and into the twentieth century.-Foundation and early years:...

, which traded globally in cargos such as foodstuffs, timber, metals, manufactured goods, case oil, jute, tea, nitrates, and general cargo, used 30 of the type for those purposes.

While used for general freight, these ships were particularly suited to the carriage of bulk cargos such as grains, coal, and ores. Several were sold to Canadian interests for use in the latter trades on the Saint Lawrence River

Saint Lawrence River

The Saint Lawrence is a large river flowing approximately from southwest to northeast in the middle latitudes of North America, connecting the Great Lakes with the Atlantic Ocean. It is the primary drainage conveyor of the Great Lakes Basin...

 and Great Lakes

Great Lakes

The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...

 of North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. The last of them, Turret Cape, operated until midcentury and was not scrapped until 1959.

Sources

. Google books has images of those pages, containing the chapter entitled Turret Deck Cargo Steamer. Retrieved on 2008-03-26..

Photographs

• Colour photograph of model of SS Nonsuch, a highly-detailed full-hull builder’s model in the collections of the National Maritime Museum
  National Maritime Museum
  The National Maritime Museum in Greenwich, England is the leading maritime museum of the United Kingdom and may be the largest museum of its kind in the world. The historic buildings forming part of the Maritime Greenwich World Heritage Site, it also incorporates the Royal Observatory, Greenwich,...
  
  . Nonsuch was built by Doxford in 1906 for Bowles Brothers and lost to air attack in 1944.
• SS Claverly Wreck Report, with a stern view of SS Claverley showing her narrow harbour decks a short distance above the water. Claverley, , was built by Doxford in 1907, owned by Sutherland Steamship Company, and torpedoed by a German U-boat near the Eddystone
  Eddystone
  See also Eddystone Rock, Falklands Islands and Eddystone, PennsylvaniaThe Eddystone, or the Eddystone Rocks, are a seaswept group of rocks situated some 9 statute miles south west of Rame Head in Cornwall, England, United Kingdom...
  
   in 1917.
• Photographs of four vessels in Great Lakes service from the Historical Collections of the Great Lakes can be found by searching on the Great Lakes Vessels Online Index maintained by Bowling Green State University
  Bowling Green State University
  Bowling Green State University, often referred to as Bowling Green or BGSU, is a public, coeducational research university located in Bowling Green, Ohio, United States. The institution was granted a charter in 1910 by the State of Ohio as part of the Lowry Bill, which also established Kent State...
  
  and entering the word "Turret" in the vessel name keyword search field. The photograph of Turret Chief shows a heavily-laden vessel with her harbour decks nearly awash.