Turret Deck Ship
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A turret deck ship is a type of
merchant ship A merchant ship, merchant vessel, trading vessel, or merchantman is a watercraft that transports cargo or carries passengers for hire. This is in contrast to pleasure craft, which are used for personal recreation, and naval ships, which are ...
with an unusual
hull Hull may refer to: Structures * The hull of an armored fighting vehicle, housing the chassis * Fuselage, of an aircraft * Hull (botany), the outer covering of seeds * Hull (watercraft), the body or frame of a sea-going craft * Submarine hull Ma ...
, 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 The waterline is the line where the hull of a ship meets the surface of the water. A waterline can also refer to any line on a ship's hull that is parallel to the water's surface when the ship is afloat in a level trimmed position. Hence, wate ...
s. This gave some advantages in strength and allowed them to pay lower canal tolls under
tonnage Tonnage is a measure of the capacity of a ship, and is commonly used to assess fees on commercial shipping. The term derives from the taxation paid on '' tuns'' or casks of wine. In modern maritime usage, "tonnage" specifically refers to a cal ...
measurement rules then in effect. The type ceased to be built after those rules changed. The last turret deck ship in existence was scrapped in 1960.


Development

Turret deck ships were inspired by the visit of the US
whaleback A whaleback was a type of cargo steamship of unusual design, with a hull that continuously curved above the waterline from vertical to horizontal. When fully loaded, only the rounded portion of the hull (the "whaleback" proper) could be seen a ...
vessel to
Liverpool Liverpool is a port City status in the United Kingdom, city and metropolitan borough in Merseyside, England. It is situated on the eastern side of the River Mersey, Mersey Estuary, near the Irish Sea, north-west of London. With a population ...
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 Sunderland () is a port City status in the United Kingdom, city and metropolitan borough in Tyne and Wear, England. It is a port at the mouth of the River Wear on the North Sea, approximately south-east of Newcastle upon Tyne. It is the most p ...
, England, built one whaleback under license from the type's designer,Doxford Engines
(archived 2/2/2007)
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 as an acronym may refer to: * Bag of waters, amniotic sac * Bartow Municipal Airport (IATA:BOW), a public use airport near Bartow, Florida, United States * Basic operating weight of an aircraft * BOW counties, made of Brown, Outagamie, and Winn ...
s and
stern The stern is the back 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 the bow, the foremost part of a ship. O ...
s instead of the upswept conoid "snout" of the whaleback. Instead of a rounded hull, the hull of a turret ship 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 may refer to: Physical spaces * Hold (compartment), interior cargo space * Baggage hold, cargo space on an airplane * Stronghold, a castle or other fortified place Arts, entertainment, and media * Hold (musical term), a pause, also called ...
. The design was patented. Doxford's first ship, ''Turret'', was notable for her abnormally long and wide hatches in the turret, and self-trimming due to the rounded shape in the upper hold and lower turret. She was thus ideal for grain. ''Turret'' was designed for tonnage of at a load line draft of at . 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. The ship 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 In traditional nautical use, well decks were decks lower than decks fore and aft, usually at the main deck level, so that breaks appear in the main deck profile, as opposed to a flush deck profile. The term goes back to the days of sail. Late-2 ...
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 long, wide girders and a 110-ton gun being easily loaded. By March 1895 the design had considerable acceptance. Nine ships were in use: ''Turret'', ''Turret Age'', ''Turret Bay'', ''Bencliff'', ''Turret Bell'', ''Progressist'', ''Royalist'', ''Hopedale'' and ''Forest Abbey''; and five more were being built.


Description and design

In side profile, turret deck ships resembled other merchant ships with
flush deck In naval architecture, a flush deck is a Deck (ship), ship deck that is continuous from stem to stern. History Flush decks have been in use since the times of the ancient Egyptians. Greco-Roman Trireme often had a flush deck but may have also ha ...
s or with small
forecastle The forecastle ( ; contracted as fo'c'sle or fo'c's'le) is the upper deck (ship), deck of a sailing ship forward of the foremast, or, historically, the forward part of a ship with the sailors' living quarters. Related to the latter meaning is t ...
s and
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, , from Latin . Thus the poop deck is technic ...
s. In cross-section the differences between turret deck ships and more conventional ships are apparent. There was no
gunwale The gunwale () is the top edge of the hull of a ship or boat. Originally the structure was the "gun wale" on a sailing warship, a horizontal reinforcing band added at and above the level of a gun deck to offset the stresses created by firing ...
; 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 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. Aboard ships and large boats On water craft, the superstruct ...
, 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 the trunk deck ship, were said to maximize strength, allowing larger ships 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 but ships to this design were not any lighter than conventional ships 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 In physics, the center of mass of a distribution of mass in space (sometimes referred to as the barycenter or balance point) is the unique point at any given time where the weighted relative position of the distributed mass sums to zero. For a ...
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 The Board of Trade is a British government body concerned with commerce and industry, currently within the Department for Business and Trade. Its full title is The Lords of the Committee of the Privy Council appointed for the consideration of ...
investigation, and cautions from Doxford on proper loading. The design was also 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 Net tonnage (NT, N.T. or nt) is a dimensionless index calculated from the total moulded volume of the ship's cargo spaces by using a mathematical formula. Defined in ''The International Convention on Tonnage Measurement of Ships'' that was adopte ...
(an approximate measure of cargo space) in comparison to their deadweight 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 The Suez Canal (; , ') is an artificial sea-level waterway in Egypt, Indo-Mediterranean, connecting the Mediterranean Sea to the Red Sea through the Isthmus of Suez and dividing Africa and Asia (and by extension, the Sinai Peninsula from the rest ...
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.
Some Marine Terminology
(definition of Turret Deck Ship).
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 and
tramp A tramp is a long-term homeless person who travels from place to place as a vagrant, traditionally walking all year round. Etymology Tramp is derived from a Middle English verb meaning to "walk with heavy footsteps" (''cf.'' modern English '' ...
service until retired, wrecked, or lost in the First or Second World War. The British
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. History Foundation and early years The company that would become the Clan Lin ...
, which traded globally in cargos such as foodstuffs, timber, metals, manufactured goods, case oil, jute, tea, nitrates, and general cargo, used 32 of the type. 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 The St. Lawrence River (, ) is a large international river in the middle latitudes of North America connecting the Great Lakes to the North Atlantic Ocean. Its waters flow in a northeasterly direction from Lake Ontario to the Gulf of St. Lawrenc ...
and
Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Lake Superior, Superior, Lake Michigan, Michigan, Lake Huron, H ...
of North America. The last of them, ''Turret Cape'', operated until mid-century and was not scrapped until 1959. Only the former ''Nonsuch'' was in operation a little longer. The ship was kept in business as ''Hermann Fritzen'' until 1959 by owner Johs. Fritzen & Sohn of Emden. Finally sold for demolition in April 1959, ''Hermann Fritzen'' arrived for breaking at Eckhardt & Co. in Hamburg in the first quarter of 1960.


See also

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References


Notes


Sources

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Photographs


Colour photographs of model of SS ''Nonsuch''
a highly detailed full-hull builder's model in the collections of the
National Maritime Museum The National Maritime Museum (NMM) is a maritime museum in Greenwich, London. It is part of Royal Museums Greenwich, a network of museums in the Maritime Greenwich World Heritage Site. Like other publicly funded national museums in the Unit ...
. ''Nonsuch'' was built by Doxford in 1906 for Bowles Brothers and lost to air attack in 1944.
SS Claverly Wreck Report
showing a stern view of SS ''Claverley'' showing 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 in 1917. {{cite web , title=SS Claverly , work=Wreck Reports , publisher=SouthWestMafia.com , year=2007 , url= http://www.southwestmafia.com/forumswm/showthread.php?p=35305 , access-date=12 November 2007 , url-status=bot: unknown , archive-url= https://web.archive.org/web/20111001054138/http://www.southwestmafia.com/forumswm/showthread.php?p=35305 , archive-date=1 October 2011 That source also reproduces pages 70–71 of Hardy (1924), with figure 28 showing a midships cross-section of a turret vessel. * ''Historical Collections of the Great Lakes'' maintained by
Bowling Green State University Bowling Green State University (BGSU) is a Public university, public research university in Bowling Green, Ohio, United States. The main academic and residential campus is south of Toledo, Ohio. The university has nationally recognized progr ...
has some photographs of turret ships. Th
photograph of ''Turret Chief''
shows a heavily laden vessel with harbour decks nearly awash. British inventions Naval architecture Ship types Shipbuilding