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A dry dock (sometimes drydock or dry-dock) is a narrow basin or vessel that can be flooded to allow a load to be floated in, then drained to allow that load to come to rest on a dry platform. Dry docks are used for the construction, maintenance, and repair of ships, boats, and other watercraft.


History


Greco-Roman world

The Greek author Athenaeus of Naucratis (V 204c-d) reports something that may have been a dry dock in Ptolemaic Egypt in the reign of Ptolemy IV Philopator (221-204 BC) on the occasion of the launch of the enormous '' Tessarakonteres'' rowing ship. It has been calculated that a dock for a vessel of such a size might have had a volume of 750,000
gallon The gallon is a unit of volume in imperial units and United States customary units. Three different versions are in current use: *the imperial gallon (imp gal), defined as , which is or was used in the United Kingdom, Ireland, Canada, Aus ...
s of water. In Roman times, a shipyard at Narni, which is still studied, may have served as a dry dock.


Medieval China

The use of dry docks in China goes at least as far back the 10th century A.D. In 1088,
Song Dynasty The Song dynasty (; ; 960–1279) was an imperial dynasty of China that began in 960 and lasted until 1279. The dynasty was founded by Emperor Taizu of Song following his usurpation of the throne of the Later Zhou. The Song conquered the res ...
scientist and statesman Shen Kuo (1031–1095) wrote in his '' Dream Pool Essays'':


Renaissance Europe

The first early modern European and oldest surviving dry dock still in use was commissioned by Henry VII of England at HMNB Portsmouth in 1495 (see
Tudor navy The Tudor navy was the navy of the Kingdom of England under the ruling Tudor dynasty (1485–1603). The period involved important and critical changes that led to the establishment of a permanent navy and laid the foundations for the future Ro ...
). This dry dock currently holds First World War monitor HMS M33. Possibly the earliest description of a floating dock comes from a small Italian book printed in Venice in 1560, called ''Descrittione dell'artifitiosa machina''. In the booklet, an unknown author asks for the privilege of using a new method for the salvaging of a grounded ship and then proceeds to describe and illustrate his approach. The included woodcut shows a ship flanked by two large floating trestles, forming a roof above the vessel. The ship is pulled in an upright position by a number of ropes attached to the superstructure.


Modern era

The Saint-Nazaire's Chantiers de l'Atlantique owns one of the biggest in the world: . The Alfredo da Silva Dry Dock in Almada,
Portugal Portugal, officially the Portuguese Republic, In recognized minority languages of Portugal: :* mwl, República Pertuesa is a country located on the Iberian Peninsula, in Southwestern Europe, and whose territory also includes the Macaronesian ...
, was closed in 2000. The largest roofed dry dock is at the German Meyer Werft Shipyard in Papenburg,
Germany Germany, officially the Federal Republic of Germany (FRG),, is a country in Central Europe. It is the most populous member state of the European Union. Germany lies between the Baltic and North Sea to the north and the Alps to the sou ...
, it is 504 m long, 125 m wide and stands 75 m tall. Harland and Wolff Heavy Industries in
Belfast Belfast ( , ; from ga, Béal Feirste , meaning 'mouth of the sand-bank ford') is the capital and largest city of Northern Ireland, standing on the banks of the River Lagan on the east coast. It is the 12th-largest city in the United Kingd ...
,
Northern Ireland Northern Ireland ( ga, Tuaisceart Éireann ; sco, label=Ulster-Scots, Norlin Airlann) is a part of the United Kingdom, situated in the north-east of the island of Ireland, that is variously described as a country, province or region. North ...
, is the site of a large dry dock . The massive cranes are named after the Biblical figures Samson and Goliath. Dry Dock 12 at Newport News Shipbuilding at is the largest dry dock in the USA. The largest floating-dock in North America is named The Vigorous. It is operated by Vigor Industries in Portland, OR, in the Swan Island industrial area along the Willamette River.


Types


Graving

A graving dock is the traditional form of dry dock. It is a narrow basin, usually made of earthen berms and concrete, closed by gates or by a caisson. A vessel is floated in with the gates open, then the gates are closed and the water is pumped out, leaving the craft supported on blocks. The keel blocks as well as the bilge block are placed on the floor of the dock in accordance with the "docking plan" of the ship. Routine use of dry docks is for the "graving" i.e. the cleaning, removal of barnacles and rust, and re-painting of ships' hulls. Some fine-tuning of the ship's position can be done by divers while there is still some water left to manoeuvre it about. It is extremely important that supporting blocks conform to the structural members so that the ship is not damaged when its weight is supported by the blocks. Some
anti-submarine warfare Anti-submarine warfare (ASW, or in older form A/S) is a branch of underwater warfare that uses surface warships, aircraft, submarines, or other platforms, to find, track, and deter, damage, or destroy enemy submarines. Such operations are typi ...
warships have sonar domes protruding beneath the hull, requiring the hull to be supported several metres above the bottom of the drydock. Once the remainder of the water is pumped out, the ship can be freely inspected or serviced. When work on the ship is finished, the gates are opened to allow water in, and the ship is carefully refloated. Modern graving docks are box-shaped, to accommodate newer, boxier ships, whereas old dry docks are often shaped like the ships that are planned to be docked there. This shaping was advantageous because such a dock was easier to build, it was easier to side-support the ships, and less water had to be pumped away. Dry docks used for building Navy vessels may occasionally be built with a roof, to prevent spy satellites from taking pictures of the dry dock and any vessels that may be in it. During World War II, fortified dry docks were used by the Germans to protect their submarines from Allied air raids (see submarine pen). An advantage of covered dry docks is that work can take place in any weather; this is frequently used by modern shipyards for construction especially of complex, high-value vessels like cruise ships where delays would incur a high cost.


Floating

A floating dry dock is a type of pontoon for dry docking ships, possessing floodable
buoyancy Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the p ...
chambers and a "U"-shaped cross-section. The walls are used to give the dry dock stability when the floor or deck is below the surface of the water. When valves are opened, the chambers fill with water, causing the dry dock to float lower in the water. The deck becomes submerged and this allows a ship to be moved into position inside. When the water is pumped out of the chambers, the dry dock rises and the ship is lifted out of the water on the rising deck, allowing work to proceed on the ship's hull. A large floating dry dock involves multiple rectangular sections. These sections can be combined to handle ships of various lengths, and the sections themselves can come in different dimensions. Each section contains its own equipment for emptying the ballast and to provide the required services, and the addition of a bow section can facilitate the towing of the dry dock once assembled. For smaller boats, one-piece floating dry docks can be constructed or converted out of an existing obsolete barge, potentially coming with their own bow and steering mechanism. Shipyards operate floating dry docks as one method for hauling or docking vessels. Floating drydocks are important in locations where porous ground prevents the use of conventional drydocks, such as at the
Royal Naval Dockyard Royal Navy Dockyards (more usually termed Royal Dockyards) were state-owned harbour facilities where ships of the Royal Navy were built, based, repaired and refitted. Until the mid-19th century the Royal Dockyards were the largest industrial c ...
on the
limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...
archipelago of
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. Another advantage of floating dry docks is that they can be moved to wherever they are needed and can also be sold second-hand. During
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
, the U.S. Navy used such auxiliary floating drydocks extensively to provide maintenance in remote locations. Two examples of these were the 1,000-foot AFDB-1 and the 850-foot AFDB-3. The latter, an
Advance Base Sectional Dock An auxiliary floating drydock is a type of US Navy floating dry dock. Floating dry docks are able to submerge underwater and to be placed under a ship in need of repair below the water line. Water is then pumped out of the floating dry dock, r ...
which saw action in
Guam Guam (; ch, Guåhan ) is an organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. It is the westernmost point and territory of the United States (reckoned from the geographic ce ...
, was mothballed near Norfolk,
Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the East Coast of the United States, Atlantic Coast and the Appalachian Mountains. The geography an ...
, and was eventually towed to
Portland Portland most commonly refers to: * Portland, Oregon, the largest city in the state of Oregon, in the Pacific Northwest region of the United States * Portland, Maine, the largest city in the state of Maine, in the New England region of the northeas ...
,
Maine Maine () is a U.S. state, state in the New England and Northeastern United States, Northeastern regions of the United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Provinces and territories of Canad ...
, to become part of
Bath Iron Works Bath Iron Works (BIW) is a major United States shipyard located on the Kennebec River in Bath, Maine, founded in 1884 as Bath Iron Works, Limited. Since 1995, Bath Iron Works has been a subsidiary of General Dynamics. It is the fifth-largest de ...
' repair facilities. A downside of floating dry docks is that unscheduled sinkings and off-design dives may take place, as with the Russian dock '' PD-50'' in 2018. The " Hughes Mining Barge", or HMB-1, is a covered, floating drydock that is also submersible to support the secret transfer of a mechanical lifting device underneath the '' Glomar Explorer'' ship, as well as the development of the '' Sea Shadow'' stealth ship. The Great Balance Dock, built in
New York City New York, often called New York City or NYC, is the most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the most densely populated major city in the U ...
in 1854, was the largest floating drydock in the world when it was launched. It was long and could lift 8,000 tons, accommodating the largest ships of its day.


Alternative dry dock systems

Apart from graving docks and floating dry docks, ships can also be dry docked and launched by: * Marine railway — For repair of larger ships up to about 3000 tons ship weight * Shiplift — For repair as well as for new-building. From 800 to 25000 ton ship-weight *
Slipway A slipway, also known as boat ramp or launch or boat deployer, is a ramp on the shore by which ships or boats can be moved to and from the water. They are used for building and repairing ships and boats, and for launching and retrieving small ...
, patent slip — For repair of smaller boats and the new-building launch of larger vessels


Other uses

Some dry docks are used during the construction of bridges, dams, and other large objects. For example, the dry dock on the artificial island of Neeltje-Jans was used for the construction of the Oosterscheldekering, a large dam in the
Netherlands ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...
that consists of 65 concrete pillars weighing 18,000 tonnes each. The pillars were constructed in a drydock and towed to their final place on the seabed. A dry dock may also be used for the prefabrication of the elements of an immersed tube tunnel, before they are floated into position, as was done with Boston's Silver Line.


Gallery

File:HM Dockyard Bermuda-Ana Brassey 1883.jpg, The Royal Naval Dockyard, Bermuda as seen by
Anna Brassey Anna Brassey, Baroness Brassey ( Allnutt; 7 October 1839 – 14 September 1887) was an English traveller and writer. Her bestselling book ''A Voyage in the Sunbeam, our Home on the Ocean for Eleven Months'' (1878) describes a voyage around the ...
in 1883, with its floating drydock in the background File:Dry Dock, Toledo Ship Building Company, Toledo, Ohio - DPLA - 026258a24e87b8b896620a2c045bd8a5 (page 1) (cropped).jpg, alt=Dry Dock, Toledo Ship Building Company, Toledo, Ohio, 1912, Dry Dock, Toledo Ship Building Company, Toledo, Ohio, 1912 File:DALPHIN I.jpg, Towboat ''Dolphin I'' in Bollinger Shipyards floating Drydock #2 on the
Mississippi River The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it ...
in Algiers, New Orleans,
Louisiana Louisiana , group=pronunciation (French: ''La Louisiane'') is a U.S. state, state in the Deep South and South Central United States, South Central regions of the United States. It is the List of U.S. states and territories by area, 20th-smal ...
File:Blohm+Voss Dock10 Hafen Hamburg 2.jpg, Blohm + Voss Dock 10, at the Port of Hamburg Germany File:Sevastopol Floating dock 2008 G1.jpg, Floating dry dock located in
Sevastopol Sevastopol (; uk, Севасто́поль, Sevastópolʹ, ; gkm, Σεβαστούπολις, Sevastoúpolis, ; crh, Акъя́р, Aqyár, ), sometimes written Sebastopol, is the largest city in Crimea, and a major port on the Black Sea ...
File:Floating drydock fo a small boat.jpg, A boat lift is a light duty form of dry dock which keeps small boats out of the water while not in use File:Schiff im Dock, Malerarbeiten am Heck.png, Ship in the floating dry dock of Bremer Vulkan shipyard during an inspection of its propeller and rudder File:Kaohsiung Taiwan Floating-dock-Jong-Shyn-01.jpg, Floating dry dock Jong Shyn No. 8 in Kaohsiung Harbour, Taiwan File:2019-03-19 SOCIBER VALPARAISO III floating drydock.jpg, SOCIBER floating drydock, ''Valparaiso III'' with tugboat ''Pequen'', being worked on in the cradle, in Valparaiso, Chile File:Great Balance Dock with Adriatic.jpg, The Great Balance Dock with the steamer ''Adriatic'' aboard, c. 1860


See also

* * * * — 1942 attack on a dry dock during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
.


References


Sources

* * *


External links


Encyclopædia Britannica, dry-dockCarnival Liberty Cruise Ship in Dry Dock in Freeport, Grand Bahamas"Docks's Life".
All about floating docks of shipbuilding firm "Almaz". St.-Petersburg. Russia. {{Authority control Coastal construction