{{Short description|Basin drained to allow work on a vessel}} [[File:USS Greeneville (SSN 772) - dry dock Pearl Harbor (1).jpg|thumb|U.S. Navy submarine {{USS|Greeneville|SSN-772|6}} in a graving dock]]
[[File:Littoral combat ship in drydock, San Diego.jpg|thumb|A US Navy [[littoral combat ship]] in a floating drydock, [[National Steel and Shipbuilding Company|NASSCO]] 2012]]
[[File:FFG 42 on 4K.jpg|thumb|A US Navy frigate on a marine railway drydock]]
A '''dry dock''' (sometimes '''drydock''' or '''dry-dock''') is used for the construction, [[maintenance]], and repair of [[ship]]s, [[boat]]s, and other watercraft. There are several basic types of dry docks: (1) Graving or Basin Docks, (2) Floating Dry Docks, (3) Marine Railways, (4) Vertical Lifts, (5) Marine Travel Lifts.
==History==
===Ptolemaic Egypt=== 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.<ref>{{harvnb|Oleson|1984|p=33}}</ref> However this is disputed by Joseph Needham, who states that a survey by Goodchild and Forbes does not substantiate its existence.<ref>Needham, Joseph (1986). Science and Civilization in China: Volume 4 Part 3. Taipei: Caves Books, Ltd. Page 660</ref>
{{Blockquote|But after that a Phoenician devised a new method of launching it (the ''Tessarakonteres''), having dug a trench under it, equal to the ship itself in length, which he dug close to the harbour. And in the trench he built props of solid stone five cubits deep, and across them he laid beams crosswise, running the laces whole width of the trench, at four cubits' distance from one another; and then making a channel from the sea he filled all the space which he had excavated with water, out of which he easily brought the ship by the aid of whatever men happened to be at hand; then closing the entrance which had been originally made, he drained the water off again by means of engines (organois); and when this had been done the vessel rested securely on the before-mentioned cross-beams.<ref>[https://www.attalus.org/old/athenaeus5b.html Athenaeus of Naucratis (Yonge, C.D., Editor) ''The deipnosophists, or, Banquet of the learned of Athenæus'', volume I, London: Henry G. Bohn, p.325 (5.204c)]</ref>}}
It has been calculated that a dock for a vessel of such a size might have had a volume of 750,000 [[gallon]]s of water.<ref>{{harvnb|Landels|2000|p=163}}</ref>
===Song dynasty China=== The use of dry docks in [[Science and technology in China#Ancient and imperial China|China]] goes at least as far back as the 10th century A.D.<ref>{{cite book|author=Levathes, Louise|title=When China Ruled the Seas|publisher=Oxford University Press|year=1994|isbn=978-0-19-511207-8|page=[https://archive.org/details/whenchinaruledse00loui/page/77 77]|url-access=registration|url=https://archive.org/details/whenchinaruledse00loui/page/77}}</ref> In 1088, [[Song dynasty]] scientist and statesman [[Shen Kuo]] (1031–1095) wrote in his ''[[Dream Pool Essays]]'':
{{Blockquote|At the beginning of the dynasty (c. +965) the two Che provinces (now Chekiang and southern Chiangsu) presented (to the throne) two dragon ships each more than 200 ft. in length. The upper works included several decks with palatial cabins and saloons, containing thrones and couches all ready for imperial tours of inspection. After many years, their hulls decayed and needed repairs, but the work was impossible as long as they were afloat. So in the Hsi-Ning reign period (+1068 to +1077) a palace official Huang Huai-Hsin suggested a plan. A large basin was excavated at the north end of the Chin-ming Lake capable of containing the dragon ships, and in it heavy crosswise beams were laid down upon a foundation of pillars. Then (a breach was made) so that the basin quickly filled with water, after which the ships were towed in above the beams. Then (breach now being closed) the water was pumped out by wheels so that the ships rested quite in the air. When the repairs were complete, the water was let in again, so that the ships were afloat once more (and could leave the dock). Finally the beams and pillars were taken away, and the whole basin covered over with a great roof so as to form a [[hangar]] in which the ships could be protected from the elements and avoid the damage caused by undue exposure.<ref>Needham, Joseph (1986). Science and Civilization in China: Volume 4 Part 3. Taipei: Caves Books, Ltd. Page 660</ref><ref>{{Cite book |title=China's Management Revolution: Spirit, Land, Energy |last= Bouée |first=Charles-Edouard |publisher=Palgrave Macmillan |year=2010 |isbn=978-0230285453 |pages=84}}</ref>}}
===Renaissance Europe=== [[Image:Floating Dock. Woodcut included in the 'Descrittione' of Venice 1560.jpg|thumb|right|Floating Dock. Woodcut from [[Venice]] (1560)]]
Before the 15th century, when the hull below the waterline needed attention, [[careen]]ing was practised: at high tide the vessel was floated over a beach of hard sand and allowed to rest on one side when the tide receded. An account of 1434 described how a site near [[Southampton]] with a bottom of soft mud was selected for the warship ''[[Grace Dieu (ship)|Grace Dieu]]'', so that the hull would bed itself in and remain upright at low tide. A timber, brushwood and clay wall was then built up around the hull.<ref>{{cite book |last1=Kirkpatrick |first1=Cyril |author1-link=Cyril Kirkpatrick |editor1-last=Jarvis |editor1-first=Adrian |title=Port and harbour engineering |date=1998 |publisher=[[Ashgate Publishing]] |location=Aldershot, England |isbn=0-86078-755-9 |page=10 |chapter=The development of harbour and dock engineering}}</ref> The first early modern purpose-built European and oldest surviving dry dock still in use was commissioned by [[Henry VII of England]] at [[HMNB Portsmouth]] in 1495.<ref>{{harvnb|Sarton|1946|p=153}}</ref> This was a timber-lined excavation, with the seaward end closed off by a temporary [[revetted]] bank of rock and clay that had to be dug away by hand (an operation taking typically 29 days, working night and day to accord with the tides<ref>{{cite book |last1=Oppenheim |first1=Michael |author1-link=Michael Oppenheim |title=A history of the administration of the Royal Navy |date=1896 |publisher=[[Bodley Head]]|location=London |page=39 |chapter=Henry VII Portsmouth Dock|volume=1}}</ref>) to allow the passage of a ship.<ref>{{cite journal |last1=Goldingham |first1=C. S. |title=The Navy under Henry VII |journal=The English Historical Review |date=1918 |volume=33 |issue=132 |pages=480–481 |jstor=550919 |url=https://www.jstor.org/stable/550919 |issn=0013-8266}}</ref> Emptying was by a pump, possibly in the form of a bucket-chain powered by horses.<ref>{{cite book |last1=Moorhouse |first1=Geoffrey |author1-link=Geoffrey Moorhouse |title=Great Harry's navy: how Henry VIII gave England seapower |date=2005 |publisher=Weidenfeld & Nicolson |location=London |isbn=0-297-64544-7 |pages=11–12}}</ref> 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''.<ref>{{harvnb|Sarton|1946|pp=153f.}}</ref> 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=== In 1866 a floating dry dock HM Dry Dock Bermuda was constructed & sailed across the Atlantic to [[Bermuda]] from [[North Woolwich]], England. It arrived in 1869 & served until 1906. It was replaced by a larger dry dock built in 1901, Admiralty Floating Dock #1. There are remnants of it still visible over 100 years later.<ref>{{cite web|url=https://www.royalgazette.com/other/news/article/20120728/history-making-floating-dock-reaches-143rd-anniversary/|title=History-making floating dock reaches 143rd anniversary|date=July 28, 2012|accessdate=July 1, 2025|author=Alves, Samantha|publisher=[[The Royal Gazette (Bermuda)|The Royal Gazette]]}}</ref>
The [[Saint-Nazaire]]'s [[Chantiers de l'Atlantique]] owns one of the biggest in the world: {{convert|1200|x|60|m}}. The Alfredo da Silva Dry Dock in [[Almada]], Portugal, was closed in 2000. The largest roofed dry dock is at the German [[Meyer Werft]] Shipyard in [[Papenburg]], Germany, it is 504 m long, 125 m wide and stands 75 m tall.<ref>{{cite web|title=Meyer Werft baut größte Dockhalle der Welt|url=https://www.spiegel.de/wirtschaft/0,1518,529589,00.html|date=2008-01-18|publisher=[[Spiegel Online]]|access-date=2009-06-25}}</ref>
[[Harland and Wolff]] Heavy Industries in [[Belfast]], Northern Ireland, is the site of a large dry dock {{convert|556|x|93|m}}. The [[Samson and Goliath (cranes)|massive cranes]] are named after the Biblical figures [[Samson]] and [[Goliath]].
Dry Dock 12 at [[Newport News Shipbuilding]] at {{convert|662|x|76|m}} is the largest dry dock in the United States. 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.<ref>{{Cite news|url=https://www.oregonlive.com/business/index.ssf/2014/11/north_americas_largest_drydock_1.html|title=North America's largest drydock floats first ship at Swan Island's Vigor Industrial (infographic and time lapse)|newspaper=OregonLive.com|access-date=2016-11-03}}</ref>
==Types== [[Image:Stockholmsbriggen i Beckholmsdocka.jpg|thumb|The Stockholm [[brig]] "Tre Kronor" in one of the historical dry docks on the island [[Beckholmen]] in central [[Stockholm]]]]
===Graving=== A {{linktext|graving dock}} is the traditional form of dry dock.<ref name=RK>{{cite web |last1=Kantharia |first1=Raunek |title=The Ultimate Guide to Dry Docks: Types, Functions, and Essential Requirements |url=https://www.marineinsight.com/guidelines/dry-dock-types-of-dry-docks-requirements-for-dry-dock/ |website=Marine Insight |date=9 January 2024 |access-date=6 August 2024 |location=Bangalore, India}}</ref> It is a narrow basin, usually made of earthen berms and concrete, closed by gates or a [[Caisson (engineering)|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 [[Underwater diving|divers]] while there is still some water left to manoeuvre the vessel. 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]] warships have [[sonar]] domes protruding beneath the hull, requiring the hull to be supported several metres above the bottom of the dry dock, or depressions built into the floor of the dock, to accommodate the protrusions.<ref>{{cite book |last1=Tobel |first1=W. M. |title=Graving Drydocks Design Manual |date=1982 |publisher=US Navy Facilities Engineering Command |location=Alexandria, VA |page=29.1-9}}</ref>
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.
[[Image:USS Michigan (SSBN-727).jpg|thumb|left|U.S. Navy ballistic missile submarine {{USS|Michigan|SSBN-727|6}} inside a flooded dry dock]] Modern graving docks are box-shaped, to accommodate newer, boxier ships, whereas old dry docks are often shaped like the ships expected to dock 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.{{citation needed|date=November 2018}}
Dry docks used for building naval vessels may occasionally be built with a roof, to prevent [[spy satellite]]s from taking pictures of the dry dock and any vessels that may be in it. During [[World War II]], the German {{lang | de | Kriegsmarine}} used fortified dry docks to protect its [[submarine]]s 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=== [[Image:Basen portowy, Gdynia 2007 (zdjęcie lotnicze).jpg|thumb|240px|Floating docks, [[Gdynia]], Poland]]
A floating dry dock is a type of [[pontoon (boat)|pontoon]] for dry docking ships, possessing [[semi-submersible|floodable]] [[buoyancy]] 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 [[valve]]s 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 tank|ballast]] and to provide the required services, and the addition of a [[Bow (watercraft)|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.<ref name="Noel1988pp81-82">{{cite book | last = Noel | first = John V. | year = 1988 | title = Knight's Modern Seamanship | publisher = [[John Wiley and Sons]] | edition = 18 | isbn = 0-471-28948-5 | pages = 81–82 }}</ref>
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, Bermuda|Royal Naval Dockyard]] on the [[limestone]] archipelago of [[Bermuda]]. 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]], the [[U.S. Navy]] used such [[auxiliary floating drydock]]s extensively to provide maintenance in remote locations. Two examples of these were the 1,000-foot [[USS Artisan (ABSD-1)|AFDB-1]] and the 850-foot [[AFDB-3]]. The latter, an [[Advance Base Sectional Dock]] which saw action in [[Guam]], was mothballed near [[Norfolk, Virginia]], and was eventually towed to [[Portland, Maine]], to become part of [[Bath Iron Works]]' repair facilities.<ref>[https://www.navybook.com/nohigherhonor/pic-ffg58repair.shtml Photos of USS ''Samuel B. Roberts'' on blocks in AFDB-3 in 1988]</ref><ref>[https://books.google.com/books?id=bCEDAAAAMBAJ&dq=popular+science+July+1946&pg=PA121 "Sea Going Navy Yard Follows The Fleet", November 1945, ''Popular Science'']</ref>
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.<ref>{{cite news |last1=SEAN GALLAGHER |title=Russia's only aircraft carrier damaged as its floating dry dock sinks |url=https://arstechnica.com/tech-policy/2018/10/russias-only-aircraft-carrier-damaged-as-its-floating-dry-dock-sinks/ |access-date=5 November 2018 |work=Ars Technica |date=20 October 2018 |quote="Due to interruptions in the supply of electric power to the PD-50, the floating dock dived out in an off-design mode."}}</ref>
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]] in 1854, was the largest floating drydock in the world when it was launched. It was {{Convert|325|ft|m}} long and could lift 8,000 tons, accommodating the largest ships of its day.<ref>{{Cite book|last=Webb|first=William H.|url=https://books.google.com/books?id=750AAAAAMAAJ&dq=%22new+york+balance+dock%22&pg=PA231|title=Monthly Nautical Magazine, and Quarterly Review|date=January 1855|publisher=Griffiths, Bates|language=en}}</ref>
===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]], [[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]] 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.<!-- isn't this a coffer dam?-->
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 (MBTA)|Silver Line]].
==Gallery== <gallery widths="250" heights="250"> File:'Atalante', Fitzroy Dock, Sydney, 1873 SLNSW FL1233688.jpg|French warship 'Atalante', Fitzroy Dock, Sydney, 1873 File:Margaret Galbraith 1878 SLNSW FL10366751.jpg|Auckland graving dock, Auckland, New Zealand, 1878 File:HM Dockyard Bermuda-Ana Brassey 1883.jpg|The [[Royal Naval Dockyard, Bermuda]] as seen by [[Anna Brassey]] 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]] in [[Algiers, New Orleans]], [[Louisiana]] 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]] File:Кронштадт, Алексеевский док сверху зимой (2).jpg|Alekseevsky dry dock at [[Kronstadt]] shipyard, Saint Petersburg, Russia 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 Shipbuilding Company|Jong Shyn]] No. 8 in [[Port of Kaohsiung|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 File:USS_Oregon_in_dry_dock,_1898.jpg|{{USS|Oregon|BB-3}} in dry dock, 1898 </gallery>
==See also== * {{Annotated link|List of dry docks}} * {{Annotated link|Semi-submersible}} * {{Annotated link|Space dock}} * {{Annotated link|St Nazaire Raid}} on a dry dock during [[World War II]]
==References== {{Reflist}}
==Sources== *{{Citation | last = Landels | first = J. G. | title = Engineering in the Ancient World | year = 2000 | edition = Revised | publisher = University of California Press | isbn = 0-520-22782-4 | url-access = registration | url = https://archive.org/details/isbn_9780520227828 }} *{{Citation | last = Oleson | first = John Peter | author-link = John Peter Oleson | title = Greek and Roman Mechanical Water-Lifting Devices: The History of a Technology | year = 1984 | publisher = University of Toronto Press | isbn = 90-277-1693-5 }} *{{Citation | last = Sarton | first = George | title = Floating Docks in the Sixteenth Century | journal = Isis | volume = 36 | issue = 3/4 | pages = 153–154 | year = 1946 | doi=10.1086/347934 | s2cid = 144849113 }}
==External links== {{Commons category|Dry docks}} * [https://www.britannica.com/eb/article-9031272/dry-dock dry-dock] in the ''[[Encyclopædia Britannica]]'' * [https://web.archive.org/web/20100302133720/http://www.picable.com/Places/Fair/Carnival-Liberty-Cruise-Ship-in-Dry-Dock.1279993 Carnival Liberty Cruise Ship in Dry Dock in Freeport, Grand Bahamas] * [http://docklife.ucoz.ru "Docks's Life"]—All about floating docks of shipbuilding firm Almaz of St. Petersburg, Russia
{{Shipbuilding-Footer}} {{Seamanship}} {{Authority control}}
[[Category:Drydocks| ]] [[Category:Coastal construction]]