Home      Discussion      Topics      Dictionary      Almanac
Signup       Login
Dry dock

Dry dock

Overview
A drydock 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. Drydocks are used for the construction, maintenance, and repair of ships, boats, and other watercraft.

According to the ancient Greek author Athenaeus of Naucratis (V 204c-d), the drydock was invented in Ptolemaic Egypt
Ptolemaic Egypt
Ptolemaic Egypt began when Ptolemy I Soter invaded Egypt and declared himself Pharaoh of Egypt in 305 BC and ended with the death of queen Cleopatra VII of Egypt and the Roman conquest in 30 BC. The Ptolemaic Kingdom was a powerful Hellenistic state, extending from southern Syria in the east, to...

, some time after the death of Ptolemy IV Philopator
Ptolemy IV Philopator
Ptolemy IV Philopator , son of Ptolemy III and Berenice II of Egypt was the fourth Pharaoh of Ptolemaic Egypt...

 (reigned 221-204 BC):
Since Athenaeus recorded the event 400 years later (around 200 AD), there is sufficient reason to believe that drydocks had been known throughout classical antiquity.
Discussion
Ask a question about 'Dry dock'
Start a new discussion about 'Dry dock'
Answer questions from other users
Full Discussion Forum
 
Unanswered Questions
Recent Discussions
Encyclopedia
A drydock 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. Drydocks are used for the construction, maintenance, and repair of ships, boats, and other watercraft.

Greco-Roman world


According to the ancient Greek author Athenaeus of Naucratis (V 204c-d), the drydock was invented in Ptolemaic Egypt
Ptolemaic Egypt
Ptolemaic Egypt began when Ptolemy I Soter invaded Egypt and declared himself Pharaoh of Egypt in 305 BC and ended with the death of queen Cleopatra VII of Egypt and the Roman conquest in 30 BC. The Ptolemaic Kingdom was a powerful Hellenistic state, extending from southern Syria in the east, to...

, some time after the death of Ptolemy IV Philopator
Ptolemy IV Philopator
Ptolemy IV Philopator , son of Ptolemy III and Berenice II of Egypt was the fourth Pharaoh of Ptolemaic Egypt...

 (reigned 221-204 BC):
Since Athenaeus recorded the event 400 years later (around 200 AD), there is sufficient reason to believe that drydocks had been known throughout classical antiquity. The Roman shipyard at Narni
Roman shipyard of Stifone (Narni)
The Roman shipyard of Stifone is an archaeological find of Roman origin recently discovered in Umbria, in the municipality of Narni, inside an artificial channel adjacent the Nera River, about 900 metres down-river from the village of Stifone...

, Italy, which is still studied, may have served as a dry dock.

China


The use of drydocks in China goes at least as far back the 10th century A.D. In 1088, Song Dynasty
Song Dynasty
The Song Dynasty was a ruling dynasty in China between 960 and 1279; it succeeded the Five Dynasties and Ten Kingdoms Period, and was followed by the Yuan Dynasty. It was the first government in world history to issue banknotes or paper money, and the first Chinese government to establish a...

 scientist and statesman Shen Kuo
Shen Kuo
Shen Kuo or Shen Gua , style name Cunzhong and pseudonym Mengqi Weng , was a polymathic Chinese scientist and statesman of the Song Dynasty...

 (1031–1095) wrote in his Dream Pool Essays
Dream Pool Essays
The Dream Pool Essays was an extensive book written by the polymath Chinese scientist and statesman Shen Kuo by 1088 AD, during the Song Dynasty of China...

:

Renaissance Europe




The first early modern European and oldest surviving drydock still in use was commissioned by Henry VII of England
Henry VII of England
Henry VII was King of England and Lord of Ireland from his seizing the crown on 22 August 1485 until his death on 21 April 1509, as the first monarch of the House of Tudor....

 at HMNB Portsmouth
HMNB Portsmouth
Her Majesty's Naval Base Portsmouth is one of three operating bases in the United Kingdom for the British Royal Navy...

 in 1495 (see Tudor navy). This drydock currently holds the world's oldest commissioned warship, HMS Victory
HMS Victory
HMS Victory is a 104-gun first-rate ship of the line of the Royal Navy, laid down in 1759 and launched in 1765. She is most famous as Lord Nelson's flagship at the Battle of Trafalgar in 1805....

.

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 times


The Alfredo da Silva Dry Dock, of the Lisnave Dockyards in Almada
Almada
Almada is a municipality in Portugal, covering an area of 70.2 km² located on the southern margin of the Tagus River. Its municipal population in 2008 was 164,844 inhabitants; the urbanized center had a population of 102,357.The seat is the city of Almada....

, Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

, was the largest in the world until 2000, when it was closed after the moving of Lisnave operations to Setúbal
Setúbal
Setúbal is the main city in Setúbal Municipality in Portugal with a total area of 172.0 km² and a total population of 118,696 inhabitants in the municipality. The city proper has 89,303 inhabitants....

.

Currently, Harland and Wolff
Harland and Wolff
Harland and Wolff Heavy Industries is a Northern Irish heavy industrial company, specialising in shipbuilding and offshore construction, located in Belfast, Northern Ireland....

 Heavy Industries in Belfast
Belfast
Belfast is the capital of and largest city in Northern Ireland. By population, it is the 14th biggest city in the United Kingdom and second biggest on the island of Ireland . It is the seat of the devolved government and legislative Northern Ireland Assembly...

, Northern Ireland
Northern Ireland
Northern Ireland is one of the four countries of the United Kingdom. Situated in the north-east of the island of Ireland, it shares a border with the Republic of Ireland to the south and west...

, is the largest in the world. The massive cranes
Samson and Goliath (cranes)
Samson and Goliath are the twin shipbuilding gantry cranes situated at Queen's Island, Belfast, Northern Ireland. The cranes, which were named after the Biblical figures Samson and Goliath, dominate the Belfast skyline and are landmark structures of the city....

 are named after the Biblical figures Samson
Samson
Samson, Shimshon ; Shamshoun or Sampson is the third to last of the Judges of the ancient Israelites mentioned in the Tanakh ....

 and Goliath. Goliath stands 96m tall, while Samson is taller at 106m.

Northrop Grumman Newport News
Northrop Grumman Newport News
Newport News Shipbuilding , originally Newport News Shipbuilding and Drydock Company , was the largest privately-owned shipyard in the United States prior to being purchased by Northrop Grumman in 2001...

 Shipbuilding's Dry Dock 12 is the largest drydock in the USA. The Saint-Nazaire
Saint-Nazaire
Saint-Nazaire , is a commune in the Loire-Atlantique department in western France.The town has a major harbour, on the right bank of the Loire River estuary, near the Atlantic Ocean. The town is at the south of the second-largest swamp in France, called "la Brière"...

's Chantiers de l'Atlantique
Chantiers de l'Atlantique
Chantiers de l'Atlantique is part of the South Korean STX Shipbuilding Group and one of the world's largest shipyards, based in Saint-Nazaire, France...

 owns one of the biggest in the world: 1200 by 60 m (3,937 by 196.9 ). The largest graving dock of the Mediterranean as of 2009 is at the Hellenic Shipyards S.A. (HSY S.A., Athens, Greece)http://www.hellenic-shipyards.gr/pg/repairs.htm. The by far largest roofed dry dock is at the German Meyer Werft
Meyer Werft
The Meyer Werft is one of the remaining large German shipyards, headquartered in Papenburg. Since 1997, it has been part of the Meyer Neptun Group together with Neptun Werft in Rostock.-History:...

 Shipyard in Papenburg
Papenburg
Papenburg is a city in the district of Emsland in Lower Saxony, Germany, situated at the river Ems. It is known for its large shipyard, the Meyer-Werft, which specializes in building cruise liners.-Districts:...

, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

, it is 504m long, 125m wide and stands 75m tall.

Types



Graving


The classic form of drydock, properly known as graving dock, is a narrow basin, usually made of earthen berms and concrete, closed by gates or by a caisson
Caisson (engineering)
In geotechnical engineering, a caisson is a retaining, watertight structure used, for example, to work on the foundations of a bridge pier, for the construction of a concrete dam, or for the repair of ships. These are constructed such that the water can be pumped out, keeping the working...

, into which a vessel may be floated and the water pumped out, leaving the vessel 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. More routine use of drydocks is for the cleaning (removal of barnacles and rust) and re-painting of ship's hulls.

Some fine-tuning of the ship's position can be done by diver
Scuba diving
Scuba diving is a form of underwater diving in which a diver uses a scuba set to breathe underwater....

s 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
Anti-submarine warfare is a branch of naval warfare that uses surface warships, aircraft, or other submarines to find, track and deter, damage or destroy enemy submarines....

 warships have protruding sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

 domes, requiring that the hull of the ship be supported several metres from 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, water is allowed to re-enter the dry dock and the ship is carefully refloated.

Modern graving docks are box-shaped, to accommodate the newer, boxier ship designs, whereas old drydocks 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.

Drydocks used for building Navy vessels may occasionally be built with a roof. This is done to prevent spy satellite
Spy satellite
A spy satellite is an Earth observation satellite or communications satellite deployed for military or intelligence applications....

s from taking pictures of the drydock and any ships or submarines that may be in it. During World War II, fortified drydocks were used by the Germans to protect their submarine
Submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

s from Allied air raids (see submarine pen
Submarine pen
A submarine pen is a bunker which is designed to protect submarines from air attack.The term is generally applied to submarine bases constructed during World War II, particularly in Germany and the occupied countries which were also known as U-boat pens .-Background:Amongst the first...

); however, their effectiveness in that role diminished towards the end of the war as bombs became available that could penetrate them. Today, covered drydocks are usually used only when servicing or repairing a fleet ballistic missile submarine
Ballistic missile submarine
A ballistic missile submarine is a submarine equipped to launch ballistic missiles .-Description:Ballistic missile submarines are larger than any other type of submarine, in order to accommodate SLBMs such as the Russian R-29 or the American Trident...

. Another advantage of covered drydocks is that work can take place independently of the 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 drydock is a type of pontoon
Pontoon
Pontoon may refer to:* Float , an air-filled structure providing buoyancy* Pontoon , the Australian/Malaysian casino game* Pontoon , a chiefly British version of the card game blackjack...

 for dry docking ships, possessing floodable
Semi-submersible
A semi-submersible is a specialised marine vessel with good stability and seakeeping characteristics. The semi-submersible vessel design is commonly used in a number of specific offshore roles such as for offshore drilling rigs, safety vessels, oil production platforms and heavy lift cranes.The...

 buoyancy
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...

 chambers and a "U" shaped cross-section. The walls are used to give the drydock stability when the floor or deck is below the surface of the water. When valve
Valve
A valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but are usually discussed as a separate category...

s are opened, the chambers fill with water, causing the drydock 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 drydock rises and the ship is lifted out of the water on the rising deck, allowing work to proceed on the ship's hull.

A typical floating drydock 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
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...

 section can facilitate the towing of the drydock once assembled. For smaller boats, one-piece floating drydocks can be constructed, potentially coming with their own bow and steering mechanism.

Shipyards operate floating drydocks as one method for hauling or docking vessels. The advantage of floating drydocks is they can be moved to wherever they are needed and can also be sold second-hand. During World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, the U.S. Navy used such (floating) drydocks extensively to provide maintenance in remote locations. One of these, the 850-foot AFDB-3, an Advance Base Sectional Dock, saw action in Guam
Guam
Guam is an organized, unincorporated territory of the United States located in the western Pacific Ocean. It is one of five U.S. territories with an established civilian government. Guam is listed as one of 16 Non-Self-Governing Territories by the Special Committee on Decolonization of the United...

, was mothballed near Norfolk
Norfolk, Virginia
Norfolk is an independent city in the Commonwealth of Virginia in the United States. With a population of 242,803 as of the 2010 Census, it is Virginia's second-largest city behind neighboring Virginia Beach....

, Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...

, and was eventually towed to Portland
Portland, Maine
Portland is the largest city in Maine and is the county seat of Cumberland County. The 2010 city population was 66,194, growing 3 percent since the census of 2000...

, Maine
Maine
Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost...

, to become part of Bath Iron Works
Bath Iron Works
Bath Iron Works is a major American shipyard located on the Kennebec River in Bath, Maine, United States. Since its founding in 1884 , BIW has built private, commercial and military vessels, most of which have been ordered by the United States Navy...

' repair facilities.

The "Hughes Mining Barge
Hughes Mining Barge
The Hughes Mining Barge, or HMB-1, is a submersible barge about 99 m long, 32 m wide, and more than 27 m tall...

", 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
Stealth ship
A stealth ship is a ship which employs stealth technology construction techniques in an effort to ensure that it is harder to detect by one or more of radar, visual, sonar, and infrared methods...

.

Alternative drydock systems


Apart from graving docks and floating drydocks, ships can also be drydocked and launched by:
  • Marine railway — For repair of larger ships up to about 3000 tons ship weight
  • Mobile boatlift (also called Travelift, for vessels up to 1000 metric tons
  • Shiplift
    Shiplift
    A shiplift is a modern alternative for a slipway, a floating dry dock or a graving dry dock. A shiplift is used to dry dock and launch ships. It consists of a structural platform that is lifted and lowered exactly vertical, synchronously by a number of hoists...

     — For repair as well as for newbuilding. From 800 to 25000 ton shipweight
  • Slipway
    Slipway
    A slipway, boat slip or just a slip, 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. They are also used for launching and retrieving small boats on trailers and flying boats on their undercarriage. The...

    , patent slip
    Patent slip
    The patent slip or Marine Railway was invented by Scot Thomas Morton in 1818 as a cheaper alternative to a dry dock for ship repair. It consisted of an inclined plane, which extended well into the water, and a wooden cradle onto which a ship was floated...

     — For repair of smaller boats and the newbuilding launch of larger vessels

Uses other than for ships


Some drydocks are used during the construction of bridges, dams, and other large objects. For example, the drydock on the artificial island of Neeltje-Jans
Neeltje-Jans
Neeltje Jans is an artificial island in the Netherlands in the province of Zeeland, halfway between Noord-Beveland and Schouwen-Duiveland in the Oosterschelde. It was constructed to facilitate the construction of the Oosterscheldedam. The island was named after a nearby sand bar....

 was used for the construction of the Oosterscheldekering
Oosterscheldekering
The Oosterscheldekering , between the islands Schouwen-Duiveland and Noord-Beveland, is the largest of the 13 ambitious Delta works series of dams, designed to protect the Netherlands from flooding...

, a large dam in the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

 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.

They may also be used for the prefabrication of the elements of an immersed tube
Immersed tube
An immersed tube is a kind of underwater tunnel composed of segments, constructed elsewhere and floated to the tunnel site to be sunk into place and then linked together. They are commonly used for road and rail crossings of rivers, estuaries and sea channels/harbours...

 tunnel, before they are floated into position.

See also

  • Semi-submersible
    Semi-submersible
    A semi-submersible is a specialised marine vessel with good stability and seakeeping characteristics. The semi-submersible vessel design is commonly used in a number of specific offshore roles such as for offshore drilling rigs, safety vessels, oil production platforms and heavy lift cranes.The...

  • Space dock
  • St. Nazaire Raid
    St. Nazaire Raid
    The St Nazaire Raid or Operation Chariot was a successful British amphibious attack on the heavily defended Normandie dry dock at St Nazaire in German-occupied France during the Second World War. The operation was undertaken by the Royal Navy and British Commandos under the auspices of Combined...

     — an attack on a drydock during World War II
    World War II
    World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

    .

External links