Capsizing or keeling over occurs when a

boat A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size, shape, cargo or passenger capacity, or its ability to carry boats. Small boats are typically found on i ...

ship A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished ...

is rolled on its side or further by wave action, instability or wind force beyond the angle of positive static stability or it is upside down in the water. The act of recovering a vessel from a capsize is called righting. Capsize may result from

broaching The BROACH warhead is a multi-stage warhead developed by Team BROACH; BAE Systems Global Combat Systems Munitions, Thales Missile Electronics and QinetiQ. BROACH stands for ''Bomb Royal Ordnance Augmented CHarge''. Development of BROACH began ...

, , loss of stability due to cargo shifting or flooding, or in high speed boats, from turning too fast. If a capsized vessel has enough flotation to prevent sinking, it may recover on its own in changing conditions or through mechanical work if it is not

stable A stable is a building in which livestock, especially horses, are kept. It most commonly means a building that is divided into separate stalls for individual animals and livestock. There are many different types of stables in use today; the ...

inverted. Vessels of this design are called self-righting.

Small vessels

dinghy A dinghy is a type of small boat, often carried or towed by a larger vessel for use as a tender. Utility dinghies are usually rowboats or have an outboard motor. Some are rigged for sailing but they differ from sailing dinghies, whic ...

sailing, a practical distinction can be made between being knocked down (to 90 degrees; on its beam-ends, figuratively) which is called a capsize, and being inverted, which is called being turtled. Small dinghies frequently capsize in the normal course of use and can usually be recovered by the crew. Some types of dinghy are occasionally deliberately capsized, as capsizing and righting the vessel again can be the fastest means of draining water from the boat. Capsizing (but not necessarily turtling) is an inherent part of dinghy sailing. It is not a question of "if" but a question of "when". For those who do not want the experience, a

keelboat A keelboat is a riverine cargo-capable working boat, or a small- to mid-sized recreational sailing yacht. The boats in the first category have shallow structural keels, and are nearly flat-bottomed and often used leeboards if forced in open w ...

monohull right A monohull is a type of boat having only one hull, unlike multihulled boats which can have two or more individual hulls connected to one another. Fundamental concept Among the earliest hulls were simple logs, but these were generally unsta ...

has physics on its side. But even yachts can capsize and turtle in extraordinary conditions, so design considerations are important. Such events can overcome skill and experience; boats need to be appropriate for foreseeable conditions. Kayak roll

A capsized

kayak A kayak is a small, narrow watercraft which is typically propelled by means of a double-bladed paddle. The word kayak originates from the Greenlandic word '' qajaq'' (). The traditional kayak has a covered deck and one or more cockpits, each s ...

may be righted with a roll or eskimo rescue. As long as the kayaker knows how to react, the water is not too shallow, and the location is not close to dangers that require evasive action by the kayaker – which cannot be taken while capsized – capsizing itself is usually not considered dangerous. In

whitewater kayaking Whitewater kayaking is an adventure sport where a river is navigated in a decked kayak. Whitewater kayaking includes several styles. River running; where the paddler follows a river and paddles rapids as they travel. Creeking usually involving s ...

, capsizing occurs frequently and is accepted as an ordinary part of the sport. Kayak rolling, in which paddlers intentionally capsize and right themselves (in synchrony, as many times as possible in a given interval, or in as many different ways as possible) is also a competitive sport, especially in Greenland. Sailing vessels' "capsize ratio" is commonly published as a guideline for zones of safe operation — less than 2.0 means as a rule-of-thumb suitability for offshore navigation. However its crude nature of displacement divided by a vessel's beam (breadth) (albeit with a constant multiplied to provide an average assessment), means thorough assessment of ship stability, immersibility and buoyancy involves other factors to address the relevant risks posed by waves, tides, weather and occurrences such as damage and collision.

Large vessels

In a storm, even large vessels may be rolled by being hit broadside by a large wave or swell or "pitch poled"

stem Stem or STEM may refer to: Plant structures * Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang * Stipe (botany), a stalk to support some other structure * Stipe (mycology), the stem of a mushro ...

over

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. Or ...

in extreme

waves Waves most often refers to: * Waves, oscillations accompanied by a transfer of energy that travel through space or mass. * Wind waves, surface waves that occur on the free surface of bodies of water. Waves may also refer to: Music *Waves (ban ...

. This is normally catastrophic for larger ships, and smaller yachts can be dismasted (i.e., lose their masts and

rigging Rigging comprises the system of ropes, cables and chains, which support a sailing ship or sail boat's masts—''standing rigging'', including shrouds and stays—and which adjust the position of the vessel's sails and spars to which they ar ...

) due to the drag as the boat is forced to roll over. A ship that sustains a hole or crack ('is holed') may capsize. This is the working of

torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, ...

and

naval mine A naval mine is a self-contained explosive device placed in water to damage or destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, an ...

warfare. In 2012 the very large

cruise ship Cruise ships are large passenger ships used mainly for vacationing. Unlike ocean liners, which are used for transport, cruise ships typically embark on round-trip voyages to various ports-of-call, where passengers may go on tours known as ...

' was holed and lost her propulsion by a mapped rock near the shallows, and drifted further where she partially sank, resting towards one side with most of her structure out of the water. This was not a capsize as her bottom was only partly exposed; rather this was a partial sinking. Fixing a hole is called plugging. Otherwise a vessel in largely upright position which capsizes has suffered too much water to enter in places normally above the waterline, and which may be caused by poor manoeuvering, overloading (see Plimsoll Line) or poor weather. As for holes, bailing may be carried out – removal of water aboard such as with a

bilge pump A bilge pump is a water pump used to remove bilge water. Since fuel can be present in the bilge, electric bilge pumps are designed to not cause sparks. Electric bilge pumps are often fitted with float switches which turn on the pump when the bilge ...

, self or hand bailer or buckets. At the stage of sinking where its buoyancy is deemed critical, the ship is unlikely to upright nor able to right itself such that stability and safety will be compromised even if the vessel is righted — a decision is made to abandon ship and any ultimate salvage may entail firm grounding and re-buoyancy pumps. Among ship types, a roll-on-roll-off (RORO or ro-ro) ship is more prone to capsizing as it has large open car decks near the

waterline The waterline is the line where the hull of a ship meets the surface of the water. Specifically, it is also the name of a special marking, also known as an international load line, Plimsoll line and water line (positioned amidships), that indi ...

. If the watertight car-deck doors fail through damage or mismanagement (as in the partial sinking of where the doors were accidentally left open, and as in one of the largest peacetime maritime disasters when

MS Estonia MS ''Estonia'' was a cruiseferry built in 1980 at the West German shipyard Meyer Werft in Papenburg. In 1993, she was sold to Nordström & Thulin for use on Estline's Tallinn–Stockholm route. The ship's sinking on 28 September 1994, in the Ba ...

sank off of the

Archipelago Sea The Archipelago Sea ( fi, Saaristomeri, sv, Skärgårdshavet) is a part of the Baltic Sea between the Gulf of Bothnia, the Gulf of Finland and the Sea of Åland, within Finnish territorial waters. By some definitions it contains the largest ...

in Finland), water entering the car-deck is subject to the free surface effect and may cause a capsize. As a RORO ferry rolls, vehicles can break free and slide down if not firmly secured, adversely altering the ship's

centre of gravity In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force may ...

, accelerating the roll, and possibly turning an otherwise recoverable roll into a capsize.

Competition

In competitive

yacht racing Yacht racing is a sailing sport involving sailing yachts and larger sailboats, as distinguished from dinghy racing, which involves open boats. It is composed of multiple yachts, in direct competition, racing around a course marked by buoys or ...

, a capsized boat has certain special rights as it cannot maneuver. A boat is deemed capsized when the mast is touching the water; when it is fully inverted, it is said to have turned turtle or turtled. Good racers can often recover from a capsize with minimal loss of time. The capsize can result from extreme

, especially if the

keel The keel is the bottom-most longitudinal structural element on a vessel. On some sailboats, it may have a hydrodynamic and counterbalancing purpose, as well. As the laying down of the keel is the initial step in the construction of a ship, in Br ...

has insufficient leverage to tilt the vessel upright. Motorlife boats are designed to be self-righting if capsized, but most other motorboats are not.

Training

Intermediate sailors are encouraged to capsize their dinghies in a safe location with supervision at least once to become acquainted with their boat's floating properties and the capsize process. The boat is then righted, bailed out, and the sails reset, so that in the event of an uncontrolled capsize, the boat and its occupants are familiar with the procedure and may recover. Most small monohull sailboats can normally be righted by standing or pulling down on the centreboard,

daggerboard A daggerboard is a retractable centreboard used by various sailing craft. While other types of centreboard may pivot to retract, a daggerboard slides in a casing. The shape of the daggerboard converts the forward motion into a windward lift, co ...

(or bilgeboard in a

scow A scow is a smaller type of barge. Some scows are rigged as sailing scows. In the 19th and early 20th centuries, scows carried cargo in coastal waters and inland waterways, having an advantage for navigating shallow water or small harbours. S ...

) to lift the mast clear of the water. Depending on the design of the

hull Hull may refer to: Structures * Chassis, of an armored fighting vehicle * Fuselage, of an aircraft * Hull (botany), the outer covering of seeds * Hull (watercraft), the body or frame of a ship * Submarine hull Mathematics * Affine hull, in affi ...

, the boat's righting moment will normally take effect once the mast is around 30 degrees from horizontal and help pull the boat vertical. Righting a catamaran that is lying on its side involves using a righting line fed over the upper hull. The crew stands on the lower hull and pulls back on the righting line. In small

catamaran A Formula 16 beachable catamaran Powered catamaran passenger ferry at Salem, Massachusetts, United States A catamaran () (informally, a "cat") is a multi-hulled watercraft featuring two parallel hulls of equal size. It is a geometry-sta ...

s such as the

Hobie 16 The ISAF International Class Hobie 16 (H16) is a popular catamaran manufactured by the Hobie Cat Company for racing and day sailing. The craft was the driving force behind the popularization of beachcats and was recently inducted into the Sai ...

it is imperative that at least one crew member assumes this task as soon as possible as there is a chance that the boat will

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked t ...

and then become extremely difficult to recover without assistance. Some monohulls and catamarans use a small flotation device mounted at the tip of the mast or mainsail to ensure that the craft cannot assume an inverted position, or at least that a fully inverted position is not stable (i.e. it would come to a position where the mast is lying on the surface of the water, which would be preferable to fully inverted). In both cases, having a crew member lift the end of the mast out of the water may help speed the process, as the greatest challenge of righting a capsized boat is shedding the weight of the water from the sails. A helpful step, where possible (on a loose footed sail), is to disconnect the clew of the sail from the boom, which prevents the sail from scooping up water as the sail lifts out of the water. The bow of the capsized vessel should be pointed towards the wind so that when the sail starts to lift out of the water the wind can catch underneath the sail and help right the boat. Care is taken not to let the boat swing all the way over and capsize on the other side, frequently with the crew on the bottom. This is more likely if the boat is not pointed into the wind.

Prevention

There is a wide range of technology that can be installed or strategically placed to prevent or deter a boat or ship from capsizing. The various technologies rely on inflating airbags also known as lift bags which increasing the vessel's

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 ...

with the water. There are many steps a crew can take to reduce the chance of capsizing, such as distributing the weight evenly and taking care during windy weather.

Yachts

Capsizing in yachts can occur when water is able to infiltrate the hull and decrease the vessels water and buoyancy leading to capsizing. Yachts can be deployed with a flotation system which is a series of strategically placed lift bags within the interior of the hull increasing the vessel's buoyancy and filling void space where water can collect, providing valuable time to remove the water, fix damage or evacuate.

Large ships

When larger ships such as cargo ships and tankers capsize or sink not only is recovery not possible but great environment damage can occur from spillage of cargo. Larger ships are being equipped with Surfacing System for Ship Recovery which is an inflatable device that is installed in the

ballast Ballast is material that is used to provide stability to a vehicle or structure. Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within a boat, ship ...

water tank or within the hull of the vessel and can be deployed within seconds of an accident to stabilize the vessel and give more time for rescue and evacuation.

Self-righting

File:Coast Guard response boat-small DVIDS1076833.jpg, A crane capsizes a small coast guard vessel to test its righting ability File:Eiswette(II) 20080627 Kentertest diff.gif, A larger self-righting vessel's stability test. Note large deckhouse, which is almost the only part submerged when fully inverted. File:Northumberland model lifeboat.JPG, The Beeching- Peake SR (self-righting) lifeboat won an 1851 competition for improved lifeboat design. Drawings show large, high buoyancy tanks, and ballast. File:RNLI Chatham Lizzie Porter Holy Island 8352.JPG, The ''Lizzie Porter'' is a Peake-class lifeboat, an early design of self-righting boat. Note the high, rounded buoyancy tanks at her bow and stern, and low sides amidships. A vessel may be designated as "self-righting" if it is designed to be able to capsize then return to upright without intervention (with or without crew on board). The angle of vanishing stability, the angle of

heel The heel is the prominence at the posterior end of the foot. It is based on the projection of one bone, the calcaneus or heel bone, behind the articulation of the bones of the lower leg. Structure To distribute the compressive forces exer ...

at which a vessel becomes unstable and does not bob back upright, does not exist; a self-righting boat will return to upright from any position, including completely upside-down. A self-righting vessel must be positively buoyant when swamped. There are three methods of making a vessel self-right: careful distribution of stationary weight and buoyancy, inflatable airbags, and movable ballast. A basic tool for calculating a vessel's stability is a static stability diagram, which plots the angle of

on the horizontal axis and the righting lever (GZ) on the vertical axis. (see metacentric height for details). If the static stability curve never crosses the x-axis, the boat is not stable upside-down. This is not sufficient to built a boat with good stability at sea, as it neglects the effects of wind, waves, and human occupants, but it is a simple, powerful way to analyze the stability of a vessel. See also primary stability and secondary stability. Self-righting through distribution of weight and buoyancy requires the weight low-down, and the buoyancy high up. It is often accomplished with a self-sealing superstructure, such as the large deckhouses on modern rescue boats. Most small craft intended as lifeboats with rigid (rather than inflatable) hulls designed since about the middle of the twentieth century are self-righting. Small radio-controlled boats may also self-right. This is particularly useful for racing.

Notable capsizings

Tromsö, Royal Air Force Bomber Command, 1942-1945 CL2830

* , 19 July 1545, capsized and sank, English carrack, 380 dead * , 10 August 1628, Swedish warship, maiden voyage, 30 –50 dead * RMS ''Empress of Ireland'', 19 May 1914, capsized and sank in the

Saint Lawrence River The St. Lawrence River (french: Fleuve Saint-Laurent, ) is a large river in the middle latitudes of North America. Its headwaters begin flowing from Lake Ontario in a (roughly) northeasterly direction, into the Gulf of St. Lawrence, connecting ...

after colliding with the Norwegian collier ''Storstad'', 1,012 dead * , 1915, excursion boat, 845 dead, greatest loss of life on the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lakes ...

* , 1915, German armoured cruiser, sunk at the Battle of Dogger Bank (1915), 770 dead * , 1918, Austro-Hungarian capital warship,

ed, 89 dead * Scuttling of the German fleet at Scapa Flow, 21 June 1919, several German battleships and battlecruisers scuttled * , 7 December 1941, U.S. battleship torpedoed at

Pearl Harbor Pearl Harbor is an American lagoon harbor on the island of Oahu, Hawaii, west of Honolulu. It was often visited by the Naval fleet of the United States, before it was acquired from the Hawaiian Kingdom by the U.S. with the signing of the ...

, 415 missing or killed * , formerly , 9 February 1942, at dock while being converted to a

troopship A troopship (also troop ship or troop transport or trooper) is a ship used to carry soldiers, either in peacetime or wartime. Troopships were often drafted from commercial shipping fleets, and were unable land troops directly on shore, typicall ...

, one casualty * , 24 August 1942, sunk by American air attacks, 120 casualties * , 15 November 1942, 212 casualties * , 24 October 1944, sunk during the Battle of Sibuyan Sea, 1,023 casualties * , 25 October 1944, sunk during the Battle of Surigao Strait, approximately 1890 casualties * , 25 October 1944, sunk during the Battle of Surigao Strait, 1,626 casualties * , 27 May 1941, Sunk after sinking HMS Hood, over 2000 casualties *

HMS Barham (04) HMS ''Barham'' was one of five s built for the Royal Navy during the early 1910s. Completed in 1915, she was often used as a flagship and participated in the Battle of Jutland during the First World War as part of the Grand Fleet. For the rest ...

, on the 25th of November, 1941, torpedoed four times and rolled over to port within 4 minutes before exploding, 862 dead. * , 12 November 1944, sunk by Royal Air Force bombers, over 1,000 casualties * , 29 November 1944, sunk by American submarine , 1,435 casualties * , 7 April 1945, 2,475 dead * HMS Prince of Wales (53), 10 December 1941, Attacked and sunk by enemy Japanese aircraft, 328 dead * HMS Repulse (1916), 10 December 1941, Attacked and sunk by Japanese aircraft, 517 dead *

HMS Royal Oak (08) HMS ''Royal Oak'' was one of five s built for the Royal Navy during the First World War. Completed in 1916, the ship first saw combat at the Battle of Jutland as part of the Grand Fleet. In peacetime, she served in the Atlantic, Home and Medi ...

, 14 October 1939, Torpedoed and sunk by German U-Boat U-47 (1938), 835 dead * , 29 October 1955, 608 dead * , 25 July 1956, killing 46 passengers at the area of the impact with the * HMS Coventry, 25 May 1982, killing 19 sailors, sunk by 3 1000 lbs bombs dropped from Argentine A-4 Skyhawks * , 6 March 1987, bow door left open, killing 193 passengers * , 14 January 1993, leaving 54 people dead * , 28 September 1994, killing 852 passengers * , 26 September 2000, 82 dead * , 26 September 2002, Senegalese ferry, at least 1,863 dead * , 19 January 2004, Dutch rock discharge vessel, capsized south of

Bergen, Norway Bergen (), historically Bjørgvin, is a city and municipality in Vestland county on the west coast of Norway. , its population is roughly 285,900. Bergen is the second-largest city in Norway. The municipality covers and is on the peninsula o ...

, killing 18 of 30 crew''

Blueprint for Disaster ''Blueprint for Disaster'' is a Canadian documentary television series that premiered in 2004 on Discovery Channel Canada. Produced by Temple Street Productions, the program investigates why and how various disasters have happened. Toronto-base ...

''. Season 2. Episode 3. * , 3 February 2006, resulting in an estimated 1,020 dead * , 30 June 2009, which sails to offshore oil and gas platforms capsized off the coast of

Qatar Qatar (, ; ar, قطر, Qaṭar ; local vernacular pronunciation: ), officially the State of Qatar,) is a country in Western Asia. It occupies the Qatar Peninsula on the northeastern coast of the Arabian Peninsula in the Middle East; it sh ...

i capital city of

Doha Doha ( ar, الدوحة, ad-Dawḥa or ''ad-Dōḥa'') is the capital city and main financial hub of Qatar. Located on the Persian Gulf coast in the east of the country, north of Al Wakrah and south of Al Khor (city), Al Khor, it is home to m ...

* , 13 January 2012, ran aground off the island of Giglio, western Italy, with about 4,200 aboard, all except 32 saved * , 16 April 2014, approximately three kilometres off Gwanmae Island,

South Jeolla Province South Jeolla Province (; ''Jeollanam-do''; ), also known as Jeonnam, is a province of South Korea. South Jeolla has a population of 1,902,324 (2014) and has a geographic area of located in the Honam region at the southwestern tip of the Korean ...

, South Korea, with over 450 people on board, 304 dead, 172 survivors. *'' Dongfang Zhi Xing'', 1 June 2015, large vessel capsized and sank cruising the

Yangtze River The Yangtze or Yangzi ( or ; ) is the longest river in Asia, the third-longest in the world, and the longest in the world to flow entirely within one country. It rises at Jari Hill in the Tanggula Mountains (Tibetan Plateau) and flows ...

in Jianli,

Hubei Hubei (; ; alternately Hupeh) is a landlocked province of the People's Republic of China, and is part of the Central China region. The name of the province means "north of the lake", referring to its position north of Dongting Lake. The p ...

: thunderstorm

downburst In meteorology, a downburst is a strong downward and outward gushing wind system that emanates from a point source above and blows radially, that is, in straight lines in all directions from the area of impact at surface level. Capable of pro ...

with high winds, with 442 dead and 12 survivors * , 18 June 2018, at Lake Toba,

North Sumatra North Sumatra ( id, Sumatra Utara) is a province of Indonesia located on the northern part of the island of Sumatra. Its capital and largest city is Medan. North Sumatra is Indonesia's fourth most populous province after West Java, East Java and ...

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Gui ...

, 3 known dead and 164 presumed so; 23 known survivors. Overloaded and improper three-deck use/design caused high uprighting moment (

). * MV ''Phoenix'', 5 July 2018, hit fellow tourist boat ''MV Serenita''; both capsized and sank in a sudden storm near

Phuket Phuket (; th, ภูเก็ต, , ms, Bukit or ''Tongkah''; Hokkien:普吉; ) is one of the southern provinces (''changwat'') of Thailand. It consists of the island of Phuket, the country's largest island, and another 32 smaller islands o ...

Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...

. Double-decker: 41 dead and 15 missing, 49 survivors; smaller boat carried 42 passengers, all saved. * MV ''Nyerere'', 20 September 2018, ferry shuttling people and cargo on

Lake Victoria Lake Victoria is one of the African Great Lakes. With a surface area of approximately , Lake Victoria is Africa's largest lake by area, the world's largest tropical lake, and the world's second-largest fresh water lake by surface area after ...

, Tanzania due to pilot distraction when docking, a sharp turn and overloading. 227 known dead, passenger log lost, tens survived. * MV ''Golden Ray'', 8 September 2019, automobile carrier in St Simons Sound off the US state of Georgia, improperly ballasted and heeled over during sharp turn. All 23 crewmembers and the harbor pilot were rescued. *, 5 August 2020, at

Beirut Beirut, french: Beyrouth is the capital and largest city of Lebanon. , Greater Beirut has a population of 2.5 million, which makes it the third-largest city in the Levant region. The city is situated on a peninsula at the midpoint o ...

as a result of nearby 4 August ammonium nitrate explosion.

References

External links

Capsize formula for displacement sailboats
* * * * {{Authority control Nautical terminology Maritime disasters