Nomenclature
Ships are typically larger than boats, but there is no universally accepted distinction between the two. Ships generally can remain at sea for longer periods of time than boats. A legal definition of ship fromHistory
Prehistory and antiquity
Asian developments
The earliest attestations of ships inMediterranean developments
Archaeological evidence in14th through the 18th centuries
Asian developments
At this time, ships were developing in Asia in much the same way as Europe. Japan used defensive naval techniques in the Mongol invasions of Japan in 1281. It is likely that the Mongols of the time took advantage of both European and Asian shipbuilding techniques. During the 15th century, China's Ming dynasty assembled one of the largest and most powerful naval fleets in the world for the Ming treasure voyages, diplomatic and power projection voyages of Zheng He. Elsewhere in Japan in the 15th century, one of the world's first iron-clads, "Tekkōsen" (:ja:鉄甲船, 鉄甲船), literally meaning "iron ships", was also developed. In Japan, during the Sengoku era from the 15th century to 17th century, the great struggle for feudal supremacy was fought, in part, by coastal fleets of several hundred boats, including the atakebune. In Korea, in the early 15th century during the Joseon era, "Turtle ship, Geobukseon"(거북선), was developed. The empire of Majapahit used large ships called Jong (ship), jong, built in northern Java, for transporting troops overseas. The jongs were transport ships which could carry 100–2000 tons of cargo and 50–1000 people, 28.99–88.56 meter in length. The exact number of jong fielded by Majapahit is unknown, but the largest number of jong deployed in an expedition is about 400 jongs, when Majapahit attacked Pasai, in 1350.Hill (June 1960). "iarchive:hikayat-raja-raja-pasai/page/2/mode/2up, Hikayat Raja-Raja Pasai". ''Journal of the Malaysian Branch of the Royal Asiatic Society''. 33: p. 98 and 157: "Then he directed them to make ready all the equipment and munitions of war needed for an attack on the land of Pasai – about four hundred of the largest junks, and also many barges (malangbang) and galleys." See also Nugroho (2011). p. 270 and 286, quoting ''Hikayat Raja-Raja Pasai'', 3: 98: "''Sa-telah itu, maka di-suroh baginda musta'idkan segala kelengkapan dan segala alat senjata peperangan akan mendatangi negeri Pasai itu, sa-kira-kira empat ratus jong yang besar-besar dan lain daripada itu banyak lagi daripada malangbang dan kelulus''." (After that, he is tasked by His Majesty to ready all the equipment and all weapons of war to come to that country of Pasai, about four hundred large jongs and other than that much more of malangbang and kelulus.)European developments
Several civilizations became sea powers. Such examples include the maritime republics of Republic of Genoa, Genoa and Republic of Venice, Venice, Hanseatic League, and the Byzantine navy. The Vikings used their knarrs to explore North America, trade in the Baltic Sea and plunder many of the coastal regions of Western Europe. Towards the end of the 14th century, ships like the carrack began to develop towers on the bow and stern. These towers decreased the vessel's stability, and in the 15th century, the caravel, designed by the Portugal, Portuguese, based on the Arabic ''qarib'' which could sail closer to the wind, became more widely used. The towers were gradually replaced by the forecastle and sterncastle, as in the carrack Santa María (ship), ''Santa María'' of Christopher Columbus. This increased freeboard (nautical), freeboard allowed another innovation: the Scupper, freeing port, and the artillery associated with it. The carrack and then the caravel were developed in Portugal. After Columbus, Age of Discovery, European exploration rapidly accelerated, and many new trade routes were established. In 1498, by reaching India, Vasco da Gama proved that access to theSpecialization and modernization
Parallel to the development of warships, ships in service of marine fishery and trade also developed in the period between antiquity and the Renaissance. Maritime trade was driven by the development of shipping companies with significant financial resources. Canal barges, towed by draft animals on an adjacent towpath, contended with the railway up to and past the early days of the industrial revolution. Flat-bottomed and flexible scow boats also became widely used for transporting small cargoes. Mercantile trade went hand-in-hand with exploration, self-financed by the commercial benefits of exploration. During the first half of the 18th century, the French Navy began to develop a new type of vessel known as a ship of the line, featuring seventy-four guns. This type of ship became the backbone of all European fighting fleets. These ships were long and their construction required 2,800 oak trees and of rope; they carried a crew of about 800 sailors and soldiers. During the 19th century the Royal Navy enforced a ban on the slave trade, acted to suppress piracy, and continued to map the world. A clipper was a very fast sailing ship of the 19th century. The clipper routes fell into commercial disuse with the introduction of steamboat, steam ships with better fuel efficiency, and the opening of the Suez Canal, Suez and Panama Canals. Ship designs stayed fairly unchanged until the late 19th century. The industrial revolution, new mechanical methods of propulsion, and the ability to construct ships from metal triggered an explosion in ship design. Factors including the quest for more efficient ships, the end of long running and wasteful maritime conflicts, and the increased financial capacity of industrial powers created an avalanche of more specialized boats and ships. Ships built for entirely new functions, such as firefighting, rescue, and research, also began to appear.21st century
In 2019, the world's fleet included 51,684 commercial vessels with gross tonnage of more than 1,000 ton (volume), tons, totaling 1.96 billion tons. Such ships carried 11 billion tons of cargo in 2018, a sum that grew by 2.7% over the previous year. In terms of tonnage, 29% of ships were tanker (ship), tankers, 43% areTypes of ships
Because ships are constructed using the principles of naval architecture that require same structural components, their classification is based on their function such as that suggested by Paulet and Presles, which requires modification of the components. The categories accepted in general by naval architects are: * High-speed craft – Multihulls including wave piercers, small-waterplane-area twin hull (SWATH), surface effect ships and hovercraft, hydrofoil, Ground effect (aircraft), wing in ground effect craft (WIG). * Offshore drilling, Off shore oil vessels – Platform supply vessel, pipe layers, accommodation and Crane vessel, crane barges, non and semi-submersible drilling rigs, Oil platform, production platforms, floating production storage and offloading units. * Fishing vessels ** Motorised fishing trawlers, fish traps, trap setters, Seine fishing, seiners, Longline fishing, longliners, Trolling (fishing), trollers & factory ships. ** Traditional Sailboat, sailing and Watercraft rowing, rowed fishing vessels andInland vessels
Freshwater shipping may occur on lakes, rivers and canals. Ships designed for those body of waters may be specially adapted to the widths and depths of specific waterways. Examples of freshwater waterways that are navigable in part by large vessels include the Danube, Mississippi River, Mississippi, Rhine River, Rhine, Yangtze and Amazon River, Amazon Rivers, and the Great Lakes.Great Lakes
Lake freighters, also called lakers, are cargo vessels that ply the Great Lakes. The most well-known is , the latest major vessel to be wrecked on the Lakes. These vessels are traditionally called boats, not ships. Visiting ocean-going vessels are called "salties". Because of their additional Beam (nautical), beam, very large salties are never seen inland of the Saint Lawrence Seaway. Because the smallest of the Soo Locks is larger than any Seaway lock, salties that can pass through the Seaway may travel anywhere in the Great Lakes. Because of their deeper draft, salties may accept partial loads on the Great Lakes, "topping off" when they have exited the Seaway. Similarly, the largest lakers are confined to the Upper Lakes (Lake Superior, Superior, Lake Michigan, Michigan, Lake Huron, Huron, Lake Erie, Erie) because they are too large to use the Seaway locks, beginning at the Welland Canal that bypasses the Niagara River. Since the freshwater lakes are less corrosive to ships than the Seawater, salt water of the oceans, lakers tend to last much longer than ocean freighters. Lakers older than 50 years are not unusual, and as of 2005, all were over 20 years of age. , built in 1906 as ''William P Snyder'', was the oldest laker still working on the Lakes until its conversion into a barge starting in 2013. Similarly, ''E.M. Ford'', built in 1898 as ''Presque Isle'', was sailing the lakes 98 years later in 1996. As of 2007 ''E.M. Ford'' was still afloat as a stationary transfer vessel at a riverside cement silo in Saginaw, Michigan.Merchant ship
Merchant ships are ships used for commercial purposes and can be divided into four broad categories: fishing, cargo ships, passenger ships, and special-purpose ships. The UNCTAD review of maritime transport categorizes ships as: oil tankers, bulk (and combination) carriers, general cargo ships, container ships, and "other ships", which includes "liquefied petroleum gas carriers, liquefied natural gas carriers, parcel (chemical) tankers, specialized tankers, reefers, offshore supply, tugs, dredgers, cruise, ferries, other non-cargo". General cargo ships include "multi-purpose and project vessels and roll-on/roll-off cargo". Modern commercial vessels are typically powered by a single propeller driven by a diesel engine, diesel or, less usually, gas turbine engine., but until the mid-19th century they were predominantly square sail rigged. The fastest vessels may use pump-jet engines. Most commercial vessels have full hull-forms to maximize cargo capacity. Hulls are usually made of steel, although aluminum can be used on faster craft, and fiberglass on the smallest service vessels. Commercial vessels generally have a crew headed by a sea captain, with deck officers and engine officers on larger vessels. Special-purpose vessels often have specialized crew if necessary, for example scientists aboard research vessels. Fishing boats are generally small, often little more than but up to for a large tuna or whaling ship. Aboard a fish processing vessel, the catch can be made ready for market and sold more quickly once the ship makes port. Special purpose vessels have special gear. For example, trawlers have winches and arms, stern-trawlers have a rear ramp, and tuna seiners have skiffs. In 2004, of fish were caught in the marine capture fishery.UNFAO, 2007, p. 11. Anchoveta represented the largest single catch at . That year, the top ten marine capture species also included Alaska pollock, Blue whiting, Skipjack tuna, Atlantic herring, Chub mackerel, Anchovy, Japanese anchovy, Trachurus, Chilean jack mackerel, Largehead hairtail, and Yellowfin tuna. Other species including salmon, shrimp, lobster, clams, squid and crab, are also commercially fished. Modern commercial fishermen use many methods. One is fishing by Fishing net, nets, such as Seine fishing, purse seine, beach seine, lift nets, gillnets, or entangling nets. Another is trawling, including Bottom trawling, bottom trawl. Fish hook, Hooks and lines are used in methods like long-line fishing and hand-line fishing. Another method is the use of fishing trap. Cargo ships transport dry and liquid cargo. Dry cargo can be transported in bulk bySpecial purpose vessels
A weather ship was a ship stationed in the ocean as a platform for surface and upper air meteorological observations for use in marine weather forecasting. Surface weather observations were taken hourly, and four radiosonde releases occurred daily. It was also meant to aid in search and rescue operations and to support transatlantic flights. Proposed as early as 1927 by the aviation community, the establishment of weather ships proved to be so useful during World War II that the International Civil Aviation Organization (ICAO) established a global network of weather ships in 1948, with 13 to be supplied by the United States. This number was eventually negotiated down to nine. The weather ship crews were normally at sea for three weeks at a time, returning to port for 10-day stretches. Weather ship observations proved to be helpful in wind and wave studies, as they did not avoid weather systems like other ships tended to for safety reasons. They were also helpful in monitoring storms at sea, such as tropical cyclones. The removal of a weather ship became a negative factor in forecasts leading up to the Great Storm of 1987. Beginning in the 1970s, their role became largely superseded by weather buoys due to the ships' significant cost. The agreement of the use of weather ships by the international community ended in 1990. The last weather ship was ''Polarfront'', known as weather station M ("Mike"), which was put out of operation on 1 January 2010. Weather observations from ships continue from a fleet of Voluntary observing ship program, voluntary merchant vessels in routine commercial operation.Naval vessels
Naval ships are diverse in List of types of naval vessels, types of vessel. They include: List of naval ship classes in service, surface warships, List of submarine classes in service, submarines, and auxiliary ships. Modern warships are generally divided into seven main categories: aircraft carriers, cruisers, destroyers, frigates, corvettes, submarines and amphibious assault ships. The distinctions among cruisers, destroyers, frigates, and corvettes are not codified; the same vessel may be described differently in different navies. Battleships were used during the Second World War and occasionally since then (the last battleships were removed from the U.S. Naval Vessel Register in March 2006), but were made obsolete by the use of carrier-borne aircraft and guided missiles. Most military submarines are either attack submarines or ballistic missile submarines. Until the end of World War II the primary role of the diesel/electric submarine was anti-ship warfare, inserting and removing covert agents and military forces, and intelligence-gathering. With the development of the homing torpedo, better sonar systems, and Nuclear navy, nuclear propulsion, submarines also became able to effectively hunt each other. The development of Submarine-launched ballistic missile, submarine-launched nuclear and cruise missiles gave submarines a substantial and long-ranged ability to attack both land and sea targets with a variety of weapons ranging from cluster munitions to nuclear weapons. Most Navy, navies also include many types of support and auxiliary vessel, such as minesweeper (ship), minesweepers, patrol boats, OPV (naval), offshore patrol vessels, replenishment ships, and hospital ships which are designated healthcare, medical treatment facilities. Fast combat vessels such as cruisers and destroyers usually have fine hulls to maximize speed and maneuverability. They also usually have advanced marine electronics and communication systems, as well as weapons.Architecture
Some components exist in vessels of any size and purpose. Every vessel has a hull of sorts. Every vessel has some sort of propulsion, whether it's a pole, an ox, or a nuclear reactor. Most vessels have some sort of steering system. Other characteristics are common, but not as universal, such as compartments, holds, a superstructure, and equipment such as anchors and winches.Hull
For a ship to float, its weight must be less than that of the water displaced by the ship's hull. There are many types of hulls, from logs lashed together to form a raft to the advanced hulls of America's Cup sailboats. A vessel may have a single hull (called a monohull design), two in the case of catamarans, or three in the case of trimarans. Vessels with more than three hulls are rare, but some experiments have been conducted with designs such as pentamarans. Multiple hulls are generally parallel to each other and connected by rigid arms. Hulls have several elements. The bow (ship), bow is the foremost part of the hull. Many ships feature a bulbous bow. The keel is at the very bottom of the hull, extending the entire length of the ship. The rear part of the hull is known as the stern, and many hulls have a flat back known as a transom (nautical), transom. Common hull appendages include propellers for propulsion, rudders for steering, and Stabilizer (ship), stabilizers to quell a ship's rolling motion. Other hull features can be related to the vessel's work, such as fishing gear and sonar, sonar domes. Hulls are subject to various hydrostatic and hydrodynamic constraints. The key hydrostatic constraint is that it must be able to support the entire weight of the boat, and maintain stability even with often unevenly distributed weight. Hydrodynamic constraints include the ability to withstand shock waves, weather collisions and groundings. Older ships and pleasure craft often have or had wooden hulls. Steel is used for most commercial vessels. Aluminium is frequently used for fast vessels, and composite materials are often found in sailboats and pleasure craft. Some ships have been made with Concrete ship, concrete hulls.Propulsion systems
Propulsion systems for ships fall into three categories: human propulsion, sailing, and mechanical propulsion. Human propulsion includes Watercraft rowing, rowing, which was used even on large galleys. Propulsion by sail generally consists of a sail hoisted on an erect mast, supported by stays and spars and controlled by ropes. Sail systems were the dominant form of propulsion until the 19th century. They are now generally used for recreation and competition, although experimental sail systems, such as the turbosails, rotorsails, and wingsails have been used on larger modern vessels for fuel savings. Mechanical propulsion systems generally consist of a motor or engine turning a propeller, or less frequently, an impeller or Wave power ship, wave propulsion fins. Steam engines were first used for this purpose, but have mostly been replaced by two-stroke engine, two-stroke or four-stroke engine, four-stroke diesel engines, outboard motors, and gas turbine engines on faster ships. Nuclear marine propulsion, Nuclear reactors producing steam are used to propel warships and icebreakers, and there have been attempts to use them to power commercial vessels (see NS Savannah, NS ''Savannah''). In addition to traditional fixed and controllable pitch propellers there are many specialized variations, such as contra-rotating and nozzle-style propellers. Most vessels have a single propeller, but some large vessels may have up to four propellers supplemented with bow thruster, transverse thrusters for maneuvring at ports. The propeller is connected to the main engine via a propeller shaft and, in case of medium- and high-speed engines, a reduction gearbox. Some modern vessels have a diesel-electric transmission, diesel-electric powertrain in which the propeller is turned by an electric motor powered by the ship's generators.Steering systems
For ships with independent propulsion systems for each side, such as manual oars or some paddle steamer, paddles, steering systems may not be necessary. In most designs, such as boats propelled by engines or sails, a steering system becomes necessary. The most common is a rudder, a submerged plane located at the rear of the hull. Rudders are rotated to generate a lateral force which turns the boat. Rudders can be rotated by a tiller, manual wheels, or electro-hydraulic systems. Autopilot systems combine mechanical rudders with navigation systems. Ducted propellers are sometimes used for steering. Some propulsion systems are inherently steering systems. Examples include the outboard motor, the bow thruster, and the Z-drive.Holds, compartments, and the superstructure
Larger boats and ships generally have multiple decks and compartments. Separate berthings and Head (watercraft), heads are found on sailboats over about . Fishing boats and cargo ships typically have one or more cargo holds. Most larger vessels have an engine room, a galley (kitchen), galley, and various compartments for work. Tanks are used to store fuel, engine oil, and fresh water. Ballast tanks are equipped to change a ship's trim and modify its stability. Superstructures are found above the main deck. On sailboats, these are usually very low. On modern cargo ships, they are almost always located near the ship's stern. On passenger ships and warships, the superstructure generally extends far forward.Equipment
Shipboard equipment varies from ship to ship depending on such factors as the ship's era, design, area of operation, and purpose. Some types of equipment that are widely found include: * Mast (sail), Masts can be the home of antennas, navigation lights, radar transponders, fog signals, and similar devices often required by law. * Ground tackle comprises the anchor, its chain or cable, and connecting fittings. * Cargo equipment such as Crane (machine), cranes and cargo booms may be used to load and unload cargo and ship's stores. * Safety equipment such as Lifeboat (shipboard), lifeboats, liferafts, and survival suits are carried aboard many vessels for emergency use.Design considerations
Hydrostatics
Ships float in the water at a level where mass of the displaced water equals the mass of the vessel, so that the downwards force of gravity equals the upward force of buoyancy. As a vessel is lowered into the water its weight remains constant but the corresponding weight of water displaced by its hull increases. If the vessel's mass is evenly distributed throughout, it floats evenly along its length and across its Beam (nautical), beam (width). A vessel's stability is considered in both this Initial stability, hydrostatic sense as well as a Ship stability, hydrodynamic sense, when subjected to movement, rolling and pitching, and the action of waves and wind. Stability problems can lead to excessive pitching and rolling, and eventually capsizing and sinking.Hydrodynamics
The advance of a vessel through water is resisted by the water. This resistance can be broken down into several components, the main ones being the friction of the water on the hull and wave making resistance. To reduce resistance and therefore increase the speed for a given power, it is necessary to reduce the wetted surface and use submerged hull shapes that produce low amplitude waves. To do so, high-speed vessels are often more slender, with fewer or smaller appendages. The friction of the water is also reduced by regular maintenance of the hull to remove the sea creatures and algae that accumulate there. Antifouling paint is commonly used to assist in this. Advanced designs such as the bulbous bow assist in decreasing wave resistance. A simple way of considering wave-making resistance is to look at the hull in relation to its wake. At speeds lower than the wave propagation speed, the wave rapidly dissipates to the sides. As the hull approaches the wave propagation speed, however, the wake at the bow begins to build up faster than it can dissipate, and so it grows in amplitude. Since the water is not able to "get out of the way of the hull fast enough", the hull, in essence, has to climb over or push through the bow wave. This results in an exponential function, exponential increase in resistance with increasing speed. This hull speed is found by the formula: or, in metric system, metric units: where ''L'' is the length of the waterline in feet or meters. When the vessel exceeds a speed/length ratio of 0.94, it starts to outrun most of its bow wave, and the hull actually settles slightly in the water as it is now only supported by two wave peaks. As the vessel exceeds a speed/length ratio of 1.34, the hull speed, the wavelength is now longer than the hull, and the stern is no longer supported by the wake, causing the stern to squat, and the bow rise. The hull is now starting to climb its own bow wave, and resistance begins to increase at a very high rate. While it is possible to drive a displacement hull faster than a speed/length ratio of 1.34, it is prohibitively expensive to do so. Most large vessels operate at speed/length ratios well below that level, at speed/length ratios of under 1.0. For large projects with adequate funding, hydrodynamic resistance can be tested experimentally in a hull testing pool or using tools of computational fluid dynamics. Vessels are also subject to ocean surface waves and sea swell as well as effects of wind and weather. These movements can be stressful for passengers and equipment, and must be controlled if possible. The rolling movement can be controlled, to an extent, by ballasting or by devices such as Stabilizer (ship), fin stabilizers. Pitching movement is more difficult to limit and can be dangerous if the bow submerges in the waves, a phenomenon called pounding. Sometimes, ships must change course or speed to stop violent rolling or pitching.Lifecycle
A ship will pass through several stages during its career. The first is usually an initial contract to build the ship, the details of which can vary widely based on relationships between the shipowners, operators, naval architect, designers and the shipyard. Then, the design phase carried out by a naval architect. Then the ship is constructed in a shipyard. After construction, the vessel is launched and goes into service. Ships end their careers in a number of ways, ranging from shipwrecks to service as a museum ship to Ship breaking, the scrapyard.Design
A vessel's design starts with a specification, which a naval architect uses to create a project outline, assess required dimensions, and create a basic layout of spaces and a rough displacement. After this initial rough draft, the architect can create an initial hull design, a general profile and an initial overview of the ship's propulsion. At this stage, the designer can iterate on the ship's design, adding detail and refining the design at each stage. The designer will typically produce an overall plan, a general specification describing the peculiarities of the vessel, and construction blueprints to be used at the building site. Designs for larger or more complex vessels may also include sail plans, electrical schematics, and plumbing and ventilation plans. As environmental laws are becoming more strict, ship designers need to create their design in such a way that the ship, when it nears its end-of-term, can be Ship breaking, disassembled or Ship disposal, disposed easily and that waste is reduced to a minimum.Construction
Ship construction takes place in a shipyard, and can last from a few months for a unit produced in series, to several years to reconstruct a wooden boat like the frigate ''Hermione'', to more than 10 years for an aircraft carrier. During World War II, the need for cargo ships was so urgent that construction time for Liberty ship, Liberty Ships went from initially eight months or longer, down to weeks or even days. Builders employed production line and prefabrication techniques such as those used in shipyards today. Hull materials and vessel size play a large part in determining the method of construction. The hull of a mass-produced fiberglass sailboat is constructed from a mold, while the steel hull of a cargo ship is made from large sections welded together as they are built. Generally, construction starts with the hull, and on vessels over about , by the laying of the keel. This is done in a drydock or on land. Once the hull is assembled and painted, it is launched. The last stages, such as raising the superstructure and adding equipment and accommodation, can be done after the vessel is afloat. Once completed, the vessel is delivered to the customer. Ship naming and launching, Ship launching is often a ceremony of some significance, and is usually when the vessel is formally named. A typical small rowboat can cost under US$100, $1,000 for a small speedboat, tens of thousands of dollars for a cruising sailboat, and about $2,000,000 for a Vendée Globe class sailboat. A trawler may cost $2.5 million, and a 1,000-person-capacity high-speed passenger ferry can cost in the neighborhood of $50 million. A ship's cost partly depends on its complexity: a small, general cargo ship will cost $20 million, a Panamax-sizedRepair and conversion
Ships undergo nearly constant maintenance during their career, whether they be underway, pierside, or in some cases, in periods of reduced operating status between charters or shipping seasons. Most ships, however, require trips to special facilities such as a drydock at regular intervals. Tasks often done at drydock include removing biological growths on the hull, sandblasting and repainting the hull, and replacing sacrificial anodes used to protect submerged equipment from corrosion. Major repairs to the propulsion and steering systems as well as major electrical systems are also often performed at dry dock. Some vessels that sustain major damage at sea may be repaired at a facility equipped for major repairs, such as a shipyard. Ships may also be converted for a new purpose:End of service
Most ocean-going cargo ships have a life expectancy of between 20 and 30 years. A sailboat made of plywood or fiberglass can last between 30 and 40 years. Solid wooden ships can last much longer but require regular maintenance. Carefully maintained steel-hulled yachts can have a lifespan of over 100 years. As ships age, forces such as corrosion, osmosis, and rotting compromise hull strength, and a vessel becomes too dangerous to sail. At this point, it can be scuttling, scuttled at sea or Ship breaking, scrapped by ship breaking, shipbreakers. Ships can also be used as museum ships, or expended to construct Breakwater (structure), breakwaters or artificial reefs. Many ships do not make it to the scrapyard, and are lost in fires, collisions, ship grounding, grounding, or sinking at sea. The Allies lost some 5,150 ships during World War II.Measuring ships
One can Molded depth, measure ships in terms of length overall, length between perpendiculars, Waterline length, length of the ship at the waterline, Beam (nautical), beam (breadth), depth (distance between the crown of the weather deck and the top of the keelson), Draft (hull), draft (distance between the highest waterline and the bottom of the ship) and tonnage. A number of different tonnage definitions exist and are used when describing merchant ships for the purpose of tolls, taxation, etc. In Britain until Samuel Plimsoll's Merchant Shipping Act of 1876, ship-owners could load their vessels until their decks were almost awash, resulting in a dangerously unstable condition. Anyone who signed on to such a ship for a voyage and, upon realizing the danger, chose to leave the ship, could end up in jail. Plimsoll, a Member of Parliament, realised the problem and engaged some engineers to derive a fairly simple formula to determine the position of a line on the side of any specific ship's hull which, when it reached the surface of the water during loading of cargo, meant the ship had reached its maximum safe loading level. To this day, that mark, called the "waterline, Plimsoll Line", exists on ships' sides, and consists of a circle with a horizontal line through the centre. On the Great Lakes of North America the circle is replaced with a diamond. Because different types of water (summer, fresh, tropical fresh, winter north Atlantic) have different densities, subsequent regulations required painting a group of lines forward of the Plimsoll mark to indicate the safe depth (or freeboard above the surface) to which a specific ship could load in water of various densities. Hence the "ladder" of lines seen forward of the Plimsoll mark to this day. This is called the "freeboard mark" or "waterline#Standard load line marks, load line mark" in the marine industry.Ship pollution
Ship pollution is the pollution of air and water by shipping. It is a problem that has been accelerating as trade has become increasingly globalized, posing an increasing threat to the world's oceans and waterways as globalization continues. It is expected that "shipping traffic to and from the United States is projected to double by 2020." Because of increased traffic in ocean ports, pollution from ships also directly affects coastal areas. The pollution produced affects biodiversity, climate, food, and human health. However, the degree to which humans are polluting and how it affects the world is highly debated and has been a hot international topic for the past 30 years.Oil spills
Oil spills have devastating effects on the environment. Crude oil contains polycyclic aromatic hydrocarbons (PAHs) which are very difficult to clean up, and last for years in the sediment and marine environment. Marine species constantly exposed to PAHs can exhibit developmental problems, susceptibility to disease, and abnormal reproductive cycles. By the sheer amount of oil carried, modern oil tankers must be considered something of a threat to the environment. An oil tanker can carry of crude oil, or . This is more than six times the amount spilled in the widely known Exxon Valdez oil spill, ''Exxon Valdez'' incident. In this spill, the ship ran aground and dumped of oil into the ocean in March 1989. Despite efforts of scientists, managers, and volunteers, over 400,000 seabirds, about 1,000 sea otters, and immense numbers of fish were killed. The International Tanker Owners Pollution Federation has researched 9,351 accidental spills since 1974. According to this study, most spills result from routine operations such as loading cargo, discharging cargo, and taking on fuel oil. 91% of the operational oil spills were small, resulting in less than 7 tons per spill. Spills resulting from accidents like collisions, groundings, hull failures, and explosions are much larger, with 84% of these involving losses of over 700 tons. Following the ''Exxon Valdez'' spill, the United States passed the Oil Pollution Act of 1990 (OPA-90), which included a stipulation that all tankers entering its waters be Double-hulled tanker, double-hulled by 2015. Following the sinkings of ''Erika (tanker), Erika'' (1999) and ''Prestige oil spill, Prestige'' (2002), the European Union passed its own stringent anti-pollution packages (known as Erika I, II, and III), which require all tankers entering its waters to be double-hulled by 2010. The Erika packages are controversial because they introduced the new legal concept of "serious negligence".Ballast water
When a large vessel such as aExhaust emissions
exhaust gas, Exhaust emissions from ships are considered to be a significant source of air pollution. "Seagoing vessels are responsible for an estimated 14 percent of emissions of nitrogen from fossil fuels and 16 percent of the emissions of sulfur from petroleum uses into the atmosphere." In Europe ships make up a large percentage of the sulfur introduced to the air, "as much sulfur as all the cars, Truck, lorries and factories in Europe put together". "By 2010, up to 40% of air pollution over land could come from ships." Sulfur in the air creates acid rain which damages crops and buildings. When inhaled, sulfur is known to cause respiratory problems and increase the risk of a myocardial infarction, heart attack.Ship breaking
Ship breaking or ship demolition is a type of ship disposal involving the breaking up of ships for scrap recycling, with the hulls being discarded in ship graveyards. Most ships have a lifespan of a few decades before there is so much wear that refitting and repair becomes uneconomical. Ship breaking allows materials from the ship, especially steel, to be reused. In addition to steel and other useful materials, however, ships (particularly older vessels) can contain many substances that are banned or considered dangerous in developed countries. Asbestos and polychlorinated biphenyls (PCBs) are typical examples. Asbestos was used heavily in ship construction until it was finally banned in most of the developed world in the mid 1980s. Currently, the costs associated with removing asbestos, along with the potentially expensive insurance and health risks, have meant that ship-breaking in most developed countries is no longer economically viable. Removing the metal for scrap can potentially cost more than the scrap value of the metal itself. In most of the developing world, however, shipyards can operate without the risk of Personal injury, personal injury lawsuits or Workers' compensation, workers' health claims, meaning many of these shipyards may operate with high health risks. Furthermore, workers are paid very low rates with no overtime or other allowances. Protective equipment is sometimes absent or inadequate. Dangerous vapors and fumes from burning materials can be inhaled, and dusty asbestos-laden areas around such breakdown locations are commonplace. Aside from the health of the yard workers, in recent years, ship breaking has also become an issue of major environmentalism, environmental concern. Many developing nations, in which ship breaking yards are located, have lax or no environmental law, enabling large quantities of highly toxic materials to escape into the environment and causing serious health problems among ship breakers, the local population and wildlife. Environmental campaign groups such as Greenpeace have made the issue a high priority for their campaigns.See also
* Admiralty law * Airship * Auxiliary ship * Boat * Chartering (shipping) * Dynamic positioning * Environmental impact of shipping * Factory ship * Ferry * Flag state * Fluyt * Galleon * Galley * Glossary of nautical terms (A-L) * Glossary of nautical terms (M-Z) * Marine electronics * Marine fuel management * Maritime history * Mother ship * Naval architecture * Naval ship * Navy * Nuclear marine propulsion * Propulsion * Sailing * Sailing ship * Sailor * Ship burial *Notes
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