Ship Ship Samuel F. B. Morse Category="Ship types"Category="Transportation"Category="Water transport"[image]

A ship is a large, sea-going Watercraft, sometimes with multiple decks. A ship usually has sufficient size to carry its own boats, such as lifeboats, dinghies, or runabouts. A Rule of thumb saying (though it doesn't always apply) goes: "a boat can fit on a ship, but a ship can't fit on a boat". Often local Law and regulation will define the exact size (or the number of masts) which a boat requires to become a ship. (Note that one refers to submarines as "boats"). Compare Vessel.

During the Age of Sail, ship signified a ship-rigged vessel, that is, one with three or more masts, usually three, all square-rigged. Such a vessel would normally have one fore and aft sail on her aftermost mast which was usually the mizzen. Almost invariably she would also have a Bowsprit but this was not part of the definition. The same economic pressures which increased sizes to the point of carrying four or five masts, also introduced the fore and aft rig to larger vessels, so few ship-rigged vessels were built with more than three masts. The five-masted Preussen was the outstanding example but the big German ships and barques were built partly for Prestige reasons.

Nautical means related to sailors, particularly customs and practices at Sea. Naval is the adjective pertaining to ships though in common usage, it has come to be more particularly associated with the noun 'Navy'.

Measuring ships

One can measure ships in terms of overall Length, length of the waterline, beam (breadth), depth (distance between the crown of the weather deck and the top of the keelson), Draft (distance between the highest waterline and the bottom of the ship) and tonnage.

A number of different tonnage definitions exist; most measure Volume rather than weight and are used when describing merchant ships.

The word "displacement" arises from the basic physical law, discovered by Archimedes, that the weight of a floating object equates exactly to that of the water which would otherwise occupy the "hole in the water" displaced by the ship.

In Britain, until the Merchant Shipping Act of 1876, ship-owners could load their vessels until their decks were almost awash, resulting in a dangerously unstable condition. Additionally, anyone who signed onto such a ship for a voyage and, upon realizing the danger, chose to leave the ship, could end up in jail.

Samuel 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 "Plimsoll Mark", exists on ships' sides, and consists of a Circle with a horizontal line through the center. 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.

Propulsion

Until the application of the Steam engine to ships in the early 19th century, oars propelled galleys or the wind propelled sailing ships.

Before mechanisation, merchant ships always used Sail, but as long as Naval warfare depended on ships closing to ram or to fight hand-to-hand, galleys dominated in marine conflicts because of their maneuverability and speed. The Greek navies that fought in the Peloponnesian War used triremes, as did the Romans contesting the Battle of Actium. The use of large numbers of Cannon from the 16th century meant that maneuverability took second place to broadside weight; this led to the dominance of the sail-powered warship.

The development of the steamship became a complex process, the first commercial success accruing to Robert Fulton's North River Steamboat (often called Clermont) in the USA in 1807, followed in Europe by the 45-foot PS Comet of 1812. Steam propulsion progressed considerably over the rest of the 19th century. Notable developments included the Condenser, which reduced the requirement for fresh water, and the multiple expansion engine, which improved efficiency. As the means of transmitting the engine's power, the paddle wheel gave way to the more efficient screw Propeller. The marine Steam turbine developed by Sir Charles Algernon Parsons, brought the power to weight ratio down. He had achieved publicity by demonstrating it unofficially in the 100-foot Turbinia at the Spithead Naval Review in 1897. This facilitated a generation of high-speed liners in the first half of the 20th century and rendered the reciprocating steam engine out of date, in warships.

The marine Diesel engine first came into use around 1912: either the Vulcanus or the Selandia (depending upon who you talk to) first deployed it. It soon offered even greater efficiency than the steam turbine but for many years had an inferior power-to-space ratio. About this period too, heavy Fuel oil came into more general use and began to replace Coal as the fuel of choice in steamships. Its great advantages were the convenience and the reduction in manning owing to the removal of the need for trimmers and of stokers in the old-fashioned numbers.

Most ships built since around 1960 have used diesel power or motors; one exception, Queen Elizabeth 2 of 1968, started with steam turbines but subsequently converted to Diesel as a cost-saving measure.

A few ships have used nuclear reactors, but this is not a separate form of propulsion. It merely makes steam to drive the turbines. Nonetheless, it has caused concerns about safety and waste disposal. It has become usual only in large aircraft carriers and in submarines, where the ability to run submerged for long periods holds obvious advantage. In such long-endurance vessels, the saving in bunkerage too, is an important consideration.

General terminology

Ships may occur collectively as fleets, flotillas or squadrons. Convoys of ships commonly occur.

A collection of ships for military purposes may compose a Navy or a Task force.

In the past, people counting or grouping disparate types of ship may refer to the individual vessels as bottoms. Groups of sailing ships could constitute, say, a fleet of 40 Sail. Groups of submarines (particularly German U-boats in the 1940s) may hunt in packs (often erroneously called wolf packs).

Shipboard terminology

See also: Glossary of nautical terms. The complexity of ships, particularly of sailing ships, led to the development of a rich and various vocabulary. Many of the following terms link to more detailed discussions of nautical terminology.

Some types of ships and boats

Some historical types of ships and boats

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See also

Quotations

I must go down to the sea again, to the lonely sea and the sky,
And all I ask is a tall ship, and a star to steer her by...
-John Masefield

External links