Fast naval vessel smaller than a frigate. In the 18th–19th century corvettes were three-masted ships with square rigging and carried about 20 guns on the top deck. Often used to send dispatches within a battle fleet, they also escorted merchant ships. Early U.S. corvettes won distinction in the War of 1812. They disappeared as a class after the shift to steam power in the mid-19th century, but in World War II the term was applied to small armed vessels that served as escorts for convoys. Modern corvettes, usually displacing 500–1,000 tons (454–900 metric tons) and armed with missiles, torpedoes, and machine guns, perform antisubmarine, antiaircraft, and coastal-patrol duties in small navies.
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A sloop (from Dutch sloep) is a sailboat with a fore-and-aft rig and a single mast farther forward than the mast of a cutter. A sloop's fore-triangle is smaller than a cutter's, and a sloop usually bends only one headsail, though this distinction is not definitive. Unlike cutters, sloops usually have only one headsail, though some sloops such as the Friendship Sloop have more than one. Ultimately the position of the mast is the most important factor in determining if the ship is indeed a sloop.
On a gaff rigged, single masted boat, the clearest distinction between a sloop and a cutter is the run of the forestay. On the sloop, it runs to the outboard end of the bowsprit, which means that spar must always stay in position and cannot be retracted. On the cutter, the forestay runs to the stem head of the hull. This allows the bowsprit to be run back inboard and stowed. This can be helpful in crowded harbours or when stowing the jib in strong wind conditions.
No design is perfect for all conditions; sloops are designed to optimize upwind sailing. However, sloops also offer an excellent overall compromise acceptable, if not optimal, to all points of sail. It is clear that the most difficult direction to sail is to the windward (known as sailing close-hauled); this requires some specific design features. The sail should be as vertical as possible to optimize the energy of the wind.
Two forces act on a vessel to push it from vertical (also known as heeling over): (1) the weight of the rig itself will tend to heel the boat, and (2) the sideways force of the wind on the sails. The sloop is a light rig with fewer lines and spars, and the sails on a sloop tend to be flat which minimizes sideways force when well trimmed. The heeling forces are also counterbalanced by the keel, which uses weight and hydrodynamics to offset the forces from the rigging and sails.
When sailing upwind, it is also important to minimize the drag of the wind on the sail and rig. A major cause of drag of the sail is a vortex of turbulent air generated by the top of the mast and sail. Secondary causes are non-optimal aerodynamic shapes of masts, stays and control lines. The sloop minimizes the drag of the tip-vortex with a high and narrow sail design (high aspect), maximizing the amount of sail for a given tip-vortex compared to a square-rigged or gaff-rigged ship. Also, the simplicity of the rig reduces the drag induced by control lines, masts and spars.
To maximize the amount of sail carried, the classical sloop may use a bowsprit, which is essentially a fixed spar that projects forward from the bow of the boat. For downwind sailing, the typical foresail may be replaced (or sometimes supplemented) by larger sails known as spinnakers or gennakers. The typical foresail known as the jib, which does not overlap the mast more than 10 to 20 percent, may be replaced by a genoa jib, which overlaps the mast by as much as 55 to 100 percent for racing rules and sometimes more. The mainsail and Genoa form an efficient double wing.
The Bermuda sloop is a type of fore-and-aft rigged sailing vessel developed on the island of Bermuda in the 17th century. In this sense, the term applied to small ships, rather than boats. In its purest form, it is single-masted, although ships with such rigging were built with as many as three masts. Its original form had gaff rig, but evolved to use what is now known as Bermuda rig, making it the basis of nearly all modern sailing yachts. Although the Bermuda sloop is often described as a development of the narrower-beamed Jamaica sloop, which dates from the 1670s, the high, raked masts, and triangular sails of its Bermuda rig are rooted in a tradition of Bermudian boat design dating from the early 17th century. Part of that tradition included long, horizontal bowsprits, and large jibs. Three jibs were commonly used on Bermudian ships. Triangular sails appeared on Bermudian boats early in the 17th century, a development of the Dutch bezaan, or leg-of-mutton rig, itself derived from the Lateen rig. This became the Bermuda rig, and was appearing on Bermudian ships by the early 19th century. A large spinnaker was carried on a spinnaker boom when running down-wind.
The naval term "sloop" referred to ships with different rigs and sizes varying from navy to navy. "Sloop-of-war" was more of a reference to the purpose of the craft rather than the specific size or sailplan. The Royal Navy began buying Bermuda sloops, beginning with an order for three sloops-of-war (HMS Dasher, HMS Driver, and HMS Hunter, were each of 200 tons, armed with twelve 24 pounders) placed with Bermudian builders in 1795 They were intended to counter the then-extant menace of French privateers, which the Navy's ships-of-the-line were ill-designed to counter. Eventually, Bermuda sloops became the standard advice vessels of the navy, used for communications, reconnoitering, anti-slaving, anti-smuggling, and other roles to which they were well suited. The most notable examples of these were HMS Pickle, which raced back to England with news of the British victory and the death of Admiral Lord Nelson at the end of the Battle of Trafalgar, and HMS Whiting (79 tons and four guns), which lowered anchor in the harbor of Hampton Roads on 8 July 1812, carrying dispatches. The American privateer Dash, which happened to be leaving port, seized the vessel. The crew of the Whiting had not yet received news of the American declaration of war, and her capture was the first naval action of the American War of 1812. Generally a sloop was smaller than a frigate; however, in the later days of the U.S. Navy's sailing fleet, some of the largest vessels were called sloops because they carried fewer guns than a frigate, as few as 20. The classification of sloop was similar to a corvette.
The first modern sloops were fitted with the Bermuda Rig, so called as a result of its development in Bermuda during the 17th century. This rig is also called the Marconi rig because of the resemblance of its tall mast and complex standing rigging to Guglielmo Marconi's wireless (radio) transmission antennas.
The state of the art in racing sloops today may be seen in the IACC yachts sailed in the America's Cup competition. This statement is only true in that the most money has been spent in this class, to build the fastest boats that meet the IACC rule. Much faster sloops have been built that don't fit the rule, using such forbidden technology as canting keels and movable water ballast. The current Volvo Ocean Race is using a new class, the Volvo 70 which boasts a canting keel, carbon construction throughout and very powerful sailplans. The 24-hour distance record was recently broken several times, with ABN AMRO 2 setting the record distance of for a monohull (January 2006). These boats routinely sail at or above wind speeds and can sustain mid- speeds hour after hour.