SHIP

any large floating vessel capable of crossing open waters, as opposed to a boat, which is generally a smaller craft. The term formerly was applied to sailing vessels having three or more masts; in modern times it usually denotes a vessel of more than 500 tons of displacement. Submersible ships are generally called boats regardless of their size. any large floating vessel capable of crossing open waters, as opposed to a boat, which is generally a smaller craft. The term formerly was applied to sailing vessels having three or more masts; in modern times it usually denotes a vessel of more than 500 tons of displacement. Submersible ships are generally called boats regardless of their size. The following is a brief treatment of ships. Articles providing fuller treatment appear in the Macropaedia. For coverage of historical aspects, see Transportation: Ships; for shipbuilding, see Ship Construction; for military aspects, see War, The Technology of: Naval ships and craft. The earliest knowledge of ships comes from Egyptian rock drawings dating from 6000 BC. These depict crescent-shaped reed craft that had no keels, the shape being held by a cable running from bow to stern. At first they were rowed, but later square sails were added that would move them when the wind was from the stern. By about 2000 BC the Minoans on Crete had developed ships that had log keels with ribs and planking on the sides joined at the stem and stern. The keel was bent upward and forward of the joint between the two sides of the ship to form a double, or bifid, bow. The Minoans and their successors, the Phoenicians, began to differentiate between fighting and merchant vessels. The long, narrow rowing galley became their warship. By Greek and Roman times the rowing galley was powered by as many as three tiers of rowers. In order to reduce the space taken up by rowers, designers of merchantmen increasingly relied on sails for propulsion. Roman models had sails that could take the wind from about 45 off dead astern, giving them greater maneuverability. During the Middle Ages the introduction of carvel planking (smooth siding) on Mediterranean ships greatly reduced skin friction. This allowed for the construction of much larger merchantmen, called nefs, which were fitted with lateen sails. Triangular in shape and set in a fore-and-aft configuration, the lateen made it possible to sail into the wind. While the nef was being developed, the Vikings were refining their double-ended fighting galleys. These ships, designed to handle the rough northern seas, had a high bow and stern, a stoutly built hull of clinker construction (overlapping planks) that was also flexible, and a single, large, reinforced square sail. By the 13th century, sailors of an improved merchant version of this ship, the cog, were venturing into the Mediterranean and making contact with lateen-rigged nefs. Over the next few years the features of the two types merged in the carrack, the forerunner of the galleon. The development of sets of smaller, more efficient sails was the beginning of the age of the full-rigged, classic ship, in which a combination of square and lateen sails was used. Both merchant and fighting ships began using the same basic hull design. By the end of the 15th century, ships were capable of sailing anywhere in the world. In the mid-19th century, sailing ships reached their peak with the sleek, swift clipper ship, but by the end of the century steam power had almost completely replaced sails. The history of the modern ship began in 1801, when the British engineer William Symington developed a practical steamboat for towing barges on the Forth and Clyde Canal in Scotland. Six years later the American inventor Robert Fulton successfully demonstrated his steamboat by making a run between New York City and Albany on the Hudson River in about one-fourth the time required by sailing craft. Soon thereafter he inaugurated the world's first regularly scheduled steamboat service. Several years of technological advances were needed before steam-powered vessels could seriously rival sailing ships; but by 1850 steamships were competitive with sail in terms of speed, and ocean crossings had become routine. Early steamships were driven by low-pressure engines, and power could be increased only by building larger engines. By 1870 the limit in size had been reached. Attempts were made to increase steam pressure by building more efficient boilers and designing engines that used the same steam two or even three times. Called double- or triple-expansion engines, they passed steam on to successively larger cylinders and by the early 1900s could develop more than 20,000 horsepower. Meanwhile, the screw propeller was perfected and replaced the paddle wheel, which was vulnerable and tended to come out of the water when the ship rolled. A major revolution in ship propulsion occurred in 1884 when the English engineer Charles Parsons demonstrated the first successful steam turbine. Turbines were far more efficient and easier to build than reciprocating steam engines, but they spun too fast to allow propellers to turn at efficient speeds. This problem was solved by about 1910 with the introduction of reduction gearing. Using these highly efficient and lighter turbines, ships of great size and speed were constructed in the early decades of the 20th century. Other important advances in propulsive systems include the marine diesel, which is more efficient than the steam turbine, and the nuclear-powered steam turbine, which when used in a submarine enables it to remain submerged for extended periods of time. Throughout the era of the sailing ship, wood was the chief construction material used. Planks were nailed to wooden ribs that were mounted on a wooden keel. By the 18th century, sheathing, and later iron cladding, was used to protect the wooden hull. The first all-iron ship was built in 1818, the hull being formed of iron plates riveted to each other and braced by iron ribs. In 1880 steel began to replace iron, and by about 1950 it became practical to build all-welded ships. The construction of larger, faster, and safer ships from the mid-19th century gave rise to a large and highly competitive passenger industry, especially across the North Atlantic Ocean. The era of the great ocean liners lasted from roughly 1900 to the outbreak of World War II. Although passenger travel resumed after the war and was highly popular during the 1950s, the advent of reliable long-distance jet aircraft in the early 1960s precipitated a rapid decline in ship travel. The expansion of postwar international trade, however, created a boom in freight traffic. Specialized carriers for such bulk commodities as grain and oil had first appeared in the late 19th century. After World War II bulk carriers, especially oil tankers, became enormous in size; by the mid-1970s tankers of 500,000 tons deadweight had been constructed. Specialized ships were also developed to carry general freight in standardized containers that could be easily loaded, unloaded, and transported to and from the dock. Other types of modern specialized vessels include the roll-onroll-off (ro-ro) ship, which can be loaded and unloaded by trucks that use ramps between the ship and the dock; and the LASH (lighter-aboard-ship) vessel, which can carry a number of lighters (barges) in its specially designed hold. Additional reading Harry Benford, Naval Architecture for Non-Naval Architects (1991); and Cyrus Hamlin, Preliminary Design of Boats and Ships (1989), are books for the nonengineer that give simple explanations of the design process and of marine design principles. Kenneth C. Barnaby, Basic Naval Architecture, 6th ed. (1969), is a basic textbook suitable for an engineer who is not acquainted with naval architecture, though some of the technology described may be obsolete. Edward V. Lewis (ed.), Principles of Naval Architecture, 2nd rev. ed., 2 vol. (1988), is a basic reference and includes research topics. Robert Taggart (ed.), Ship Design and Construction (1980), on the design of commercial ships, is of interest to the nonspecialist because of its illustrations. A basic reference for those areas of marine engineering relating to ship machinery is Roy L. Harrington (ed.), Marine Engineering (1971, reissued 1992). John B. Woodward, Low Speed Marine Diesel (1981), emphasizes how the diesel engine is integrated into ship design. Christen Knak, Diesel Motor Ships' Engines and Machinery, trans. from Danish (1979, reissued in 2 vol., 1990), a textbook for operating engineers, describes a number of diesel engines in great detail. Lane C. Kendall, The Business of Shipping, 5th ed. (1986); and Roy L. Nersesian, Ships and Shipping (1981), both for the nonspecialist, treat the varied aspects of the marine transportation business, including chartering and maintenance. National Research Council (U.S.), Commission on Engineering and Technical Systems, Crew Size and Maritime Safety (1990), surveys the technical and sociological problems of crew size and the divisions of labour. Jane's Merchant Ships (annual) provides a comprehensive source of textual and pictorial description of current commercial shipping. John B. Woodward