Sailing
Sailing employs the wind—acting on sails, wingsails or kites—to propel a craft on the surface of the water (sailing ship, sailboat, windsurfer, or kitesurfer), on ice (iceboat) or on land (land yacht) over a chosen course, which is often part of a larger plan of navigation.
Until the middle of the 19th century, sailing ships were the primary means for marine exploration, commerce, and projection of military power; this period is known as the Age of Sail. In the 21st century, most sailing represents a form of recreation or sport. Recreational sailing or yachting can be divided into racing and cruising. Cruising can include extended offshore and ocean-crossing trips, coastal sailing within sight of land, and daysailing.
Sailing relies on the physics of sails as they derive power from the wind, generating both lift and drag. On a given course, the sails are set to an angle that optimizes the development of wind power, as determined by the apparent wind, which is the wind as sensed from a moving vessel. The forces transmitted via the sails are resisted by forces from the hull, keel, and rudder of a sailing craft, by forces from skate runners of an iceboat, or by forces from wheels of a land sailing craft to allow steering the course. This combination of forces means that it is possible to sail an upwind course as well as downwind. The course with respect to the true wind direction (as would be indicated by a stationary flag) is called a point of sail. Conventional sailing craft cannot derive wind power on a course with a point of sail that is too close into the wind.
Throughout history sailing has been a key form of propulsion that allowed greater mobility than travel over land, whether for exploration, trade, transport, or warfare, and that increased the capacity for fishing, compared to that from shore.
Early square rigs generally could not sail much closer than 80° to the wind, whereas early fore-and-aft rigs could sail as close as 60–75° off the wind.[1] Later square-rigged vessels too were able to sail to windward, and became the standard for European ships through the Age of Discovery when vessels ventured around Africa to India, to the Americas and around the world.[2] Sailing ships became longer and faster over time, with ship-rigged vessels carrying taller masts with more square sails. The Age of Sail (1570–1870) reached its peak in the 18th and 19th centuries with merchant sailing ships that were able to travel at speeds that exceeded those of the newly introduced steamships.
Austronesian peoples sailed from what is now Southern China and Taiwan with of Catamarans or vessels outriggers,[3] and crab claw sails,[4] which enabled the Austronesian Expansion at around 3000 to 1500 BCE into the islands of Maritime Southeast Asia, and thence to Micronesia, Island Melanesia, Polynesia, and Madagascar.[5] They traveled vast distances of open ocean in outrigger canoes using navigation methods such as stick charts.[6][7]
A. Luffing (no propulsive force) — 0-30°
B. Close-hauled (lift)— 30–50°
C. Beam reach (lift)— 90°
D. Broad reach (lift–drag)— ~135°
E. Running (drag)— 180°
True wind (VT) is the same everywhere in the diagram, whereas boat velocity (VB) and apparent wind (VA) vary with point of sail.
Left-hand boat: Down wind with detached airflow like a parachute— predominant drag component propels the boat with little heeling moment.
Right-hand boat: Up wind (close-hauled) with attached airflow like a wing—predominant lift component both propels the boat and contributes to heel.