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Lift on a sail (L), acting as an airfoil, occurs in a direction perpendicular to the incident airstream (the apparent wind velocity, V A, for the head sail) and is a result of pressure differences between the windward and leeward surfaces and depends on angle of attack, sail shape, air density, and speed of the apparent wind.
Tacking or coming about is a sailing maneuver by which a sailing craft (sailing vessel, ice boat, or land yacht), whose next destination is into the wind, turns its bow toward and through the wind so that the direction from which the wind blows changes from one side of the boat to the other, allowing progress in the desired direction. [1]
The force of the sail is balanced by the force of the keel. This keeps the boat from moving in the direction of the sail force. Although total sail force is to the side when sailing into the wind, a proper angle of attack moves the boat forward. [1] Another way of stating this is as follows: The more the sail is angled from the centerline of ...
Because of a small β, the sail is sheeted in for all three points of sail. Apparent wind is the wind velocity (direction and speed), V A, measured aboard a moving sailing craft; it is the net effect of the boat wind, V B —the air flow over the craft induced by its speed over the earth (equal to in magnitude, but opposite in direction to the ...
The purpose of the daggerboard (or any keel) is to balance the force of the wind on the sails. Without a daggerboard or keel, a sailboat could not sail up-wind and would simply be blown sideways. [1] During a storm, daggerboards can help reduce the tendency of a small boat to tip over ("breach") due to waves.
This motion is generated directly either by the water and wind motion, particularly lateral wave motion, exerting forces against the hull or by the ship's own propulsion; or indirectly by the inertia of the ship while turning. This movement can be compared to the vessel's lateral drift from its course.
A sailboat on three points of sail The waves give an indication of the true wind direction. The flag gives an indication of apparent wind direction. True wind can also be indicated by a fixed wind indicator (flag, windsock, etc., not attached to the boat or any moving object).
During the ill-fated 1979 Fastnet race, of 300 yachts, 158 chose to adopt storm tactics; 86 "lay ahull", whereby the yacht adopts a "beam on" attitude to the wind and waves; 46 ran before the wind under bare poles or trailing warps/sea anchors, and 26 hove to. 100 yachts suffered knock downs; 77 rolled (that is turtled) at least once.