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A polar diagram, or polar plot, is a graph that shows a sailboat's potential speed over a range of wind speeds and relative wind angles. [1] It normally consists of the right side of a line chart with the radius representing the yacht speed and the angle representing the wind direction blowing from top to bottom.
It is the vector sum of true wind velocity and the apparent wind component resulting from boat velocity (V A = −V B + V T). In nautical terminology, wind speeds are normally expressed in knots and wind angles in degrees. The craft's point of sail affects its velocity (V B) for a given true wind velocity (V T). Conventional sailing craft ...
Hull speed can be calculated by the following formula: where is the length of the waterline in feet, and is the hull speed of the vessel in knots. If the length of waterline is given in metres and desired hull speed in knots, the coefficient is 2.43 kn·m −½.
A velocity prediction program (VPP) is a computer program which solves for the performance of a sailing yacht in various wind conditions by balancing hull and sail forces. VPPs are used by yacht designers, boat builders, model testers, sailors, sailmakers, also America's Cup teams, to predict the performance of a sailboat before it has been built or prior to major modifications.
The apparent wind on board (a boat) is often quoted as a speed measured by a masthead transducer containing an anemometer and wind vane that measures wind speed in knots and wind direction in degrees relative to the heading of the boat. Modern instrumentation can calculate the true wind velocity when the apparent wind and boat speed and ...
Velocity made good, or VMG, is a term used in sailing, especially in yacht racing, indicating the speed of a sailboat towards (or from) the direction of the wind. [ 1 ] [ 2 ] The concept is useful because a sailboat cannot sail directly upwind, and thus often can not, or should not, sail directly to a mark to reach it as quickly as possible.
Diagram of a chip log attached to a log-line and reel on a ship. A chip log, also called common log, [1] ship log, or just log, is a navigation tool mariners use to estimate the speed of a vessel through water.
The points of sail: A. Into the wind; shaded: "no-go zone" where a craft may be "in irons". B. Close-hauled (used when beating to windward) between B and C. Close reach C. Beam reach D. Broad reach E. Running downwind . A point of sail is a sailing craft's direction of travel under sail in relation to the true wind direction over the surface.