Sailing glossary

Apparent Wind

The wind flow observed when the vessel is in motion, relative to the vessel’s heading. Apparent wind is different from True wind in that it takes into account your vessel’s movement, i.e.: speed and direction of travel. Apparent wind is the raw data that is reported by wind transducers, which can then be used in conjunction with other data sources to calculate True wind.

Supported data:

• NMEA 2000: PGN 130306

• NMEA 0183: MWV

Apparent Wind Angle (AWA)

The wind angle observed when the vessel is in motion, relative to the vessel’s heading. AWA is a combination of the true angle of the wind and the angle that is experienced due to the direction and speed of travel.

Apparent Wind Speed (AWS)

The wind speed observed when the vessel is in motion. AWS is a combination of the true speed of the wind and the speed at which you are travelling.

Close-hauled / Beating

Generally, when sailing upwind, the tighter the angle at which the vessel sails with respect to the wind, the faster the vessel will travel. When a vessel’s sails are pulled in tightly to the vessel’s centerline in order to maximize the vessel’s speed when travelling upwind, it is known as sailing “Close-hauled” or “beating”. There's a "no-go" zone directly into the wind where a vessel cannot sail in a forward motion. Also, sailing too close to the wind ("pinching") can reduce both speed and efficiency in terms of the vessel’s forward motion. Therefore, maximizing forward motion when sailing upwind requires the optimization of both the vessel’s sail rigging and the vessel’s angle with respect to the wind direction, which is typically 30 to 45 degrees.

Distance to Tack

The travel distance remaining until you need to tack.

Distance to Line

Distance remaining to the closest point along the race start line.

Downwind

Moving in the direction that the wind is blowing.

Ground Wind Direction (GWD)

The direction of the wind relative to north, as observed on land. This is the actual direction the wind is blowing.

In addition to Apparent Wind Angle (AWA), Course Over Ground (COG) from a GNSS receiver is also required in order to calculate GWD.

Ground Wind Speed (GWS)

The wind speed observed when stationary, as observed on land. GWS is the actual speed at which the wind is blowing over land.

In addition to Apparent Wind Speed (AWS), Speed Over Ground (SOG) data from a GNSS receiver is also required in order to calculate GWS.

Header

A wind shift which causes your vessel to turn more downwind.

Laylines

Vector lines showing the course the boat will take when sailing at the optimum angle to the wind, on either tack.

Leeway

The difference in angle between desired heading and actual course, caused by sideways movement of a sailing boat due to the wind.

Lift

A wind shift which allows your boat to turn upwind and closer to your destination.

Line bias

The distance advantage conferred by crossing the start line at the favored end (the end which is more upwind) of the race start line.

Polar table

A performance profile for a vessel, showing the vessel speed achievable at varying angles to the wind, with varying wind speed. In sailing, the Velocity Made Good (VMG) principle demonstrates that travelling in a straight line is not always the quickest route, and polars enable you to optimize your vessel's performance to its best advantage, by improving the accuracy of laylines to display how far you need to sail on a current tack to reach a target waypoint after tacking, and taking wind conditions into consideration.

RSW-Wired

(Raymarine Smart Wind)

The Raymarine Smart Wind transducer series. The RSW-Wired series of transducers include a built-in attitude sensor, which is used to provide more accurate readings than standard wind transducers.

Sail plan

Sail configuration recommendations based on wind conditions.

Sailing upwind

Sailing close to the wind direction.

Tack

A course change made by a sailing vessel, by turning its heading into and through the wind.

Tacking

The zig-zag maneuver a sailing vessel makes when travelling upwind.

Time To Burn (TTB)

The time remaining during race start countdown before the vessel needs to start moving towards the start line at full speed.

Time to Tack

The amount of time remaining until you need to tack, if the current course and speed are maintained based on the calculated laylines.

True Wind

The actual wind flow; the wind flow that you experience on the water, when stationary. True wind is calculated from Apparent wind data from a wind transducer and STW (Speed Through Water) data from a speed transducer.

True Wind Angle (TWA)

The angle of the wind over water, relative to the vessel’s bow, observed when stationary.

True Wind Direction (TWD)

The direction of the wind relative to North. This is the actual direction in which the wind is blowing.

In addition to Speed Through Water (STW), Heading data is also required in order to calculate TWD.

True Wind Speed (TWS)

The wind speed observed when stationary, on the water. TWS is the actual speed at which the wind is blowing over water.

Velocity Made Good (VMG)

Sailing term related to the component of a sail vessel’s velocity vector that is in the direction of true wind.

Wind shift

The amount of variation in True Wind Direction (TWD) over time.