Boat Wind (Motion Wind)

The airflow component attributable to a vessel’s own motion through the surrounding air.

It is a teaching term used when constructing apparent wind. The motion-wind vector acts opposite to the vessel’s velocity through the air; during ordinary forward motion it therefore appears to come from ahead and becomes larger as that velocity increases.

Boat wind is not a separate meteorological wind and is not always aligned with the centreline if the vessel has sideways motion or is moving astern. Vector addition of boat wind and the ambient wind gives the apparent wind measured aboard.