Join Date: Feb 2000
Location: Annapolis, Md
Thanked 195 Times in 159 Posts
Rep Power: 10
Wind speed detectors
Winds speed and direction indicators have a lot of uses in sailing but really come into their own for racing applications or for electronic navigation. This is especially true when tied into other instruments such as a knotmeter, electronic compass and an autopilot.
The bad news is that electronic wind instruments are terribly inaccurate in an absolute sense. Air density varies with temperature and since most wind instuments operate on impact (Newton''s theory) rather than due to aerodynamics (like an airplane wing) the readings of a wind instrument calibrated in summer can be very inaccurate in colder weather. But racers generally are only looking for relative information (as in is there more wind and more speed than their was a moment ago) and so wind instuments work fine for most racing applications.
On racing sailboats the sail trimmers and helmsman need information to fine tune thier performance. If you are tring to agdjust course and sail trim for maximum speed and you only had a knotmeter to tell how fast the boat is moving you could not tell if a speed change was because of something you were doing differently or whether the wind had changed. After a while, you learn what the ''numbers'' should be for a given boat and can quickly look and tell if your boatspeed is consistent with the windspeed.
Tied to a knotmeter, more sophisticated wind instuments can tell you true wind speed and true wind direction and tied to an electronic compass it can give you Velocity made good (the speed at which you are actually moving upwind or down) so you can find the best course to the upwind or downwind mark.
For cruisers, Autopilots can use a combination of true wind speed, true wind direction and information from an electronic compass on the boat''s compass course to allow an electronic autopilot to keep a boat on course relative to the wind.
Good luck with your project,