Calibration of wind speed.

[AngusMcDoon]

Most useful cal may be to motor into wind at 5knots and check the indication goes up by 5, then motor downwind and check it reduces true wind by 5.
As others have said, the sails tell you how windy it is, but I find a windspeed reading valuable when sailing downwind, to tell me what I'm going to see when I head up onto a beat.
Apparent wind can be very deceptive on deck when running.

Wind speed can vary with height by different amounts on different days, so cal'ing to another anemometer can send you around in circles.

I really can't see calibrating against natural wind however you do it is going to give a useful result as it is just too variable, changing by the second.

 

[rob2]

...you would not use a speedo in a car, just stick your neck out of the window to gauge the apparent wind speed.

Could be true! My observation is that the more a car costs, the less likely it is to have a speedo - perhaps the window is closed and the aircon on full blast?

Even if the manufacturers were to calibrate the sensors, the fact is that they are designed to be compact and as such they are very prone to affects of the state of the bearings. Usually the first indication of a problem is that the cups won't rotate in lower wind speeds, so I would also expect them to be subject to increased drag across the range and would therefore read a lower speed than when new. The second effect is that they give up the ghost and maybe blow away! If they weren't so expensive, I'd love to try one of those sensors with no moving parts (bad day - can't think of the correct terminology).

Don't get me wrong, I like being able to get a comparitive reading of speed and direction without getting a crick in my neck, but a burgee also gives both direction and strength by the way it flies - not always a direct reading, but repeatable - you just have to modify your seating position at the helm to get a look at it. To be honest, while wind speed is the major factor in chosing when to reef, you don't need a readout to know when it's time - boat motion angle of heel and observed leeway should tell you and it's surprising how often the boat picks up speed once reefed.

Rob

 

[lw395]

I really can't see calibrating against natural wind however you do it is going to give a useful result as it is just too variable, changing by the second.

Not always.
It's a simple check you can do anytime, whenever you find the wind is steady.
One baseline is to motor on a totally still day of course.
It's generally the light end of the scale where you can't trust the instruments, like not turning at all in 3kts apparent.
I tend to be reluctant to fiddle with instrument settings until I've done a lot of checks and built up a useful picture.
Some boats, the wind sensor is hopelessly in shadow or turbulence, particularly on a dead run.

 

[AngusMcDoon]

Not always.
It's a simple check you can do anytime, whenever you find the wind is steady.

We will have to agree to differ. My observation is that natural wind is never near enough constant over the timescale required to do the procedure you suggest and any "calibration" against a varying datum is going to end up with your wind instrument in an unknown and therefore uncalibrated state, probably worse than not doing anything at all.

 

[SHUG]

Forget it and use a candle.
If it stays alight ,there isn't enough wind for sailing and if it blows out then it's too windy for sailing.

 

[Daydream believer]

I think the factory settings will be accurate enough for sailing but if you record your windspeed at various times during the day you can then cross-check with the windspeed recorded at Glasgow Airport.http://www.weatherhq.co.uk/weather-station/glasgow-airport
If you wan't to develop the idea , sail up to Renfrew.

Is it easy to get a landing slot?

 

[dunedin]

Compare readings with other boats in the same marina / location and average out?

Suspect the racy modern boats with fancy B&G kit will try to have pretty accurate readings (to compare with their design polars for checking they are hitting their target speeds). And if moored alongside the wind readings will be at similar heights.
The sailmakers (and RYA dinghy coaches) are also likely to have access to reasonably accurate wind speed gauges, more than sufficient for any cruising usage.

 

[jwilson]

Compare readings with other boats in the same marina / location and average out?

Suspect the racy modern boats with fancy B&G kit will try to have pretty accurate readings (to compare with their design polars for checking they are hitting their target speeds). And if moored alongside the wind readings will be at similar heights.
The sailmakers (and RYA dinghy coaches) are also likely to have access to reasonably accurate wind speed gauges, more than sufficient for any cruising usage.

If you really want to calibrate a seriously top-end race boat my be your best bet: you need someone who sails to target speeds and trims constantly (not just now and then) to maintain them. That boat just might have fairly accurate instruments. But for cruising (even for cruisers who do like to trim pretty well and sail efficiently) it's irrelevant.