Wind instrument - airflow behind mast

[roland stockham]

Hi all, need to fit a new wind instrument and don't have an easy way to get up the mast (solo and hate doing it alone unless it is an emergency). I was looking at the windvane, which steers the boat no problem, mounted at deck level and about 3ft behind the stern. Made me think that if that works why would it not work if I mounted the wind instrument on the back of the stern arch/solar panel mount which is directly above it? Anyone tried it?
Not super bothered about accuracy in terms of how many kn, if it reads 80% of true wind speed consistently thats fine. Main concern is that it shows any change and I can get a good idea of how much from my bunk!

[Stumble]

You can put it anywhere you want. But accuracy for both direction and speed falls off quickly when it isn't placed on top of the mast. Upwind it will be close to useless, on a reach moderately so, downwind it will probably be ok, but show weird wind shifts regularly as the wind bends upwards around the hull.


There is a reason why even on maxi race programs they take the penalty of putting wind instruments at the very top of the mast (really on wands above the top of the mast). It's the only really clean air available.

[El Pinguino]

Originally Posted by roland stockham

Hi all, need to fit a new wind instrument and don't have an easy way to get up the mast (solo and hate doing it alone unless it is an emergency). I was looking at the windvane, which steers the boat no problem, mounted at deck level and about 3ft behind the stern. Made me think that if that works why would it not work if I mounted the wind instrument on the back of the stern arch/solar panel mount which is directly above it? Anyone tried it?
Not super bothered about accuracy in terms of how many kn, if it reads 80% of true wind speed consistently thats fine. Main concern is that it shows any change and I can get a good idea of how much from my bunk!

After my mast top wind instrument blew away 10 years ago I used the output from my wind gen for many years. I have an ammeter at the chart table and a little table taped to the panel next to it... 20 amps is 60 knots....

Accurate enough for me.... its either windy or its not... all you get with fancy instruments is bragging rights .. 'we had 42.3 knots last night!'.... 'oh really?...yawn.........'