Forums > Kitesurfing   Western Australia

Safety bay wind meter?

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Created by doonut > 9 months ago, 21 Jan 2018
doonut
WA, 251 posts
21 Jan 2018 5:53PM
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How accurate does everyone think the safety bay wind meter is? It always reads +5kts more than everywhere else?

Is it actually located near the pond or somewhere else?

THE PIN PULLER
WA, 465 posts
21 Jan 2018 7:34PM
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A few mates and I headed up there today we were actually conveying on the matter on the drive homein the car. It was saying 30 knots I was on my 10 and if didn't fell like 30 the bar did not have grunt in the upper 1/3. Some dude was on an 11m shooting to the moon. So I would think maybe the meter is on or near that Island to the north ? Further out with no wind restrictions ?

August does the same it's up on the light house at the point.

cauncy
WA, 8407 posts
21 Jan 2018 9:44PM
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Select to expand quote
doonut said..
How accurate does everyone think the safety bay wind meter is? It always reads +5kts more than everywhere else?

Is it actually located near the pond or somewhere else?


Might be up here
if so you've still got 20/25


KiteBud
WA, 1515 posts
22 Jan 2018 8:59AM
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The Safey Bay meter is known to always over read by 5+ Knots. Not sure why but there must be a technical explanation to this. Use the Garden Island meter for a more accurate reading

Christian

doonut
WA, 251 posts
22 Jan 2018 4:21PM
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Yes it does seem to be inaccurate sometimes, but saying that so does Garden Island

SimonM
WA, 125 posts
28 Jan 2018 6:55AM
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Hey guys, the meter is on top of my place across the road from the jetty (blue house). Since we went up a storey the readings have jumped up 5kn on a SW. I think it is due to the wind gaining velocity as it goes over the house. Have been thinking about a higher mast to get cleaner air. Or alternatively just recharacterising the meter readings. If anyone has an old windsurf mast and some excess line/wire rope drop it by.

doonut
WA, 251 posts
28 Jan 2018 8:46AM
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Yeah, that would be sweet fix that puppy up.

davinchi
WA, 31 posts
7 Feb 2018 8:51AM
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Select to expand quote
SimonM said..
Hey guys, the meter is on top of my place across the road from the jetty (blue house). Since we went up a storey the readings have jumped up 5kn on a SW. I think it is due to the wind gaining velocity as it goes over the house. Have been thinking about a higher mast to get cleaner air. Or alternatively just recharacterising the meter readings. If anyone has an old windsurf mast and some excess line/wire rope drop it by.


The BoM use a standard height of 10m for their observations. Perhaps you could measure how high your anemometer is from ground level so a conversion to reduce the reading to roughly a 10m height can be made before it gets into seabreeze.

A good conversion to use is:
U = Ur*(10/Zr)^(1/7),
U = wind speed at 10m, Ur = your anenomometer wind speed, Zr = your anemometer height.

more info here:
en.wikipedia.org/wiki/Wind_profile_power_law

psychojoe
WA, 1804 posts
7 Feb 2018 8:36PM
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Your math doesn't take into account the venturi effect and other contributing factors .

SimonM
WA, 125 posts
7 Feb 2018 9:28PM
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Thanks for the link mate. I've fixed up the calibration using a bunch of data points. Looked good yesterday and today.. what do u think? Will have to see more wind directions to complete the job.

davinchi
WA, 31 posts
8 Feb 2018 6:01AM
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SimonM said..
Thanks for the link mate. I've fixed up the calibration using a bunch of data points. Looked good yesterday and today.. what do u think? Will have to see more wind directions to complete the job.


No worries! I would think that in a consistent SW'ly seabreeze you should be very close to Garden Island obs...

doonut
WA, 251 posts
8 Feb 2018 6:35PM
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Yeah sweet work dude, your number one

davinchi
WA, 31 posts
19 Feb 2018 8:27AM
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Select to expand quote
SimonM said..
Hey guys, the meter is on top of my place across the road from the jetty (blue house). Since we went up a storey the readings have jumped up 5kn on a SW. I think it is due to the wind gaining velocity as it goes over the house. Have been thinking about a higher mast to get cleaner air. Or alternatively just recharacterising the meter readings. If anyone has an old windsurf mast and some excess line/wire rope drop it by.


Seems like its going well lately and pretty close to Garden Island . Also... it looks like your have already applied this but... BoM wind obs are a 10 minute average (gusts are instantatneous)

SimonM
WA, 125 posts
19 Feb 2018 6:55PM
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What'd u think of results today? First real strong day since adjustments. Didn't get a chance to get out.

My gust is based on a 20 sec rolling average of speed and direction. Then the highest occurrence of that in the 5 minute reporting window is sent as the gust.

davinchi
WA, 31 posts
19 Feb 2018 9:22PM
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Select to expand quote
SimonM said..
What'd u think of results today? First real strong day since adjustments. Didn't get a chance to get out.

My gust is based on a 20 sec rolling average of speed and direction. Then the highest occurrence of that in the 5 minute reporting window is sent as the gust.


looks like it was reading a little higher than Garden Island obs today... it may just be to local effects and turbulence over your roof.
So you use a 20sec rolling average over a 5 min period for wind gusts but what do you use for the mean wind? 10 min period?

I got out at melville beach between 3 and 5 today... strongest wind Ive managed to get there all summer felt like my 8m was reading 30 knots over some rolling average chop



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