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Daniel Holman View Drop Down
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Post Options Post Options   Quote Daniel Holman Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 12 at 12:23pm
I reckon approx 2% of club sailors - and even then those in more heavy air friendly craft - could get round the course in a true 30kts.
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G.R.F. View Drop Down
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Post Options Post Options   Quote G.R.F. Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 12 at 12:25pm
Originally posted by mozzy

Originally posted by G.R.F.

So, nobody tell me they can sail in any control in wind over 30 knots, it's not possible, even winching the boats up the beach with bare poles we still had a Contender blow clean over...



I think 30 knots is doable. 
That isn't 30 + knots, no whitecaps downwind, that water state? 25 if that..
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 12 at 12:51pm
2.5 hour race starting from 12 with the wind trace given at the start of the video. Average is always between 25-30 with gust up to 35 knots. It's in the harbour though, so relatively flat. Although the chop is often more difficult than proper waves. 

Edited by mozzy - 25 Jun 12 at 12:55pm
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Post Options Post Options   Quote ellistine Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 12 at 1:23pm
Something I noticed during the last Sail for Gold, the Portland Harbour anemometers were reading nearly 30knots yet the on the water commentators where reporting 16knots on their handhelds. As somebody who basis whether to sail or not on what the wall says, I wouldn't be surprised if I've ever sailed in much more than 20knots.
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 12 at 1:37pm
Originally posted by ellistine

Portland Harbour anemometers were reading nearly 30knots yet the on the water commentators where reporting 16knots on their handhelds.

Wind shear. Handhelds will be too low to be very reliable. Its wind speed ten to 15 feet up that really counts.
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Post Options Post Options   Quote RS400atC Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 12 at 1:45pm
Originally posted by ellistine

Something I noticed during the last Sail for Gold, the Portland Harbour anemometers were reading nearly 30knots yet the on the water commentators where reporting 16knots on their handhelds. As somebody who basis whether to sail or not on what the wall says, I wouldn't be surprised if I've ever sailed in much more than 20knots.


Windspeed is normally standardised at 10 metre height.
For weather people anyway.
At the sea surface it will be a fraction of that.
What happens at the height of  a dinghy rig will vary according to how turbulent the air is.
So 16 knots at deck level could easily be 30knots at 10 metres.
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Post Options Post Options   Quote Contender443 Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 12 at 1:48pm
Originally posted by RS400atC

Originally posted by ellistine

Something I noticed during the last Sail for Gold, the Portland Harbour anemometers were reading nearly 30knots yet the on the water commentators where reporting 16knots on their handhelds. As somebody who basis whether to sail or not on what the wall says, I wouldn't be surprised if I've ever sailed in much more than 20knots.


Windspeed is normally standardised at 10 metre height.
For weather people anyway.
At the sea surface it will be a fraction of that.
What happens at the height of  a dinghy rig will vary according to how turbulent the air is.
So 16 knots at deck level could easily be 30knots at 10 metres.
There are no many dinghies with 10metre rigs. Is there an equation to calculate at mid rig height say about 3m?
 
Mind you most ROs on a committee boat will be measuring the wind strength at about that height. They may also be using a yachts mast head anenometer.
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Post Options Post Options   Quote Neptune Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 12 at 1:59pm
A common one we use in offshore calcs is

wind speed at height z = wind speed at 10m X (height z/10) ^0.1, but its more appropriate for heights higher than 10m really.

the little ^ means to the power of, so 30knots at 10m would be equate to approximately 26.6kn at 3m and 23.8kn at 1m where a rib driver may be sat. 
RS300 and RS200, ex Musto Skiff
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Daniel Holman View Drop Down
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Post Options Post Options   Quote Daniel Holman Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 12 at 2:11pm
The anemometers at Weymouth tend to overread a fair bit, as do the bramble/chi/camber/sotonmet ones to a lesser extent.
I think that what we dinghy sailors refer to as x kts is the wind speed at yacht mast height.
Of course the handheld at an angle to the wind next to the rib console behind the fat bloke will read a fair bit less.
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Post Options Post Options   Quote Contender443 Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 12 at 2:13pm
Originally posted by mozzy

2.5 hour race starting from 12 with the wind trace given at the start of the video. Average is always between 25-30 with gust up to 35 knots. It's in the harbour though, so relatively flat. Although the chop is often more difficult than proper waves. 
Can I ask which station your trace comes from? If it was Chimet and you were sailing in the horbour I would expect the wind strength to be at least one force less. Plus as we now see there is also a height issue as Chimet will be well above your mast.
 
So it seems it is another case of forum wind.
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