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 Post subject: Going upwind at >wind speed
PostPosted: Mon Apr 30, 2012 1:24 pm 
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Seems like from interviews that when the wind is less than 10 knots, the top guy are going upwind at or near twice the wind speed. Do they have to consciously slow themselves down to make a better upwind angle? It seems like at the high speeds the apparent wind would shift too much in front of you and although you are going very fast, your upwind angle would be low, lowering your VMG.

I've noticed this issue myself, having trouble getting as good of an upwind angle in low winds as I do in 10+ knots. (I'm also on a 183x59 board with 25 cm quad fins though)

So is it better to get as much speed as possible when going upwind, or is there a happy medium where you slow yourself down and point higher to get the best VMG?


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 Post subject: Re: Going upwind at >wind speed
PostPosted: Mon Apr 30, 2012 3:59 pm 
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I think you need to leep the kite low, not work it too vertically but rather horizontally, sheet out a bit to keep it forward in the window, turn you hips upwind is important. You definitely need board speed, pure grunt, bottom of the window kite is useless.


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 Post subject: Re: Going upwind at >wind speed
PostPosted: Mon Apr 30, 2012 4:36 pm 
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In sailing you sail at your optimum tack angle until you reach the layline. The layline is an imaginary line to the mark based on the optimum pointing angle for that particular craft in that particular wind. So the answer is "yes" there is what you call a happy medium, the optimal pointing angle different for every boat, current, and wind speed. Correspondingly in a direct downwind course you have to zig zag to the mark, not aim directly at it.


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 Post subject: Re: Going upwind at >wind speed
PostPosted: Mon Apr 30, 2012 6:13 pm 
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Develop the sense for your vmg....
maybe use some electronics to help with this...
Go out with gps and record some tracks.
On the computer, analyse it.
Come up with a "polar diagram" of how you board goes in different wind angles and windspeeds.
8)


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 Post subject: Re: Going upwind at >wind speed
PostPosted: Mon Apr 30, 2012 6:17 pm 
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edt wrote:
In sailing you sail at your optimum tack angle until you reach the layline. The layline is an imaginary line to the mark based on the optimum pointing angle for that particular craft in that particular wind. So the answer is "yes" there is what you call a happy medium, the optimal pointing angle different for every boat, current, and wind speed. Correspondingly in a direct downwind course you have to zig zag to the mark, not aim directly at it.


So on the current 70cm race boards is it best to go slow and point as high as possible or head down a bit to achieve the best VMG?

My reason for asking is because these boards are going so fast compared to wind speed, that as you start going really fast, your apparent wind shifts around in front of you considerably.

BWD wrote:
Come up with a "polar diagram" of how you board goes in different wind angles and windspeeds

I'm lazy, can't someone else just do it for me? :D


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 Post subject: Re: Going upwind at >wind speed
PostPosted: Mon Apr 30, 2012 6:35 pm 
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davesails7 wrote:
So on the current 70cm race boards is it best to go slow and point as high as possible or head down a bit to achieve the best VMG?


u can't make such generalizations. Depends on the wind speed. For instance here's a polar made by 76 trombones I think some random blogger but it's a good example

Image

Take a look at the red 20 knot line. Right about 30 degrees it begins to steeply slope in, which means, you do not want to tack upwind at 30 degrees. You also can notice at 20 knots that there is not a lot of difference between 42 degrees and 50 degrees, so you can see that you want this particular boat riding about 42 maybe 43 or 44 degrees when going upwind. Going downwind you see that the curve drops off steeply at 150 so you don't want more angle than that downwind. On the red curve you get a few knots of speed going from 90 to 110, but then from 110 to 150 it's pretty level. For this particular boat at 15 knots you would go directly downwind to the mark.

Now look at the 6 knot bright green curve. This one slopes much harder at 45 degrees so here you would want an angle of 45 degrees maybe 46 or 47 not 42. And also you want it directly downwind for that wind speed on the downwind leg. For 30 knots though, you might want the boat at 100 degrees not 90 when racing downwind you can tell by looking at the curve.

And no we can not make a polar for your kite and board because they don't exist you have to make one for yourself.

You can make a polar based either on true wind speed or apparent wind whichever seems to work best for you.


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 Post subject: Re: Going upwind at >wind speed
PostPosted: Mon Apr 30, 2012 7:35 pm 
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Wow, that's pretty awesome! I'll have to try to come up with one of these based on GPS files I've been recording. Is there a program that does this for you if you input the wind direction?

Seems like a yacht would be easier to get consistent data with though. Less up and down in speed due to small chop etc.

Anyone already have a plot like this for a 70 cm race board?


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 Post subject: Re: Going upwind at >wind speed
PostPosted: Mon Apr 30, 2012 7:47 pm 
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davesails7 wrote:
Is there a program that does this for you if you input the wind direction?


yes the above plot was made by one of the software programs just plug in the numbers and let it figure out the chart for you. I can't recommend any particular software over another tho. Not sure why you want someone else's polar diagram just because they are both 70cm wide, it's like going to the junk yard and asking for a computer out of a car that is 500 cm long, not caring what brand it is or even how many pistons it has. All kites, all boards, are different, even fins will be different. If you are too lazy to do it yourself, you'll have to pay someone to do it for you riding on your kite and board if you want the charts.


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