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apparent wind upwind #261136
07/10/13 07:13 AM
07/10/13 07:13 AM
Joined: Jun 2007
Posts: 25
Netherlands
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Leo Ambtman Offline OP
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Leo Ambtman  Offline OP
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Joined: Jun 2007
Posts: 25
Netherlands
Sailing best vmg upwind is a problem to me. I realise that the problem could be the course I sail after the gust. I tend to steer down a bit to get lift and maintain speed. But as the true wind is down there is probably nothing to gain. Suppose after the gust the tru wind dies completly. Because of boat speed there is still apparent wind, however how much you steer down the apparent wind will always come from the front. So in true circumstances it is best to limit steering to the most. Anybody wants to comment?

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Re: apparent wind upwind [Re: Leo Ambtman] #261141
07/10/13 08:16 AM
07/10/13 08:16 AM
Joined: Aug 2007
Posts: 3,969
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brucat Offline
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A puff will give you a lift (I believe the technical term is velocity lift), as your apparent wind moves aft faster than your boat will accellerate. As you accelerate, the apparent wind moderates.

When the puff dissipates, the effect is a header. As you slow, the apparent wind will move aft.

If you sail into a hole, in theory, the telltales will show a header, until you bleed enough speed such that they point straight down.

How you react coming in and out of puffs has a lot to do with the strength of the puff relative to the true wind, position on the course, etc.

Speed & Smarts had an issue on this a whole back.

Hope this helps.

Mike


Re: apparent wind upwind [Re: Leo Ambtman] #261191
07/11/13 03:17 AM
07/11/13 03:17 AM
Joined: Jun 2007
Posts: 25
Netherlands
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Leo Ambtman Offline OP
newbie
Leo Ambtman  Offline OP
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Joined: Jun 2007
Posts: 25
Netherlands
If the boat accelerates the apparent wind does not moderate but increases in my opnion (upwind). Speed & Smarts? Where can I find this?

Re: apparent wind upwind [Re: Leo Ambtman] #261199
07/11/13 09:49 AM
07/11/13 09:49 AM
Joined: Aug 2007
Posts: 3,969
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brucat Offline
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brucat  Offline
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By moderates, I was referring to the angle.

The apparent wind moves aft when the puff hits. As you accelerate, the apparent wind moves forward (angle is moderated compared to when the puff first hits).

Speed & Smarts is a sailing (subscription) newsletter with a webpage. Google is your friend...

Mike


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