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graeme_wilson View Drop Down
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Posts: 4 		Post Options Post Options   Quote graeme_wilson Quote  Post ReplyReply Direct Link To This Post Topic: Upwind Problems
    Posted: 20 Feb 13 at 1:56pm
Originally posted by G.R.F.

It's probably tide. Are the instruments GPS based?

Did you get a reply to this ? would like to know myself
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 12 at 1:27pm
How many times do old threads need reviving? Seems to be a specialty of yours DFF?

One way or another, I hope the OP's problem has been sorted by now!
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G.R.F. View Drop Down
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Posts: 4028 		Post Options Post Options   Quote G.R.F. Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 12 at 1:17pm
It's probably tide. Are the instruments GPS based?
https://www.ease-distribution.com/
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DFF View Drop Down
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Posts: 19 		Post Options Post Options   Quote DFF Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 12 at 11:49am
All my money would be on the IRC break this boat sails in: you are against 33 ft - 40ft all and sundry most likely and they will :
1) go faster upwind due to pure water line legnth- tweaks to rig get you quarter of a knot , 8 feet on the water line give you a knot!
 
2) give you masses of wind shadow and disturbed flow as they sail ahead of you due to 1: try sailing out to the right hand side of the course asap, even start behind the transom of a bigger boat at the committee boat end and tack away as soon as you can to the RHS.
Crewing on a Melges 24, against my better judgement...
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NickM View Drop Down
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Posts: 328 		Post Options Post Options   Quote NickM Quote  Post ReplyReply Direct Link To This Post Posted: 03 Feb 12 at 6:51pm
I once sailed in a Sonata that had a slightly sideways bent mast and it behaved exactly as you desibe: much faster and higher on the tack towards which the mast was bent.  Have you looked up your track to check it is straight?
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bert View Drop Down
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Posts: 584 		Post Options Post Options   Quote bert Quote  Post ReplyReply Direct Link To This Post Posted: 03 Feb 12 at 2:43pm
"all my money" would be on the question being answered ----- last year
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nathan View Drop Down
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Posts: 143 		Post Options Post Options   Quote nathan Quote  Post ReplyReply Direct Link To This Post Posted: 03 Feb 12 at 1:40pm

All my money would be on dodgy instruments...
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Isis View Drop Down
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Posts: 2753 		Post Options Post Options   Quote Isis Quote  Post ReplyReply Direct Link To This Post Posted: 03 Feb 12 at 11:48am
Im willing to bet your observed change in speed and TWA is an instrumentation setup or calibration issue. Remember that even when everything is central you have things like wind sheer which affect readings from tack to tack. On high end instrumentation its possible to dial all this out so that your numbers are identical, but many people prefer to leave it as it and calculate the shear offset in their heads as you go.

If you are sure its a boat speed issue then making sure the rig is central and in line with the keel is the first priority. If you cant get the boat out the water then measuring from the mast tip to the toe rail on each side as suggested above is a reasonable approach but never assume anything is truly symetrical. Its more important to have the mast in line with the keel than to have it perpendicular to the deck.

There are any number of other things it might be related too but the rig being out is the most common and easiest to sort out so its worth starting there.
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rb_stretch View Drop Down
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Posts: 742 		Post Options Post Options   Quote rb_stretch Quote  Post ReplyReply Direct Link To This Post Posted: 01 Nov 10 at 5:06pm
Originally posted by nmartin

Thanks for the advice - I'll double check the cars and measure how central the rig is.


Have to say I've never had a keel boat where both tacks were identical, despite checking everything was central. It is very difficult to calibrate the wind to be spot on, often waves are not always directly in line with the wind and then you have tidal effects......almost impossible to account for it all.
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nmartin View Drop Down
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Posts: 2 		Post Options Post Options   Quote nmartin Quote  Post ReplyReply Direct Link To This Post Posted: 01 Nov 10 at 1:09pm
Thanks for the advice - I'll double check the cars and measure how central the rig is.
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