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Sail effective sweep

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Created by fpw9082 > 9 months ago, 25 Nov 2020
John340
QLD, 3363 posts
26 Nov 2020 3:11PM
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Pacey said..

John340 said..
Keeping the mast laterally vertical is ideal, i.e. zero cant is the optimum for GPS speed sailing.



Evidence would suggest otherwise. Antoine Albeau on a world record 53.27 knot run:




Fair enough, still if you draw a line from the tip of the mast to the base, its not too far off vertical

decrepit
WA, 12767 posts
26 Nov 2020 1:53PM
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there's also apparent wind to consider. if the wind is side on, canting the sail reduces the size the wind sees, if the wind is front on cant has no effect. In practise it's somewhere in between.

Pacey
WA, 525 posts
26 Nov 2020 2:44PM
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John340 said..
Fair enough, still if you draw a line from the tip of the mast to the base, its not too far off vertical


Except that most of the drive is coming from the bottom of the sail, the top is more twisted and is working at a lower lift coefficient. There is significant vertical lift coming from the rig.

Cant has a directly beneficial effect on performance, try sailing with true zero cant and you won't go very fast.

olskool
QLD, 2459 posts
26 Nov 2020 5:25PM
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1 Do we induce the cant?
Or
2 Is it a by product of the sails slightly sideways pull reacting on the fin n board?
To balance that there must be a slight cant to windward of the sail.
For a certain board/sail/fin combo thered be a 'optimal' amount of cant for the conditions experienced.



olskool
QLD, 2459 posts
26 Nov 2020 5:29PM
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Fpw9082, if you don't want to rake the sail,just chuck a centreboard in. You will be able to dance all around the board with the mast vertical. You won't be fast as wetted surface area is huge. But you may learn the basics of windsurfing.

Ian K
WA, 4155 posts
26 Nov 2020 4:17PM
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Pacey said..

John340 said..
Keeping the mast laterally vertical is ideal, i.e. zero cant is the optimum for GPS speed sailing.



Evidence would suggest otherwise. Antoine Albeau on a world record 53.27 knot run:




So just looking at that pic would you say the air deflected by the sail exits on a slightly upward trajectory, a slightly downward trajectory or essentially horizontal?

decrepit
WA, 12767 posts
26 Nov 2020 5:56PM
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I'd say slightly downward at the bottom, but maybe upwards at the top?

Ian K
WA, 4155 posts
26 Nov 2020 6:51PM
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decrepit said..
I'd say slightly downward at the bottom, but maybe upwards at the top?


That's about what I'd guess. But if we could determine that one is more than the other we could apply rocket science 101 and know if the sail has a lifting or settling effect at speed.

decrepit
WA, 12767 posts
26 Nov 2020 8:38PM
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Madge said..
Why is this bloke asking such stupid questions.......???????????


I've no idea but it's bringing out some interesting discussion

Swindy
WA, 456 posts
26 Nov 2020 9:31PM
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Fpw's cousin has started on the foiling channel now.

Ian K
WA, 4155 posts
26 Nov 2020 10:37PM
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decrepit said..

Madge said..
Why is this bloke asking such stupid questions.......???????????



I've no idea but it's bringing out some interesting discussion


Trouble is many who know how to initiate a thought-provoking thread succumb to the peer group pressure to not think. We never hear of them again.



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"Sail effective sweep" started by fpw9082