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08-10-2017, 04:40
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#2
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Registered User
Join Date: Dec 2010
Location: W Carib
Boat: Wildcat 35, Hobie 33
Posts: 13,488
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Re: anti vortex board
Never encountered them on cats, but there are of course many "winged" keels and rudders out there, just not common on cats...theory is the same though and should work.
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08-10-2017, 05:18
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#3
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Registered User
Join Date: Sep 2017
Posts: 24
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Re: anti vortex board
please read first the article,,,,, before writing,,,
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08-10-2017, 07:46
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#4
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Registered User
Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 20,441
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Re: anti vortex board
I have seen these on many monohulls. Can't remember any on cats though.
b.
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08-10-2017, 11:12
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#5
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Registered User
Join Date: Dec 2010
Location: W Carib
Boat: Wildcat 35, Hobie 33
Posts: 13,488
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Re: anti vortex board
Quote:
Originally Posted by barnakiel
I have seen these on many monohulls. Can't remember any on cats though.
b.
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Aparrently you dont follow instructions well either. [emoji1]
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08-10-2017, 12:34
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#6
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Registered User
Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 20,441
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Re: anti vortex board
Ooooppss. Yes ;-)
b.
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09-10-2017, 07:46
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#7
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Registered User
Join Date: Dec 2005
Location: Cat in New Zealand, trawler in Ventura
Boat: 46' custom cat "Rum Doxy", Roughwater 41"Abreojos"
Posts: 2,053
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Re: anti vortex board
OK, I read the article (Sort of, I looked at the pictures). People were sticking these on Wharrams for a while in an effort to increase weatherliness, but, if I recall, they did not work out so well in practice and the added wetted surface was not worth it.
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09-10-2017, 14:24
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#8
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Registered User
Join Date: Sep 2017
Posts: 24
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Re: anti vortex board
BERN KOHLER SAYS , I COULD SAIL AS CLOSE TO THE WIND AS MONOHULL WITH HIS 11 METERS CATAMARAN PELICAN (WITH ANTI WORTEX PANEL),,, ANY ONE WITH AN EMAIL FOR BERN,,,, AND WE COULD HAVE HIS OPINION,,,,
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09-10-2017, 14:30
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#9
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Registered User
Join Date: Oct 2010
Location: TX
Boat: Whitby 42
Posts: 348
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Re: anti vortex board
In case nobody noticed, but the name is Bernd, not Bern
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09-10-2017, 17:12
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#10
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Registered User
Join Date: Dec 2005
Location: Cat in New Zealand, trawler in Ventura
Boat: 46' custom cat "Rum Doxy", Roughwater 41"Abreojos"
Posts: 2,053
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Re: anti vortex board
A lot of cats will sail as close to the wind as a monohull without anti-vortex panels. Was the boat built with anti-vortex panels or did he add them later? If he added them later and noticed an improvement in performance, that would be significant. If the boat was launched with them, then there is no way of knowing whether the panels helped or hindered performance.
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09-10-2017, 17:32
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#11
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Registered User
Join Date: Dec 2010
Location: W Carib
Boat: Wildcat 35, Hobie 33
Posts: 13,488
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Re: anti vortex board
Quote:
Originally Posted by vanvan450
BERN KOHLER SAYS , I COULD SAIL AS CLOSE TO THE WIND AS MONOHULL WITH HIS 11 METERS CATAMARAN PELICAN (WITH ANTI WORTEX PANEL),,, ANY ONE WITH AN EMAIL FOR BERN,,,, AND WE COULD HAVE HIS OPINION,,,,
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Many cruising cats already sail as close to the wind as many cruising monohulls. There are a lot more factors involved than just "anti-vortex" panels.
My cat easily sails at 40-45d AWA, and will pinch to about 30, perfectly acceptable for a cruising boat and comparable to many cruising monos. My Hobie 33 (racing mono) will sail at 28d AWA (yep, 28!)....no matter how I mod the keels of my cat, it wont ever do that.
Sea state affects cats and monos very differently too in terms of the sailing angle they can actually make good, regardless of angle they can sail to the wind.
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09-10-2017, 17:47
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#12
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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anti vortex board
I know a little about aerodynamics, just a little.
Are they talking about end plates and calling them anti vortex boards?
If so end plates were pretty fashionable in the 1930’s, yet you haven’t seen them for almost 100 years.
However you see them on race cars where the aspect ratio of the wing is severely restricted.
I assume you put these things on the keels? Being a fully symmetrical airfoil, how much lift does a keel generate? I would assume nearly zero as it has pretty much a zero angle of attack? If it’s not generating lift, then there is no difference in pressure, and therefore no vortex.
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09-10-2017, 17:49
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#13
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Registered User
Join Date: Jul 2012
Location: Hobart
Boat: Alloy Peterson 40
Posts: 3,919
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Re: anti vortex board
Check out Mat Laydens chine runner concept as used on paradox, Same basic idea. Ive seen one of Bernds catamarans sailing down here, seems to go very well.
I put an delta shaped end plate on SnowPetrel1's rudder. Certainly improved control, and I think speed.
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09-10-2017, 17:56
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#14
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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anti vortex board
I would assume most performance boats keels and rudders are elliptical, like the Supermarine Spitfire? If so an elliptical wing tip is much more effective at reducing drag from wing tip vortices than an end plate.
However it wasn’t the go to wing planform for military aircraft due to it being harder to build with higher parts counts and therefore more expensive and lower production rates or you would have seen it more often.
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09-10-2017, 18:16
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#15
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Registered User
Join Date: Feb 2013
Location: Oregon
Boat: Seafarer36c
Posts: 5,563
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Re: anti vortex board
These are not end plates they are winglets. Every new jet has them.
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