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Old 08-10-2017, 04:06   #1
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anti vortex board

ANY ONE WITH A CATAMARAN WITH ANTI WORTEX PLAN BOARD , BERN KOHLER STYLE,,http://www.ikarus342000.com/Antivortexp.pdf
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Old 08-10-2017, 05:40   #2
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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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Old 08-10-2017, 06:18   #3
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Re: anti vortex board

please read first the article,,,,, before writing,,,
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Old 08-10-2017, 08:46   #4
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Re: anti vortex board

I have seen these on many monohulls. Can't remember any on cats though.

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Old 08-10-2017, 12:12   #5
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Re: anti vortex board

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Originally Posted by barnakiel View Post
I have seen these on many monohulls. Can't remember any on cats though.

b.
Aparrently you dont follow instructions well either.
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Old 08-10-2017, 13:34   #6
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Re: anti vortex board

Ooooppss. Yes ;-)

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Old 09-10-2017, 08:46   #7
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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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Old 09-10-2017, 15:24   #8
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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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Old 09-10-2017, 15:30   #9
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Re: anti vortex board

In case nobody noticed, but the name is Bernd, not Bern
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Old 09-10-2017, 18:12   #10
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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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Old 09-10-2017, 18:32   #11
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Re: anti vortex board

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Originally Posted by vanvan450 View Post
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,,,,
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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Old 09-10-2017, 18:47   #12
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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 1930ís, yet you havenít 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 itís not generating lift, then there is no difference in pressure, and therefore no vortex.
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Old 09-10-2017, 18:49   #13
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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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Old 09-10-2017, 18:56   #14
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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 wasnít 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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Old 09-10-2017, 19:16   #15
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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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