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Old Jan 31, 2013, 07:18 PM
Love RC Yachts!!!
Australia, VIC, Melbourne
Joined Aug 2012
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It would nice to have that gain, but I've never seen a model boat race where you sail 100 metres without tacking, or altering course. To my mind, acceleration out of a tack, or in puffs is the priority.

Remember the Italiko / Topiko family of boats are well noted light air performers..

Whether you leave a wet n' dry finish, or a polished one, I don't think there's anything in it, as long as everything below the water is suitably free from dents and imperfections.

The late Frank Bethwaite had a great theory:
You can sand a keel, hull etc. smooth to touch. Side on, it will appear a dull or matt finish. You rub it back until when you hold it up, and sight down along it. and when it reflects light like a mirror, its done. This is how I do all my foils using 1200 wet and dry.
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Old Jan 31, 2013, 07:25 PM
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United States, MI, Bloomfield Hills
Joined Feb 2010
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According to Lester Gilbert....

http://www.onemetre.net/Design/Roughnes/Roughnes.htm
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Old Jan 31, 2013, 08:41 PM
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United States, MA, Wenham
Joined Jan 2007
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Quote:
Originally Posted by Tom Corbett View Post
We are talking about rough/smooth at a very fine level. The idea is that you want to have a level of roughness in your finish sufficient to trap a microscopic layer of water to the hull. This is because the friction difference between water and water is lower than between water and wax (hence less drag). Anything that repels water--like wax--is a bad thing. This is not an "opinion' thing it is established, basic hydrodynamic fact.
This is 100% right.
For a racing finish, Don't wax. Sand.
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Old Feb 03, 2013, 08:22 PM
20M northeast of Hell Mi
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United States, MI, Howell
Joined Jul 2012
259 Posts
did one of the late 80s or early 90s America cup boats have a "shark skin" coating on it?
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Old Feb 03, 2013, 08:50 PM
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Stars and Stripes '87 http://en.wikipedia.org/wiki/Stars_and_Stripes_87
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Old Feb 05, 2013, 12:59 AM
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Australia, VIC, Paynesville
Joined Sep 2009
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Frank Bethwaite

Quote:
Originally Posted by bigpat View Post
The late Frank Bethwaite had a great theory:
You can sand a keel, hull etc. smooth to touch. Side on, it will appear a dull or matt finish. You rub it back until when you hold it up, and sight down along it. and when it reflects light like a mirror, its done. This is how I do all my foils using 1200 wet and dry.
Hi BIGPAT, I wasn't aware Frank had passed. I worked with him and mainly Chris Mitchell on developing the SKUD18 Paralympic yacht - converting Frank's CAD drawings to full sized stations for Chris to build. I'm a disabled sailor so was a project close to my heart as I'd helped in testing Access 303 and Liberty yachts before that.

The Skud is similar to a 29er but was almost a TS-2 clone as we were talking with Gary Cameron and I wish it had gone that route as I liked the theory and practice behind the TS-2 (still have TS-2 CAD files but wouldn't release them to anyone - I wouldn't even build one myself as I believe in IP Rights). The TS-2 hull's ability to maintain a similar wetted surface profile as it heeled over, as a yacht with a bulb weighted keel and sailors on centreline (no hiking yet) I think was a better option but Frank convinced Chris to go the flat chined hull shape. The SKUD18 is a fun yacht to sail but needs to be upright to get hull planing - great fun under Asy on downwind.

Would have been interesting to see a TS-2 style hull 5.5 times bigger though!!! I race an old Orca design by BLUE FIN RADIO YACHTS, Qld. - wide skiff type hull IOM.
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