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Re: Fairing Keel & Rudder???




Mike Foreman wrote:

> Hi There
>
> I'm kicking around the idea of fairing my rudder. keel and centre board,
> in the aim of more performance. On my keel (mark 1) the rear is cut off
> with no attempt to taper the keel. This has to create significant drag
> but by extending the keel back in a reasonable smooth taper this would
> increase the keel area at the very back of the keel. I have been looking
> at the web site of Computer Keels (www.computerkeels.com) but want the
> opinions of non salespersons first.
>
> So here are the questions......
> 1. Has anyone fair their San Juan 23 Mark I ????
> 2. The rear cut off portion in 2" X 12", so extending the keel back in a
> smooth taper would  increase the keel area. Wouldn't this change the
> handling considerable??? (hopefully decreasing drag??)
>
> --
> Mike & Joyce Foreman      mforeman@sas.ab.ca
> Home of  "Joy IV"
>
> San Juan 23 Internet Fleet:  http://www.geocities.com/Yosemite/Rapids/5493/
> San Juan 23 Tech Tips:  http://www.geocities.com/Yosemite/2358/index.html
> mailing list commands:  mailto:majordomo@peak.org?body=help

This a very interesting idea you have here.  I remember a similar thing that
Bruce Bingham did to his boat about 15 years ago.
He faired his prop hole in the keel to improve the thrust.  By simply rounding
the corners he could drive the boat about 20 to 30 % faster with the same
throttle setting.  He chose instead to travel at the same speed with reduced
fuel costs.  So your idea should work.  However, I suggest you try it out with
a temporary jig before you go to all the effort of glass work.

Cut a suitable length of matching diameter ABS tubing and attach it temporarily
to the aft end of the keel.  Plug the ends to eliminate the turbulence.  This
should eliminate about 80% of the drag with minimal effort. If you can measure
an improvement, let us all know.  In fact I think I will try this idea myself
next summer.

--
Regards

Bob Schimmel
Spruce Grove, Alberta
Canada



San Juan 23 Internet Fleet:  http://www.geocities.com/Yosemite/Rapids/5493/
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