Posted by: Paul Goodwin on November 03, 2005 at 08:57:32:
In Reply to: Re: Chicago area DN Clinics posted by Peter Hoeper on November 02, 2005 at 18:49:35:
If you round the top of the plank and leave the bottom flat,
you will create a lifting foil. It will have more drag and
less lift than a similar foil with a sharp trailing edge.
I think Jeff's planks have a symmetrical foil (same curve top
and bottom). These foils do no creat lift unless there is an
angle of attack. There is an angle of attack when the boat
squats in the back, but any lift generated would certainly be negligible.
However, a plank that does not have a symmetrical cross section
front to back (such as Jeffs) can create significant headaches
trying to control twist as it bends. Not impossible, it just
makes things more difficult.
Anyway, my suggestion would be to taper towards the leading
and trailing edges, and round them off nicely. Keep the
section symmetrical top to bottom, and front to back. This
will give a nice elliptical cross section with faily low
drag and minimal twist when bending.