Tom,
Thanks much for the detailed explanations!
We are privileged to have you in our little group.
Even though the links don't work I found all the papers in the
Max_airfoil
folder of the WingBoats files section.
Do you think the often quoted max lift of a sail at CL = 0.7 to 0.8 is
too low?
Seems that being a thin airfoil it might be a lot higher.

Deane

-----Original Message-----
From: wingboats@yahoogroups.com [mailto:wingboats@yahoogroups.com] On
Behalf Of Tom Speer
Sent: Thursday, July 31, 2008 12:30 AM
To: wingboats@yahoogroups.com
Subject: [wingboats] Re: Thin or Thick airfoils?

--- In wingboats@yahoogroups.com, "Williams, Deane G HS"
<deane.williams@...>
wrote:
>...
> In playing with the airfoil simulator "Foil Sim II" at
> http://www.grc.nasa.gov/WWW/K-12/airplane/foil2.html
> you see that increasing the thickness causes the lift (units=pounds)
to
> rise.
> Also many of the high-lift airfoils I see are very thick....

I've uploaded some papers to the Max_Airfoils files folder that might
help. Take a look at
Figure 13 in http://tinyurl.com/5rwp8p. The higher the design lift
coefficient, the thinner
the section gets. A.M.O. Smith explains why in
http://tinyurl.com/574bal.

Basically, there are two ways you can look at an airfoil. You can
represent it as a camber
line clothed in a thickness distribution, or you can view it as an upper
surface and a lower
surface.
--- snip ---