On Friday, February 20, 2015 at 10:09:07 PM UTC-6, Bob Kuykendall wrote:
On Friday, February 13, 2015 at 9:49:02 PM UTC-8, Bruce Hoult wrote:

...but they lose badly to the new thin airfoils at high speed...

It's kind of a nitpick, but there's really nothing new about thin airfoils. What has changed in the last decade and a half is the cost-effectiveness of the structure required to implement them in competitive sailplanes.

Thanks, Bob K.

I think there is something new about the thin airfoils in use today, though, Bob. Laminar flow over a greater percentage of chord. Laminar flow over that chord at much lower reynolds numbers. Ability to maintain low drag to higher C/L.

Chicken and egg sort of question. Did structural design philosophy dictate airfoil design in terms of thickness, or did the airfoil design encourage continued use of the same old structural design techniques?

Steve Leonard