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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.

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

On Saturday, February 21, 2015 at 5:09:07 PM UTC+13, 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.

Sure, carbon spars enabled them.

On Saturday, February 21, 2015 at 1:49:46 AM UTC-5, Bruce Hoult wrote:
On Saturday, February 21, 2015 at 5:09:07 PM UTC+13, 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.

Sure, carbon spars enabled them.

Spars AND skins. Torsional stiffness is a big consideration in these structures.
UH

I owned a Jantar-1 many years ago. From the weight of each wing panel, I surmise that the main spar was a steel girder, probably a recycled railway line. Modern technology enables thinner, lighter, stronger structures (and no steel girders!)

Mike

On Saturday, February 21, 2015 at 4:04:19 PM UTC-5, Mike the Strike wrote:
I owned a Jantar-1 many years ago. From the weight of each wing panel, I surmise that the main spar was a steel girder, probably a recycled railway line. Modern technology enables thinner, lighter, stronger structures (and no steel girders!)

Mike

Ever rig a Diamant 16.5? The list of who has done it once is long, the list for twice+ is VERY short....
I'm on the short list (used to crew for pay & food...)