Vance Jaqua wrote:

I think that the Clark Y class airfoils are being
given a bad rap on drag - The Clark Y is not
identified in Abbot and Von Doehoff but the 4412 is so
close that it must have been copied. The prop blade
spends a lot of time at low Reynolds number and higher
lift coeff (like climb etc) - the 4412 holds roughly
.007 clear out to 0.8 cl for a l/d of over 100. Some
of the fancy foils
get low drag coeff down in the "drag bucket" but they
climb up past .008 Cd before they reach 0.8 Cl. And
you cannot keep the whole prop down in that bucket
like you can a wing (and higher Relnolds Numbers with
the wider chords.

 Obviously, out at the tip, it pays to get thin, with
max thickness pushed back to minimize Mach No effects,
But don't sell the flat bottm foils short.
Vance - Mechanical Engineer and part time airplane designer.

I think Bill Freeman agrees with you on that Vance. Did you see 
the new Hartzel prop on the Baron at Sun & Fun or at Reno?

What is your opinion on aluminum foam?

Paul Lamar
 
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