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Roughness at or very near the leading edge has a detrimental effect on
maximum lift coefficient. Vortex generators are added farther aft to
energize the boundary layer and delay/prevent flow separation. The
attached JPG is NACA data taken from "Theory of Wing Sections", p.147.
It shows the effect of a roughness strip which is .08c in length
consisting of .011 inch grains covering 5-10% of the strip area placed
at various chord positions.
Chris Zavatson
>>> Rob.Logan@Philips.com 11/19/02 01:08PM >>>
> bug buildup on [Martin Hollmann's blended 64212 airfoil ;
> 30% laminar flow on top and 70% laminar flow] resulted in
> an increased stall speed of about 15 knots.
I'm confused, if vortex generators make a turbulent layer
that stays attached to the wing longer, there by *lowering*
ones stall speed, how is the above true?
I do know the slightest frost on the leading edge of a LNC4
results in 7kts loss of cruse speed and very thin electric
ice boots [or LE tape] eats 5kts on the same plane. Having
never flown without at least one of the above, I had always
assumed my stalls were lower than a clean wing.
I'm confused..
--
Utopian Maturity: Eternity, Liberty, Equality and now Fraternity &
Altruism.
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