On Sun, 18 Jul 2004 12:45:02 -0700, Eric Greenwell
wrote:

I was talking about the separation on the top surface at high AOA
during a "stall situation". I now realize you were talking about laminar
flow separation on the bottom surface, which isn't related to the stall
situation.

Actually, I was talking about upper surface separation at low speed -
thermalling regime. Our oldest club Discus has zigzag turbs just ahead
of the aileron hinges and those were the turbs I was thinking about.
I'm not sure how common there are, come to think of it, because the
other club ship (Czech-bult with tiplets) doesn't have them.

I forgot about the lower surface turbs, but I think their placement is
due to airfoil shape rather than anything else. I've only seen them in
front of the narrow undercambered area under the TE and assumed they
were to stop separation in the undercamber dish at the top end of the
speed range.

I hope I didn't cause too much confusion there.

For the modern laminar airfoils, the transition (from laminar flow to
turbulent flow on the bottom of the airfoil) is at least 80% or more. On
my ASH 26 E, the turbulators are on the flaps and ailerons at about 95%.

Interesting - I've never seen a 26E close enough to know what its
airfoil looks like. Does it also have a somewhat hooked trailing edge?

The transition from laminar flow to turbulent flow on the top of the
airfoil is sooner, perhaps in the 60%-80% range. There is rarely a
laminar flow separation, though the Speed Astir is a well-known example.

Could it have been more of a problem on the early glass? I've read
Will Schueman's article about the development of his triple break
leading edge a couple of times. The separation bubble on his ASW-12
seems to have been huge and thick. His analysis of the problem and the
way he went about developing the fix is a classic.

--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :