While not approved for certified craft STOLSPEED (www.stolspeed.com)
has some inexpensive VG's for a number of airframes.
Some good info on their website...
Kim Blackseth
N2332H
On Apr 10, 2009, at 7:14 AM, Ed Burkhead wrote:
Robert asked:
> Does anyone know if there are any Vortex generators approved for the
> ercoupe specifically the Alons .
Robert,
Very interesting question.
I don't know of any approved vortex generators for any model of Coupe.
It occurs to me that vortex generators are likely to be useless or
counterproductive on Coupes.
1. Coupe's minimum flying speed is not a stall speed.
2. In extensive discussions on vortex generators on the Challenger
ultralight/eLSA forum, it was agreed that while vortex generators
do lower
the stall speed, the stall, when it does happen, is more abrupt.
3. The airfoil used on the Coupe's wings is pretty efficient for
our gross
weight range, speed and minimum flying speed. I have read that this
airfoil
has a downside of an abrupt stall break. That stall break doesn't
affect
Coupes as we don't allow the wing to stall (more than a tiny bit at
the
root). [I'm sorry I can't cite the source of this.]
It seems to me that combining an airfoil which has an abrupt stall
break with vortex generators which might acerbate the stall break
might be
undesirable.
4. The Coupes design includes the inability to be held in a spin
because it
can't be held in a condition where the wing is seriously stalled.
The limit
on elevator effectiveness prevents the tail from being pushed and
held down
to give enough angle of attack for that serious stall. With no serious
stall, there's no asymmetric stall resulting in autorotation, i.e.
no spin.
The wing root does begin to stall with full up elevator. This is
controlled by the fillet shape between the wing and fuselage and by
the
small ridge on the leading edge of the wing at the wing root. The
stalled
air only extends in a fan shape from the wing root a small way out
the wing.
The turbulent air from this small stalled zone then travels over the
empennage, reducing the tail's negative "lift" and helping limit
the down
push on the tail. Removing this stall could allow the tail to be
pushed
somewhat farther down which could allow too much of the wing to
stall for us
to predict the behavior.
Summary: I know of no vortex generators for Coupes. It doesn't seem
like a
good idea for our unique birds.
If you are adventurous and wealthy, you might hire an FAA authorized
Designated Engineering Representative (DER) who's especially good at
aerodynamics and do extensive flight testing to see if any benefit
could be
obtained.
Great question.
These are just my humble opinions. Remember that I'm not a
mathematical
aerodynamicist.
Ed
Kim Blackseth, ICC, CASp
310 17th St
Oakland, CA
510-839-1760
