Re: [Jsbsim-devel] Aitfoils at high alpha

[Ron F. <ron...@at...>]

----- Original Message ----- 
From: "Jon S Berndt" <js...@ha...>
To: <jsb...@li...>
Sent: Wednesday, July 21, 2004 3:08 PM
Subject: Re: [Jsbsim-devel] Aitfoils at high alpha


> On Wed, 21 Jul 2004 13:43:32 -0600
>   "Peter C. Buechler" <pc...@sa...> wrote:
> >Can you reach this from outside?
> >
> >http://infoserve.sandia.gov/sand_doc/1980/802114.pdf


    I see the shtml answer on High Alpha was from Jeff Scott.  Who did a lot
of the FlightGear models that were posted on the WEB. Of course
aerospace.org is Jeff's current site.

    I have some images of curves in "Horner" that give Cd and CL for some
airfoils up to 90 deg alpha.  They are about what Jeff mentioned.  After the
initial drop in CL past stall, it starts to peak, reaching a max at, I
think, 45 deg.  While Cd is also about what one would expect. It is not
simply proportional to CL^2 in these regions.

    In fact, now that the images in Jeff's reply have appeared, I see they
are similar to the Horner curves.  Though, I think Horner's plots don't peak
as close to CLmax at 45 deg.

    I think the shape of the CL curve is important in modeling spins  (also
Cm vs alpha).  I suspect CL  gets stuck a bit past the bottom of the dip at
20 degs in a stall/spin.  Something has to keep Alpha relatively constant
since a spin tends to stay in a constant state.

  Ron