At 09:57 PM 4/11/2004, you wrote: > > "Ronald Metcalf" <poberfl...@hotmail.com> writes: > > The AS504x airfoil sections appear to be a big improvement > > over the RAF48. > > I am interested in the strange "tuck" underneath the trailing > > edge - the last few mm seem to droop down leaving a > > concave area right at the back (underneath).
That trailing edge cusp does several different things. When comparing to a related airfoil without the cusp, the coefficient of lift will be higher at a given angle of attack, the pitch moment will be more negative, and the boundary layer separation will tend to stay closer to the trailing edge. The maximum coefficient of lift of the two different airfoils will be approximately the same, but the cusped airfoil will reach it at a lower angle of attack. All of these parameters are compromises that affect the overall design of the airplane. It can be an acceptable airfoil for a wing root but will be a poor choice for a control surface. Aileron control forces will be high. It is a less than optimum choice for an airfoil that is intended to be laminar over a wide range angle of attack. Don Reid - donreid "at" erols.com Bumpass, Va Visit my web sites at: AeroFoil, a 2-D Airfoil Design And Analysis Computer Program: http://www.eaa231.org/AeroFoil/index.htm KR2XL construction: http://users.erols.com/donreid/kr_page.htm Aviation Surplus: http://users.erols.com/donreid/Airparts.htm EAA Chapter 231: http://eaa231.org Ultralights: http://usua250.org VA EAA State Fly-in: http://vaeaa.org
