I'm am looking for an airfoil shape (without flaps etc.) with a very high max. lift coefficient. Obviously the ratio of lift to drag coefficient should be high as well in that point. Is there an 'ultimative' airfoil shape ?

Mark

Hello Mark, Yes, there exists such a thing and it is called a Liebeck airfoil after its originator. The most complete reference I know is AIAA Paper 76-406 "On the Design of Subsonic Airfoils for High Lift" by Robert H. Liebeck. You can also look in "High-Lift Aerodynamics" by A.M.O. Smith, Journal Of Aircraft, Vol.12, No.6, June 1975, pp.501-530 or: "A Class of Airfoils Designed for High Lift in Incompressible Flow" by Robert H. Liebeck, Journal of Aircraft, Vol.10, No.10, Oct. 1973, pp.610-617. The theoretical maximum Cl for a single element airfoil at a Reynolds number of 5x10^6 is 3.06 with a lift to drag ratio of 600!

Read the articles introduced from Johan. For highest lift, from my experience, one should modify the shape of an original airfoil such as introduce stepwise discontinuity on the airfoil.

Could you explain in more detail what you mean by that ?

Mark

Hi Johan,

haven't read these papers I guess that this airfoil is not symmetric. Do you know a high lift single element airfoil that is symmetric ?

Thanks in advance,

Tim

Hello Tim,

Yes, the Liebeck airfoils are highly cambered to achieve high lift at low drag. To me it seems rather contradictory to speak of a symmetric high lift airfoil. If I may rephrase your question to: "What would be the highest lift for a symmetric airfoil?", I can refer you to the Resources\References\Airfoils of this Website. A maximum Cl of 1.6 [NACA 0012] is typical for symmetric airfoils of moderate thickness.