Airfoil Data
E668

The EPPLER 668 AIRFOIL is a 10.8% chord-thickness airfoil with a maximum camber of 5.4% at 42% chord, suited to general-aviation and UAV wing design. At zero angle of attack the cambered geometry generates positive lift, giving an estimated zero-lift angle of -5.4°.

Thin airfoil theory predicts a stall angle near 11.7° and a peak lift-to-drag ratio around 66 at typical UAV and light-aircraft Reynolds numbers — useful benchmarks before running a full XFOIL or NeuralFoil polar. The 11% thickness provides structural depth for main-spar placement without excessive drag penalty at moderate speeds.

Designers evaluating the E668 typically compare it against profiles of similar thickness: SD7062 (14%), EPPLER 548 AIRFOIL, CLARK YM-15 AIRFOIL, GOE 15K AIRFOIL, GOE 619 AIRFOIL. The BTE-FK is another reference profile frequently considered alongside it.