Airfoil Data
E638

The EPPLER 638 AIRFOIL is a 10.6% chord-thickness airfoil with a maximum camber of 5.3% at 28% 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 -5.3°.

Thin airfoil theory predicts a stall angle near 11.7° and a peak lift-to-drag ratio around 65 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 E638 typically compare it against profiles of similar thickness: USA 40 B AIRFOIL, SPICA 11.73% smoothed, FX 61-147 AIRFOIL, GOE 775 AIRFOIL, USA 27 AIRFOIL. The BW 05 02 09 is another reference profile frequently considered alongside it.