Airfoil Data
E561

The EPPLER 561 AIRFOIL is a 12.9% chord-thickness airfoil with a maximum camber of 6.5% at 32% chord, suited to high-lift UAV wings, RC sailplanes, and low-Reynolds-number slow-flyers. At zero angle of attack the cambered geometry generates positive lift, giving an estimated zero-lift angle of -6.5°.

Thin airfoil theory predicts a stall angle near 11.3° and a peak lift-to-drag ratio around 70 at typical UAV and light-aircraft Reynolds numbers — useful benchmarks before running a full XFOIL or NeuralFoil polar. The 13% thickness provides structural depth for main-spar placement without excessive drag penalty at moderate speeds.

Designers evaluating the E561 typically compare it against profiles of similar thickness: DAI 1335, GOE 797 AIRFOIL, FX 73-K-170/22, USA 98 AIRFOIL, GOE 683 AIRFOIL. The USA 45 M AIRFOIL is another reference profile frequently considered alongside it.