Airfoil Data
S4094

The S4094 (root airfoil designed for and used on the E-flite UMX ASK-21 scale RC sailplane) is a thin 7.3% chord-thickness airfoil with a maximum camber of 3.7% at 29% chord, suited to high-speed UAVs, sailplane tip sections, and propeller blade design. At zero angle of attack the cambered geometry generates positive lift, giving an estimated zero-lift angle of -3.7°.

Thin airfoil theory predicts a stall angle near 11.8° and a peak lift-to-drag ratio around 56 at typical UAV and light-aircraft Reynolds numbers — useful benchmarks before running a full XFOIL or NeuralFoil polar. The slim profile minimises pressure drag at higher speeds but leaves limited spar depth for structural integration.

Designers evaluating the S4094 typically compare it against profiles of similar thickness: NASA/LANGLEY RC-12(N)1 AIRFOIL, EPPLER 817 HYDROFOIL AIRFOIL, NACA 66,2-(1.8)12 A=.6 P-51 TIP AIRFOIL, LOCKHEED C-141 BL113.6 AIRFOIL, EPPLER E852 AIRFOIL. The GOE 490 AIRFOIL is another reference profile frequently considered alongside it.