Airfoil Data
S9104

The S9104 is a thick 18.6% chord-thickness airfoil with a maximum camber of 9.3% at 35% 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 -9.3°.

Thin airfoil theory predicts a stall angle near 9.3° and a peak lift-to-drag ratio around 77 at typical UAV and light-aircraft Reynolds numbers — useful benchmarks before running a full XFOIL or NeuralFoil polar. The 19% thickness provides structural depth for main-spar placement without excessive drag penalty at moderate speeds.

Designers evaluating the S9104 typically compare it against profiles of similar thickness: S9104BTE, FX 69-PR-281, EPPLER 863 STRUT AIRFOIL, HAM-STD HS1-430 AIRFOIL, FX 77-W-270S. The FX 69-PR-281 is another reference profile frequently considered alongside it.