Airfoil Data
SP4721BS

The SP4721BS is a 13.8% chord-thickness airfoil with a maximum camber of 6.9% at 37% 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 -6.9°.

Thin airfoil theory predicts a stall angle near 11.0° and a peak lift-to-drag ratio around 71 at typical UAV and light-aircraft Reynolds numbers — useful benchmarks before running a full XFOIL or NeuralFoil polar. The 14% thickness provides structural depth for main-spar placement without excessive drag penalty at moderate speeds.

Designers evaluating the SP4721BS typically compare it against profiles of similar thickness: MH 113 14.62%, EPPLER 1233 AIRFOIL, Glenn Martin 3, GOE 449 AIRFOIL, GOE 366 AIRFOIL. The AH-7-47-6 AIRFOIL is another reference profile frequently considered alongside it.