Polar charts are the shared language of airfoil selection. HFOIL generates Cl–α and Cl–Cd curves so you can judge candidates under realistic UAV Reynolds numbers.
What to look for on Cl–α
A usable linear slope, a clear Cl max, and a stall break that matches your mission. Sudden hard stalls may be acceptable for racing UAVs but risky for training aircraft.
What to look for on Cl–Cd
Find the low-drag bucket near your cruise lift coefficient. Endurance designs often live at modest Cl with low Cd; short-field designs may accept more drag for higher Cl max.
Compare before you commit
Use HFOIL batch compare to overlay two or three sections. Document Re sensitivity — a polar that looks excellent at Re = 5×105 may degrade at Re = 1×105.
Engineering takeaway
Airfoil selection is a trade among lift, drag, stall gentleness, and pitching moment. Document Reynolds number, Mach assumptions, and geometry provenance whenever you share polars with a team.
How HFOIL helps you act
Use HFOIL on Windows to iterate sections, generate polars, move into wing loading, and prepare review-ready plots. For licensing in any country, use Contact Us or email support@hendoi.com.
Learn more
Students: treat each case as a lab notebook entry. Companies: shortlist two or three sections before freezing CAD. Academies: assign compare-and-justify exercises using batch plots.