Selig Airfoil Series: How Researchers Develop Profiles for Small Aircraft

Development means design plus a test at the right scale

Michael Selig’s sections, including the SD series used on models and small unmanned aircraft, are the product of a loop. A candidate shape is drawn for a low chord Reynolds number and a design lift coefficient. It is tested in a low-speed tunnel at Reynolds numbers like those of models and small vehicles, often with a boundary-layer trip study as well as a clean run. The published polar is a measurement at those conditions, not a theoretical family like NACA 2412. The coordinate format many of those files use — upper surface from trailing edge to leading edge, then lower surface back — is the Selig order described in the coordinate lessons. The format is not the aerodynamic series. A file in Selig order can be any airfoil.

What the research loop is actually doing

1. Fix the Reynolds-number band and the lift coefficient of the application: a hand-launched model, a small UAV, a tail at an even lower Re.
2. Shape the pressure recovery so a laminar bubble, if it exists, stays short, and so the stall is not a surprise at that Re.
3. Build a model accurate enough that the leading-edge radius in the tunnel is the radius in the file.
4. Measure lift, drag and moment, correct the tunnel, and publish the conditions with the curves.
5. Change the shape when the bubble or the stall misbehaves, and test again. The designation is the shape that survived that loop, not the first sketch.

What you may carry into your own work

You may carry the method: design for the Reynolds number, test or recompute at that Reynolds number, and keep the surface condition in the record. You may carry a polar only for the Reynolds number, the trip and the geometry that were tested. You may not paste a published SD polar onto a heavier, faster airplane and call it validated. You also may not treat a downloaded coordinate file as yours to republish. In HENFOIL a named research section stays a citation until the ordinates are ones you generated or have the right to use. The scientific content of the series is the low-Reynolds-number evidence, not a folder of unlabelled DAT files.

---

Where this sits in the series

In simple words: what this page is for

Selig sections for models and small aircraft were developed by designing a shape, testing it at low Reynolds number, and publishing the result. The wind-tunnel Reynolds number is part of the design.

This lesson exists because section decisions fail when geometry, method labels and selection reasons are scattered. Selig Airfoil Series: How Researchers Develop Profiles for Small Aircraft helps you keep a clean trail from shape to polar to choice.

Why the topic matters

Engineers lose time when a title sounds clear but the page only sketches the idea. This article expands Selig Airfoil Series: How Researchers Develop Profiles for Small Aircraft so you can answer three questions without jargon: what is the idea, when do you use it, and how do you check it in a HENDOI product.

Read the sections above for the core definitions. Use the steps below to move from reading into a real project trail you can share with a teammate.

How to apply this in HENDOI

In practice: create a HENDOI account or log in, open HENFOIL, bring a section in (create, import DAT, or digitize), pass the geometry gate, climb the analysis ladder only as far as the decision needs, then compare and archive. Every calculated number should keep its method label.

When the section choice is ready for the aircraft, continue in HENSYNTH for mission, compliance and trades. Same account. Same plans.

What this page will not claim: a teaching polar or geometry note is not a flight-Re certificate. HENFOIL labels methods so you know what you bought. Tunnel data and professional judgement still sit outside any single software run.

Checklist before you leave this page

• Can you state the idea of Selig Airfoil Series: How Researchers Develop Profiles for Small Aircraft in one sentence?
• Do you know which product owns the next action — HENFOIL or HENSYNTH?
• Will every number you keep carry a method label or a stored-run source?
• If you are new here, have you opened Register or Login?

Related reading on this site

• Active Flow Control on Airfoils: Suction, Blowing and Synthetic Jets
• How Adverse Pressure Gradients Affect Airfoil Boundary Layer Separation
• What Is the Aerodynamic Center of an Airfoil? Location, Meaning and Applications
• What Is Airfoil Aerodynamic Efficiency Across a Range of Flight Conditions?
• All HENDOI blog articles
• HENFOIL product page
• HENSYNTH product page
• Pricing — Student, Professional & Team
• FAQ
• Login · Register now

• Previous: Eppler airfoils
• Next: Pressure recovery, drag and separation
• Index: all HENFOIL airfoil lessons

These pages teach the ideas. They are not wind-tunnel data and not a certification analysis. When a number matters, compute it at a stated Reynolds number, Mach number and transition setting, and keep the method label on the result. In HENFOIL that production polar is a VIC polar — see the analysis ladder and the polar field guide.