Clark Y Airfoil: Geometry, Aerodynamic Characteristics and Aircraft Applications

A section shaped for the shop

Virginius E. Clark’s Y section, from the early 1920s, is one of the few airfoils people still name when they mean a particular drawing rather than a formula. The lower surface is essentially flat from about 30% of the chord to the trailing edge. A builder can pin that flat to a table and wrap the ribs. Maximum thickness is about 11.7% of chord. The camber is moderate and sits forward of the mid-chord, so the section produces lift at zero geometric angle and carries a nose-down pitching moment. None of those facts is a polar. They are the geometry that made the section buildable.

What the shape implies

At the Reynolds numbers of light aircraft the Clark Y was a respectable, well-documented choice. At the Reynolds numbers of a small model it can carry a laminar bubble the original application never saw. A famous name does not move with scale. Run it at the chord and speed you have, clean and with a trip, before you adopt it.

Where it still belongs

Use it when the airframe wants a flat-bottom rib and a conventional cambered wing, and when you have the coordinates of the real Clark Y rather than a tracing someone relabelled. It is a poor choice when you need a wide laminar bucket, a very small pitching moment, or a transonic rooftop. Compare it with a NACA 2412 or 4415 at the same Reynolds number if you want to know what the flat bottom cost you. The comparison is a polar, not a legend. If you do not have the right to the coordinate set you are using, cite the section and generate or measure your own ordinates. A renamed file is not a Clark Y.

---

Where this sits in the series

In simple words: what this page is for

The Clark Y is a moderately cambered section with a flat lower surface over the rear half. It was drawn so a builder could set that flat on a board. It is not a laminar-flow section.

This lesson exists because section decisions fail when geometry, method labels and selection reasons are scattered. Clark Y Airfoil: Geometry, Aerodynamic Characteristics and Aircraft Applications 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 Clark Y Airfoil: Geometry, Aerodynamic Characteristics and Aircraft Applications 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 Clark Y Airfoil: Geometry, Aerodynamic Characteristics and Aircraft Applications 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: Airfoil performance mapping
• Next: NACA 23012
• 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.