NACA 0015 vs NACA 0018: Comparing Symmetric Airfoil Profiles

The cleanest thickness comparison in the catalog

NACA 0015 and NACA 0018 share a camber of zero and the same thickness family. Only the maximum thickness changes, from 15% to 18% of chord. Zero-lift angle is about zero for both. Quarter-chord moment in attached flow is about zero for both. Any difference on a polar at the same Reynolds number is a thickness difference, which is why the pair is a better lesson than two cambered sections of different thickness.

What 3% of chord actually changes

In the 4-digit thickness equation the leading-edge radius grows with the square of thickness. As a fraction of chord it is about 1.1019 τ². For 0015, τ = 0.15 and the radius is about 0.025 chord. For 0018, τ = 0.18 and the radius is about 0.036 chord. The thicker nose is the stall story: a milder suction peak at angle of attack, and usually a higher usable maximum lift and a rounder break, until Reynolds number or roughness moves the stall type. The thicker spar bay is the structural story. Eighteen percent is a lot of depth for a tail, a strut fairing or a root section that must carry bending.

How to compare them fairly

Generate both, cosine-spaced, with the same trailing-edge closure. Run the same Reynolds number, Mach number and transition setting. Read drag near zero lift, because that is where a symmetrical surface on a fin actually lives, and read the positive and negative stall. A tail that only looks good at CL = 0.6 has been scored as a wing. If 0018 wins the stall and loses a drag you cannot afford, the answer may be 0015 with a larger chord rather than a thicker section. Thickness and chord are both ways to buy spar depth.

---

Where this sits in the series

In simple words: what this page is for

Both sections are uncambered. NACA 0018 is thicker, so the leading-edge radius, the spar and usually the stall margin grow, and low-lift drag and critical Mach usually pay for it.

This lesson exists because section decisions fail when geometry, method labels and selection reasons are scattered. NACA 0015 vs NACA 0018: Comparing Symmetric Airfoil Profiles 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 NACA 0015 vs NACA 0018: Comparing Symmetric Airfoil Profiles 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 NACA 0015 vs NACA 0018: Comparing Symmetric Airfoil Profiles 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

• Airfoil Parameterization Methods: NACA Equations, CST and Spline-Based Geometry
• How to Compare NACA 0012, NACA 2412 and NACA 4412 Airfoil Profiles
• NACA 23012 Airfoil: Design Features, Lift Characteristics and Applications
• How to Read NACA 4-Digit Airfoil Designations: NACA 2412 Explained
• All HENDOI blog articles
• HENFOIL product page
• HENSYNTH product page
• Pricing — Student, Professional & Team
• FAQ
• Login · Register now

• Previous: NACA 4415
• Next: Eppler airfoils
• 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.