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Clark Y airfoil

What is the Clark Y airfoil? · Standard part · basis: Design rules and figures from the cited sources; example geometry by Xem Studio

Also called: clark y, clark y coordinates, clark y dat, flat bottom airfoil, clark y rc, clark y cl max, clark y airfoil template, clark y vs naca 2412, classic model airfoil

Exact dimensions. True size, with no printing tolerance added.

sizes
4 in table

Notes

  • The Clark Y has a maximum thickness of 11.7% and a lower surface flat from 30% chord aft (Mason, Virginia Tech, citing Riegels). The flat bottom makes it easy to build on a flat board.
  • NACA tested it widely, including TR-431 on very low aspect ratios (0.5-3), which found stall delayed and maximum lift increased at aspect ratios around 1 (NACA TR-431).
  • NASA's 1979 PAR ground-effect model used a 12% Clark-Y section (NASA TM-78793).
  • Used on: NASA PAR WIG test model (TM-78793).

Clark Y airfoil size chart

parametervalue or rangesource
Max thickness11.7% chordMason (Virginia Tech)
Lower surfaceflat from 30% chord aftMason (Riegels 1961)
Low-AR testsAR 0.5-3; CLmax higher near AR 1NACA TR-431
Coordinates sourceMason / Riegels; NACA R 427, 428, 431Mason

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

Virginia Tech (W.H. Mason)Airfoil definitions (Configuration Aerodynamics notes)webPublisher's page; dimensions are facts
NACA (C.H. Zimmerman)Characteristics of Clark Y Airfoils of Small Aspect Ratios, NACA TR-431 (1933)webPublisher's page; dimensions are facts
NASA Langley / DTNSRDC (Thomas, Paulson & Margason)Powered Low-Aspect-Ratio Wing in Ground Effect (WIG) Aerodynamic Characteristics, NASA TM-78793 (1979)webPublisher's page; dimensions are facts

Xem scan

File coming

No downloadable true-size file yet: the published figures do not fix the whole shape, and Xem never guesses a number. A measured scan is planned; request it and it moves up.

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Plain text: sheet.txt · JSON: /api/geometry?object=clark-y-airfoil

Schematic, not to scale.

Fits with

Selig S1223 airfoil7 sizes★ sheet
Eppler E387 airfoil3 sizes★ sheet
MH 32 airfoil6 sizes★ sheet
AG35 airfoil (Drela AG series)5 sizes★ sheet

Questions

Why is Clark Y popular with builders?

Its lower surface is flat from 30% aft, so ribs sit on a flat board (Mason).