Clark Y airfoil — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/clark-y-airfoil/  (sheet CC BY 4.0)
Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
Catalog version: 2026-10-20

Sizes: see table below
- 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).

parameter  value or range  source
Max thickness  11.7% chord  Mason (Virginia Tech)
Lower surface  flat from 30% chord aft  Mason (Riegels 1961)
Low-AR tests  AR 0.5-3; CLmax higher near AR 1  NACA TR-431
Coordinates source  Mason / Riegels; NACA R 427, 428, 431  Mason

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Virginia Tech (W.H. Mason): Airfoil definitions (Configuration Aerodynamics notes) — web — Publisher's page; dimensions are facts — https://archive.aoe.vt.edu/mason/Mason_f/C23AirfoilDefinitions.pdf
- NACA (C.H. Zimmerman): Characteristics of Clark Y Airfoils of Small Aspect Ratios, NACA TR-431 (1933) — web — Publisher's page; dimensions are facts — https://ntrs.nasa.gov/citations/19930091504
- NASA Langley / DTNSRDC (Thomas, Paulson & Margason): Powered Low-Aspect-Ratio Wing in Ground Effect (WIG) Aerodynamic Characteristics, NASA TM-78793 (1979) — web — Publisher's page; dimensions are facts — https://ntrs.nasa.gov/api/citations/19790022970/downloads/19790022970.pdf

No true-size file yet: the published figures do not fix the whole shape; a measured scan is planned.
API: https://xemstudio.com/api/geometry?object=clark-y-airfoil