A variable camber aerofoil and a miniature boundary layer traverse unit have been designed and built to investigate the nature of flow around two-dimensional, highly cambered, sail-like aerofoil sections with circular masts. Data has been obtained in the form of static pressure distributions and boundary layer velocity profiles over representative ranges of Reynolds number, camber ratio, incidence angle, mast diameter/chord ratio and mast angle for both NACA a = 0.8 and NACA 63 mean-line camber distributions. All flow regimes present have been identified and related to the salient model and flow parameters. Using knowledge gained from the experimental results, a new partially separated flow theory was developed based on a discretized vortex/source panel technique. Comparison between experimental and theoretically predicted static pressure distributions showed excellent agreement.