This paper is a numerical analysis of the flow over a exible sail with the usual
two-dimensional model of ideal weightless incompressible fluid. The sail is assumed
to be impervious, inelastic and weightless, and may or may not be mounted on a
mast. Separated or attached flows are considered at any angle of attack. Our method
is validated by numerical and experimental results, i.e. the sail shape and velocity field
are determined by particle imaging velocimetry, and lift and drag by aerodynamic
balance. Despite the simplicity of the wake model we use (the Helmholtz model),
the computed free streamline geometry and especially the sail shape are in good
agreement with the experimental and numerical data.