Abstract: A process for modelling a sail with a sandwich configuration and a three-dimensional convex shape, wherein the “mould” is formed by a semirigid film material which has a shape identical to that of the sail to be produced. On this kind of “parent sail”, a cloth is prepared by adhering, by means of a removable adhesive, synthetic weft (1) and warp (2) filaments onto the “parent sail”. This cloth will form the inner layer of the final “sandwich”. Two thin external plastic laminates are applied on the cloth, one on each side, after removal of the cloth from the “parent sail”. The thin external plastic laminates are applied in individual pieces adapted to follow the convexity of the cloth. The application of the external laminates is performed on a plane support.