A method of manufacturing a Z-section component from composite material uses a mold having a convex mold portion and a concave mold portion. The method includes the preparation of a vacuum bag for a polymerization cycle, including the covering the fresh component with a layer of peel ply formed from a plurality of strips of peel ply and fixing the layer of peel ply perimetrically to the mold using an adhesive tape. A line of sealant is positioned perimetrically above the adhesive tape around the fresh component and a separator film is positioned above the layer of peel ply so as to cover the layer of peel ply and the perimetric line of sealant. A ventilation textile is placed perimetrically on the mold, the textile having an aperture which is positioned so as to leave uncovered an underlying part substantially coinciding with the fresh component. A vacuum bag is applied for the polymerization cycle.