The present disclosure relates to methods for manufacturing a part made from a composite material by means of a drape forming operation as well as to a tool for implementing the methods. In particular, the part has at least one inner convex surface. The methods use at least one outer manufacturing mold and at least one intermediate mold. The inner surface of the outer manufacturing mold substantially defines outer lines of the part to be manufactured, and the intermediate mold is arranged opposite the inner surface of the outer manufacturing mold such that an inner surface of the intermediate mold at least partially defines the molding lines of an intermediate portion of the part to be produced.