Abstract: Impellers for ventilators are manufactured from fibre-reinforced synthetic plastics material by forming a flat base disc of resin impregnated fibres on a suitable support and forming notches around the periphery of the base disc. The portions of the batt adjacent the notches are bent upwardly or downwardly over suitable supports on which are laid further pieces of resin impregnated fibre to form the impeller blades. A cover plate, also of resin impregnated fibres can be applied to the free edges of the impeller blades to complete the impeller.One moulding apparatus for carrying out the method has a notched flat plate with supporting walls extending downwardly from the plate adjacent the notches. The base disc of the impeller is laid on the flat plate and the supporting walls serve as supports for the blades. Another moulding apparatus for carrying out the method comprises a hollow mould and inwardly extending supporting walls.