A method of replacing a portion of a composite airfoil in a turbine. The method comprises the steps of providing a turbine with a plurality of composite airfoils mounted on a wheel. At least one of the composite airfoils has a core made of a non-plastic material and a plastic airfoil portion to envelope at least a portion of the core. A composite airfoil having an airfoil portion in need of replacement is accessed. The plastic airfoil portion is removed to expose the core while the core is mounted on the wheel. A plastic airfoil portion is molded to envelope the core while the core is mounted on the wheel.