A method of forming an external rib on a helically wound article is disclosed. The method includes the steps of, in any suitable order, forming bunched strands or tows of continuous fiber, each bunch being held taught in-line with the major axis of the intended rib and successively winding each bunch or tow between successive sequentially helically wound fibers around an article former whereby the bunched strands or tows are each separated by helically wound strands of fiber, to thereby form on completion a wound article having integrally formed external support ribs of generally pyramidal section. A similar method is provided for forming an internal rib in a helically wound article.