U.S. Patent Specifications

The method of producing a hollow metal propeller blade from a tubular blank, which consists in providing the blank on opposite sides thereof with wall‐portions of varying thickness, flattening the outer portion of the tubular blank upon itself with the greater wall‐thickness at the folds, trimming the edges of the flattened portion of the blank to form face‐sections extending approximately from mid‐length of the blade to the tip along lines conformably to the leading and trailing edges of the blade, joining the sections along the leading and trailing edges, and expanding the joined sections to airfoil shape.