US Patent 6979270 Golf club face flexure control system

An improved line of golf clubs tailored to the golfer. The face wall firstly is designed so that the face wall modulus of elasticity increases from a low modulus for the low swing speed range to progressively higher modula for the higher swing speed ranges. Face modulus can be altered by a variety of techniques including face wall thinning, material selection and heat treatment or a combination thereof. In each of the swing speed range clubs, the face has a first modulus of elasticity determined by the face itself and after the face deflects to a predetermined value, the face modulus is significantly increased by a secondary wall parallel to and closely spaced behind the face wall.