US Patent 7803068 Cavity back golf club head

A golf club head having a cavity back design with a cavity therein for placement of lightweight dual-durometer silicone. The club head is prepared by brushing an adhesive onto the interior wall, but omitting a pre-selected area of the wall to allow silicone to shrink away at the omitted area to allow for control of the shrinkage. A first shot of 80 Shore A silicone is placed into the cavity and disposed against the interior wall. Next, a softer 50 Shore A silicone is juxtaposed against the first shot of silicone and it is pressed using a hot mold finishing tool wherein a substantial portion of the cavity is filled. A polycarbonate insert is attached to an outer surface of the second silicone to provide a zero gap appearance. A tan delta ratio of the first silicone to the second silicone is greater than 1.6. A storage modulus of the first silicone is at least three times greater than the second silicone. And, a loss modulus of the first silicone is at least ten times the second silicone.