Abstract: A golf club head is provided with a center of gravity positioned within a partial ellipsoid defined in an impact reference frame that has its origin at the hit center of the face of the golf club head. The majority of the partial ellipsoid is located toward the golfer from the hit center and all of the partial ellipsoid is below the hit center in the impact reference frame.

Abstract: Improved golf club heads indicating the location of an optimum hit point on the striking face for maximum shot distance of any hit location on the face (“maximum distance spot”, called MD) and an indication of a second optimum hit point giving best distance, with the condition of minimum or no change of torque caused feel as perceived by the golfer at impact (“best feel spot,” called BF) are disclosed. Methods to locate these optimum locations are described. It has been widely assumed and believed that these two points have the same location. The present inventors have found that this is not true. The principal application is to “wood” type golf clubs designed to hit golf balls from a tee, but can provide useful information for clubs hitting balls from the ground. The indication of MD and BF locations on the club face may take any of various forms.

Abstract: A golf club head, more specifically a driver head, has a shell structure aft of the face that has ample strength but also can deform in the fore-aft direction for off-center hits sufficiently to provide good spring effect for such hits, comparable to hits at the center. Unwanted scatter caused by off-center hits is reduced with the spring design used in the shell structure. The shell structure can be applied to other hollow wood-type club heads. The shell structure can be provided with a coat or cover to close openings in the shell structure, and selected to make little change in stiffness or mass of the shell.

Abstract: A golf club head, more specifically a driver head, that has deformation for center hits that is typical of current spring-effect drivers having a slightly springy face, but atypical in that it has substantially more deformation for off-center hits as compared to current designs. This is achieved by providing a shell structure aft of the face that has ample strength but also can deform in the fore-aft direction for off-center hits sufficiently to provide good spring effect for such hits, comparable to hits at the center. Current designs also change slope of the face surface for off-center hits, causing unwanted scatter of the launch angle and/or direction. That effect may also be reduced by appropriate design of the novel design. These features are accomplished by a novel spring design in the shell. The novel design can also be applied to other hollow wood-type heads.