Golf clubs take various forms, for example a wood, a hybrid, an iron, a wedge, or a putter, and these clubs generally differ in head shape and design (e.g., the difference between a wood and an iron), club head material(s), shaft material(s), club length, and club loft.
Woods and hybrids generally have a longer shaft and lower loft than irons and wedges. Thus, a golf ball that is struck with a wood or a hybrid generally travels a greater distance than a golf ball struck with an iron or a wedge. While a longer shaft and a lower loft provide increased golf ball travel distance, this combination also results in less forgiveness. The longer shaft requires a golfer to stand farther away from the golf ball at address. This leads to greater difficulty during the golf swing to return the club head squarely to impact the golf ball. A golf club that is slightly open or slightly closed at impact results in reduced accuracy as the golf ball is not launched on the desired target line. Further, the higher swing speeds from the longer length shaft can lead to greater difficulty in making consistent contact with the center or “sweet spot” of the golf club face. Off-center contact can lead to imparting increased side spin on the golf ball. At reduced lofts of woods and hybrids, less back spin is imparted on the golf ball at impact, further exacerbating imparted side spin and leading to undesirable hooks or slices, which further decrease accuracy.
To improve directional forgiveness, golf club manufacturers have made efforts to increase the moment of inertia of a golf club at impact. The moment of inertia (or “MOI”) is a measure of a body's resistance to angular acceleration, or twisting. The higher the MOI of a golf club head, the more the golf club head resists twisting at impact, improving golf ball accuracy, especially on off-center contact (or mishits). In addition, the increased stability of a higher MOI golf club head results in a golf ball losing less ball speed on off-center contact due to reduced energy loss associated with reduced twisting. A higher MOI of a golf club head further increases consistency in spin rate and launch angle of a golf ball on off-center contact.
While woods and hybrids have a variety of known designs, there is a need for enhancing directional forgiveness (e.g., a reduction in side-to-side variation) to improve accuracy, especially on off-center hits (e.g., contact of the golf ball with a location on the golf club face other than the sweet spot).