Golf club

A golf club head for an iron-type golf club, the golf club head comprising:

• a body having a heel portion, a toe portion, a top-line portion, a rear portion, a face portion comprising a striking face, a sole portion extending rearwardly from a lower end of the face portion to a lower portion of the rear portion,
• wherein the body is a unitary cast body, and
• wherein the striking face:
• comprises an unsupported face area between about 2300 mm2 and about 3500 mm2, and
• includes a geometric center defining an origin of a club head coordinate system when the club head is at a normal address position, the club head coordinate system including:
• a club head x-axis being tangent to the striking face at the origin and parallel to a ground plane, wherein the x-axis extends in a positive direction from the origin to the heel portion of the club head body,
• a club head y-axis intersecting the origin being parallel to the ground plane and orthogonal to the x-axis, wherein the y-axis extends in a positive direction from the origin to the rear portion of the club head body, and
• a club head z-axis intersecting the origin being orthogonal to both the x-axis and the y-axis, wherein the z-axis extends in a positive direction from the origin to the top-line portion of the club head body, wherein:
• the heel portion extends towards, and includes, a golf club shaft receiving portion from a y-z plane passing through the origin;
• and
• the toe portion is defined as the portion of the club head extending from the y-z plane in a direction opposite the heel portion,
• wherein the striking face comprises variable thickness regions that surround or are adjacent to an ideal striking location of the striking face,
• wherein a sole bar defines a rearward portion of the sole portion,
• wherein a cavity is defined by a region of the body rearward of the face portion, forward of the rear portion, above the sole portion, and below the top-line portion,
• wherein the striking face comprises a central region coordinate system defined by a 36 millimeter (mm) by 18 mm rectangular area centered on the geometric center of the striking face, wherein the central region coordinate system is defined with the club head at zero-degrees loft and the central region is positioned on a face plane normal to a ground plane, wherein the central region coordinate system is elongated in a heel-to-toe direction, the central region coordinate system including:
• a central region x-axis being tangent to the striking face at the origin and parallel to a ground plane, wherein the x-axis extends in a positive direction from the origin to the heel portion of the club head body, and
• a central region y-axis intersecting the origin being perpendicular to the ground plane and orthogonal to the x-axis, wherein the y-axis extends in a positive direction from the origin to the top-line portion of the club head body,
• wherein the striking face comprises a first coefficient of restitution (COR weighting factor and a first COR drop off value positioned on the striking face 9 mm below the geometric center of the striking face corresponding to an (xcr, ycr) coordinate of (0, −9) of the central region coordinate system,
• wherein the striking face comprises a second COR weighting factor and a second COR drop off value positioned on the striking face 9 mm toe-ward of the geometric center of the striking face corresponding to an (xcr, ycr) coordinate of (−9, 0) of the central region coordinate system,
• wherein the striking face comprises a third COR weighting factor and a third COR drop off value positioned on the striking face at the geometric center of the striking face corresponding to an (xcr, ycr) coordinate of (0, 0) of the central region coordinate system,
• wherein the striking face comprises a fourth COR weighting factor and a fourth COR drop off value positioned on the striking face 9 mm toe-ward and 9 mm below the geometric center of the striking face corresponding to an (xcr, ycr) coordinate of (−9, −9) of the central region coordinate system,
• wherein the striking face comprises a fifth COR weighting factor and a fifth COR drop off value positioned on the striking face 9 mm heel-ward and 9 mm below the geometric center of the striking face corresponding to an (xcr, ycr) coordinate of (9, −9) of the central region coordinate system,
• wherein the striking face comprises a sixth COR weighting factor and a sixth COR drop off value positioned on the striking face 18 mm toe-ward of the geometric center of the striking face corresponding to an (xcr, ycr) coordinate of (−18, 0) of the central region coordinate system,
• wherein the striking face comprises a seventh COR weighting factor and a seventh COR drop off value positioned on the striking face 9 mm heel-ward of the geometric center of the striking face corresponding to an (xcr, ycr) coordinate of (9, 0) of the central region coordinate system,
• wherein the first COR weighting factor is 0.2347, the second COR weighting factor is 0.1935, the third COR weighting factor is 0.1715, the fourth COR weighting factor is 0.1518, the fifth COR weighting factor is 0.1230, the sixth COR weighting factor is 0.0740, and the seventh COR weighting factor is 0.0515,
• wherein a summation of the first, second, third, fourth, fifth, sixth, and seventh COR weighting factors is 1,
• wherein the first, second, third, fourth, fifth, sixth, and seventh COR drop off values are relative to a calibration plate having a measured COR value,
• wherein the first, second, third, fourth, fifth, sixth, and seventh COR drop off values are calculated by subtracting the measured COR value of the calibration plate from a COR value measured at the respective coordinate for the respective drop off value;
• wherein the first COR drop off value is between −0.100 and −0.130, the second COR drop off value is between 0.000 and −0.090, the third COR drop off value is between 0.040 and −0.050, the fourth COR drop off value is between −0.100 and −0.200, the fifth COR drop off value is between −0.090 and −0.160, the sixth COR drop off value is between −0.100 and −0.170, and the seventh COR drop off value is between 0.000 and −0.090,
• wherein a weighted COR drop off value is between 0.000 and −0.064, the weighted COR drop off value comprising a summation of:
• the first COR weighting factor multiplied by the first COR drop off value;
• the second COR weighting factor multiplied by the second COR drop off value;
• the third COR weighting factor multiplied by the third COR drop off value;
• the fourth COR weighting factor multiplied by the fourth COR drop off value;
• the fifth COR weighting factor multiplied by the fifth COR drop off value;
• the sixth COR weighting factor multiplied by the sixth COR drop off value;
• and the seventh COR weighting factor multiplied by the seventh COR drop off value.