Golf club head with flexure

1. A golf club head, comprising:

a crown defining an upper surface of the golf club head;

a sole defining a lower surface of the golf club head, comprising a transmittal portion, a flexure and a rear portion;

a side wall extending between the crown and the sole;

a hosel extending from the crown and including a shaft bore; and

a face defining a ball-striking surface and intersecting the transmittal portion at a leading edge, wherein the face includes a face insert that forms at least a portion of the ball-striking surface, wherein the face insert is constructed of maraging steel and has a thickness less than 2.0 mm,

wherein the flexure is spaced aftward of the ball-striking surface by the transmittal portion, and comprises a front wall, an apex and a rear wall, wherein the front wall extends into a cavity defined by the golf club head and the rear wall extends into the cavity, and the front wall and the rear wall are coupled at the apex,

wherein the flexure is spaced from the ball-striking surface by a distance that is between 20% and 50% of a CG-Z-fc distance between the geometric face center of the golf club head and the center of gravity of the golf club head along a horizontal Z-axis that extends from the face to the aft of the golf club head,

wherein the front wall and the rear wall form convergent flanges that are angled toward each other as they extend further toward the interior from the sole so that the fore/aft distance between the members decreases from the lowest portion, when the golf club head is in the address position, to the most inward, upper ends.

2. The golf club head of claim 1 , wherein the flexure is spaced from the ball-striking surface by a distance that is between 25% and 45% of the CG-Z-fc distance between the geometric face center of the golf club head and the center of gravity of the golf club head along a horizontal Z-axis that extends from the front to the aft of the golf club head.

3. The golf club head of claim 1 , wherein the sum of the height and the width of the flexure is within 20% of a CG-Y-g distance between a ground plane and the center of gravity of the golf club head along a vertical Y-axis.

4. The golf club head of claim 1 , wherein the thickness of the transmittal portion decreases from a location adjacent the face toward the flexure, and wherein the transmittal portion thickness tapers by at least 4%.

5. The golf club head of claim 1 , wherein the thickness of the front wall and the thickness of the rear wall are different by less than 40% of the thickness of the front wall.

6. The golf club head of claim 1 , wherein the thickness of the apex is different from the greater of the thickness of the front wall and the thickness of the rear wall by less than 30%.

7. The golf club head of claim 1 , wherein the CG-Z-fc distance is at least 33.0 mm and the moment-of-inertia about a vertical axis extending through the center-of-gravity is at least 450 kg-mm 2 .

8. A golf club head, comprising:

a crown defining an upper surface of the golf club head;

a sole defining a lower surface of the golf club head, comprising a transmittal portion, a flexure and a rear portion, wherein the flexure is defined by a front wall that is spaced from a rear wall to define a cavity, wherein each of the front wall and the rear wall extend from the sole toward an interior of the golf club head;

a side wall extending between the crown and the sole;

a hosel extending from the crown and including a shaft bore;

a face defining a front ball-striking surface and a back surface, the face intersecting the transmittal portion at a leading edge; and

a filler member at least partially filling the cavity defined between the front wall and the rear wall of the flexure,

wherein the golf club head defines an origin at a location on a shaft axis defined by the shaft bore in a plane defined by the proximal end of the hosel, an x-axis extending from the origin in a heel to toe direction and parallel to a plane that is tangent to the face at a geometric face center of the ball-striking surface, a y-axis extending vertically through the origin and perpendicular to a ground plane when the golf club head is in an address position on the ground plane, and a z-axis extending in a face to aft direction parallel to the ground plane when the golf club head is in an address position,

wherein the transmittal portion of the sole defines a first positive angled bounce surface between the face and the flexure of the golf club head, and

wherein the rear portion of the sole defines a second positive angled bounce surface between the flexure and a rear end of the golf club head,

wherein the front wall and the rear wall form convergent flanges that are angled toward each other as they extend further toward the interior from the sole so that the fore/aft distance between the members decreases from the lowest portion, when the golf club head is in the address position, to the most inward, upper ends.

9. The golf club head of claim 8 , wherein the first positive angled bounce surface includes a linear portion and defines a bounce angle that is between about 2° and about 20°.

10. The golf club head of claim 9 , wherein the first positive angle bounce surface has a bounce angle of between about 6° and about 16°.

11. The golf club head of claim 8 , wherein the second positive angled bounce surface includes a linear portion and defines a bounce angle that is between about 2° and about 20°.

12. The golf club head of claim 11 , wherein the second positive angle bounce surface has a bounce angle of between about 6° and about 16°.

13. The golf club head of claim 8 , wherein filler member is constructed from at least one viscoelastic polymer having a hardness value in a range of Shore A20 Shore D80.

14. A golf club head, comprising:

a crown defining an upper surface of the golf club head, wherein the crown comprises a portion having constant thickness of between about 0.3 mm to about 0.4 mm;

a sole defining a lower surface of the golf club head;

a side wall extending between the crown and sole;

a hosel extending from the crown and including a shaft bore;

a face defining a ball-striking surface and intersecting the lower surface at a leading edge, wherein a perimeter of the face is coupled to the crown and the sole; and

an elongate flexure is recessed into the sole and defined by a first portion and a second portion, wherein the length of the first portion is different than the length of the second portion, wherein the first portion extends from the sole toward the interior of the golf club head and the second portion extends from the sole toward the interior of the golf club head, wherein the first portion interfaces the second portion at an apex, wherein the flexure has a curl length and a width each measured along the same axis, wherein the curl length is greater than the width, and

wherein the flexure extends across the body in a generally heel-to-toe direction within about 5.0 mm to about 20.0 mm from the leading edge of the golf club head and intersects at least a portion of the side wall of the golf club head.

15. The golf club head of claim 14 , wherein the first portion has a wall thickness of about 0.9 mm to about 2.0 mm.

16. The golf club head of claim 14 , wherein the flexure has a width of about 7.0 mm to about 11.0 mm.

17. The golf club head of claim 14 , wherein the flexure has a height of about 6.0 mm to about 11.0 mm.

18. The golf club head of claim 14 , wherein the flexure is machined with a tool having an axis of rotation that is generally parallel to the sole and perpendicular to the leading edge.

19. The golf club head of claim 14 , wherein at least a portion of the flexure is constructed of a β-Ti alloy.