Golf club with flexure

1. An iron-type golf club head, comprising:

a face, wherein the face defines a forward ball-striking surface that is flat;

a body coupled to the face, wherein the body forms a perimeter portion of the golf club head and a rear wall spaced from the face, wherein the combined face and body define a sole, wherein the sole includes an aperture;

a hosel extending away from the face and body and providing an attachment structure for a golf club shaft; and

a flexure forming a portion of a perimeter of the aperture, wherein the flexure is a curved vertical wall that is spaced from a rear surface of the face by a thin sole portion, wherein a height of the flexure measured in a vertical direction relative to a ground plane when the golf club head is resting on the sole surface in an address position is in a range of about 2.0 mm to about 4.0 mm, wherein a thickness of the flexure measured in a horizontal direction relative to the ground plane when the golf club head is resting on the sole surface in an address position is in a range of about 1.0 mm to about 4.0 mm, wherein a thickness of the thin sole portion measured in a vertical direction relative to the ground plane when the golf club head is resting on the sole surface in the address position is in a range of about 1.0 mm to about 3.0 mm, wherein the height of the flexure is greater than the thickness of the thin sole portion, wherein a thickness of the flexure measured in a horizontal direction relative to the ground plane is greater than a thickness of the thin sole portion, wherein the aperture creates an opening into an interior of the body via a portion rearward of the flexure that is the curved vertical wall, wherein the flexure is curved so that a distance between the flexure and the face is greater at a heel end and a toe end of the flexure than a central portion of the flexure, and wherein the heel end and the toe end of the flexure contact a rear surface of the sole that defines a rear wall of the aperture.

2. The iron-type golf club head of claim 1 , wherein the sole includes a plurality of apertures.

3. The iron-type golf club head of claim 1 , wherein the aperture is elongate and generally extends in a heel to toe direction in the sole of the golf club head.

4. The iron-type golf club head of claim 3 , wherein a maximum length of the aperture in a heel to toe direction is in a range of about 40.0 mm to about 70.0 mm.

5. The iron-type golf club head of claim 4 , wherein a maximum length of the aperture in a heel to toe direction is about 55.0 mm.

6. The iron-type golf club head of claim 1 , wherein the flexure is formed as a separate component and coupled to the body.

7. The iron-type golf club head of claim 6 , wherein the flexure is removably coupled to the body.

8. The iron-type golf club head of claim 7 , wherein the flexure is mechanically coupled to the body at a plurality of locations along the flexure.

9. The iron-type golf club head of claim 1 , further comprising a cap, wherein the flexure is recessed from an outer surface of the sole, and wherein the cap is disposed in a recess so that an outer surface of the cap is flush with the surrounding portions of the outer surface of the sole.

10. The iron-type golf club head of claim 9 , wherein the cap is fixed in the recess over only a portion of the perimeter of the aperture.

11. An iron-type golf club head, comprising:

a face, wherein the face defines a forward ball-striking surface that is flat;

a body coupled to the face, wherein the body forms a perimeter portion of the golf club head and a rear wall spaced from the face, wherein the combined face and body define a sole, wherein the sole includes an aperture;

a hosel extending away from the face and body and providing an attachment structure for a golf club shaft; and

a flexure forming a portion of a perimeter of the aperture, wherein the flexure is a curved vertical wall that is spaced from a rear surface of the face by a thin sole portion, wherein a height of the flexure measured in a vertical direction relative to a ground plane when the golf club head is resting on the sole surface in an address position is in a range of about 2.0 mm to about 4.0 mm, wherein a thickness of the flexure measured in a horizontal direction relative to the ground plane when the golf club head is resting on the sole surface in an address position is in a range of about 1.0 mm to about 4.0 mm, wherein a thickness of the thin sole portion measured in a vertical direction relative to the ground plane when the golf club head is resting on the sole surface in the address position is in a range of about 1.0 mm to about 3.0 mm, wherein the height of the flexure is greater than the thickness of the thin sole portion, wherein a thickness of the flexure measured in a horizontal direction relative to the ground plane is greater than a thickness of the thin sole portion, wherein the aperture is elongate and generally extends in a heel to toe direction in the sole of the golf club head, wherein the flexure is formed as a separate component and coupled to the body, wherein the aperture creates an opening into an interior of the body via a portion rearward of the flexure that is the curved vertical wall, wherein the flexure is curved so that a distance between the flexure and the face is greater at a heel end and a toe end of the flexure than a central portion of the flexure, and wherein the heel end and the toe end of the flexure contact a rear portion of the sole that defines a rear wall of the aperture.

12. The iron-type golf club head of claim 11 , wherein a maximum length of the aperture in a heel to toe direction is in a range of about 40.0 mm to about 70.0 mm.

13. The iron-type golf club head of claim 12 , wherein a maximum length of the aperture in a heel to toe direction is about 55.0 mm.

14. The iron-type golf club head of claim 11 , wherein the flexure is removably coupled to the body.

15. The iron-type golf club head of claim 14 , wherein the flexure is mechanically coupled to the body at a plurality of locations along the flexure.