Golf club head with flexure

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;
• 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;
• and
• a flexure that is spaced aftward of the ball-striking surface, extending in a generally heel-to-toe direction and parallel to the leading edge of the golf club head,
• wherein the sole is constructed of a first material having a first Young's modulus and the flexure is constructed of a second material having a second Young's modulus that is lower than the first Young's modulus,
• wherein the flexure is tuned so that the width across the flexure in a face-to-aft direction varies sinusoidally, immediately after impact, at a frequency of about 2900 Hz to about 4000 Hz,
• wherein at least a portion of the flexure is constructed of a β-Ti alloy, and
• wherein the flexure extends across the body in a generally heel-to-toe direction and within between about 5.0 mm and 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.