Golf club head with flexible sole

A golf club head comprising:

• a body having a front end, a back end opposite the front end, a crown, a sole opposite the crown, the sole defining a sole surface;
• wherein the front end, the back end, the crown, and the sole form a hollow interior cavity;
• wherein a ground plane is tangent to the sole surface when the golf club head is at an address position to strike a golf ball;
• a heel, a toe opposite the heel, and a hosel structure having a hosel axis extending centrally through a bore in the hosel structure, a strike face positioned at the front end and defining a geometric center, and a loft plane tangent to the geometric center,
• wherein the geometric center further defines a coordinate system having the geometric center, the coordinate system comprising an x-axis extending through the geometric center between the heel and the toe, a y-axis extending through the geometric center and perpendicular to the x-axis, between the crown and the sole, a z-axis extending through the geometric center and perpendicular to the x-axis and to the y-axis, between the front end and the back end, the y-axis and the z-axis together define a YZ plane extending between the crown and the sole and between the front end and the back end;
• the x-axis and the z-axis together define a XZ plane extending between the heel and the toe and between the front end and the back end;
• an indented region;
• wherein the indented region is defined where the sole veers inward in a direction toward the hollow interior cavity;
• a sole transition point defined by an intersection of the sole and the strike face;
• the indented region comprises a sole curvature profile defined by an intersection of the sole surface and the YZ plane;
• wherein the sole curvature profile comprises a first inflection point and a second inflection point;
• wherein the sole curvature profile comprises a first concave section extending from the sole transition point to the first inflection point and is concave relative to the XZ plane;
• a convex section extending from the first inflection point to the second inflection point and is concave relative to the XZ plane;
• a second concave section extending from the second inflection point to the back end and is concave relative to the XZ plane;
• wherein the first concave section comprises a radius of curvature (R3), the convex section comprises a convex section radius of curvature (R4), the second concave section comprises a radius of curvature (R5);
• wherein the sole curvature profile further comprises a nadir;
• wherein the nadir represents a point of the sole curvature profile that is closest to the XZ plane;
• wherein the nadir is located on the convex section;
• wherein the strike face forms a crown return such that the crown return extends rearward from the front end and forms a portion of the crown;
• the crown return comprises a face-crown transition profile having a face-crown transition radius (R6)
• the crown return comprises a crown transition point defined where the face-crown transition profile departs of from the face-crown transition radius (R6);
• the crown return comprises a return section radius of curvature (R7);
• the crown comprising a crown radius of curvature (R8);
• a return transition point defined where the return section radius of curvature (R7) transitions to the crown radius of curvature (R8);
• a crown return plane extending in a heel-to-toe direction and intersecting the crown transition point and the return transition point;
• a reference plane parallel to the ground plane and intersecting the crown transition point;
• and
• a draft angle measured between the crown return plane and the reference plane, wherein:
• the draft angle is between 0 degrees and −10 degrees.