A head includes a head body, an additional member in which a contour shape obtained by a projection onto a plane has a rotational symmetric axis, and a holding mechanism for holding the additional member. The head body has a recess portion in which at least a part of the additional member can be fitted. The holding mechanism is constituted to enable a mutual transition of a holding state in which the additional member is held in the recess portion and a releasing state in which the hold is released. The recess portion inhibits a rotation around the rotational symmetric axis of the additional member in the holding state. The additional member is rotatable around the rotational symmetric axis in the releasing state. A phase of the additional member in the holding state is changed so that a position of a center of gravity of the head can be varied.
1. A golf club head comprising a head body, an additional member in which a contour shape obtained by a projection onto a plane has a rotational symmetric axis, and a holding mechanism for holding the additional member,
wherein the head body has a recess portion in which at least a part of the additional member can be fitted,
the holding mechanism is constituted to enable a mutual transition of a holding state in which the additional member is held in the recess portion and a releasing state in which the hold is released,
the recess portion inhibits a rotation around the rotational symmetric axis of the additional member in the holding state,
the additional member is rotatable around the rotational symmetric axis in the releasing state, and
a phase of the additional member in the holding state is changed so that a position of a center of gravity of the head can be varied.
2. The golf club head according to claim 1 , wherein the contour shape of the additional member is N-fold rotational symmetric, and N is a natural number of three or more.
3. The golf club head according to claim 1 , wherein a through hole is provided on a bottom face portion of the recess portion,
a bar-shaped member which can be inserted into the through hole is protruded from an internal surface of the additional member,
one of ends of the bar-shaped member is provided with the additional member,
the other end of the bar-shaped member is provided with an engaging portion which cannot be inserted into the through hole,
a central axis of the bar-shaped member is coincident with the rotational symmetric axis of the additional member,
the bar-shaped member is inserted into the through hole, and
the internal surface of the additional member abuts on the bottom face of the recess portion in the holding state.
4. The golf club head according to claim 3 , wherein the additional member is formed by at least two materials having different specific gravities from each other,
an elastic member is provided between an internal surface of the bottom face portion and the engaging portion,
the elastic member performs biasing to increase an interval between the internal surface of the bottom face portion and the engaging portion in the holding state, and
the elastic member is elastically deformable to take the releasing state.
5. The golf club head according to claim 4 , wherein an elastic member is disposed in at least a part between a side surface of the additional member and a wall surface of the recess portion.