A golf club 2 includes a head 4 , a shaft 6 and a grip 8 . The shaft 6 includes a plurality of layers, a tip end Tp and a butt end Bt. If a distance between a center of gravity of the shaft and the butt end Bt is defined as Lg (mm), a shaft full length is defined as Ls (mm), and a ratio of the distance Lg to the shaft full length Ls is defined as a ratio of the center of gravity of the shaft, the ratio of the center of gravity of the shaft is 44.5% or less. If a torsional rigidity at a point of 90 mm distant from the tip end Tp is defined as GJt (kgf·m 2 ), and a torsional rigidity at a point of 210 mm distant from the butt end Bt is defined as GJb (kgf·m 2 ), GJb/GJt is 5.5 or less.
1. A golf club comprising a shaft, a head and a grip, wherein
the shaft has a plurality of layers, a tip end, and a butt end;
if a distance between a center of gravity of the shaft and the butt end is defined as Lg (mm), a full length of the shaft is defined as Ls (mm), and a ratio of the distance Lg to the full length Ls of the shaft is defined as a ratio of the center of gravity of the shaft, the ratio of the center of gravity of the shaft is equal to or less than 44.5%,
if a torsional rigidity at a point of 90 mm distant from the tip end is defined as GJt (kgf·m 2 ), and a torsional rigidity at a point of 210 mm distant from the butt end is defined as GJb (kgf·m 2 ), GJb/GJt is equal to or less than 5.5,
GJt is calculated by the following formula 1 based on a torsion angle A1 (radian) generated by applying a torque of 0.139 (kgf*m) to a region including a point separated by 90 mm from the tip end as a center and having a range of 0.1 m,
GJt (kgf*m 2 )=0.1*0.139/ A 1, and formula 1:
GJb is calculated by the following formula 2 based on a torsion angle A2 (radian) generated by applying a torque of 0.139 (kgf*m) to a region including a point separated by 210 mm from the butt end as a center and having a range of 0.3 m,
GJb (kgf*m 2 )=0.3*0.139/ A 2. formula 2:
2. The golf club according to claim 1 , wherein
the shaft has a flex point ratio of equal to or less than 0.50, wherein
if a forward flex is defined as f 1 , and a backward flex is defined as f 2 , the flex point ratio C of the shaft is calculated by the following formula:
C=f 2/( f 1+ f 2).
3. The golf club according to claim 1 , wherein
the layers include a full length bias layer, a full length straight layer, and a butt partial layer,
if a region between a point of 180 mm distant from the tip end and the tip end is defined as a specific tip part,
a region between a point of 420 mm distant from the butt end and the butt end is defined as a specific butt part,
a weight of the specific tip part is defined as W 1 , and a weight of the full length bias layer on the specific tip part is defined as W 1 a , and
a weight of the specific butt part is defined as W 2 , a weight of the full length bias layer on the specific butt part is defined as W 2 a , and a weight of the butt partial layer on the specific butt part is defined as W 2 b , then
W 1 a /W 1 is equal to or greater than 0.20,
W 2 b /W 2 is equal to or greater than 0.40, and
W 2 b /W 2 a is equal to or greater than 1.7.
4. The golf club according to claim 1 , wherein the head has a weight of equal to or greater than 200 g.
5. The golf club according to claim 1 , wherein
the shaft has a flex point ratio of equal to or less than 0.495, wherein
if a forward flex is defined as f 1 , and a backward flex is defined as f 2 , the flex point ratio C of the shaft is calculated by the following formula:
C=f 2/( f 1+ f 2).
6. The golf club according to claim 5 , wherein the flex point ratio of the shaft is equal to or less than 0.49.
7. The golf club according to claim 1 , wherein
the layers include a full length bias layer, a full length straight layer, and a butt partial layer,
if a region between a point of 180 mm distant from the tip end and the tip end is defined as a specific tip part, and
a weight of the specific tip part is defined as W 1 , and a weight of the full length bias layer on the specific tip part is defined as W 1 a , then
W 1 a /W 1 is equal to or greater than 0.20.
8. The golf club according to claim 1 , wherein
the layers include a full length bias layer, a full length straight layer, and a butt partial layer,
if a region between a point of 420 mm distant from the butt end and the butt end is defined as a specific butt part, and
a weight of the specific butt part is defined as W 2 , and a weight of the butt partial layer on the specific butt part is defined as W 2 b , then W 2 b /W 2 is equal to or greater than 0.40.
9. The golf club according to claim 1 , wherein
the layers include a full length bias layer, a full length straight layer, and a butt partial layer,
if a region between a point of 420 mm distant from the butt end and the butt end is defined as a specific butt part, and
a weight of the full length bias layer on the specific butt part is defined as W 2 a , and a weight of the butt partial layer on the specific butt part is defined as W 2 b , then
W 2 b /W 2 a is equal to or greater than 1.7.