Golf club shaft for wood club
A golf club shaft which satisfies strength and is lightweight is provided by the present invention. This golf club shaft comprises one or more fiber-reinforced resin layers, and is characterized by satisfying the following relationship (1), wherein x [mm] is the displacement in a cantilever bending test, M [g] is the mass of the golf club shaft, and L [mm] is the length thereof, and by satisfying the following strength standard values [1]-[4]: M×(L/1168)<49.66 e −0.0015x (relationship 1); [1] the three-point bending strength at T-90 (the position 90 mm apart from the smaller-diameter end) is 800 N or higher; [2] the three-point bending strength at T-175 (the position 175 mm apart from the smaller-diameter end) is 400 N or higher; [3] the three-point bending strength at T-525 (the position 525 mm apart from the smaller-diameter end) is 400 N or higher; and [4] the three-point bending strength at B-175 (the position 175 mm apart from the larger-diameter end) is 400 N or higher.
1. A golf club shaft formed of one or more fiber-reinforced resin layers, wherein the golf club shaft satisfies Formula 1 below and strength reference values of [1] to [4] below when flex in a cantilever bending test is defined as x [mm], a mass of the golf club shaft is defined as M [g], and a length thereof is defined as L [mm],
M ×( L/ 1168)<49.66 e −0.0015x (Formula 1)
and,
wherein the golf club shaft satisfies Formula 7 below,
42.40 e −0.001x ≤M ×( L/ 1168) (Formula 7)
[1] Three-point bending strength at T-90, which is a position 90 mm apart from a small-diameter end part, is 800 N or more;
[2] Three-point bending strength at T-175, which is a position 175 mm apart from the small-diameter end part, is 400 N or more;
[3] Three-point bending strength at T-525, which is a position 525 mm apart from the small-diameter end part, is 400 N or more; and
[4] Three-point bending strength at B-175, which is a position 175 mm apart from a large-diameter end part, is 400 N or more; and
wherein the flex x in the cantilever bending test is flex of the small-diameter-side end part denotes which is in mm, when the shaft is supported from a lower side at a position 920 mm apart from the end part of the small-diameter side and is supported from an upper side at a position 150 mm further apart therefrom in the large-diameter side direction (a position 1070 mm apart from the end part of the small-diameter side), and a load of 3.0 kgf is dropped to the shaft at a position 10 mm apart from the small-diameter side.
2. The golf club shaft according to claim 1 , wherein the golf club shaft satisfies Formula 2 below:
M× ( L/ 1168)<49.20 e −0.0015x (Formula 2).
3. The golf club shaft according to claim 1 , wherein the golf club shaft satisfies Formula 3 below:
M ×( L/ 1168) <46.73 e −0.0013x (Formula 3).
4. The golf club shaft according to claim 1 , wherein torsional strength of the shaft is 800 N·m·deg or more.
5. The golf club shaft according to claim 1 , wherein the golf club shaft is formed of one or more fiber-reinforced resin layers and includes:
a bias layer that is formed by overlapping fiber-reinforced resin layers, in which orientation directions of reinforcing fibers are +35° to +55° and −35° to −55° relative to a longitudinal direction of the shaft, with each other;
a straight layer that is formed of a fiber-reinforced resin layer in which an orientation direction of the reinforcing fiber is −5° to +5° relative to the longitudinal direction of the shaft; and
a hoop layer that is formed of a fiber-reinforced resin layer in which an orientation direction of the reinforcing fiber is +85° to +95° relative to the longitudinal direction of the shaft,
wherein the hoop layer is formed of two fiber-reinforced resin layers of a first hoop layer and a second hoop layer,
the two hoop layers have an overlapped portion,
one end of the overlapped portion is located between 125 mm and 375 mm from the small-diameter end part of the shaft, and
the other end of the overlapped portion is located between 675 mm and 925 mm from the small-diameter end part of the shaft.
6. The golf club shaft according to claim 5 , wherein one end of the first hoop layer is located at the small-diameter end part of the shaft and the other end thereof is located between 675 mm and 925 mm from the small-diameter end part of the shaft, and
one end of the second hoop layer is located between 125 mm and 375 mm from the small-diameter end part of the shaft and the other end thereof is located at the large-diameter end part of the shaft.
7. The golf club shaft according to claim 5 , wherein the first hoop layer has a thickness thinner than that of the second hoop layer, and at least one of the straight layer and the bias layer is laminated between the first hoop layer and the second hoop layer.
8. The golf club shaft according claim 5 , wherein the shaft has a thickness Th of 0.7 mm or more and 1.3 mm or less at a position 90 mm apart from the small-diameter end part.
9. The golf club shaft according to claim 5 , wherein the small-diameter end part has a shaft outer diameter Rs of 8.0 mm or more and 9.2 mm or less,
a length Ls of a straight part in the small-diameter end part is 40 mm or more and 125 mm or less,
a tapered degree Tp of a shaft inner diameter is 6/1000or more and 12/1000or less, and
a shaft inner diameter Rm is 5.20 mm or more and 8.26 mm or less at a position 90 mm apart from the small-diameter end part.
10. The golf club shaft according to claim 5 , wherein the golf club shaft includes:
a front-end straight reinforcing layer that is formed of a fiber-reinforced resin layer in which an orientation direction of the reinforcing fiber is −5° to +5° relative to the longitudinal direction of the shaft and is configured such that the small-diameter end part of the shaft is a winding start position and an intermediate part thereof is a winding end position; and
a rear-end straight reinforcing layer that is configured such that the intermediate part of the shaft is the winding start position and the large-diameter end part thereof is the winding end position,
the winding end position of the front-end straight reinforcing layer coincides with a winding start position of the second hoop layer or the front-end straight reinforcing layer and the second hoop layer are partially overlapped with each other, and
the winding end position of the rear-end straight reinforcing layer coincides with a winding end position of the first hoop layer or the rear-end straight reinforcing layer and the first hoop layer are partially overlapped with each other.