Racket

Abstract

A racket 2 includes a frame 4, a grip 6, a grommet 10, and a string 12. In the racket 2, an in-plane stiffness index Gi, which is a ratio of a top pressure stiffness value Git (kgf/cm) to a side pressure stiffness value Gis (kgf/cm), is 1.40 or greater; an out-of-plane stiffness index Go, which is a product of a throat stiffness value Gos (kgf/cm) and a ball-hitting face stiffness value Goh (kgf/cm), is from 60000 to 85000; a moment of inertia Mi about an axis of the racket 2 is from 13500 g·cm2 to 15000 g·cm2; and an index of inertia Ii is 0.150 or greater, which is calculated by the following mathematical formula: Ii=Mi/(Wr·Lc) (where Wr is a mass (g) of the racket, and Lc is a distance (mm) from a grip end to a center of gravity of the racket).

What is claimed is: 
     
         1 . A racket, wherein:
 an in-plane stiffness index Gi, which is a ratio of a top pressure stiffness value Git (kgf/cm) to a side pressure stiffness value Gis (kgf/cm), is greater than or equal to 1.40;   an out-of-plane stiffness index Go, which is a product of a throat stiffness value Gos (kgf/cm) and a ball-hitting face stiffness value Goh (kgf/cm), is greater than or equal to  60000  and less than or equal to 85000;   a moment of inertia Mi about an axis of the racket is greater than or equal to 13500 g·cm 2  and less than or equal to 15000 g·cm 2 ; and   an index of inertia Ii is greater than or equal to 0.150, which is calculated by the following mathematical formula:   
       
         
           
             
               Ii 
               = 
               
                 Mi 
                 / 
                 
                   ( 
                   
                     Wr 
                     · 
                     Lc 
                   
                   ) 
                 
               
             
           
         
       
       (where Wr is a mass (g) of the racket, and Lc is a distance (mm) from a grip end of the racket to a center of gravity of the racket). 
     
     
         2 . The racket according to  claim 1 , wherein the mass Wr is greater than or equal to 285 g and less than or equal to 305 g. 
     
     
         3 . The racket according to  claim 1 , comprising a frame, wherein:
 a material of the frame is a fiber reinforced resin including a plurality of reinforcement fibers; and   a ratio of the reinforcement fibers with an inclination angle having an absolute value of greater than or equal to 40° and less than or equal to 50° to all of the plurality of reinforcement fibers included in the frame is greater than or equal to 8% by mass and less than or equal to 30% by mass.