| 摘要 |
<p>PURPOSE:To make it possible to enhance the speed and directional properties of a ball hit by the tip end of a frame racket section by letting the dimensional distribution in thickness at the frame racket section, a shaft section and a grip section be equal in a specified range along the axial line in the longer direction of a frame, and thereby setting the natural frequency of the frame in a specified range. CONSTITUTION:A frame is formed with a hollow section 10 made of FRP in a rectangular cross section. And as for the dimensional distribution in thickness along the axial line in the longer direction of the frame, t1 of a frame racket section 2, t2 of a throat section 3 and t3 of a shaft end section 4a on the grip section 5 side except the throat section 3 shall be equal in thickness within a range of 23-28mm, and the thickness S2 of the FRP outer shell of the throat section 3 is concurrently made greater than S1 of the frame racket section 2 and S3 of the shaft section 4 on the end section 4a side so that the natural frequency of the frame 1 is set in a range of 160-260Hz. This constitution thereby allows the restorating position of the frame racket section at the time of hitting a ball to be in good agreement with the position where the ball is separated from the gut stretched surface so as to keep the ball accurate in direction, thereby enabling oscillation energy to be effectively utilized for accelerated driving force at the time of reflex action to the ball.</p> |
