| 摘要 |
In a tennis racket having a frame portion and a shaft portion formed integrally with the frame portion of a fiber-reinforced plastic, the shaft portion has in a direction perpendicular to a striking area a minimum thickness (T2) at a longitudinally intermediate part thereof, the minimum thickness (T2) being between 60% and 80% of the thickness (T1) at the lower end of the shaft portion, while the frame portion has in the same direction a maximum thickness (T3) at the side portions thereof corresponding to a striking sweet spot and a minimum thickness (T4) at the top thereof, the maximum thickness (T3) being between 110% and 140% of the thickness (T1) and being between 135% and 160% of the minimum thickness (T4), whereby a time elapsed until the shaft portion reaches an initial maximum amplitude value when vibrating in the ball striking direction at an impact of a ball is approximated to a time elapsed until the side portions of the frame portion reach an initial maximum amplitude value when vibrating toward the center of the striking area at the impact. |
