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Old 02-08-2013, 08:25 AM   #34
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Join Date: Feb 2006
Location: Stuck in the Matrix somewhere in Santa Clara CA
Posts: 10,073

^ I do not believe that I am missing the point at all. However, I am not following you on the points that you are attempting to make. I do not agree with your assertion that we cannot apply spiral spin with the racquet. For the underspin shot you speak of, the axis of rotation is not perpendicular to the flight of the ball. In fact, it is more in line with the path of the ball. I am not following your thinking on this.

I have not just blindly accepted everything that Rod Cross has said about spins and their effect on trajectories and bounces. Because much of this stuff is not intuitive, I've had to prove it for myself with fairly simple, informal experiments. Everything that I've tried bears out what Rod Cross, Howard Brody, Kathy Krajco and others have said about the various spins that can be imparted to a tennis ball.

For instance, I was skeptical about the claim that (vertical-axis) sidespin does not directly affect the bounce of a ball. I performed a series of tests with tennis balls (as well as with a basketball and a volleyball). The tests included imparting a vertical axis spin while dropping a ball, while throwing a ball and while hitting a ball (with a racquet). I compared these various tests to ones where little or no spin was imparted to the ball. No effect to the bounce was detected with vertical-axis spin.

I've conducted similar tests with topspin, underspin and spiralspin. Topspin and underspin was seen to have an effect on both the flight trajectory and the bounce. Different effects were noted for different angles of incidence on the bounce.

With spiralspin, no effects were detected during flight but very significant effects where seen on the bounce. Note that the post-bounce spin was primarily topspin regardless of the type of prebounce spins present. In the case of a ball bouncing off to the side (due to spiralspin) or a ball bouncing backward (due to an overpowering underspin), the ball took on a topspin in the new direction. However, we might consider the ball bouncing backward as still having underspin with respect to our original frame of reference -- but it is really just topspin in the new direction.

Why do you believe that table tennis players can impart spiral spin (corkscrew spin) but tennis players cannot? I can impart corkscrew spin to a ping pong ball with a simple brushing motion -- just as I would do with a tennis ball and racquet. The corkscrew technique that you describe for ping pong might very well yield a more dramatic cork spin then I can with my simple brush -- but I can still apply the spin with a simpler motion. The degree of spin potential is different for for ping pong than for tennis but the basic ideas of spin are the same.

Last edited by SystemicAnomaly : 02-08-2013 at 12:53 PM.
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