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Old 01-11-2013, 01:21 PM   #32
Chas Tennis
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Join Date: Feb 2011
Location: Baltimore, MD
Posts: 2,581
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Quote:
Originally Posted by 10isfreak View Post
The face are virtually always closed, first. At the first approximation, they are always closed and you can't tell unless you have a super slow-motion.

Here's Federer and Nadal. Yellow marks the face before contact, green is at contact and Red is after contact.

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"At impact for the forehands shown here, Federer’s racket face is tilted forward 11 degrees at impact and Nadal’s racket face is tilted forward 15 degrees (relative to a perfectly vertical racket face).

And the racket path used by each player for the same forehand as shown above is interestingly the same: the racket for both Federer and Nadal are moving 18 degrees upward…"
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http://blog.tennisspeed.com/2011/05/...nd-part-1.html
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Some points -

1) I believe that most racket face reorientations after the ball impact - the red shown in the excellent Tennisspeed illustrations above - could be closely correlated with how far off the racket centerline the ball impact is located. That is, mostly the impact torque during impact turns the racket. I've looked at this issue in a few high speed videos but not enough to be sure. For pros, I believe that if the ball hits on the area of the strings in the bottom half of the racket face the top edge of the racket tends to go forward (closes). And if the ball hits on the strings in the top half of the racket face the top edge of the racket goes backward (opens). The pros more consistently hit in the same part of the string face. On most videos of my strokes, hits are more random above and below the centerline. The racket turns up if above or down if below the racket centerline. What the racket face is doing can easily be seen in high speed videos. Where were the ball hits on the Tennisspeed illustrations?

2) I have read more than once that the impact time between the ball and racket strings is very short (was it 0.005 sec? or 5 milliseconds?) and the racket effectively does not change orientation during the time that it is in contact with the ball. What is the research for that view? How fast does it change orientation and what is the effect of the elastic strings on the forces given to the ball.

3) While the pros hit slightly top edge forward (closed), is the racket tending to open or close a little more just before impact? In other words what are the hand forces/torques doing at impact.

4) Does both hitting on the bottom half of the racket face and using a slightly closed racket face make for better control as well as add topspin. Does the racket close slightly to cover the ball a little in the few milliseconds during impact? Also, if the strings are closed the top half of the ball is always impacted and vice versa.

Last edited by Chas Tennis : 01-11-2013 at 03:00 PM.
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