Originally Posted by TennisCJC
I think racket face angle, swing path angle and swing speed all contribute to spin.
I think a closed face on the same swing path angle and at the same swing speed will produce slightly more topspin.
And, yes racket face angle also impacts departure trajectory angle.
TW has a study on serve where that have "proven" that hitting the top 1/2 of the ball produces more spin. A closed face on the topspin FH is in effect hitting the top 1/2 of the ball and you encounter a smidge less resistance at impact and maintain a higher racket speed thru contact resulting in more RPMs on the way out.
Practically, I don't consciously muck with racket face angle and just use my hands in conjunction with my swing path to get the up/down trajectory that I want. I have accepted that a slightly closed face is good and use this on topspin shots but again, I never think I am closing the racket 2 degrees more than normal. The racket face angle just sort of happens with practice.
1) think racket face angle, swing path angle and swing speed all contribute to spin.
Right on. The article's author was incorrect by saying and giving diagram of only two variables which contribute to top spin: racket face angle and swing path angle, and missing the third variable: swing speed. Example: if Fed and Nadal repeat the same shot as shown on the article, but swing slower, then the ball would spin less, and also land into the bottom of the net.
2) I think a closed face on the same swing path angle and at the same swing speed will produce slightly more topspin.
Fault. Top spin, or RPM of ball rotation, is depend ONLY on swing path angle and swing speed, period.
A correct statement should be like this:
" I think a closed face on the same swing path angle and at the same swing speed will produce slightly lower ball trajectory."
In other word, as in Physics text book, ball rotation speed after impact depends ONLY on racket speed VECTOR (direction of swing and swing speed). However, a very fast swing as Fed or Nadal FH, impact the ball at 3 o'clock (vertical racket face) would land the ball out side the baseline. Therefore, to keep the ball in at this fast FH, they HAVE TO impact the ball at slightly higher than 3 o'clock position (closed face), which create a downward force to land the ball inside. In other word, the article was right about you can hit topspin with a closed racket face ( as oppose to armchair researcher Vic Braden who insisted that the face never closed). However, the article was WRONG about "topspin was created by closed racket face". Fact is that closed racket face does not create more (or less) topspin. Here is another look about this: brushing the ball at 3 (vertical face) , 2 (20 degree close), or 12 (90 degree close) o'clock position does not change the spin speed, but it changes the ball path after impact.
Anyway, this serves us no purpose in real life tennis, since we never can tell, during hitting the ball, what is the racket face angle. Through trial and error (practice), we automatically compensate a fast, high topspin shot by slightly closing the racket face without knowing, to keep the ball in the court.