Originally Posted by SystemicAnomaly
^ The video I posted and others clearly show the ball rising. When I hit my twist and other kick serves, the ball is also rising just after contact -- definitely more than my flat serve. (BTW, I am 5'10" and probably jump about 10 cm or so on my serves).
the only way you can make the stationary ball raise is to hit it below the equator. (I mean that is assuming we disregard the effect of the friction between the strings and the ball. I suppose when friction is considered it could be argued that the ball could be hit above the equator and still pulled up - but I would be surprised if that was in any way significant).
Which is why the tip about hitting from 8 to 2 makes sense (at least to me). But when one says that the contact does not start until around 10, which is above the equator, I just do not see how it would make the ball raise.
Note, that forehand stroke of the incoming ball, the one that is raising and spinning is different than a serve. There's a pretty good article on all of that on TW University (or few papers by Broody).
What you see on the video is someone hitting below the equator. And it is really hard to see where the initial impact happens so sometimes it looks like it is around 10.
But you make a good observation - the ball does raise most of the time. Just look at any of those drills where people serve from their knees, and the ball goes up really high over the net. It is because they hit it below the equator.