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Old 02-18-2013, 03:17 PM   #12
ChicagoJack
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Hi Ashley

Flight Path and Depth Vs Power: We don't often take radar guns to our matches, so it's important to note first... that as players we have got some fairly wacky ways to estimate racquet power. Mostly we have no freaking idea about ball velocity, (MPH) and we are inferring about racquet power from depth, or height over the net. Those are things we do notice very well and pretty accurately. But both of these things are highly sensitive to string tension, string pattern, and string type. Open patterns, or slippery co-poly string will create a higher arc over the net given the same stroke. If the player compensates for this, by closing the racquet face, the result will be more spin. If the player does not compensate for this, the ball will land deeper in the court, not because it is traveling faster, but simply because it has a higher arc. Conversely, a tighter pattern, or sticky string will create a lower trajectory over the net. A player could easily perceive this as low power, because it is landing shorter in the court, or simply not clearing the net. Your rebel 95 has a fairly dense pattern in a fairly small head. Pair that with your sticky nylon string like X One Bi phase, which has the highest COF (string on string friction) of any string tested, and you have got the makings of a very low flight path compared to just about any other racquet. The more open patterns of the Blade team, (18x19, 104sq) and Donnay Pro One (16x19,105sq), is probably what creating a higher arc over the net... this is probably what you are interpreting as more power.

Having said all of that....A few important concepts:

1. Racquet stiffness has little or no effect on power when you hit the sweet spot ( Sweetspot = Center Of Percussion plus the Vibration Node) or just below (Best Bounce).

2. Stiff racquets offer more power for impacts in the top 10-15% of the hoop. Every racquet ever made has a dead spot, right near the tip of the frame. There is a spot, generally located right around the 1st, 2nd, 3rd cross strings down, where the ball just does not want to bounce at all. Complete dudsville. Stiffer frames flex less, so they offer incrementally more power at the very top of the hoop.

3. While stiff frames flex less, and offer fractionally more power in the dead zone right at the tip, you should put this into the context of a real tennis swing. In a volley motion, the tip of the racquet is moving pretty slowly, and nearly as fast as the handle. However, in a serving motion the tip of the frame is moving quite a bit faster than the center of the strings. For a med SW racquet with an ACOR of 1.40, the center of the strings is moving at about 72 MPH, and the tip is moving about 100 mph, on a 100 mph serve. What this means is that dead spot deficiency on a serve gets a big fat boost of juice from the racquet tip speed. That's why you can mishit near the tip on a serve and still get a pretty good result. However, if you mishit near the tip on a volley, or blocking back a 100 mph serve, the result is often that the ball hits the bottom of the net. What this also means is that the speed of the serve is almost directly related to the speed of the tip of the frame. If you want to hit your serve 1 mph faster, the best way to do that is to swing the racquet 1 mph faster.

4. The speed of the tip of the frame, plus the high sw of wood frames helps explain the following event. In 1997, in a comparative test done by Tennis magazine, [1] Mark Philippoussis, the six-foot-five, 217-pound Australian renowned for his powerful serve, averaged 124 mph when serving with his own composite racket. With a classic wooden racket, (where the stiffness ratings average in the low 30's, and a 72 sq inch head) he averaged 122 mph. Racquet power is a mostly a matter of swing speed and swingweight. Scud is able to hit nearly his top speed with a flexy racquet in the 30s, and a 72 inch head, because the swingweights of most of the woodies is north of 360, and he can stil swing it pretty fast. The other factors matter slightly, but only in terms of fractions of MPHs.

Link [1] Mark Philippoussis Serve Test, Wood Vs Graphite
http://www.time.com/time/magazine/ar...899876,00.html

-Jack
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(9x) Donnay Pro One 16x19 | RPNY Leather | 12.6oz, -12Points, ~335sw | M:16g Wilson Nat Gut, X:16g MonoGut Zx Red, 60/58 | Benchmarked USTA 4.5

Last edited by ChicagoJack : 02-18-2013 at 08:12 PM.
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