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Changing the COP

Q: Is there a method of determining the amount of change of a racquet’s center of percussion (COP) when placing lead tape on the frame? On my Babolat Aerotour OS, the COP is around 53 cm. From looking at my strings, I’m hitting the ball around 45-48 cm. Will placing lead tape at that area lower the COP, or does it even need to be lower? Also, how much is needed to affect the COP?

A: To calculate the change in COP that occurs when adding (or removing) lead tape from your racquet, plug the specs for your racquet into our Racquet Mass Mover tool, which can be found online in the Calculators portion of the Tools section at http://www.racquettech.com/members/tools/racquetmassmover.html.

Once you start playing with the numbers, however, you’ll soon see that to move the COP to 48 cm would require roughly 384 grams of lead tape at 45 cm. The reason you add lead tape at your hitting area is not to lower the COP, but rather to “focus” the swingweight at the point of impact. For example, adding a much more reasonable 4 grams of lead tape at 47 cm increases the swingweight by almost 5.5 kg·cm². (You’ll find that this change increases recoilweight and hittingweight, as well.)

Just about any amount of lead tape will change the COP, but it’s difficult to change it by much. As for the best location for the COP, generally speaking the higher in the stringbed, the better. Shots hit below the COP result in the racquet being pushed back into your hand. Shots above the COP result in the racquet trying to rotate out of your hand. It is more comfortable to have the racquet push into your hand than pull out.

From the June 2006 issue
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