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Raising the sweet spot

Q: I have noticed that my daughter hits the ball most of the time just above the sweet spot, and I was thinking of putting lead tape at the 2 and 10 o’clock positions of the head. Should I counterweight the butt end to keep the balance the same, or will that negate the raising of the sweet spot?

A: Adding mass in the upper part of the hoop may be just what your daughter needs to make her racquet perfect for her, but unless you add a huge amount of mass there, it won’t raise the sweet spot very much. It will change other characteristics of the racquet, though, which may give you the improvement you seek.

You don’t say what racquet your daughter uses, so we’ll use a Babolat Pure Storm Team for illustration. Strung with a poly/gut hybrid, and with an overgrip, it might have the following characteristics:

If you add 3 grams of lead tape about 6 centimeters down from the tip (around 2 and 10 o’clock), the racquet will have these characteristics:

You will note that the COP moved only about 2 millimeters, while the balance, swingweight, and hitting weight changed pretty dramatically. The higher swingweight will make it more difficult to accelerate and decelerate the racquet, but once it’s in motion, the higher hitting weight will give the racquet more power. The higher recoil weight should make the racquet more comfortable on impact.

If your daughter could cope with the higher weight and swingweight, but liked the original balance, you could restore it by adding 3.82 grams of lead tape at 10 centimeters up from the butt cap. The racquet would then have these characteristics:

With the additional mass in the handle, the original balance is restored, but the new higher swingweight, COP, and hitting weight are preserved. The yet-higher recoil weight once again should make the racquet more comfortable on impact. So, counter-balancing additional mass in the hoop with additional mass in the handle does not negate the gains from the additional mass in the hoop. Your actual figures depend, of course, on where you put the additional mass, and how much you add in which location(s).

USRSA members have access to several on-line tools and calculators to help model the effects of modifications such as these, including an all-new three-in-one version of the Racquet Customizer, and the Racquet Mass Mover. These and other tools and calculators can be found at http://www.usrsa.com/top/tools_toc.html.

From the February 2007 issue
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