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Swingweight vs. aerodynamics

Q: I have been using head tape at the throat of the racquet instead of a dampener. The tape is 1½” wide, and I use one piece on each side of the stringbed, pressed together, covering the throat area. My customers like it. One said it slowed down his swing. By creating wind resistance in the face of the frame; am I increasing swing weight?

A: You are increasing the swingweight because you have added mass between the tip of the racquet and the “pivot point” of the racquet, which is 10 cm up from the end of the butt cap. But it’s almost certain that neither the added mass nor whatever small increase there is in air resistance is enough to throw off your customer’s swing.

We took a racquet and added two pieces of duct tape, 2×5.5 inches each (significantly bigger than what you’re using), to the stringbed of a racquet near the throat, centered at 41.9 centimeters up from the end of the racquet. This huge (and illegal for play) tape dampener added only 2.5 grams to the total mass of the racquet, and increased the swingweight by 3 kg·cm2, which is exactly what you would expect when adding 2.5 grams at that location. In other words, there was no unexplained difference in swingweight, as there would be if the increase in air resistance was so large that it changed the swingweight measurement. Also, when compared in a blind test against an identical racquet without the tape dampener, our tester couldn’t feel or hear any difference when swinging the two racquets.

A racquet with a low swingweight but high air resistance will be easy to accelerate from a dead stop, while a racquet with a high swingweight and low air resistance will be difficult to accelerate from a dead stop. Obviously, if you make the air resistance high enough, the racquet will be more difficult to swing. However, swingweight is a linear resistance, while air resistance increases with racquet head speed. Any aerodynamic difference due to your added tape is only going to be an issue at higher swing speeds, especially so given the fact that you are placing the tape so low on the racquet face.

So, it’s likely that your customer isn’t actually feeling the air resistance or the increase in swingweight. But if your customer believes there is a difference, it is unlikely that you will be able to convince him otherwise. The good news is that you can always switch him back to a traditional dampener.

From the September 2008 issue
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