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Proportional stringing

Q: I string for a talented local junior player, and her father has asked that I string her racquets using the proportional stringing method. I have no idea what he’s talking about. How do you do it?

A: “Proportional stringing” refers to changing the reference tension while you string so that each string receives the theoretically correct tension in proportion to its length, compared to the length of the longest string (typically, the center two mains). If you have ever strummed the main strings before starting your crosses, you know that the outer mains sound at a higher pitch than the center mains, and the rest are usually somewhere in between. This is due in part to the fact that a shorter string pulled to the same tension as a longer string will be tighter (which is why it sounds higher when plucked). The goal of proportional stringing is to reduce the tension on shorter strings so that the installed stiffness of each string is the same, which in theory enables the stringbed to respond to off-center hits more like it responds to on-center hits, optimizing rebound across the face of the racquet.

Whatever its merits, there are some downsides to proportional stringing. First, it is time-consuming and error-prone because you must change your reference tension setting often, sometimes for each pull on the crosses. Also, it works best if you are able to set the reference tension on your stringing machine to tenths of a pound. Keep in mind that proportional stringing does not take into account the fact that installing the crosses increases the tension of the mains, while — due to friction — the crosses are never at the reference tension on the side of the frame farther from the tension head.

You should also be aware that proportional stringing can radically alter the stresses on the racquet. In a traditionally-strung Wilson Pro Staff 6.1 Classic, for example, with the mains and crosses both at 60 pounds, the pull on the frame by the mains is roughly 89 percent of the pull on the frame by the crosses. Using proportional stringing, that ratio changes to roughly 118 percent. That is, instead of the crosses exerting more pull on the frame than the mains, the mains exert much more pull than the crosses. As always, measure the dimensions of the hoop before and after stringing to ensure that the amount of frame distortion is acceptable.

Before you get yourself into a situation where your junior must have her racquet proportionally strung or she simply cannot play, you should conduct a blind test, wherein you string up two identical racquets for her. Have her hit with each to see if she can tell the difference, and if so, that she prefers the proportionally-strung racquet. Depending on how much time you spend stringing her frames proportionally, you might want to consider charging more per frame.

Finally, USRSA members can use our on-line Proportional Stringing Calculator to determine the correct tensions for proportional stringing.

From the April 2004 issue
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