The Pro Shop

Question of the Day: Do Poly and Gut Still Mix?

Wednesday, September 26, 2012 /by

TENNIS.com gear editor Justin diFeliciantonio and his technical advisers answer your equipment questions each day. Click here to send in a question of your own.

The industry consensus seems to be that monofilament strings, as opposed to natural gut or other types of synthetics, are able to impart extra spin by deflecting and snapping back while the ball is still on the stringbed. Given that this is the case—and that, more specifically, the main strings are doing most of the moving—what snap-back advantage is there, if any, to installing polyester in the crosses and gut/multifilament in the mains?—Ananth Raghavan

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Thanks for your question, Ananth. As I recently discussed with John Lyons, Wilson’s Global Product Director for racquets and strings, research does show that monofilaments, when pitted against other string varieties, deflect (i.e., move out of place) further and “snap back” faster upon impact with the ball. According to tests done with high-speed video and other ball-tracking devices, it’s this additional string movement that accounts for the increased spin intermediate and advanced players experience with polyester. (Next year, Wilson as well as Prince will release racquets with modified string patterns; the companies claim these patterns will accentuate snap-back.)

Unfortunately, the verdict isn’t quite out as to the snap-back characteristics of mono/multi hybrids. Early research does indicate that hybrids are more spin-friendly than full beds of synthetics or gut, and less spin-friendly than full beds of poly. But there hasn’t been enough analysis done to definitively determine exactly how the specifics of hybridization—whether the monofilament, as you inquire, is installed in the mains rather than the crosses—affect string movement and spin generation.

What we do know, though, is that the extent of snap-back is dictated largely by frictional forces—more technically, the coefficient of friction between the mains and the crosses. (COF, according to Wikipedia, “describes the ratio of the force of friction between two bodies and the force pressing them together.”)

As Ron Rocchi, Wilson’s Global Tour Equipment Manager, explains, “snap-back is primarily dependent on a low coefficient of friction between the strings, as well as the space required to first move and then ‘snap back.’ In a hybrid configuration, the space [for the strings] to move becomes more important to the frictional forces. That’s not to say that the same amount of snap back will not occur, but in most cases the two different string materials [compared to a single monofilament] yield a greater coefficient of friction, thus slowing down the snap-back effect.”

To recap: The strings in a hybrid bed seem to deflect about the same distance as those in a full-poly bed, all else being equal. But the speed—the speed at which a hybrid snaps back appears to be slower than that of full poly, likely because of the former’s increased COF.

Perhaps how a hybrid is configured affects this dynamic; perhaps not. (Perhaps other unknowns are at play.) When the evidence comes in, we’ll let you know.

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