Tennis Industry magazine

 

Is Your String in Shape?

When it comes to spin potential, do shaped or textured strings provide an advantage?

By Bob Patterson

Shaped or textured strings have been around for a long time. But lately, we’re seeing more strings being introduced in this category than ever.

The popularity of polyester-based monofilament strings seems to be fueling this, as it is easy for manufacturers to extrude material in any shape that may appeal to consumers. Triangle, square, pentagon, octagon, hexagon — you name it, there is likely a string, or several, in that shape.

All of these shaped strings are touted to enhance spin, but do they? The same question can be asked of textured strings — which, while they may also be shaped, are strings that have raised bands or other characteristics to produce a rougher surface to bite the ball.

In the USRSA Racquet Professional Study Guide, here’s how we answer it:

“The verdict is not conclusive on whether the shape of the string offers the performance benefits claimed. However, they remain extremely popular and many players feel they are beneficial in enhancing spin.”

Beauty is in the eye of the beholder, and perception can become reality. If someone believes he or she is benefitting from shaped or textured string, then they should continue to use it.

Figuring in the Variables

In an age of high-tech video and computerized analysis, how can we not know whether shaped or textured strings actually enhance spin? There are a few variables to take into account.

First, there are all the different shapes. Then there are varying materials, different string patterns, head sizes and tensions. So a definitive answer, from a scientific view, is challenging to come by. Scientists like to compare apples to apples, and in this instance, that is almost impossible to achieve.

Our friends and unparalleled experts in this field, physicist Rod Cross and technical expert Crawford Lindsey (co-authors of Technical Tennis and The Physics and Technology of Tennis, both available on RacquetTech.com) have both done a substantial amount of research on this topic. Check out various experiments they conducted on the TW University pages on the Tennis Warehouse website into shaped and textured strings.

From all of their research on the subject, though, you’ll see why it is still considered to be “not conclusive.”

Snapback and Friction

One element that we know affects spin on the ball is string “snapback.” The string’s ability to return quickly to its original position adds spin generation when the ball impacts the string bed, and this has been shown definitively on high-speed video and computer analysis to have an impact on spin.

For snapback to occur, the player has to swing the racquet with sufficient velocity to bend the strings in the first place, and the angle of the string bed plane to the ball has to be such that the strings can move. The greater a players’ racquet-head speed, the more spin will be applied, regardless of the string used.

In addition to snapback, friction is at the center of all things that create spin. But it’s not that simple.

There are two friction interactions occurring every time the ball is struck: friction is created between the ball and the strings, and friction is created among the strings themselves, with the main strings sliding on the cross strings. Often, these two forces are at odds with one another.

For example, strings with a rough texture are said to bite into the ball, creating more friction with the ball and enhancing spin. But, that same texture could also create more friction between the main and cross strings, curtailing the snapback effect.

Research by Cross and Lindsey shows how each type of friction enters into the equation and how providing definitive answers about spin can be daunting.

Options, and More Options

Consider the more than 1,100 string types available in the marketplace today, and how many different combinations of hybrid string jobs these different strings can create. That massive number would then need to be doubled, because hybrid set-ups using string A for the crosses and string B for the mains will perform differently when you switch them around.

We must also consider how shaped strings interact with each another in the string bed. Consider a triangle-shaped string at the intersection of a main and a cross string. If the string happens to end up with a corner against a corner, there will be a significantly different coefficient of friction than if that string was on a corner on a flat side, or two flat sides. That variance is likely to be slightly differ on every single main/cross intersection of the string bed.

Now take into account the added texture that comes about as strings notch or fray from use over time. Also factor in the dirt and grime picked up and deposited on the strings during the course of play, and the change to the ball surface as it gets hit repeatedly. This will give you some idea of all the factors and moving targets that contribute to generating spin, and why is it nearly impossible to definitively determine the exact impact.

Finding What Works

Laboratory analysis aside, though, if a string works for you or for your clients, then it works. There are substantial physics at work in tennis, but the sport is a mental game, as well — players rely on feel and confidence that can’t be quantified by science.

The key here is to know what is going on with the interaction between the ball and string bed. We know that snapback imparts spin, so anything that enhances snapback should enhance spin, and anything that inhibits snapback will reduce spin potential.

Knowing this and knowing your client should help you determine the best string set-up for their game. If their swing speed or swing path doesn’t enhance spin, then it is likely that neither will the string they used.

However, if your client has sufficient swing speed, then knowing how their strings are interacting with one another and the ball should help you get them the string they want.

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About the Author

Bob Patterson , the founder of the RacquetMAXX customization service, is a Master Racquet Technician with more than 20 years of experience. He was RSI's Stringer of the Year in 2005. He is Executive Director for the U.S. Racquet Stringers Association.

 

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