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Old 01-10-2013, 07:02 PM   #513
The Big Kahuna
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Best article on the subject I have seen is "Strings and Spin: Applying What We Know About Copoly" by Joshua Speckman.

I have posted portions of this artcile within this very thread in the past. Anyone looking to learn more about the theory and the science of string for tennis should read this article. Google it and check it out.

By popular demand (the unedited version - part 1):

Strings and Spin: Applying What We Know About Copoly
by Joshua Speckman


In the first article in this series on strings and spin, we learned that slippery strings, like copoly, generate extra spin because the main strings slide, stretch and snapback, applying an extra spin-boosting torque on the ball.

In the second article, we saw how copoly strings are actually similar to their ancestor from the 1970s, spaghetti strings. Both technologies use the same sliding and snapback mechanism to give players more spin.

But what does this mean for you? In this third article, let's go over some of the ways copoly strings are used in pro tennis, see what the applications are at other levels, then suggest a few new ground rules for equipment selection and care.

It's important to emphasize at the start that the most important factors for spin generation remain racket head speed and swing angle. To generate more spin, the most important thing to address is technique.

On some balls, pro players tilt the racket head forward a few degrees.
"If you want more spin the first thing you need to do is hit the ball harder," says tennis physicist Rod Cross. "The second thing is to hit at a steeper angle.

"The third thing is to tilt the racket head forward a little bit, and that's something that I don't think a lot of coaches know about, that if you tilt the racket you'll get more spin.

"Now the next thing you do is eat and sleep better and go to the gym more so you can hit harder. And then the fifth thing you do is change from nylon to polyester."

Despite the average player's desire for a magic bullet, copoly simply won't substitute for the other factors that go into generating more spin. But with nearly every ATP pro now using copoly strings, more and more recreational players who want to take part in the game's evolution are jumping on the copoly bandwagon.

Many professional stringers, however, steer their amateur clients clear of copoly strings because they are so stiff. This stiffness is one of the reasons why they snapback and produce spin so well, but it also makes them hard on the arm.

The copoly recipe: string loose, swing hard, and impart more spin.
One safer option with copoly (especially for young juniors who insist on using it) is to string at much lower tensions than most players have ever considered. Manufacturers routinely advise tensioning copoly 10% lower than nylon (multifilament or syngut) strings. But ATP pros often go lower than that.

"For my clientele, which is almost exclusively pro players, they can string it loose, swing hard, and impart more spin without losing control," says Nate Ferguson, the personal stringer of Roger Federer, Novak Djokovic and Andy Murray. "They string in the 40s and low 50s; really loose tension, which was unheard of ten years ago."

But in the United States, in particular, there seems to be a fondness for "crisp" stringbeds and high tensions. Perhaps this has something to do with Pete Sampras, who famously had Ferguson string his 85 square inch rackets with natural gut at 75 pounds.

The drum-tight string bed helped Pete with control, but most players don't realize that natural gut is unique among strings in that its stiffness does not increase appreciably at higher tensions. Natural gut at 75 pounds is only slightly stiffer than natural gut strung at 50 pounds.

But nylon and copoly don't share this characteristic – the tighter they are strung the stiffer they become - so dropping tension can dramatically improve comfort with these materials. An arm-killing copoly at 60 pounds will feel rather soft at 40 pounds.

In fact, a copoly like Luxilon Alu Power at 35 pounds is about as stiff, and transfers as much shock, as nylon strung at 55. But even at those tensions both materials are still stiffer than Pete's gut at 75 pounds.

Surprisingly, anecdotal reports from players suggest that copoly strung at 30, 20, even 10 pounds of tension, can, depending on the player, result in more spin, power and feel than at higher tensions, with surprisingly little loss of control.

Nate Ferguson notes that Italian pro Fillipo Volandri strings his racket with copoly strings at 26 pounds, and sometimes drops to around 19 when playing on clay. Volandri beat Federer in Hamburg several years ago playing at these super-low tensions.

"Poly has evolved," Ferguson says, "and now these guys who love the spin…they can lower the tension because the ball's not going to fly off. You're getting that cupping feeling, you're getting the feeling of more control, even though you're going looser."

The Italian player Fillipo Volandri strings with poly at 19 pounds on clay.
Another way to take advantage of the copoly spin boost, but with more comfort, feel and power is to hybrid with nylon or natural gut. Roger Federer has been using natural gut mains and Luxilon Alu Power Rough crosses since prior to hiring Nate Ferguson in 2004.

Federer is one of the few pros today that played with full natural gut for a significant part of his career. He was pretty good with it too, beating Sampras at Wimbledon in 2001 with a full bed of gut. So why did he add copoly strings to the mix?

"Spin control," answers Ferguson. "Spin is part of control, and he gains both. Definitely more spin, and with that comes control. And with that control he can string way down low. He strings at 21.5 or 22 kilos (47 or 48.5 pounds)," he adds.

Federer's setup actually bears some resemblance to spaghetti strings, as that invention also used natural gut in the mains and a synthetic in the crosses. Many players find the combination of extremely elastic gut mains with stiff, hard and slick copoly crosses to be as, or more, spin-friendly than a full bed of copoly, while also being more comfortable, powerful and giving better feel for the ball.

In string-on-string friction tests, tennis equipment researcher Crawford Lindsey found that gut mains slide with less friction along copoly crosses than any other string or string combination. And he found that - unlike other strings, where notching ramps up friction and disables the snapback mechanism – inter-string friction actually gets lower as the notches get deeper.

Why? Lindsey and Cross speculate that natural oils seep out of the gut at the notches and lubricate the string intersections. This suggests that a gut/poly hybrid might retain its spin-generating potential for longer than any other string or combination. Well, at least until the gut breaks.

Surprisingly, the opposite configuration – poly mains/gut crosses – slides much less easily. Lindsey says the two materials are sticky in reverse perhaps because the surface of the gut crosses quickly abrades, pulling up microscopic fibers that get hung up on the copoly mains as they try to slide.

The reason poly strings initially became popular with professional players was because of their inherent durability. Although modern copolymer strings are softer than "1st generation" polyester strings, they are still stiffer and harder than nylon or gut, and typically take longer to notch and break.

But, on the other hand, one well-known drawback of copoly strings is that they lose much more tension than gut and nylon. Consequently, advanced players often cut them out when they start losing control, saying they've "gone dead."

This is often assumed to be due to loss of resiliency. But lab tests show that strings don't really lose elasticity as they lose tension, which means that they should actually become more lively with tension loss.

The loss of depth control experienced with a well-played copoly could also be attributed to string wear resulting in impairment of the snapback mechanism. Werner Fischer, the inventor of spaghetti strings, points out that, although copoly is harder than nylon or gut, the surface of the strings can still becomes worn, roughened and notched over time, particularly if playing on clay.

Werner Fischer, the inventor of spaghetti strings, notes copoly can still becomes worn, roughened and notched over time. "Once a polyester string reaches a certain amount of playing time, the main strings lose their gliding ability, so that the mechanism does not work as well, or stops working completely," Fischer explains. "The [spin-boosting] effect works only as long as the strings are relatively new." Having lost the downward diving spin of their copoly strings when new, players may suddenly find the ball flying long.

For pros, this isn't a problem – they generally only play with new strings for several games or a set anyway - but for amateur players the premature loss of the snapback mechanism cancels out copoly's durability advantage.

As a general rule then, it would make sense for players to replace their copoly strings as soon they get stuck out of place, or begin to "move" in the parlance of players.

"The moment it goes out of line you've lost control. If the strings get stuck out wide you lose control and you lose spin as well," adds Barry Phillips-Moore, a former pro player and coach who played with spaghetti strings in the 70s and has been trying to recreate their effect ever since.
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