Strings (tennis)

In tennis, the strings are the part of a tennis racquet which make contact with the ball. The strings form a woven network inside the head (or "hoop") of the racquet.

Composition

The material used in tennis string can significantly affect a player's performance, and even health. Several materials are used to make tennis strings. They vary in terms of elasticity, durability, rebound efficiency, tension holding capability, and manufacturing cost, among other considerations.

Natural Gut

Natural gut is considered by many to be the best string in terms of overall playability, as it offers both power and control over the ball. It is the softest string material, and holds its tension better than any other type. However, some grades of natural gut break or unravel easily (especially uncoated gut when it is wetted) and it is the most expensive kind of string. The first natural gut tennis string was manufactured in 1875 by Pierre Babolat, who would launch the VS brand of gut fifty years later. Natural gut is usually offered in coated form, to reduce its tendency to unravel, particularly when humid.

Contrary to popular belief, and the manifestation of that in the term "cat gut", gut string has never been produced from cat intestines.

Natural gut is produced by drying fibers extracted from a part of the cow intestine called the serous membrane, or serosa, which contains collagen designed to withstand the stretching and contraction of the intestine. It is this elasticity that makes the fibers useful for tennis string. Sheep intestines have also been used for racquet strings in the past.

Synthetic Gut

Synthetic gut is not gut at all. It is nylon, nearly always composed of a single filament. It is a very inexpensive string to manufacture and is generally the least expensive string to purchase.

Small changes from pure nylon are usually found in strings sold as "synthetic gut". Textured coatings, colorants, and the addition of a small amount of Kevlar are the most common changes. Some manufacturers, such as Gosen, label nylon strings with words like "sheep", as in sheep intestine, although such strings contain no gut.

Multi-filament, or "Multi"

Multi-filament strings, known commonly as "multis" are strings that have more than one filament. They are most commonly made of many filaments of nylon, but can incorporate other materials such as polyurethane, Zyex, Vectran, Kevlar, and other materials. Multi-filament strings offer better elasticity than single filament strings, but usually inferior durability. No multi-filament string holds its tension as well as natural gut, and none of them are as soft.

However, in comparison to mono-filament "synthetic gut", multi-filament strings can offer a much closer approximation of natural gut's performance. The softest multi-filament strings can be made with either polyolefin or Zyex. However, several of the softest multi-filaments strings are no longer available for purchase which means that several nylon-based strings are now among the softest multi-filaments available.

Nylon

Nylon is the most popular string material for amateur players due to its low cost and the improvement in elasticity offered by multi-filament strings.. Wear-resistant coatings for nylon strings are common, especially with multi-filament strings, because the outer filaments tend to break first as the racquet is used.

Polyester

Polyester is a stiff and durable string material, originally intended for use by frequent string breakers. It took the string time to become popular, primarily due to its poor tension holding capability. However, due to the reduced potential for unwanted string movement, players are able to apply more topspin to balls while maintaining control. Polyester's support for heavy topspin in particular has made it the most popular material in the pro tour.

Kevlar

Kevlar is the stiffest, most durable synthetic string available, and is thus extremely hard to break. It also has the poorest tension holding capability and is the most dangerous string when it comes to developing tennis elbow. Kevlar is often strung with another string, such as nylon), in order to combine both strings' qualities, as Kevlar by itself feels too stiff for many tennis players, especially when combined with a stiff racquet. Some advocate using a very thin gauge Kevlar for increasing comfort, but even in the thinnest gauge it is a stiff string. Another strategy to increase comfort and improve rebound efficiency is to string Kevlar at a low tension.

Vectran

Vectran is the penultimate string in terms of stiffness and durability. It is perhaps the least commonly used contemporary string material. It is usually added to nylon string to increase nylon's durability and stiffness, as with Kevlar. Yonex, for instance, offers two badminton strings, made primarily from nylon, which have Vectran strands. However, the Ashaway company offers a braided Vectran tennis string.

Zyex

Zyex string offers more rebound efficiency, i.e. gut-like dynamic stiffness, than other synthetic strings, particularly when strung at low tensions. This gives it playability that is more similar to natural gut than, arguably, other synthetic materials. It also has low overall stiffness. The Pro Kennex IQ Element Z string, for instance, has the lowest stiffness of any synthetic string yet tested. The drawback of Zyex is that the outer wrapping materials in Zyex tennis string tend to be much less durable than the Zyex filaments inside the string and do not bond with them. This can lead to the outer wrapping wearing away relatively quickly, leaving the inner Zyex filaments to splay. However, some have said the bonding issue has been resolved.

Polyolefin

Polyolefin is the softest synthetic string. It offers mediocre durability and tension retention, so it is generally used as the cross string in a hybrid string setup. For those who do not break strings very quickly, however, 100% polyolefin stringing may be a good alternative to natural gut and multi-filament strings. This is especially true for those who have had tennis elbow and find natural gut string to be too costly.

The Gauge

The "gauge" number determines the thickness of the string. A string rated with a high gauge number is a thinner string; some gauge ratings also have a "Light" version, which is referred to by placing an "L" after the original rating's number (e.g., "15L"). Strings are usually rated at one of five common gauges; 15 (thickest), 15L, 16, 16L, and 17 (thinnest). String gauge is usually not of much concern to beginning tennis players, but can be very important to advanced and professional players.

Typically, a higher gauged string performs better. For example, the thinner 16-, 16L-, 17-, and 18 gauge strings are more lively and elastic than the thicker 15 or 15L. Thin strings are also known for better performance in creating spin and providing better feel. However, high-gauge strings also break faster, simply because there is less material to wear out.

Stringing pattern

A strung tennis racquet

Virtually all modern raquets are strung in a criss-cross horizontal-vertical pattern. Various other patterns have been used in history with varying success.

Double strung tennis racquets were introduced in 1977 but the "spaghetti racquets" were later banned because they permitted excessive spin and were too successful. However, a modern version of the double strung racquet has been introduced that it is legal to use.

Racquets are strung either with two separate strings (and thus four knots), or with a single string (resulting in only two knots). Sometimes, a hybrid of two different string types may be used in the same racquet. Traditionally, a double half hitch has been used to tie off tennis string, along with a starting knot.. Recently, a new kind of knot has been used called the "pro-knot" or "Richard Parnell knot".. Along with the use of a starting clamp, this can make all the knots identical, and improve the aesthetics of a string job.

Stringing

The process of installing strings in the racquet is called "stringing," and is done with a racquet string machine. These machines vary in complexity, accuracy and price. Stringing a racquet can take up to an hour for a novice, or around twenty minutes for a skilled stringer; during professional tournament a very skilled stringer may be asked to string a racquet while the player is on court. These stressful string jobs may not even take 10 minutes for a seasoned tournament stringer.

Drop Weight stringers

These inexpensive stringers use a weighted bar to achieve the desired string tension. They are the smallest of all stringing machines, making them the easiest to transport. This, plus their affordability, makes them popular among those beginning to learn racquet stringing. However, they take much longer than other stringers, and so are impractical for professionals.

Manual crank (lockout) stringers

These stringers use a crank to achieve the proper tension, at which point it locks into place. These stringers allow racquets to be strung quickly.

A Tecnifibre electronic stringer

Electronic Stringers

These stringers control the tension with a computer-directed electric motor. This is the most common kind of stringer found in stores and pro shops, but is also the most expensive. There are 2 types of electronic tension: constant pull and lock out. Constant pull, as the name suggests, pulls the string and continues pulling until the desired tension is reached making stringing more consistent and accurate as they compensate for the string stretching, the clamp loosing and slippage. Lock out electronics are similar if not the same as cranks; they will pull to your desired tension and will pull no more. Therefore lock outs are not as accurate as the constant pulls because they don't compensate for tension loss.

String Tension

The "string tension" of a racquet, usually expressed in pounds, indicates the pressure under which the strings are secured to the frame. The string tension affects a racquet's playing characteristics, such as the "feel" of the ball, control over the ball, as well as maximizing power.

All racquets come with recommended string tensions, most of which lie between 50 to 70 pounds (220 to 310 N).

A loosely strung racquet will usually have a larger sweet spot and will hit farther but, when swung hard enough, it will shoot balls unpredictably; a tighter string job will help make delicate shots with more finesse and control.

An extremely tightly strung racquet cuts down on a tennis player's feel on the ball, but can give the player excellent control if swung hard enough, with a smooth stroke. Such tension may make delicate shots more difficult, but makes play from the baseline more constant. However, if a player often hits powerful shots, a tightly strung racquet may quickly tire the arm, possibly resulting in tennis elbow.

It is advised by many professional stringers to string your racquet with the lowest tension possible while still being able to maintain control of the ball. Beginning players trying to find their tension should start in the middle of the recommended tension range and adjust the tension from there to meet their needs. The recommended tension is usually printed on the racquet. Remember, with a lower tension the racquet will have more power and less control, with a higher tension it will have less power and more control.

Restringing

Due to the tension present on the strings, elasticity and tension begins to decrease the moment they are installed in a racquet. "Dead strings", or strings which have lost their tension, cut down on the performance of a racquet. Dead strings may also hamper a tennis player's ability to generate power and pace, and may even make his arm sore.

The frequency of restringing depends on the player and the racquet, but there are a few recommended intervals. One is to restring the racquet as many times in a year as the player uses it in a week; e.g., if the racquet is used three times per week, it should be restrung three times per year. Another guideline is to restring after every 40 hours of play; if the racquet is used three times per week and three hours per session, it should be restrung approximately every five weeks. If the player has access to a tennis string tension meter (or access to a pro shop equipped with one), he may restring his racquet after he measures a loss of 25% or more of stringbed stiffness. However, many players who hit the ball hard to break the strings simply restring rackets whenever the strings break.

United States Racquet Stringers Association

The United States Racquet Stringers Association (USRSA) offers two levels of certification for stringers: the Certified Stringer and the Master Racquet Technician, of which around 350 exist worldwide. The Master Racquet Technician certification process includes testing of the stringer's ability to string a racquet, perform grip work, identify mistakes in an improperly strung racquet, and pass a written test that covers not only strings, but racquet technology as well.

Since 2004, RSi, the USRSA's monthly magazine, has named a Stringer of the Year. Past winners were:

• Randy Stephenson, Texas (2004)
• Bob Patterson, Alabama (2005)
• Grant Morgan, Tennessee (2006)
• Tim Strawn, Virginia (2007)
• Nate Ferguson, (2008)
• Ron Rochi, Ilinois (2009)