Is it a club, or a feather?

 

It can be heavy, light, or anything in between.  On top of that the weight of a racquet can be distributed along its length in many different ways.  These two statements are the foundation beneath three commonly published racquet specifications - weight, balance, and swingweight.

 

        Weight - Due to the international nature of tennis, static weight (“mass” from physics class) is mostly referred to in grams. Adult racquets typically range between 275 and about 340 grams fully strung and accessorized. This number is what should register when you put it on a scale. It starts to define our relationship - it can be too light, too heavy, or something in between. Note that the most common weight printed on racquets is the frame without strings. A normal bed of strings will be around 18 grams.

       

        Balance - The most common length for an adult tennis racquet is 27 inches (686 mm). If you place it on a fine edge looking to find where both ends were evenly balanced that would be  somewhere around the physical middle. Some have more weight out by the strings - termed “head heavy”, while others have more weight at the handle end - “head light”. Where the bulk of the mass resides contributes to how the racquet feels in the hand. Lighter racquets tend to be more head heavy so they don’t get pushed around too much by the ball. Heavier racquets tend more towards head light so they aren’t too hard to swing.

 

        Swingweight - The most complex of these three specifications is a little harder to explain. Swingweight is a measure of how hard the racquet is to swing. Having a larger number means it takes more force to move it at a given speed but like many things in tennis there are pros and cons. If it takes more work to get the racquet moving, that energy translates into greater momentum, resulting in a faster ball speed when you hit with it.

 

Just like Goldilocks, you play best when these three parameters are “just right”. A way to think about it is to compare your racquet to a hammer. If the hammer head is too heavy you can’t swing it with one hand. We would describe it as over-the-top head heavy - its balance point would be far from the middle of its length. Because of its high swingweight, if we could hit the tennis ball squarely in the centre with the hammer head it would fly off at a pretty high rate of speed. Unfortunately finishing a point with a finesse volley at the net would be close to impossible. So would your chance of ripping a high RPM topspin shot with that low to high swing path. For that we need strings, what some marketing calls “the engine of your racquet”.

  

Aren’t all strings the same?

 

The short answer on many levels is no. They all have the same job - stop the ball, absorb its energy, and return that energy to fling it back in the opposite direction. How that works in a racquet can vary depending on a few factors. The size of the hoop, the density of the weave, the string tension, and finally, the type of string all come into play.

 

The size of the hoop, or “headsize”.

 

The head size of a modern racquet can legally be huge, in excess of 130 square inches of space to be filled with strings and today’s technology means it can still be very light and maneuverable. At the other end of the spectrum, modern production racquets aren’t typically less than 95 square inches. This means the spacing of the strings using a common pattern of 16 mains by 19 crosses creates quite a different surface to greet the ball depending on head size. Also very significant is the fact that longer string lengths from edge to edge on a large head have more material to stretch on impact.

 

This makes your mini trampoline feel and respond differently if the head size is smaller than if it is larger. The smaller tend to feature more of a connection to the ball - a more controlled feeling. The downside is it requires more skill and consistency to reliably connect the centre of the strings to the ball, therefore catching and releasing the ball’s energy in an efficient way.

 

On the flip side a larger head size makes it easier to find the ball with the strings and the time the two parts stay connected is longer. Since the racquet is generally moving in some direction, the longer the “dwell time”, the less predictable the ball’s direction will be. Although the bigger surface area makes it harder to miss the ball, the added length of the strings can have a mushy feel unless you increase the tension to compensate.

 

The density of the weave.

 

Also playing a role is the density of the string weave, which gives you a ratio of more or less string to the spaces between. The number of main to cross strings can vary with any head size.  It creates a different feel much like head size when the racquet design features a closed pattern - more strings, rather than an open pattern - fewer strings. When the ball contacts fewer strings because of open spacing, the energy tends to stretch them more for any given impact. When the pattern is more dense it tends to act as a firmer surface to meet the ball.

 

The String Tension

 

Another way to affect the impact with the ball is by varying the tension the string is pulled to during the stringing process. Like both a denser pattern and a smaller head size, increasing the tension the individual strings are pulled during stringing will reduce the time the ball spends on the strings during impact. The feel this creates is generally one of more control but less power. Stringing at a lower tension typically yields the opposite result.

 

Recommended tensions for modern racquets seem to be trending lower as newer string types are engineered to grip the ball, stretch, and then snap back in the hope of generating more spin. Where tensions like 60 pounds used to be common for recreational players the trend is now more towards the low 50s or below.

 

The Type of String

 

There are a large number of different strings available but the most useful way to think of them is by their stiffness. A weave using a stiffer string type will yield a firmer hitting surface much like a smaller head size, a more closed pattern, or a higher string tension. The result of that should be a feeling of more control but less power. Modern polyester strings are the usual choice for these characteristics. For a softer feel with more power the strings are often made of nylon and commonly built from multiple or even large numbers of fibres. These are usually labelled as synthetic gut or a multifilament string.

 

The Thickness of the String

 

Just like rest of the string characteristics we’ve just covered, the thickness of the string will also affect the interaction between the ball and the racquet. In North America strings commonly use American Wire Gauge (AWG) measurements, where the larger the number, the thinner the string. Most players will be using 17 gauge (approx.1.23 mm) or 16 gauge (approx. 1.30 mm). If the player wants more “bite” on the ball they may go down to an 18 gauge but the tradeoff will be less durability. If the player frequently breaks strings, they could choose a thicker 15 gauge but that may come at the expense of grip on the ball and “feel”.

 

How Stiff is Your Racquet

 

Going back to racquet frame, another feature making your racquet unique is its stiffness. By varying the amount the racquet will flex, and even where on its length the flex happens, the designer can dictate a number of performance characteristics. When the ball impacts the strings there can be surprising physical forces involved.

 

When you watch ultra slow-motion video of the racquet to ball impact you will see an odd mixture of the strings stretching, the ball deforming, the racquet head being driven backwards, and the whole frame flexing and wobbling. This is usually accompanied by a stretching of the muscles in the player’s hand, wrist and forearm but most videos only show the ball and string bed.

 

The stiffness of the racquet affects all of these things to some degree. If you think about an extremely soft racquet made of rubber, the frame would absorb more of the impact energy and spare the ball, strings, and player’s arm much of the collision stress. At the other end, a racquet  made of steel or ultra stiff material will push the impact stress back to the strings and ball, and to some degree, the hand.

 

When they developed your racquet the designer not only had a target for the overall stiffness, they were also looking for the delicate balance between protecting your hand from vibration and allowing tactile feedback for you to know how the impact went.  There are numerous patented materials and techniques for “dampening” the vibrations in just the right way to match the demands of the targeted player. If you can imagine a raw beginner to the sport is happy enough just to hit the ball whereas a seasoned professional needs nuanced feedback.

 

Another characteristic of the stiffness spectrum is that there are two issues to consider. One is shock and the other is vibration. Shock happens at the instant of impact. With our hypothetical steel racquet, when it impacts a large force at one end it will send that energy immediately to the hand at the other end. Vibration comes when the racquet flexes like a pool noodle and waves of bending travel up and down the frame until they die out. Either of these types of force in extreme amounts can eventually cause arm issues.

 

Stiffness also impacts your tennis in other ways. When you are trying to react to a hundred mile an hour serve having a softer frame can help cushion the incoming energy. Too soft could make the ball uncontrollable but the right amount of flex coupled with a little extra overall weight can make returning serves more fun. Racquet designers typically use beam thickness to control the stiffness of the hoop. This is the thickness of the hoop perpendicular to the string bed when the racquet is placed on a table. A beam diameter of 20 mm is usually reserved for softer, heavier frames whereas a very stiff and light alternative can be double that. The Wilson Hammer line is a well-known example of a very thick, and therefore stiff beam.

 

To conclude, the individual characteristics that make your racquet unique are not important only by themselves, they also interact with one another to yield the end result. Weight impacts how much your hand feels at impact but that is in conjunction with how large the head is, and how stiff,  tight and thick the strings are. Where the weight is placed on the length of the frame and how stiff the hoop is are also ingredients in the mix.

 

Hopefully understanding what makes your racquet unique can help shine a light on that weapon you have in your hand as you try to get that one more ball back over the net. If you have any comments or questions I would love to hear from you.