You probably haven’t had the opportunity, or desire, to hack off a portion of your racquet to see what is really in there. Well, I have. On many occasions, actually, when customizing a clients racquet to get the exact specifications they want.
You may be surprised. I thought I would give you a peek at some of the things you may find. First you need to understand why there is anything at all in your racquet! The reason is weight, or the more technical term, mass. But why?
When a racquet is “molded” the graphite composite “tube” has a certain weight and distribution of that weight. If no weight is added to the “rear end” of the racquet you end up with what Wilson termed a “hammer” (head heavy) system. Not everyone wants to play with a “hammer” system so the manufacturers need to add weight.
Where and how much depends on what style the racquet will be. We normally think in terms of “player”, “tweener”, and “game improvement” with “game improvement” having no weight in the rear end.
Let’s take a look at some “weight”.
This is a quick overview of the variations. Can you tell which “style” each piece represents?
Here you can see both steel plates on the inside of the tube. Also included is a “foam” that is normally used to prevent any rattling caused by the metal. This pallet is a molded polyurethane over a carbon fiber tube.
Here is a view of steel pins that are molded into the center membrane during manufacturing. In case you don’t know, a tennis racquet is a long tube made of a composite held together by a resin system that is forced into a mold that has the shape of the finished racquet. So, where the two tubes come together in the grip area is a perfect place to put steel pins or steel plates. When the racquet is molded under heat and internal pressure the weight is permanently installed.
This is a good example of steel and silicone. The steel adds a gross weight and the silicone is added to fine tune the weight if necessary. This is an example of a single tube grip pallet. That is the grip size and shape are formed by the carbon fiber tube during molding. Obviously this grip size can not be reduced.
This is an example of silicone only weight. This racquet was a “game improvement” racquet so very little weight was required. You can see how thin the material is at this position of the racquet.
This is the view of a racquet that has not been cut off. You can see the bulges that are caused by the “molded in” steel pins. This is a one piece molded grip pallet.
This is an example of using more fiber and resign to create the desired weight. This is a two (2) piece bonded on grip pallet. You can see how thin the molded pallet is at the corners. This is another example of a grip that can not (should not) be reduced.
SBS is “String Bed Stiffness” and is the stiffness of the entire strung area of a tennis racquet. SBS is not the same as “tension” and this is important to understand. Why?
When you talk to your racquet technician about “tension” it is, normally, about what number to set on the stringing machine. This number is usually called “reference tension” and every stringing machine has a way to set how many pounds, or kilo’s, it will pull each string before it stops.
Here is the problem with “reference tension”. It means different things to different machines! A “reference tension” of 55 pounds will result in a different SBS when set on different machines. If you take your racquet to technician “A” who uses a lockout machine it will have a different SBS than technician “B” that uses a constant pull machine . Over time, perhaps, each technician will arrive at the perfect machine setting to satisfy your requirements.
Why do all of this? You need to request a SBS! When talking to your technician you will talk about resultant SBS. So each time you have the racquet strung it will have the same SBS regardless of what machine it is strung on. The SBS number will be based on the diagnostic device the technician uses to collect data. There are three (3) or four (4) devices that will be familiar to all technicians:
The two Beer’s devices will return virtually the same number since they use the same technology.
The Babolat RDC uses, as far as I can determine, a combination of deflection and voltage. The FlexFour uses a deflection and includes the racquet stiffness..
So, the numbers may be different but it is the variation between tests that are crucial. If you are serious about your SBS I suggest you get a Beer’s ERT300 (about $180.00) and keep it in your bag. If the racquet has a SBS of 41 right after stringing you should consider having it strung when the SBS has decreased to about 33. For any device you should consider a reduction of twenty (20%) percent a reminder to have the racquet strung, soon!