Bats and Rubbers
Rowden Fullen (1990’s)
Much of the advertising material which is written in the various brochures on materials is of very little use to the ordinary player and often misleading. The hardness of the wood and the make-up of the ply, how it is bonded and whether you have carbon fibre or titanium mesh layers will all affect the speed and control. Generally one ply will be more rigid and the ball will kick off the blade quicker, multi-ply will be more flexible with more control and stability. The choosing of a blade is a rather more personal matter than the rest of the equipment and it should feel right to the player. Tests in one or two countries appear to indicate that there is an ideal racket weight for the player at differing stages in his or her development and variation by even a few grams can cause a drastic loss of form.
Most rubber manufacturers use speed, spin and control ratings which are at best misleading — many of the tests they use are very simplistic and bear little or no relation to how a rubber is used in a match. Players also use the same rubber in different ways and with different feeling.
Let us examine the characteristics of the rubber as it is this which contacts the ball.
Dwell time — This is how long the ball stays on the racket during the contact phase of a stroke, (bear in mind this is a mere fraction of a second, if you have ever chalked a ball and thrown it to a player who slow loops and tries to maintain a long contact you find that the mark on the ball is never more than one centimetre). Rubbers have different dwell times for different strokes. The ball will be held longer for a slow loop as opposed to a kill. Some players also ‘carry the ball’ longer than others even for the same stroke. A long dwell time will often benefit spinners and blockers while a short dwell time will suit defenders and hitters. The dwell time is also affected by the blade you use and how the ball comes off the racket depends much on the rubber and sponge and how quickly it penetrates through these to reach the wood layer underneath.
Resilience — The energy stored in the rubber during the contact phase of the stroke. Some rubber and sponge combinations are much more elastic than others and will hold the ball longer on the surface at a closed racket angle. This stored energy is converted to produce spin. While elasticity levels will certainly increase we must bear in mind that the sponge cannot create energy, but can only minimize energy losses. Compared to a hard bat a ‘sponge’ bat can be swung in a much flatter plane so giving the ball more forward speed and spin. The sponge helps to lift the ball over the net.
Impact behaviour — A rubber and sponge can have differing performances at different impact speeds. At a slow speed there may be very little elasticity but you may get very good spin and speed when the ball comes into the racket with more pace. When you achieve maximum impact speed you can swing the racket harder but you will get little or no more effect. Some rubbers are said to have good gearing for spin and speed, which means they produce and maintain good effect over a wide range of impact speeds.
Throw-angle — The angle of the flight of the ball as it comes off the racket surface in the direction the bat is travelling. Differing blades and rubbers affect the throw-angle considerably as will different strokes (the angles would be very different if you were looping for example with very tacky rubber or with anti-loop). The throw-angle will also vary depending on whether the contact is on the outside of the racket or in the middle, or whether low, in the middle or high on the ball. High throw-angle rubber generally has a higher ratio of spin than speed, compared to low throw-angle rubber. (Flexible, slower blades typically increase the angle).
Stall-angle — The contact angle at which speed/spin of a rubber is dramatically reduced — at certain angles all rubbers will stall and not store energy (the ball will just drop off the racket, as it sometimes does when it contacts the outside edge). The stall-angle can be used effectively for dummy loops or short serves. A rubber with a wide range of stall-angles (or used with a badly matching blade) will have little or no control. A stall can also occur when the racket contact speed is too fast at a particular contact angle.
Friction — The grip of the rubber. Under certain conditions and with certain techniques some super-high friction rubbers can give less spin/speed than ones with much lower friction characteristics. Sometimes super-grippy rubbers have less spin at high speed — there is a critical level above which little or nothing is gained. Some very tacky rubbers have the characteristic of slowing the ball dramatically at low impact speeds, a function which is very useful in certain strokes. A low friction rubber has difficulty generating speed at closed racket angles. Remember always the friction of many rubbers is impact-dependent, they are more effective when the ball is coming at speed.
Sponge — Sponge can vary from soft to hard and from about 0.4 mm to 2.5 mm and the density of the sponge contributes to the weight of the racket. The amount of spin generated by a rubber is closely related to the elasticity of the sponge (irrespective of the top sheet of rubber), below a certain critical level for a given sponge, the spin of the rubber will be considerably reduced. This can be improved through the correct use of speed glues/optimisers which will increase the resilience by up to 30%. Players who glue usually prefer soft or medium sponges.
Glue — Adhesives and glue sheets are used to put the rubbers on the blade. Speed-glues/optimisers are used to increase the performance of the rubber in respect of spin, speed, control, throw and stall-angles. It is always recommended that you allow each coat of glue/optimiser to thoroughly dry before applying the next coat — otherwise you can get a ‘mushy’ effect which seriously affects performance when the glue is a little wet.
Properly applied speed-glues/optimisers can increase the spin and speed capabilities of the rubber by up to 30% (remember however that some glues/optimisers do not work well with certain sponges, especially most hard and more dense sponges). Also the glue must be regularly ‘removed’ from the rubber sheet and the build-up must not be allowed to become too thick. All rubbers (where speed-glue is used) should be taken off the blade as soon as possible after play so that the tension in the rubber is released.
One interesting characteristic of speed-glued/optimised rubber is that it has a very predictable effect over a wide range of strokes. Its ability to store energy is nearly constant over a large range of impact speeds, (in normal rubber the storage of energy bottoms out at higher speeds).