We discuss the different ideas behind popular blade compositions ( 5-ply, 7-ply. carbon etc. ) in table tennis and possible blade and rubber combinations.
1. Wood | An alternative man’s best friend
1.1. Inside the trunk – a microscopic investigation
Before we start with the different wood layers, we want to take a closer look at the structure of wood itself.
Wood is nothing more than a huge bundle of something similar to drinking straws, which point from the ground into the air to transport nutrients.
Below you can see a simple illustration, for better pictures have a look in this document.
It’s important to appropriately cut the wood into plies. By appropriately we mean:
- regular parallel grid ( ||| ) of the grain lines (rift sawing – best quality, then quarter sawing), examples here and here
- again: grain patterns who look like clouds or mermaids are pleasant to the eye as well but are useless for high quality table tennis blades
- grain direction is parallel or orthogonal to the grip direction, “counterexample: blade(\)grip(|)”
- an even blade surface without any inclusions in general
A personal counter example with a crooked grain direction (/|) and traces of a bad production type ( quarter sawing ):
(click to enlarge)
On the contrary, a decent blade example is given below and another image to illustrate how the “straws” or wood pores generate the grain.
(click to enlarge to see the wood structure of the above blade better)
After years of research and billions of invested dollars, I found this quite cost effective real world model:
If you have a soft surface layer wood, you can try to spot these pores as shown below.
If you can’t see it, you may try another test which consists of using your finger nails. Attention! This damages your blade permanently and it’s hence unlikely that your local table tennis shop likes this test.
By using your finger nails at the bottom of your grip and on its side you can determine in which direction the center ply ( or any other ply ) is arranged. For example, the picture above shows a Hurricane WL. The soft core layer is softer on the side of the grip and hardly deformable at the bottom of it. Hence the center ply is parallel aligned to the grip – just like the top ply.
Let’s move on to another aspect.
There are generally two options to align the surface wood. Parallel to the handle direction as described and seen above ( || )or orthogonal to the handle direction like this ( |- ).
If grain direction is ||, then the force of the incoming ball works along the axis of each straw, which makes this wood layer stiffer and less flexible. On the contrary if a wood is placed orthogonal to the handle direction, then the flexibility is increased but the stiffness is really low.
Since we speak of surface wood layers, we assume a thin thickness of this ply and hence need parallel grain direction. If we would chose an orthogonal alignment with a thin ply thickness then the surface wood would break like two KitKat bars.
1.2 Wood types and mechanic properties
Several wood types exist which are more or less suited for table tennis. We start with the mechanic properties a wood can possess and use our straw model to explain the different qualities.
The ball impact applies a force onto the wood. Hence we need information how our specific wood type handles this force. At this point we remember our straw model and that a force can be applied from every direction. This leads to the conclusion that the mechanical properties of wood are different in every direction, depending on their relative position to the grain.
As an example, remember our finger nail experiment. It was easier to compress the wood on its side ( force applied orthogonal to several straws ( white above) ) compared to the same force parallel to the grain on the bottom of the handle. This holds true for the straw model above as well.
Some more illustrations:
Still remember the finger nail test and how it left permanent damage? Here you can see the straw equivalent of too much force:
The equivalent for real wood would be splintering along its grain.
Another form of permanent damage was given during our grain investigation under point 1, where we saw the permanent damage done by poor wood cutting methods.
We now explain the usually given parameters to a given wood.
1) Hardness ( Janka test)
The hardness of a wood is its ability to resist a force regarding a deformation. The Janka test now measures how much force is needed to press a ball into our wood.
An exact procedure can be found under the wiki article. Pay attention, the Janka hardness is different depending on the grain direction as previously discussed.
Easy speaking: higher Janka value -> higher hardness and vice versa.
2) Flexibility ( modus of elasticity / Young modulus )
This parameter roughly measures how stiff or flexible a wood is. Stiff and flexible are opposites of each other, a stiff wood is not flexible and vice versa.
It’s important that the actual stiffness of an object is always dependant on its form, in our table tennis case on the thickness of the layer. A thin layer of a certain wood has a different stiffness than a thicker layer of the same wood type.
Just like the parameter above, the stiffness varies depending from which angle you apply your force to the grain.
Easy speaking: given the same ply thickness: higher Young modulus -> more flexible and vice versa
3) Specific gravity
You may know the density of a thing, its mass per volume unit. Wood unfortunately contains water and is able to absorb humidity from the air among other things (tuners,glue) which alters its mass. The big amount of pores which can expand or contract under different temperatures or air pressures also change the density of the wood. Hence the density is divided through the density of water under the same temperature and pressure conditions.
Easy speaking: high specific gravity -> high weight and vice versa
A bit more about wood properties and a extensive data base for different woods can be found here.
Another, more simple database for most table tennis woods can be found here.
The shortest list with table tennis woods and a little picture beside the wood type can be found here.
2. String theory | I like the way you move …
“If you want to find the secrets of the universe, think in terms of energy, frequency and vibration.” – N.Tesla
Don’t worry, this section isn’t really about string theory. However, it’s not too far from it.
String theory assumes everything is composed from strings. If such a string is poked by a certain source, it begins to move or vibrate. After a while this movement become so regular, that you call such events standing waves.
Remember the drinking straw model from above. It might has reminded you of your high school physics course where you may have heard of waves for the first time.
Below is a nice demonstration, it starts a bit later because the announcer first tells what is going to happen.
An only slightly related video for standing waves using a water tank.
So far the aim was to understand that every system which is able to vibrate, forms so called standing waves. And guess what, table tennis blades can vibrate.
Remembering our straw model or the wave machine from the video, you saw that a power source is needed to induce the vibrations. In our case this energy comes from the ball impact.
Because we don’t have a single string but several as seen on our straw model we can think of a vibrating membrane. Below you can see some nice animations of such standing wave of a vibrating membrane from the corresponding wiki article. The animations were made by Oleg Alexandrov.
The animations below show an “up and down” bending. The energy of all animations increases from left to right.
A real life example for the third picture can be seen at the end of the video below:
In case you liked the straw model, here is a highly scientific photo of the above bending:
The next form of bending rotates the membrane through an axis along its midpoint ( imagine you rotate your bat around the grip axis ).
Another option where the axis goes vertically through the midpoint of the membrane.
John Staley made a nice simulation for blades here.
For the next section you need the program Audacity and any type of microphone. Even the standard in-built notebook microphone is sufficient. Additionally you need a table tennis ball and a “naked” blade.
If you can’t do it just now, we’ll do it together here.
I know it’s gets a bit technical but I promise it’s as easy as possible and we will highly benefit from this thought process.
Step 1) Install and open Audacity.
Step 2) Press ‘R’ and start bouncing the ball on your blade. Let the ball roughly bounce to the height of your eyes and try to hit the middle of your blade. Don’t worry, you don’t need to be perfect.
Press the button with the yellow square after you are done.
Step 3) Press ‘Analyze’ and ‘Plot spectrum’. Then change the values to the values in the picture below.
(click to enlarge)
Let’s analyse what we can see:
(click to enlarge)
The diagram shows how strong the racket reacts (sound emitted in dB) to certain energies ( frequency in Hz ).
In our table tennis case the impact energy is the power of the incoming speed of the ball coupled with the amount of power we invest to hit the ball.
Now the question might appear, what the emitted sound in dB has to do with rebound speed of our racket.
The moment the impact happens, the blade begins to vibrate in form of the previously mentioned standing waves.
This vibration (energy) is transferred to the surrounding air molecules, which pass it to the next molecules and so on. At the moment the last air molecule passes the energy to your ear ( which is some sort of membrane) and your eardrum measures the energy level and type. Fascinating, isn’t it?
Anyway, back to table tennis. The amount of emitted sound is directly linked to the amount of vibration, in particular the rebound speed.
The big red circle is somewhat uninteresting because it roughly just means that the points close to the blades edge vibrate strongly for small impact energies.
Going back into the diagram, any sound below 1000 Hz ( black line ) can’t be heard.
This means the sound you hear on impact is the biggest peak after this value in the red circle.
This peak is produced from the following standing wave which is called membrane mode for obvious reasons.
Try to recall the usual image of the sweet spot of a blade. It roughly follows the membrane for its positive peak. This follows logically from the supposed meaning of sweet spot, a map of the blade with the rebound power at each position. Here is a sweet spot picture of the new ZJK Super ZLC.
Let’s summarize our results for the membrane mode so far.
If you do the analysis above for several rubber and mark the biggest peak after 1000 Hz you know the following:
- the height of the peak (dB) measures the amount of rebound at the blades midpoint
- the position (Hz) measures at which speed ( incoming speed+your speed) this rebound/catapult is going to happen
Let’s move on and focus the left half, which can’t be heard.
In the 500 to 1000 Hz range ( small red circle ) lies another important frequency peak, the so called chips mode.
You can see an image of the chips mode below and also a picture to explain why it’s called this way.
If you do the analysis while holding the blade with your hand, then the peak can hardly be seen as displayed above. The reason for this is that our hand absorbs most of the vibration from the ball impact. However if you use a clamp, then the vibration isn’t damped, can be reflected back into the blades direction and creates a bigger peak in the frequency analysis above.
If you do a mental overlay of the chips mode with your blade you may ask, why it should be a good thing if the blade rebounds like mad on it’s sides where you hardly hit a ball.
You’re right of course, we aren’t interested in the bounce on its side. But what’s the interesting part here is the midpoint of the blade, it doesn’t move. Hence the ‘catapult’ or rebound from the blade is zero there. Perfect for the short / touch play, isn’t it?
Going back to the plot spectrum we can draw some conclusions.
Let’s suppose the frequency peak for the ‘clamp case’ happens at 800 Hz. This means a ball with this energy triggers our desired chip movement. The height of the peak (dB) determines how much the sides of our blade vibrate due to this impact. The greater the peak, the greater the blade vibration.
This enables us to define feel / vibration of a blade. To understand it a even better, grab a long ruler and let it vibrate/swing as seen below.
During the big overhang of the ruler you achieve a bigger bending of the ruler with your used force compared to the case with the short overhang. This small amplitude is then transmitted to your finger which holds the ruler. As you can see and hopefully felt, in the first case the vibration/amplitude is much stronger and appears to last longer due to the higher wavelength ( distance between two red peaks ) .
If you want to get the same strong vibration from case 1 at case 2 you need to increase your force with which you bend the ruler. This observation leads to an interesting conclusion for our chips mode:
The higher the frequency at which the chips mode occurs, the less you feel the vibration. The height of the peak is more or less irrelevant because we are not interested in the rebound height here.
As an interesting side note, there was a time when it popular to cut your rubber which a rather large overhang on its sides and the grip. These were called wings or flippers. This artificially made the blade/rubber combination more flexible ( ruler comparison: case 2 becomes case 1 ) and the blade vibrated noticeable more. As a self test, the next time you cut a rubber glue the complete quadratic rubber sheet to the blade and bounce the ball a few times while holding your blade in your hand. It will vibrate heavily.
3) Hollow handles | There’s a hole in your
3.1 A hole in the blade
Let’s go back to our blade and the ball impact.
Unfortunately our blade doesn’t form a perfect circular disk for our membrane mode. Hence it might be a good idea to give the “energy wave” something to reflect at the beginning of our handle to overcome this problem.
As you can see, the moment the wave reaches the gap or hole, it gets reflected because there’s no wood into the left direction to transmit the vibration (of course there’s air which can vibrate but it simply reflects the wave back there). This enables us to force the vibration to stay mostly on the blades face which is at least somewhat round compared to our whole blade with the handle.
Let’s discuss the effects of our “hole idea”.
1) The blade gets a better ( more uniform, bigger peak ) membrane mode.
2) We used less mass in form of wood.
This means the moment of inertia ( ability to withstand changes to the current movement of the blade ) is smaller. As an example, a heavy wood can accelerate a ball better than a lighter wood. Luckily this drawback of our “hole idea” isn’t as bad as it sounds.
The amount how much the mass affects the “power” of our racket is determined by the position of the mass in a quadratic dependence to the impact location of the ball. Because the handle is located far away from the blades midpoint we don’t hurt our power as much as we benefit from our better membrane mode.
This also explains why penhold players can glue the rubber with a little gap between the handle and the rubber, it doesn’t matter that much.
The “freed” mass of our hole can also be reinvested into a heavier ply for the blade.
Of course you see that a reduced mass enables us to accelerate the blade faster with the same force and our recovery will be faster aswell. Since we get nothing for free in this world, this results in less hitting power as mentioned above.
3) Because the hole is filled with air which can vibrate way better ( more ) compared a certain wood the player experiences more vibration in his hand and might conclude that he has a better control and feeling for the ball. However, from a technical point of view the vibrations which reach the hand are useless. The amount of vibration you feel in your hand is no sign of quality but rather a matter of personal taste.
4) Finally, because the handle is so light compared to the blades face with rubbers the blade gets “head heavy”. If we now accelerate our arm and hand, the wrist/handle region can be accelerated faster then the blades face with the rubbers and our fingers ( remember: moment of inertia: ability to withstand a acceleration ). This leads to a natural “snap” of the wrist region and to an usually better stroke. The drawbacks are the increased forces on the wrist and a slightly more unstable blade movement.
A common example of this “hole idea” is Stigas so called WRB system.
As interesting side note, most times only the thick center ply receives this hole. The reason for this will be explained later on.
Please also note how the wood ply below the top plies are placed in an 90° angle to the top ply. The reason for this will also be explained later on.
3.2 A hole in the wood grip
After understanding the idea from above, it’s no big mental leap to apply this idea to the grip. Here’s a nice picture of user “fatt” from mytabletennis.net.
We remove a hole from the wood grip and get the same advantages and disadvantages as above.
A common example is the Donic Senso Carbon. As you can see from the linked pdf file, they offer two versions, V1 and V2. Applying our knowledge from above, we can forecast their properties before Donic tells us. The V1 has a higher speed (rebound height at membrane mode) because the “wall” of the air filled void is closer to the blades face. On the contrary, the V2 has only a tiny air gap end the handles end and hence the blade is slower ( Donic phrased it differently 😉 ).
Many manufacturers are so afraid of their buyers ( and their superstition ), that they don’t explicitly state they they use a hollow handle and/or grip.
3) Carbon | Need for Speed
For this section you’ll need an apple and a pillow (no joke).
[Experiment 1] Throw the apple up in the air and let it fall on your open flat hand. From a suitable height this should slightly hurt.
[Experiment 2] Now do the same but move your hand towards the apple ( pretend to push the ball up with your hand ). This should hurt a bit more and your apple will get (more) brown spots.
[Experiment 3] Finally do the same two experiments with the pillow on top of your hand ( you can also use a winter glove instead of a pillow ).
At this point you might eat the apple because it’s of no further use and hasn’t developed brown (yet).
Before we explain the table tennis relevance, let’s discuss what happened on our apple “iBounce” experiment.
The apple applies a force onto our hand. On the contrary you apply a force with your hand onto the apple with resisting this force. Some of the impact energy is gone because you surely moved your hand a bit down while the apple landed on your palm ( try to do the experiment again but lay your hand onto the table incase you haven’t eaten the apple yet ). Additionally the apple got a bit damaged aswell on its inner side.
If you remember the result from the second experiment where your hand moved towards the ball, the apples force was still the same but your hand applied a bigger force onto the ball.
You may have been able to push the apple a bit up, but your hand should have hurt more and the apple should have gotten one more scar aswell.
The pain in your hand and the apples deformation might be summed up as ‘shock’, energy lost due to the apples deformation and the pain in your hand.
Now we have two options. We can cushion our hand and forge an iron fist around it to damp the shock for your hand and ‘show strength’ into the apples direction. Sadly the apple will be damaged even more this way. We have chosen option two, by using a pillow. This reduced the shock almost completely and neither our hand nor the apply where damaged. Additionally we should have been able to throw the apple a bit higher.
This can be compared to landing on the fire fighter jumping blanket instead of the solid ground.
Before you forget that this blog is about table tennis, here comes the table tennis analogy for our physics lab above.
The two options of reducing the impact shock are
- a hard surface layer (‘iron fist’)
- woven combination with carbon(‘pillow’)
The carbon+X option is the best of both worlds because it combines the ‘iron fist’ mentality of the carbon with the damping ability (‘pillow’) of the other material (Arylate, Zylon – have a look here for close up pictures of such meshes).
Pay attention to get a blade with such a combination and not a single component like carbon/glassfiber only. It’s additionally important to avoid blades with so called ( marketed ) unilateral or uniaxial carbon, which just means that the carbon fibers are aligned in direction. While this leads to a stiffer blade it does nothing for achieving a uniform membrane mode or named differently a good sweet spot area.
The reason to avoid these early types were given in section one and two. The impact energy wave wants to travel once it hits your blade. This travelling is easy along the grain direction(tip to handle), but hard from wood straw to wood straw(side to side). Hence a mesh with the carbon fibers placed at 0° and 90° gives the most uniform transmission of this wave and gets us the best membrane mode. Especially avoid carbon meshes which place their #-carbon like a ‘drunk hashtag’ in a 45° angle to the handle (keyword:
sharknado carbonado). This should explain why FZD likes the 90° (190) version as seen below:
Pure wood blades place the wood ply below the top ply in a certain angle ( usually 90° to the top ply ).
Other methods to reduce the impact shock were tested aswell, as an example Andros ‘Kinetic’ idea:
Side note: I previously promised you to give you the reason for the 90° angle between the top ply and the ply below and the reason why the possible hole is only made in the center ply if its done.
In the above section we already provided an explanation but let’s state it clearly again.
The 90° orientation between the top ply and the ply below guarantees an optimal shock absorption in all directions.
A hole is only made in the thick center ply because we want to absorb the impact shock at the other layers, not build standing waves as in the case with our core ply.
4) 5 or 7 ply | To be or not to be
Let’s build an actual racket. We saw that we need a core ply or in general at least one ply. Because we want to achieve a good shock absorption, we need two additional plies in a 90° angle to each other on top of the center ply in both directions. This leaves us with a minimum of 5 plies.
Of course there are blades with a smaller number of plies (even 1-plies) but for reasons stated above they can’t be seen as state of the art.
Because we want to benefit from the carbon technology we arrive at a total of 7 plies, 5 wood plies and 2 carbon+X meshes. The center ply is as thick as possible, while the shock absorption plies are really thin. Because the carbon+X mesh is rather flexible ( think of a blanket ) you need to fixate it between two wood plies.
The out most ply can’t be your carbon+X mesh for obvious reasons. The ply above the core ply would make no sense to be the carbon+X mesh because you want to absorb the impact shock and hence you want to place the carbon as close as possible to the out most ply. This leaves us with the following blade “formula” : wood – carbon+X – wood – core wood – wood – carbon+X – wood.
Again, if you recall the arguments above, you might think we can remove the wood ply above the center ply because the carbon would still be located between two wood plies and such 3+2 blades actually exist. However, with such a construction you would pass the “bad” shock vibrations from the carbon+X layer directly onto our vibrating center ply and we would destroy our possibly good membrane mode. To avoid this, the additional wood layer between the carbon and the center ply is needed.
If you now start shopping for a new blade, you’ll notice that there are blades with even more plies, for example 7+2. These blades are usually a bit thicker than 5+2 blades.
Instead of the one thick center ply they have a slightly thinner center ply plus one extra ply around it. This “3 wood core” ply usually makes the blades thicker than 5+2 blades. The rest of the blade follows the same construction principles as above.
The rule of thumb is that 5+2 blades provide more “catapult” while 7+2 blades provide more power through higher mass. Depending on your playing style you might chose accordingly. If you smash,block, hit, play half distance etc. you might want to try the 7+2 blades. If you play close to the table and you mainly use topspin shots you should stick to 5+2 plies.
5) Blade and rubber matching | Speed-Dating
We successfully build our blade and start playing. Unfortunately we aren’t able to give the ball any spin (yet). We lack an invention which is used to be able to impart spin on the ball – a so called rubber.
A rubber is nothing more than a thick damping sponge. You read right, any rubber slows your blade down compared to a blade which has the same mass as our blade+rubber combo. As previously stated, we still need this damping to generate spin which the blade isn’t capable of itself.
At that point I’d like to add, that the common descriptions of a blades throw angle is therefore slightly misleading. A blade itself has no throw angle, only a rebound speed if you let a ball bounce on it. Only in combination with a rubber you get something like an arc.
If you now pair two identical blades with the same rubber but blade A has a higher rebound(speed) than blade B, then blade A produces a lower trajectory than B.
Recently people go crazy about high throw angles, even if our above thought experiment shows that a faster blade has a lower throw angle compared to a slower one by using identical rubbers.
Hence a high throw angle is no sign of a blades quality but vice versa.
Let’s go back to rubbers and focus on one particular. The sponge thickness determines how much spin can be applied with this rubber, a thin sponge can “store” less energy than a thick sponge.
A thin sponge reaches its “energy storing” limit faster. Once this happens the impact energy is shattered over the blades faces and hopefully damped out by our non core plies and our carbon layer.
You might think this is good for blocking or in general an indicator for a good “control”, whatever the word “control” may be here.
Sadly, this is not the case. If you block a topspin ball with – let’s say a 1.8mm sponge – and it reaches it’s storing limit the “non storable” energy is lost. You may block the ball properly and you are happy because your 1.8mm sponge gives you so much control. Now you face a stronger player in the next game with a much stronger loop. At this point, you need the ability to reverse to incoming topspin into out coming topspin in order to still be able to land the ball on the opponents side. Without a suitable thick sponge, you can’t store enough energy to changes the balls spinning direction strong enough to drag the ball down with your block.
Hence you should always get the max sponge thickness of your desired rubber if you don’t want to lose against stronger players every time you encounter them.
I often wrote the phrase that nothing in life is free and this is still the case. A thicker sponger is heavier than a thinner one and you have to keep the total weight in mind when assembling rubbers and blades.
Another sponge characteristic is the sponge hardness. In the previous table tennis chemistry article we used the trampoline example to illustrate the impact of different rubber hardness. Harder rubbers need more energy to be activated ( to be bouncy ) and can store more energy. On the contrary, softer rubbers are bouncy from the start but lack power on higher speeds.
Previously we gave the recommendation to use at least medium to medium hard rubber because most balls in (even amateur) table tennis are too fast to be properly controlled with soft rubbers and this recommendation still stands.
Combining this advice with our knowledge from the membrane mode ( at which speed the blade is able to produce the biggest bounce ) we can provide some matching suggestions:
Rubber types: soft,medium,hard
Blade types: early bounce, medium late bounce, late bounce ( again: this means the “big peak” happens close to 1000 Hz or rather late like 1600 Hz for the “late” case )
We get 9 different cases.
At first we exclude symmetric ones like soft+early,medium+medium and hard+late because they only peak at one speed and have hardly any speed and spin on all different levels. You might know this under the term “gears” for a blade and rubber combo.
As an example, a soft rubber with an “early bouncing” blade, is nearly uncontrollable at lower ball speeds and lacks the ability to add spin and speed at any other speed level. On the contrary, a hard+late bounce combo plays like “dead” on most balls but loop “kills”.
In general I’d like to exclude combos with soft rubber + X, because the main function of the rubber is the ability to produce spin and soft rubbers can’t do that from medium speeds on.
Collecting the remaining 4 cases we get
- early bouncing blades (example: most all-round blades) with medium or hard rubbers
- medium late bouncing blades (example:Viscaria/ZJK ALC/TBS etc.) with hard rubbers
- late bouncing blades (example: Garaydia T5000) with medium hard rubbers.
Let’s discuss these cases a bit more detailed.
The late bouncing blades with medium hard rubbers provide decent spin and speed at medium ball speeds but the rubber fails at generating spin at higher ball speeds where the blades catapult kicks in. Because we can’t fully utilize this combo it’s not recommended aswell.
Medium late bouncing blades with hard rubbers are the typical professional setup. The blades catapult starts at medium high speed and ends at high speeds where you need the extra precision from the maximally deformed hard rubber to counteract incoming topspin but you don’t need additional catapult(speed) at this point. At low speeds the combo plays nearly dead and hence controllable as desired.
For some amateur players this isn’t optimally, because they might not be able to swing the blade fast enough to compress the hard sponge on most of their shots.
The most common setup for amateurs is the early bouncing blade with medium rubbers. This enables them to use sufficient speed at lower levels from their blade and a good spin with decent speed at medium ball speed levels. An obvious drawback is the dead behaviour at higher ball speeds, you can swing as fast as you want – your power will stay the same as if you had used far less effort.
One step further we arrive at the early bouncing blades with hard rubbers leading to decent speed at lower levels and a high control on blocks and loops. At higher speeds the missing blade catapult and the hard rubber provide a very good looping and blocking environment. Here we have the drawback of a “dead” zone during medium speed strokes.
Amateurs will a solid forehand ( which means the are able to generate the necessary swing speed in most cases) should therefore use a “slow/all-round” blade with a hard rubber on the forehand side and the same blade with medium to medium hard rubbers on the backhand side.
If the player gets better, a “medium fast/off-” blade with hard rubbers on the forehand side is the next possible step. If he keeps his medium hard sponge on the backhand, his backhand might be too bouncy ( “symmetric case” from above ) and he might even need to change his backhand rubber to a hard rubber aswell.
6) Which wood type for which ply? | Survive 300 years: check | Get felled for a tt blade: check
We previously spoke about the different wood types or at least about their table tennis relevant characteristics.
After knowing how a blade is constructed, we can find suitable wood types for each layer.
In general, we want to use light wood types. Because a lighter wood usually contains more air gaps which makes the energy wave transmission easier. Thus we get a higher membrane mode bounce.
If we don’t use a carbon+X layer we need an outer layer with a very high Janka hardness like walnut.
In case we use the recommend carbon+X mesh, we can use slightly softer wood types like Ayous, Limba and Koto.
This leaves us with the choice of the core ply. Because it isn’t effected by the impact shock, it can be really soft and should lead to a high membrane mode bounce. The usual suspects are Kiri and Balsa (technical keyword: modus of elasticity).
At this point a short episode of Mythbusters. Balsa wood is not a special ‘nonlinear’ wood or anything similar as sometimes claimed in forum posts. It behaves like any other wood type with the same properties ( hardness, weight etc. ). The only reason why it’s rarely used as center ply is its inconsistency. It’s quite hard to get a uniform piece of balsa compared to a similar Kiri ply.
Interestingly, as long as the rubber types are similar enough in the layer specific attribute ( Janka hardness or modus of elasticity ) it doesn’t matter which wood type you chose. See here for more details.
7) Summary | Auld Lang Syne
I hope you learned something new and you aren’t more confused about your rubber and blade choice after reading the article than before. By the way you can click the song title above to listen to the song while we recap this article.
The blade consists of several wood layers or plies. The recommend number of plies is 5 wood layers and 2 carbon plus some kind of fiber mesh. The two topmost wood plies on each side together with the carbon+X layer are responsible for reducing the impact shock and the center ply ensures a good bounce at a certain ball speed.
Make sure your top ply has a straight, uniform grain structure with no sawing compression.
The time at which this bounce or catapult effect of the blade happens can be measured by recording the ball bounce on the naked blade with Audacity and spotting the biggest peak after 1000 Hz. The further away from the 1000 Hz the peak happens, the later the catapult effect happens. If you have a good ear, the higher the pitch of the ball, the later the catapult effect happens.
The amount of vibration can be measured in the same way, but you have to look in the range between 700 and 1000 Hz. Sadly you can’t hear this frequency so you rely on your PC there.
The vibration you might feel is a matter of taste and no sign of a blades quality.
Most actual blades have a hollow handle and / or grip to improve the rebound height of the rubber and to provide a better “feel”.
A blade which produces a lower “throw” with the same rubber compared to another blade is usually faster ( higher rebound height ).
A beginner should start with an all-round blade ( early catapult effect ) and at least medium to medium-hard rubbers. The forehand should be harder than the backhand and the max sponge thickness should be used.
If he gets better, an off- blade ( medium late catapult effect ) and even harder rubbers can be used. Pay attention that you don’t stick to your medium rubber on the backhand side if you “upgrade” your blade, because this combination might be hard to control. In this case, upgrade the backhand rubber to medium-hard aswell.
The blade should be regularly changed, because the material deforms differently in different directions and accumulates water over time.
The above recommendations are for two winged loopers. As usual, if you find errors or have further questions, let me know below :).