OOAK Table Tennis Forum

Hi Dean. I build bats using a balsa core but have found lately that the balsa density is far too high. I would be interested in talking to you outside this forum if possible. Not sure if the forum is ok with this but I can be contacted on [email protected].

That is true.
We manufacture sheets and balsa block for windmill turbine blade.
The requirement for blocks is 200kg/m3 density or less, means there will be components ranging from 100-250kg/m3, some even at 300kg/m3.

But in a batch, there will be not more than 20% of this crème de la crème ultra light balsa. Hence time and labor are set specifically for this task since the sawmill.

We can do this because we are not too large a factory and we have the balsa tree from our seedling programs around the district.

I'll tend to the many private message/email later today.

Thank you all for the attention.
Dean

Hi Dinobalsa!

That is quite interesting! I had trouble finding such wood. Even though I finally found it, I would very much like to be in contact for possible future projects!

_________________
Re-Impact - Taipan --- Donic Vario Big Slam (RH+VH)
JOOLA - K3 --- Donic Desto F1 (RH+VH)
TSP - Balsa 6.5 --- Donic Desto F2 (RH+VH)
Re-Impact - (Achim) M3 --- Donic Desto F1 (RH+VH)

Ok, I finally did it! I built my first blades. I started with modifiying two existing blades (a very thin Victras 3.5mm and the well-known Donic Applegreen Allplay), then I moved to my first blade, where I was still messing around with way too much glue (too much weight...), but then I started to understand better how to do it, and built these four blades below.

All of them have balsa cores, in fact all of the three thicker blades have end-grain cores. For the thinner (6mm) defense blade I used also balsa in core, but not end-grain. Here, for that defense blade, I have used an even number of plies: 6ply. (Is "plies" the correct plural of "ply"? Anyhow...) and the core is therefore made of 2 plies of balsa, yet not end-grain and instead the regular fibre direction: in-plane with the ply.
These two plies in the core are at an angle of about 30° to each other, with the bisecting line of their 30° angle along the "long" direction of the blade. So one can argue that there is nevertheless a little assymmetry between backhand and forehand, but I don't think this matters (will see). Since these balsa plies are 1.5 mm, this double ply core can therefore almost be regarded as a 3mm (non-end-grain) balsa core.

All of the bright wood plies that you see are either such 1.5mm balsa wood plies, or 6mm end-grain balsa. The dark wood is 0.5mm walnut.
The 8mm Fast Attack blade has two of such walnut plies, and hence it looks like a 3ply, but it actually is 5ply.

I chose balsa for the handles. It is very soft, but I treated it with a "hard oil", which gives the surface some strength. Still, you can damage it with your finger nail, but after the oil treatment it is sufficiently hard to be practical, and since it is an oil treatment, and not a varnish or lacquer, it remains "breathable", i.e. feels dry and warm, and not slippery, even with sweaty hands.

Balsa for the handles was initially just a practical choice, because I do not have good tools for shaping the handles, and it is sooo much easier with balsa wood. I also have made good practical experience with balsa handles on blades of Re-Impact, so I know that it is not impractical, even though it is -of course- possible to damage it if you force it. (But in many years of playing them, I had never an issue.)
For shaping the balse handles, you just need a knife for the rough shape, and then the rest can be done with sand paper.
Most importantly, though: The choice of using balsa for the handles turned out to be an excellent choice, at least as judged by how the handles feel in the hand.

All of these blades have a weight of about 60g, so clearly on the light end of the spectrum.

I am going to do a study on their playing characteristics.
Sure, tested by players. That is at the end the ultimate test.
However, I will also test them objectively with a robot and stroboscope photography, to test (this is my particular interest and reason, why I made these blades) how the wood properties influence the spin generation potential and the spin susceptibility. I;e. all will be tested with the same rubbers.
I was motivated to test this due to the often ridiculously far-reaching claims of blade manufacturers about the playing characteristics of their blades. Of course, blades play a huge role in the playing characteristics of a racket. But when you read all that "colorful language" about the claims on how the spin and ball flight curve is optimized by the woods, you cannot avoid the think: "Ok, let's slow down and test that objectively. It just doesn't sound plausible."
Well, let's see how these notably different surfaces of these blades influence not only the speed of the blade, but also (if at all) the spin generation potential and the spin susceptibility, ...as measured objectively.

These tests will take a while, but at some stage the results will be published and compared to subjective impressions of skilled players.

_________________
Re-Impact - Taipan --- Donic Vario Big Slam (RH+VH)
JOOLA - K3 --- Donic Desto F1 (RH+VH)
TSP - Balsa 6.5 --- Donic Desto F2 (RH+VH)
Re-Impact - (Achim) M3 --- Donic Desto F1 (RH+VH)

Hi MalR, I am somewhat puzzled by your post: "Balsa density far too high"???
Balsa has the lowest density of all woods. Ok, possibly we can find one or two even more exotic species that are even less dense, but Balsa is of soooo low density that you will hardly be able to find a match. And there are excellent woods that do not use balsa at all, thus have an "even denser core" than balsa.

Anyhow, could you please explain what you mean by saying "balsa density is far too high"?

Or did you mean to say that the balsa variety that you have accessible has a higher density as you would like to find?
...after all, balsa wood does come in quite a range of densities, yet even the densest is of much lower density than "regular" wood.

_________________
Re-Impact - Taipan --- Donic Vario Big Slam (RH+VH)
JOOLA - K3 --- Donic Desto F1 (RH+VH)
TSP - Balsa 6.5 --- Donic Desto F2 (RH+VH)
Re-Impact - (Achim) M3 --- Donic Desto F1 (RH+VH)

Hi Viel.
Visit your Bunnings or large toy store and feel the weight of different balsa sheets of the same thickness. The white ones have the less density and are lighter. The darker boards are heaviest. The lower the density gives the bat its dwell time and "feel". The more dense the core is will make the ball leave the bat quicker and will have less control. Fine tuning can be done with the veneer selection or carbon layers but it is the core that determines the main qualities of the bat's performance.

Has anyone built a pickle ball bat? If so what structure are you using?

Cool. This perception is part of my experiment:
Three times the same core, but notably different layer (sequence) on to of that.
Let‘s see how the „feel“ is différent, and let‘s see what the objective measurements will say.

_________________
Re-Impact - Taipan --- Donic Vario Big Slam (RH+VH)
JOOLA - K3 --- Donic Desto F1 (RH+VH)
TSP - Balsa 6.5 --- Donic Desto F2 (RH+VH)
Re-Impact - (Achim) M3 --- Donic Desto F1 (RH+VH)

[/quote]
Anyhow, could you please explain what you mean by saying "balsa density is far too high"?
[/quote]

Balsa density can vary from 70kg/m3 up to 300kg/m3.
What we usually get from available stores is about 150-200kg/m3, that is the most common at least expensive price.
Anything Ultra light (contest grade) or extra heavy demand twice or more the price.

Blade manufacturers work with different densities depending how light they can get their hands on in a continuous supply.
Some insist on under 100, but others has to settle for heavier one.
Of course the lighter the better, otherwise the heavier it gets, the less dynamic and less catapult effect it has which is peculiar to balsa.

If we were to use heavy balsa, might as well use other light density wood such as Ayous, Spruce (Engelmann), Cedar or Paulownia.

End grain balsa sheet is something else, it is the strongest and most rigid pound for pound than any other wood, provided they are sandwiched.

Yes to all of that.

So we agree that the initial statement of the OP needed clarification:
It is not that „balsa density is far too high“, and rather that probably the OP only got access to balsa varieties that did not meet his expectations about the density.

_________________
Re-Impact - Taipan --- Donic Vario Big Slam (RH+VH)
JOOLA - K3 --- Donic Desto F1 (RH+VH)
TSP - Balsa 6.5 --- Donic Desto F2 (RH+VH)
Re-Impact - (Achim) M3 --- Donic Desto F1 (RH+VH)

Is Ross Leidy still in business ?
I sent an email at his website http://rossleidy.com/contact/index.php
But no reply

Congratulations on your efforts Viel. You have stuck with it and your bats look good.
A couple of tips. Do a 5 ply, not 6 ply. Don't bond the core as 2 pieces. It must be one piece. 6.5mm balsa will give you an all round bat, 5mm will give you a defensive bat if you use soft veneers such as hoop pine. The outer veneers must be put at right angles, the bottom across, the top vertical to stiffen the balsa. But you can also make a 5mm core bat play offensively.
I think I remember you had some glueing problems earlier. The glue has a big effect on the bat performance noticed by top players if not done correctly.
Use an exterior grade poly vinyl acetate glue. Normal glues will not give you the bond strength you require. The vinal acetate molecules bind strongly with the lignin and create cross linked bonds. This gives a very strong bond and stiffens the bat.
The amount is critical. You need enough so that the molecules in the glue and in the wood bond equally. Broadly speaking 2 bonds in the glue must equal 2 bonds in the lignin. If you use 3/2 you will have excess glue on the wood which you don't want. Excess glue effects the bat's harmonics. This is the most common mistake people make when doing this work and it is far more critical in musical instrument manufacture.
Basically, and in practice you apply a very thin coat onto the veneer, not the balsa. Use a brush or plastic scraper to scrape the excess off and level it. If you apply it to the balsa the solvent which carries the glue will penetrate the pores of the balsa and carry the glue into it.
Leave the glue to dry slightly until tacky. This evaporates some of the solvent and the glue is still active. Use a press to press fairly hard to ensure all surfaces are in direct contact which allows the bonds to link. Don't press so hard that you distort the balsa structure. 3 hrs will allow the solvent to dissipate and the bonds to set. After that the glue cures. If glue comes out the sides you have put too much on. ie 3/2 or greater.
It may be easier to press each layer one at a time when you are starting out. My press does 8 bats but I cannot prepare that many because the glue cures too quickly before I can press them.
Bonding end grain balsa is far more critical because you are dealing with something similar to glueing the ends of a bundle of straws and the glue will penetrate. If you need to bond the end grain for any reason you can use a flash coat then a final coat.
For balsa selection do not worry about gsm unless you buy from a recognised supplier and know what you are ordering. If from a shop look for the whitest timber. The lighter it is the lower the density and the better the bat will perform.
Make your handles out of balsa to keep the weight down. If you use wide, thin (2-3mm) strips separated by veneers they look nice when you shape the handle. If you want some pizzaz soak some in potassium permanganate (Condes crystals) and they come out pink. I guess food dyes will also do the same thing but may run with sweat. Seal the bat and handle with a timber sealer or the veneers will tear.
If you are getting 60gms you are right in the ball park.
Trying to lower the cost lowers bat performance. It is expensive to build a bat that has the same performance as a commercial bat. I know of two commercial builders who have closed and I suspect lost a fair bit of money so don't enter this as a money making exercise. Treat it as a hobby a lot of personal satisfaction and fun. The more bats you build the more you will understand how to control dwell, speed and bat harmonics.
Stick with it!

Hi MalR, there are surely not many "musts" in blade building, but a whole lot of experience and some arguments.
An even number of plies is highly unusual, because (_IF_ sticking strictly to the rule "90 degree fibre angle between adjacent plies") it is not possible to have for the two outermost layers the fibers running in the "handle direction". That's why I chose in my 6 ply bat for the two center plies a relatively small angle (25-30 degrees) with the bisecting line running in the "handle direction" (let's call it "vertical"), and then carry on with "horizontal" fiber direction for the next layers.
This results nevertheless (yet only in theory) in slightly different torsional and vibrational patterns for forehand and backhand, yet it is completely unclear (not investigated) whether this is an advantage, disadvantage or irrelevant. More relevant in this context, though, is that the bending properties of the core layer (in this 6 ply case two plies forming "the" core layer) have hardly any influence on the bending-stiffness properties of the final bat. Stiffness against bending is (from the point of view of numerical relevance: exclusively) determined by the layers further away from the plane in the center of the bat, ...and therefore also the thickness of the core ply: The "geometrical moment of inertia" goes with the cube of the thickeness, see e.g. https://en.wikipedia.org/wiki/Second_moment_of_area
(This is why one finds (for example in case of balsa cross-cut cores) that with everything else being identical a thicker balsa core results in a much stiffer (and generally "faster") bat, even though the cross-cut ("end grain") balsa core itself brings hardly any bending strength to the table.)
By the way, another technique to still have the outermost plies in the preferred "vertical direction" ("handle direction") while still having two plies in the center would be to have Zero degrees between these two core layers.

The question is rather _WHY_ would one want to have two layers in the center (or, in another way of looking at it: a glue interface in the very center)???
One legitimate reason is curiosity. In a highly experience-based and hardly science-based discipline like TT-blade building, curiosity is always a good motivation.
(It's interesting to read scientific literature on TT blade properties. Very little is sufficiently understood to conclude from mechanically well defined properties to the playing properties. Well, that's another topic, and I will add one or two more papers on that body of literature in the future...)
The other reason for making an even-numbered ply (e.g. 6 ply) blade can be pragmatism: You may have two 1.5mm plies, abut you want a 3mm core.
While not ideal, due to the glue joint and unnecessary weight from the glue, this is a valid reason.
In my case, it was a combination of the two reasons above, consciously "violating" traditional design rules.
A third reason is this, and I will possibly explore that in the future: One may be interested in creating a bat with notably different character for forehand and backhand. To some degree that can be done with the choices for the outer layers, but the different playing properties for forehand and backhand can also be increased by using two different wood types (and even two different thicknesses! ...increasing the asymmetry!) of a "2 ply core".

So no: there is no "must be one piece rule" for the core, although there are good arguments for it for blades that shall have symmetric properties.

Regarding glue bond strength: That is hardly an issue. Letting aside severe gluing errors, bond strength will hardly ever lead to failure, given the large area of the gluing interface.

Regarding your statement that a strong bond stiffens the bat: Stiffness is not necessarily what I am striving for, at least not by means of the glue. I want to design the blade properties by the wood layers, and not by the glue. Ideally, the glue layer is so thin (and ideally does not penetrate the plies) that it does not create any influence on the vibrational or compression properties. Of course, if the glue layer is too thick, it can have an influence, but one that I doubt can be positively used for designing favorable properties.
I made excellent experience with hide glue (after initial learning, i.e. mistakes). The temperature of the hide glue allows very nicely to get it to the desired viscosity, and sanding the plies (which can be a pain and difficult to do manually in an even, uniform fashion) is highly recommended to minimize the amount of glue necessary.

I do support your recommendation to not apply the glue onto the balsa, and rather on the other adjacent ply. When gluing balsa on balsa, you still need to do it, though. In that case, if one is an end grain balsa, and the other ply is not, then applying the glue to the "not end grain ply" is the better choice also in my view. This is for the argument that you described by the analogy of "gluing (the ends) of a bundle of straws". To minimize this, and even when not applying it directly to the end grain ply, I find that on the one hand side hide glue is quite good (does not penetrate as much as other glues), and also some ideas can be found here: viewtopic.php?f=43&t=11969&p=398312#p398312 The essence of this is for me in practice: Sand the end grain balsa with your finest sanding paper. (e.g. No. 600), but extreme care has to be taken, since the balsa is so easily reduced in thickness by sanding, ...and when doing it manually you can very easily end up with intolerable thickness variations.

Pressing too hard on the balsa is something that I was also concerned about. I therefore determined the pressure that causes damage. I found though, when gluing the plies and pressing them with two even plates on both sides of the blade it is very unlikely that you can reach those damaging pressure levels with normal manual clamping arrangements. It turned out to be a "non concern" in practice.

My main attention is not so much on the balsa density (although for fine tuning probably a very important parameter), but rather the homogeneity of the balsa. This is of particular importance for end grain balsa, which (according to my knowledge) is always made from gluing different pieces to one block, and you can end up having areas where high-density balsa is right next to low density balsa. Such end grain balsa I do not judge primarily by color, but rather by transparency: Hold it against a light source (best is a homogeneous light source, and a practical low-tech option is a window on a sunny day) for that purpose.
This technique is also useful for "non end grain balsa", and you will see that the judgement by color sometimes needs correction.

You wrote: "Make your handles of balsa to keep the weight down."
That's what I described in my earlier post. There I also described to make such balsa handles more practical by using an appropriate oil. Pure untreated balsa is particularly "sensitive" and quickly gets ugly. Yet applying a "lacquer" or varnish can lead to an unpleasant "feel", ...but some people like the feel of a lacquered handle (I don't). I find a "hard oil" produces an excellent compromise of the warm, non-slippery feel of wood, and yet a sufficiently resistant surface in case of a balsa handle. I recommend considering those aspects before choosing the type of "timber seal" that you mention.
Note though: Focusing on the handle weight alone is not necessarily the best approach. Frankly, it is what I am currently doing, because my "manufacturing throughput" is limited. But I am aware that (particularly for very light balsa blade) the center of gravity is far away from the center of the handle, particularly with balsa as material for the handle. Such weight distribution is not for all playing styles advantageous. Perhaps one day I will experiment with concepts like in Stiga's cybershape, where you can add some weights at the end of the handle: The best place to change the weight distribution while adding the least possible total amount of weight: https://www.stigasports.com/product/cybershape-wood-cwt

I very much disagree with one of your last statements, particularly the second phrase here:
"Trying to lower the cost lowers bat performance. It is expensive to build a bat that has the same performance as a commercial bat."

While I don't even look at the cost (i.e. have never decided to opt for a cheaper option just out of cost considerations) the total "bill of materials" of my bats does not even faintly reach the price of commercial bats, and while I have not yet fully characterized my bats, I doubt that they stand behind in performance of commercial bats.
No, what makes bats "expensive" is the labor costs, i.e. in case of my private activity: My time, ...and that I am not yet efficient in doing this, needing to think longer than a professional builder would with his/her standard processes. In a truly professional setting, there'll be also a whole lot of other things, such as waste minimization, throughput, production volume (and hence access to customers...) that will strongly influence your cost structure.
I doubt that any blade manufacturer died from the cost of the raw materials.
(Good news for us hobby builders: The raw material costs do not limit us.)

How are your bats coming along, MalR ?

_________________
Re-Impact - Taipan --- Donic Vario Big Slam (RH+VH)
JOOLA - K3 --- Donic Desto F1 (RH+VH)
TSP - Balsa 6.5 --- Donic Desto F2 (RH+VH)
Re-Impact - (Achim) M3 --- Donic Desto F1 (RH+VH)

Cut your balsa core so one piece includes the handle and body. Cut your bottom veneers to do the same but make sure the grain runs at right angles to the bat. Cut your top veneers so the grain runs vertically. Manufacture your handles so the grain runs vertically. Use several pieces and laminate them.
Glue and shape the body then attach and shape the handle. Aim for 60gm for best performance which means you will need balsa in the handle. I'm not a fan of routering the centre of the handle.
If any of this is unclear buy some commercial bats and dismantle them. They use a standard design, just vary in materials.

Ok, I see you like giving advice, MalR. We heard that.
Do you also have experience to share, other than "rules"?
How is your blade building coming along?

_________________
Re-Impact - Taipan --- Donic Vario Big Slam (RH+VH)
JOOLA - K3 --- Donic Desto F1 (RH+VH)
TSP - Balsa 6.5 --- Donic Desto F2 (RH+VH)
Re-Impact - (Achim) M3 --- Donic Desto F1 (RH+VH)

That's amazing. Thanks a lot for sharing this journey and experience with us! It's really motivating.