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 Post subject: Re: Make your own blade
PostPosted: 20 Oct 2020, 06:41 
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 Post subject: Re: Make your own blade
PostPosted: 15 Jun 2022, 18:29 
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A bit of a beginner's question, what kind of woodworking equipment would you need to cut thin wood boards (3-4mm) out of a big plank (2+cm)? I would try and find a woodworking shop that has these machines. Thanks!


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 Post subject: Re: Make your own blade
PostPosted: 17 Jun 2022, 19:21 
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rova wrote:
A bit of a beginner's question, what kind of woodworking equipment would you need to cut thin wood boards (3-4mm) out of a big plank (2+cm)? I would try and find a woodworking shop that has these machines. Thanks!


The process of cutting a thick square board (eg: 100mm wide x 1000mm long x 20mm thick) into thinner or smaller slices (or veneers) (eg: 100mm wide x 1000mm long x 1.5mm thick) is called resawing.

Resawing is best done on a bandsaw, using what's called a 'cutting fence' to control the wood as you go.

Resawing wood is not a job suitable for a cheaper bandsaw - you really want something decent. Also I would not try to do this without some proper lessons first, lest you lose a finger or two.

If you are thinking of making your own blades with it, you will need a bandsaw where the throat width (ie the distance across the cutting surface between the bandsaw blade itself and the inside edge of the bandsaw) is at least 250mm, as this is the minimum length of a standard size blade (260mm or 265mm is a little more like it frankly).

If you are thinking of having others do it for you, ask them what size wood they can resaw.

Don't be surprised if it takes you a while to find a place - manufacturing veneers is really a specialty job, though if you are careful and skilled, you can still get a great result using basic equipment.

TO do it yourself will require you to buy a bandsaw - renting one is not advisable (though technically possible).

To buy a decent bandsaw (new) that should do the job will cost you $650 at the very least. Check online for decent brands / reviews before you buy, and don't go for anything that has less than a 750watt motor, as it will be underpowered.

Stay away from anything cheaper or smaller that you might see at Bunnings. They are woefully underpowered - you will need a sharp blade, a steady hand, a feather-board, a push pad, and a LOT of patience and practice.

To buy something bigger (and more useful) will cost you well over $1k - $2k, and you might conceivably end up needing 3-phase power in your workshop as well, depending on the unit you buy. Bandsaws can be power-hungry buggers, as you need a fair bit of grunt to re-saw the denser wood species out there.

Hope this helps.

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 Post subject: Re: Make your own blade
PostPosted: 02 Jul 2022, 18:24 
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Has anyone done much building using high density styrene foam as the core? I'm thinking something like 6mm and I was going to use a double stitch carbon fabric. I guess I will have to use Vpoxy instead of laminating resin because I am worried that the resin may chemically react with the styrene. Vpoxy should give me the bond strength required. I will then try it with a single outer walnut veneer as a base model. The logic in this is the styrene should keep the weight down and I expect it will give me a little more dwell time than 6.5mm balsa that I normally use. I expect the carbon fabric will stiffen it and take most of the deadness out of it. The thin walnut outer in conjunction with the carbon should give me good hitting power. I may need a second veneer. In theory all this sounds like it should work but I wondered if anyone has tried doing this? If so, are you using a particular type of styrene? There are numerous grades. I expect the highest density would work if it is procurable in a thin sheet.
I cannot see any thin styrene online that is very high density. Because styrene is rolled under pressure into sheets I do not think it will be wise to cut or sand a wide sheet down because it will lose its tough, sealed outer surface.
I should say I play mostly defensive with hard bh/fh when needed and use LP/SP so I expect that this material will work for me. I don't play tournaments any more so am not worried about legalities. Just like trying different materials and building bats! I think this would be an interesting experiment.
I mention this because it looks in one of Ross' photos that he might have tried it.


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 Post subject: Re: Make your own blade
PostPosted: 03 Aug 2022, 14:08 
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MalR wrote:
Has anyone done much building using high density styrene foam as the core? I'm thinking something like 6mm and I was going to use a double stitch carbon fabric. I guess I will have to use Vpoxy instead of laminating resin because I am worried that the resin may chemically react with the styrene. Vpoxy should give me the bond strength required. I will then try it with a single outer walnut veneer as a base model. The logic in this is the styrene should keep the weight down and I expect it will give me a little more dwell time than 6.5mm balsa that I normally use. I expect the carbon fabric will stiffen it and take most of the deadness out of it. The thin walnut outer in conjunction with the carbon should give me good hitting power. I may need a second veneer. In theory all this sounds like it should work but I wondered if anyone has tried doing this? If so, are you using a particular type of styrene? There are numerous grades. I expect the highest density would work if it is procurable in a thin sheet.
I cannot see any thin styrene online that is very high density. Because styrene is rolled under pressure into sheets I do not think it will be wise to cut or sand a wide sheet down because it will lose its tough, sealed outer surface.

I should say I play mostly defensive with hard bh/fh when needed and use LP/SP so I expect that this material will work for me. I don't play tournaments any more so am not worried about legalities. Just like trying different materials and building bats! I think this would be an interesting experiment.
I mention this because it looks in one of Ross' photos that he might have tried it.


Personally I've never tried foam cores in a blade, and I honestly don't know many others who have either. Given the ITTF's 85% timber rule, I just don't think it's something that most blade makers have bothered to try.

I imagine that you are correct though, and that the styrene wouldn't stand up well to epoxy ...but I honestly don't know for sure - really I'm guessing.

But TBH, even with the carbon fibre twill medial layers, I very much doubt you will get the playing feeling you are describing. As a general rule of thumb, big differentials in density and hardness between outer layers and your core will give your blade a very "hollow" feeling... This is especially noticeable with hard outers like walnut, jarrah or Tassie Oak. You're not including any softer mid-density medial layers, so I imagine the vibrations are going to be all top-end / high frequency, with no lower to mid-range feedback at all.

Rather than go with a synthetic foam core, may I recommend you try looking for some ultra-low density balsa instead? Most store-bought balsa is in the mid-density range of 140-160 kg/m3, but it can go as low as 65kg/m3 or as high as 300kg/m3. The ultra light stuff feels a lot like styrofoam when you pick it up and has huge natural flex to it. It should give you most of the weight gains you're after, it won"t be chemically compromised by the epoxy, and you'll end up with a blade you can actually use in competition (though I acknowledge that's not a requirement for you.) It still won't give you much low end feedback mind,bbut such is the lot of ultra-light blades in general.

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 Post subject: Re: Make your own blade
PostPosted: 06 Nov 2022, 00:15 
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Hi All! I am forum newby, joining bec ause I am attracted by the interesting and competent contributions on blade building, which is a topic that I intend to experiment with a bit. That means, I am also a newby in the topic of this thread. I hope you more experienced posters have some patience with some beginner's questions.

I am presently searching for sources of good material: verneers and glue:
I think I found some companies that supply verneers, but since most/all of them supply their material for furniture building, and may not always be the best supplier choice for TT-blade making, I will greatly appreciate recommendations for companies/websites to buy verneers from!!

In particular, I do not yet know a single source of "endgrain" balsa sheets.
Does anyone have a suggestion where to get "endgrain" ("crosscut") balsa sheets?
I am talking about sheets where the grain direction is perpendicular to the plane of the sheet itself. TSP, now Victas, uses these as cores and I think adyy ( @adyy ) used such cores also.

I would also love to get some advice on which glue to choose for the lamination. I have seen impressing close-up pictures by adyy ( @adyy ) of the porous structure of wood sheets. Glue that seeps into these pores must change drastically to mechanical (playing) properties compared to a situation where it was avoided to have glues seeping into the pores.
Can someone provide advice on:
- Suitable glues for the lamination
- Whether or not it is beneficial to avoid that glues seeps into the pores
- ...and how to avoid it, if it is deemed beneficial.

Finally I have a potentially stupid question, based on really enjoing to treat wood with oil:
What kind of experience is available on the effect of "surface-treating" TT-blades with oil? I believe that all commercial blades are "just wood", without any "finishings" on the wood (possibly apart from the "surface sealing" that some apply before gluing a rubber), so that might be an indication that the wood should better be left alone. Whenever I put oil on wood for funiture I have the sensation to do something good to the wood, think (nourishing, protecting). Is there anything known good (or bad) happing from such treatment for TT-blades? (...or rubber adheasin for that matter...)

Thanks so much in advance in case of any answers!

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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)


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 Post subject: Re: Make your own blade
PostPosted: 06 Nov 2022, 09:23 
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I buy balsa from Bunnings or toy shops because I can see what I am buying. Balsa can vary from around 80 to 300Kg/m³. These days supply seems to be not as good. Balsa cores are used because the control part of the bat comes from the balsa. This is also called the dwell time or the time that the ball remains on the rubber before it flies off. Thicker cores and low density balsa give greater dwell time (control) but somewhat restrict the speed. There is a payoff depending on the level of your skill. I build most of my bats using 6.5mm cores. You then put soft laminates such as Huon on the backhand for greater control and fast laminates, (eg walnut) on the FH to improve speed.
I have been asked to build some carbon fibre bats and actually went to Bunnings to get the balsa yesterday but found their stock at the moment is high density so i walked out. As a guide, low density balsa is white. High density is brown. Hold a white piece and a dark piece and you can feel the difference in weight. Poke your fingernail in it is also a good guide. I have delayed the project until I can get the right balsa. The bat just would not work. We need as low a density as possible.
There are specific veneer companies such as veneers online but these sell to furniture people who then sand and process the veneers so they are somewhat flexible in their needs. Bat people need very specific things in a veneer so it is good to establish a rapport with the owner and he should supply what you want. I now tend to buy from people who are retiring that make musical instruments. That stuff is very good and i buy all their stock.
Don't get too involved with the grain on the veneers. They either run up and down or across. The whole deal in making bats is to use the strength of the veneers to stiffen the bat by alternating the grain and bonding them to a less strong substrate (balsa) using a contact bond that does not interfere with the properties of the wood. Don't get involved in putting more than 2 layers on each side. You select your veneers based on what you intend the bat to do and adding more layers is like taking heaps of tablets! I have experimented numerous times and am convinced it is a marketing ploy. I guess sometimes they can fluke it. I'll stick my neck out. In my experience the bat is about 70% of the performance (if it is built correctly) and the rubbers maybe 30% for average players. Many would disagree and this is why there are so many $100 rubbers sold. This also relates to above and below average players. Players above 1300 do benefit from better rubbers. I can hold my own against good players using $15 Ooak rubbers. To each his own.
You need a cross linked PVA glue. The cross linked bonds give the PVA its strength and restrict shrinkage when it dries. I use Sellys Aquadhere Exterior and never had a failure but Titebond 2 is also a good cross linked glue and it is the most economical in terms of strength and price of their 3 grades. TB 3 is more waterproof and expensive which does not concern us. The cross linkage stops creeping when it dries which is vital. You do not want stress between the veneers. Don't use standard contact glues (Maxibond) as they have to be applied as a thick layer which upsets the feel of the ball for better players. You want the veneers and balsa to create the effect only. Be very careful about HM you put on. It will soak into balsa if you are not careful which gives a somewhat deader effect if it is too much. I put on one side only (as per manuf instr) and scrape then press hard and quickly. You are making a contact not a chemical bond. Apply the glue to the veneer, not the balsa.
I use a press not vac. I build my own presses using form ply with 6 bolts, not 4 to get an even compression. I can do 6 bats at a time. Watch that the plates come down equally. There is a tendency for the end of the press opposite the handle to clamp lower. Don't let that happen. Clamp hard but not enough to distort the balsa or it will glue under stress when released. Use baking paper as a release agent.
All good bats are sealed although some may not look like it. The sealer is used to prevent the timber from shredding when the rubbers are removed. I use slate sealer. Watch it does not soak. The sealer should never penetrate. Therefore I would not use a polyester liquid ("oil" as you mention) because it is designed to provide another layer on timber and to soak. The essential thing is the glue needs to bond with the sealer in order to stick the rubber with a low strength mechanical bond. Then it needs to unbond cleanly when you replace the rubber without effecting the bat performance or leaving residual glue on the bat. Several processes and if you do it wrong you might get only one of them working correctly.
There are many guys building bats and they all have their ideas that work for them. These statements are just the logic I follow for the bats I build.


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 Post subject: Re: Make your own blade
PostPosted: 07 Nov 2022, 00:40 
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Hi MalR! Thank you very much for your quick reply. Your comments on the verneer suppliers seem to reflect my intuitive concerns, that just buying from furniture companies can be limiting. So your advice is to get in personal contact with (smaller) verndors and communicate. That makes perfect sense. My question was therefore targeting to get some recommendations who to approach concretely.
Is there anyone who could recommend some sources concretely that ship (saw-cut, not knife-cut) verneers ? (I live in Europe, France.)

The recommendation to buy balsa from e.g. toy stores seems to me does not address what I am after:
There is probably good balsa sheets available at toy stores for e.g. model airplanes, agreed. But as far as I have seen it these are all sheets where the grain is parallel to the plane of the sheet, whereas I am looking specifically to "end grain" or "cross cut" balsa sheets (by that I mean sheets where the grain, or wood fibres are perpendicular to the plane of the sheet).

Regarding to what you wrote, MalR, about grain direction and more so about the balsa layer thickness, I found that your description is different to what I read elsewhere, and regarding the balsa thickness different to my own experience.
My own experience is based on three Re-Impact blades, as well as a handful of TSP blades (now being soled under the name Victas), and one additional blade that I bought under the name Victas. For all of them there is the clear correlation: "The thicker the balsa, the faster the blade".
I do not know about the Re-Impact blades, but for the TSP (and Victas) blade, I am pretty sure that the grain direction of the balsa core is "cross cut". Possibly your experience with balsa (you wrote that thicker balsa creates slower blades) is related to using a grain direction that is parallel to the plane of the verneer. "Cross cut" balsa is quite pressure resistant (compared to its weight), and the fibres can act for small deformations like "springs". From that perspective it is quite plausible that thicker cross-cut balsa cores are capable to procude more cataput than thinner cores, where the E-modules is easier forced out of the linear (elastic) range than thicker cores.
Possibly with grains parallel to the verneer plane (as you seem to use it) the elasticity of the balsa is much reduced and you have predominantly a dampening, and hence your experience "thicker balsa core causes slower racket", contrary to my experience.

Thank you, MalR, for your recommendation of PVA glues. I am (as my original post/reply) implies still new to blade making and hence to glues, but a quick search for PVA glues seemed to tell me that they are water soluble. Even though we normally don't go swimming with our TT blades, my gut feeling makes me think that a water soluble glue cannot be the ideal choice. Is there anybody's experience on this? (Or does "water soluble" only imply solubility of the glue before the final bonding has been accomplished, and the finished bond is not soluble by water?)
I have seen a professional (yet "boutique") blade manufacturer (www.soulspin.de) using epoxy glue.

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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)


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 Post subject: Re: Make your own blade
PostPosted: 07 Nov 2022, 01:16 
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One more thing on the balsa core thickness: I argued about something like a "spring effect" of the vertical fibres in cross-cut / end grain verneers.
I am not sure how big that effect is. But judged from basic mechanics, two things should hold:
- The "stiffness" is mostly determined by the strength of the "outermost" layers
- The stiffness increases with thickness
So while Balsa is certainly not stiff in itself, a thick balsa in conbination with strong outer layers should produce a much stiffer blade than a thin balsa core with the same outer layers of "strong" wood. And since (I believe) stiffer blades are typically faster than less stiff blades, this may be the true origin of the correlation between a thicker balsa core and the speed of the blade, ...and not as I argued before the "spring effect" of the vertical balsa fibres.

Interestingly, MalR, this argument also runs against your experience that a thicker balsa core produces a slower blade.

Are there some other voices that can add to this discussion and possibly enlighten this by additional information/perspectives?

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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)


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 Post subject: Re: Make your own blade
PostPosted: 07 Nov 2022, 03:30 
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Of you blade-makers, have you experimented with "vibration" design, such as Re-Impact discusses?
https://www.re-impact.de/info/ksl-system

Do such cuts (or possibly other measures in/under the handle) have any impact on the "feel" of the blade? (...feedback, etc)

How you tried other geometries / cut-outs / hollow handles etc?

In your opinion/experience, does this -if at all- change only hte "feel" (sensation of vibration) or does it also change anything about the playing properties?
Are your opnions on this only based on subjective judgement (important enough...) or do you also have any objective data (measurements) on these effects?

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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)


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 Post subject: Re: Make your own blade
PostPosted: 07 Nov 2022, 06:30 
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Wakkibatty wrote:
Personally I've never tried foam cores in a blade, and I ...

Man, I like your website ...


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 Post subject: Re: Make your own blade
PostPosted: 07 Nov 2022, 08:13 
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You are getting into an area that I am not familiar with Viel. I entered this post only as I said to throw in some suggestions and let the reader make his own decisions. There is so much in table tennis that people have different opinion on. You only have to read the marketing blurb about bats. The same can be said about rubbers. The descriptions and off/def numbers differ between sites.
My gut feel is cross cut balsa would have no strength and be very reliant on the veneers and how well they are attached whereas vertical grain balsa has reasonable strength and is a contributor to ball speed and control.
When a ball is hit, the bat angle could be say 35°. The rubber dimples in and provides the grip on the ball. The bat structure is one of reasonable rigidity to allow the sponge and rubber to do its job. Thus, although you might be correct, my thoughts are that cross cut balsa would not have the "spring" effect that you mention under these circumstances because the force is "side-on". What does happen though is there is some (albeit small compared to a tennis racquet or golf club) effect on flex in a normal bat. There is a fair bit written on the harmonics of table tennis bats. Let's simply call it the vibration which is tied up with the sweet spot. I would expect that cross cut balsa would not have much of this and possibly would play as a dead bat but it would be very interesting to see what happens when you do it. My gut feel is a bat designed this way would have to have a cross stitched carbon fibre layer.
You can buy blocks of balsa and get a wood working shop to cut off a number of slices for you. Quite easy but expensive. You are going to have to quote density so make yourself familiar with that. If you go down this path please post as many would be interested.


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 Post subject: Re: Make your own blade
PostPosted: 07 Nov 2022, 10:03 
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VielAntrob wrote:
I am presently searching for sources of good material: verneers and glue:
I think I found some companies that supply verneers, but since most/all of them supply their material for furniture building, and may not always be the best supplier choice for TT-blade making, I will greatly appreciate recommendations for companies/websites to buy verneers from!!

In particular, I do not yet know a single source of "endgrain" balsa sheets.
Does anyone have a suggestion where to get "endgrain" ("crosscut") balsa sheets?
I am talking about sheets where the grain direction is perpendicular to the plane of the sheet itself. TSP, now Victas, uses these as cores and I think adyy ( @adyy ) used such cores also.

I would also love to get some advice on which glue to choose for the lamination. I have seen impressing close-up pictures by adyy ( @adyy ) of the porous structure of wood sheets. Glue that seeps into these pores must change drastically to mechanical (playing) properties compared to a situation where it was avoided to have glues seeping into the pores.
Can someone provide advice on:
- Suitable glues for the lamination
- Whether or not it is beneficial to avoid that glues seeps into the pores
- ...and how to avoid it, if it is deemed beneficial.

Finally I have a potentially stupid question, based on really enjoing to treat wood with oil:
What kind of experience is available on the effect of "surface-treating" TT-blades with oil? I believe that all commercial blades are "just wood", without any "finishings" on the wood (possibly apart from the "surface sealing" that some apply before gluing a rubber), so that might be an indication that the wood should better be left alone. Whenever I put oil on wood for funiture I have the sensation to do something good to the wood, think (nourishing, protecting). Is there anything known good (or bad) happing from such treatment for TT-blades? (...or rubber adheasin for that matter...)

Thanks so much in advance in case of any answers!


I am mentioned in a post and somebody wants me to get answers from me ?!!!!
My God, it seems like I have reached a certain level as a home builder 8) 8) 8)

So, here it is:

VielAntrob wrote:
In particular, I do not yet know a single source of "endgrain" balsa sheets.
Does anyone have a suggestion where to get "endgrain" ("crosscut") balsa sheets?
I am talking about sheets where the grain direction is perpendicular to the plane of the sheet itself. TSP, now Victas, uses these as cores and I think adyy ( @adyy ) used such cores also.

Actually I have no source. Like you, I have searched a source in Europe and found none. The only source was on Alibaba at a factory in China, but the minimal order was 1 cubic meter of endgrain. The shipping itself was more expensive than the balsa itself. So, next step was to find an alternative way to make it myself. And I have bought some balsa lumber (5x5x100cm), went to a carpenter and asked him to cut for me slices of 5mm from that lumber. I ended up with something like this:
Attachment:
thumbnail.jpg
thumbnail.jpg [ 92.04 KiB | Viewed 1523 times ]


Than I glued the "squares" with some cheap paper glue and obtained something good enough for a blade core.
Another alternative way, was to cut manually the crosscut "slices". It can tell you that it works, but you need to build a jig for that and buy a good japanese type handsaw.
I can tell you that it works. But you will spend a lot of time and make a lot of wood dust.

VielAntrob wrote:
I would also love to get some advice on which glue to choose for the lamination.


Glueing blades is like searching Eldorado or the eternal life. Its a constant search for a better glue and a better process. Here I have no clear advice to give you, since I am not happy with anything that I have tested until now.
I have tested many and even threw to garbage a few. They were that bad.

But from my tests, I can tell you that:
- the first glue I have used was epoxy. From the durability point of view and if you want to use synthetic fibers, that is the glue to go with. Also, performane wise, its a good glue.
Once hardened it never cracks, it is elastic/flexible and some no problems with water and chemicals. Chemically it is almost inert, once cured. One problem with epoxy is that you need to mix the parts properly otherwise you endup with a sticky plastic that never hardens. The other one is that depends how fast it hardens, because there are hundreds of types of epoxies. If it is a slow cure (takes long time to harden) it will go into the wood pores, soak up the wood and make the wood plastic-hard. You will get some sort of stabilized wood that feels and behaves like a plastic laminate, not like wood. If it cures to fast, you will need to work very fast with mixing the glue and put the wood veneers very fast into the press and close the press. Otherwise you will get a badly laminated blade, that may even have blisters of air between the veneers. I have one blade blank that ended up like that. Anyways, after 10-15 test prototype tests I have quit using epoxy on wood-wood bonds.
- the PVA glues. Here MalR explained very well the way to go with PVA. I have tested a few and from my tests, this is a simple to use glue, very suitable for DEF and ALL blades.
Cures relatively fast and if the glueing is properly done, it also durable. I have not used the type that MalR sugested. I just checkd if they are D3 or D4 class. D3 means that it is suitable to be used outside and D4 is for marine environments. Yachts furniture basically. Currently I am not using PVA to laminate blades. I use it only to laminate handles and sometimes to glue the handles to the blade blanks.
- hide glue. I have tested 2 hide glues, one made from rabit skin and one from fish bones.
These glue are water based. Basically, you get some pellets and dillute them in mild water until you get some sort of cream. The biggest no-go for me is the smell. It stinks like crazy. The second is that they are water based and it takes a lot of time to cure/harden. While curing, the water needs to evapore and pass through the veneer some how to get out. This takes a lot of time and you need to keep the veneer under pressure until that happends. Otherwise, the bonds between the veneers will get loose or the blade will curl/bends. In a press like MalR recommended to build, it will take days to harden. For me it took 2-5 days until they were ready. I have built Acoustic and Violin clones to see what I can get and I ended up after a few tests with some good enought blades. Due to this glue, they had better feel than blades glued with any other glue. But in time they curled. Basically they twisted 1-1.5 milimeters away from a straight plane. This glue is still an open territory for me. Someday I want to resume the tests and build a press special for working with this glue, since it has potential to create some very unique blades.
- PU based glue - pressure activated type. Similar to glues present in scotch tapes and/or glues used in the past to repair shoes or glue leather. The results were interesting and the feel of the blades was close to hide glue.
Anyway, it comes with its own problems. If you add the glue on only one of the veneers you want to glue, you will need to add a thick layer and this is not good for the final blade, since it dampends the feel and cuts speed on hard shots. The better way is to add very thin layers (as thin as you can) on both veneers before glueing. This improves the results but its very hard to get there. These glues are very sticky and while applying them there are very high chances that the veneer will splinter or tear. And it will be hard to join it back and resume the glueing.
- PU based glue - the type that reacts with the air humindity and expands while it hardens. This is what I am currently using.
It does not stink, its not very sticky when you apply it and its easy to apply. It takes 3-4 hours to cure (depending on the brand) and once cured, is there forever. There are almost no chances of delamination. Also blades do not bend/curl with time, since this glue is not water based.
But the big problem with this glue is that it expands, especially if the veneer is not very-very dry. If the veneer is mild wet or if added in a thick layer it will expand so much that it will fill all the pores of the veneer, go through the veneer and glue the release agent/foil to the blade. And there will be no way to remove it. The way to use this glue is to apply a layer as thin as you can and in case there is some excess, clean it away with some soft paper. This glue changes the feel of the wood a little and makes the blades feel sharper and the dwell time will be shorter. Depending on the veneers used, the ball impact will feel a bit more vivid than with the other glues and on hard shots the blade will feel a bit more stable/powerfull. This "a bit" I am talking about is a 5-10% difference, not more.

Anyways, this is a short knowhow share from me. And as I said I am not 100% happy with any.
Even Mr. Moon@Nexy talked a bit about this topic somewhere (here or another forum).
Depending on the application, some glueing methods will work better and some not. The glueing process, is one of the reasons that similar blades - made from the same veneers and having similar thickness - from different companies feel different. The glue used and the way it is applied participates in the feel of the blade. Sometimes a lot.

My advice is that you should make some tests with different glues and see what works for you.

VielAntrob wrote:
I have seen impressing close-up pictures by adyy ( @adyy ) of the porous structure of wood sheets.
Glue that seeps into these pores must change drastically to mechanical (playing) properties compared to a situation where it was avoided to have glues seeping into the pores.[/quote]

The pictures are from this website: https://www.wood-database.com/limba/

If you want to understand how a wood laminate works, you will need to see what are the Janka hardness, the Elastic Modulus and the pore structure of the woods used in that laminate.
Also that site is good to read about the different types of woods and "learn" how those woods look. You will need that later when you will see pictures like this: http://www.mytabletennis.net/forum/uploads/New/20100614_040944_IMG_4885.JPG

VielAntrob wrote:
Can someone provide advice on:
....
- Whether or not it is beneficial to avoid that glues seeps into the pores
- ...and how to avoid it, if it is deemed beneficial.

The glue process is a trade-off between durability and feel.
No matter which type you use, some glue will anyway go into some the wood pores. You cannot avoid that.
What is important is that you should avoind using too much glue. There should be only a super thin layer of glue between the veneers. Otherwise, the more glue it is, the more will kill the feeling of the wood.

VielAntrob wrote:
Do such cuts (or possibly other measures in/under the handle) have any impact on the "feel" of the blade? (...feedback, etc)
How you tried other geometries / cut-outs / hollow handles etc?


I have tried a cut similar to Re-Impact, but not on a balsa blade. I have used it on a limba/limba/ayous/limba/limba blade. I felt nothing special about it and did not investigated further. Maybe for balsa blades really makes a difference ...
Hollowing out, yes. Most of my blades have hollow handles and some cuts in the blade blank under the handle. Otherwise the blades that are 80+ grams would be 90+ grams. Feeling wise, hollowing out the handle, at least from my tests, makes the blade to feel a bit smoother if its dedicated to a spin based game.
But I have not made any serious comparative tests to be able to tell you exactly what happends. Its just comparing how blades feel hitting a ball on bare wood.

VielAntrob wrote:
One more thing on the balsa core thickness: I argued about something like a "spring effect" of the vertical fibres in cross-cut / end grain verneers.
I am not sure how big that effect is. But judged from basic mechanics, two things should hold:
- The "stiffness" is mostly determined by the strength of the "outermost" layers
- The stiffness increases with thickness
So while Balsa is certainly not stiff in itself, a thick balsa in conbination with strong outer layers should produce a much stiffer blade than a thin balsa core with the same outer layers of "strong" wood. And since (I believe) stiffer blades are typically faster than less stiff blades, this may be the true origin of the correlation between a thicker balsa core and the speed of the blade, ...and not as I argued before the "spring effect" of the vertical balsa fibres.

Its almost like that!

VielAntrob wrote:
Interestingly, MalR, this argument also runs against your experience that a thicker balsa core produces a slower blade.
Are there some other voices that can add to this discussion and possibly enlighten this by additional information/perspectives?

It depends on the type of balsa.
He mentioned - if I have understood well - that he uses the type of balsa that is very low density. The type that is almost pure white. That type of balsa, really absorbs impact. I can confirm that.
Anyway have not made so much tests with balsa, but I would not be amazed if I would see an 10mm thick blade that is slow.


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 Post subject: Re: Make your own blade
PostPosted: 07 Nov 2022, 23:21 
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I found a couple of interesting information on wood properties. It is not all that surprising, but it might shed some light onto the discussion of the basa core.

The two papers that I found (and where I am pasting excerpts from) are:

https://www.researchgate.net/publicatio ... balsa_wood

and

https://charles-oneill.com/aem341/Lesso ... erials.pdf

First, a sketch on the definitions of the different mechanically distinct directions in wood:

Attachment:
Directions.png
Directions.png [ 16.17 KiB | Viewed 1471 times ]


And now three tables that show actual values of the mechanical properties (or their ratios) for these different direction:

Attachment:
Balsa-Mechanical-Properties.png
Balsa-Mechanical-Properties.png [ 134.88 KiB | Viewed 1471 times ]


Attachment:
WoodStrengthTable.png
WoodStrengthTable.png [ 211.29 KiB | Viewed 1471 times ]

_________________
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)


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 Post subject: Re: Make your own blade
PostPosted: 07 Nov 2022, 23:55 
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FH: Donic Vario
BH: Donic Vario
Oh, and I forgot this table, listing various properties for three differente weight (or density) classes:

Attachment:
BalsaPropertiesByWeightClass.png
BalsaPropertiesByWeightClass.png [ 167.92 KiB | Viewed 1469 times ]



In the light of discussing the "cross cut" / "end grain" balsa versus "normal (grain parallel to verneer)" configuration, the data in this and in the tables above tables shows that (possibly unsurprisingly) the compression strength is highest parallel to the grain, and correspondingly also the hardness is highest in this axial direction (=grain direction).

The Eurpean-Journal-of-Wood-Product article writes about the application case of this property:
<< Balsa end-grain panels are primarily used as a core catalyst for its compressive strength properties and minimal weight
in commercial industries such as marine, road and rail, wind energy, aerospace, defence and other industrial applications >>

And I think here we are getting to the the core (pun not intended, but fitting quite well) of balsa as a core material:
It allows to not only build a lightweight core, but also to have such core with a rather high compressive strength!
Not as high as really hard hardwoods have, ...but quite strong with respect to its density.
A conventional verneer cut (grain parallel to the plane of the veneer) would not provide the same compressive strength.

This would be of relevance for blade/ball interactions such as this:

Attachment:
Sketch2.png
Sketch2.png [ 33.48 KiB | Viewed 1469 times ]


But even if we focus only on stiffness (often associated with speed, and and closely related to stiffness and hence speed is the "Eigenfrequency" of the blade) the compressive strength of the core plays a core, as these sketches intend to illustrate:

Attachment:
Sketch.png
Sketch.png [ 183.4 KiB | Viewed 1469 times ]


A (vertically) non-compressible core leads to reduced bending, as it strains (stretches/compresses) the outer layers more when bending.
For a compressible core, the elongation differences (as caused by the deflection) between the outermost top and bottom layer is less, as the images probably describe better as I would do it in words.

I would expect that the compression (vertical to the surface) for balsa veneers with grains parallel to the surface is rather visco-elastic, i.e. dampening and taking energy away from the ball and its rebounce. Thus balsa verneers with "normal" grain directions (not "end grain") would provide a comparatively soft and thus comparatively slower blade.

So I think -given everything else equal- that a balsa core with an end grain cut will produce a stiffer and faster blade.
(No, the end grain balsa core itself is not stiffer, probably to the contrary, but as a core layer between tough outer layers it is rather the compressive property of the balsa that matters.)

_________________
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)


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