Question about shop made plywood

[Paul F Franklin]

I need to glue up some shop made plywood to make a custom table tennis blade or two for my BIL out of some red oak with sentimental value. The blank needs to be about 7" x 12" and will end up about 7mm thick (sorry for mixed units!) I am thinking 5 plies(alternating grain of course) or could do 3 plies if that would be better/stiffer/flatter? I have done test cuts and have proved I can successfully saw 1/16 veneer and sand to .055 to get 7mm final thickness. I'll make the outside veneers thicker and sand to final thickness (drum sander) after the blank is laminated.

Because of the limited stock I have (which came from a tree on their property) and my desire to have straight grain (not face grain) the slices will only be about 4 inches wide, so I'll have to lay up 2 strips for the long direction and 3 strips for the cross grain layers.

I plan to use West system epoxy and slow hardener (since I have it) and don't really see any benefit to using something like Unibond 800, but welcome advice to the contrary. I have a vacuum bag to do the pressing.

(Finally!) the question: Should I edge glue the two or three strips for each ply together first and then laminate them after they dry, or can I just lay them next to each other as I build up the stack, making sure to get epoxy on the mating edges? My concern is making sure the edges of the adjoining pieces stay tight if don't pre-glue them. I obviously can't use tape to hold them together if I don't pre-glue. If I should pre-glue, can I just use titebond for that part? I would edge glue them while the pieces are at sawn thickness and then sand them to make sure there's no hump from the glue.

Thanks for any advice!

[andy bessette]

Just glue it all at once. And no need for a vacuum bag on such a small, simple layup; just clamp or weight.

[Cameron Wood]

I would pre-glue to make the individual plies, and definitely use more the three plies to make the blade.

There is a retired high level player where I sometimes go who makes custom paddles from various exotics but unfortunately I only know the basics about his process.

I would make super flat cauls for clamping, maybe from scraps of stone countertop.

[Steve Demuth]

Paul,

I'm not certain I'd bother with the vacuum bag for something that size. Platens of 3/4" plywood, and a bunch of clamps would be faster and easier. The clamps should be sized closely to the sheets being pressed, so you can see and deal with moving veneer as you press. Particularly with epoxy, whether you press with clamps or air pressure, there is real risk of the sheets sliding around as you squeeze them, leading to disappointment.

Definitely go with 5 plys.

As for edge gluing - it won't make any difference in the final strength of the product. It can make the sheets easier to handle and position though. This is particularly true if you're going to use epoxy, because epoxy isn't very tacky at all, and the pieces can want to slide all over as you add layers and clamping pressure. As an alternative to edge gluing (which isn't easy on 1/16" stock), if you're pieces can be oversized by an inch or so, tape at the edges with painters tape. Makes nice, easily handled, stable sheets.

[John TenEyck]

Since you have a vacuum bag, use it. Nothing gives more uniform pressure. The more plies the stiffer it will be, so 5 plies. I edge glue the pieces that make up each layer because it's easy to do and keeps them from shifting/separating during glue up. There's no need to use epoxy for flat parts. You can, of course, but TB II works just as well.

John

[David Zaret]

Since you have a vacuum bag, use it. Nothing gives more uniform pressure. The more plies the stiffer it will be, so 5 plies. I edge glue the pieces that make up each layer because it's easy to do and keeps them from shifting/separating during glue up. There's no need to use epoxy for flat parts. You can, of course, but TB II works just as well.

John

i agree with john, but would go a bit further and say don't use epoxy. epoxy soaks in deep. unless you thicken it, it'll migrate through the wood, and if it seeps through the outer layers (very possible) it will either glue itself to the caul (unless you're careful), or at least make it tough to finish that open-grain wood. use PVA, or better yet, unibond 800 with a blocker. just my $0.02.

[Jamie Buxton]

To tape slices together for interior plies, you can buy paper veneer tape with holes in it. The holes allow laminates to glue together. For instance https://www.amazon.com/Rockler-Three-Hole-Veneer-Tape-650/dp/B001DSZWB0/ref=asc_df_B001DSZWB0/?tag=hyprod-20&linkCode=df0&hvadid=642117705268&hvpos=&hvnetw=g&hvrand=4212355120722260444&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9031926&hvtargid=pla-2147499643432&psc=1&mcid=71319720e3c73d188ee203a6ffb9b524 The usual pics show the tape running the length of the seam, but I'd just put it occasionally across the seam.

[al ladd]

It's not difficult or very time consuming to glue strips of 1/16" veneer together to width, especially pieces that short. Use regular wood glue. Use Green 3M tape or "artists tape" from Dick Blick or the like, and tape on both sides, being careful to align the seams. The green tape is especially good, as it stretches, allowing a 3" piece to act as a clamp. Maybe 3-4 pieces on each side at each seam. No need for any other clamping. The resulting sheet will survive thickness sanding if you need it, but careful seam alignment will keep that from being necessary.

[Cameron Wood]

For a table tennis paddle, uniform thickness and density are priorities, but the surfaces will be covered so appearance is less important.

[Richard Coers]

I'd ask on a table tennis forum. I have to believe there are custom makers and they might explain that the action of the blade is critical. As with all high end sports equipment, flex and strength will alter the action of the ball. It surely is more than just a slab of plywood. My wife almost never uses a mountain dulcimer I made her from birds eye maple. The sound is just too harsh.

[Paul F Franklin]

I'd ask on a table tennis forum. I have to believe there are custom makers and they might explain that the action of the blade is critical. As with all high end sports equipment, flex and strength will alter the action of the ball. It surely is more than just a slab of plywood. My wife almost never uses a mountain dulcimer I made her from birds eye maple. The sound is just too harsh.

Good thought. I did a lot of research into high end blades and custom makers, and talked to several advanced players that my SIL secretly put me in touch with. Almost all makers use glued up plywood as the base. Wood variety is a factor, but I don't have a choice there because of the sentimental factor. There are a couple of high end manufactures that use two plies of carbon fiber and the rest wood plies, but that is about as exotic as they get, no doubt due to the table tennis federation rule that blades have to be 85% wood by weight. Most of the advanced players I talked to indicated the rubbers have more bearing on how a given blade plays than the wood. I'm in luck there because I know which rubbers my BIL favors. Handle style and shape are also a big variance, but again I know what my BIL likes for handle size/shape.

In any case, when my BIL first asked me to do this, he said it didn't matter if it didn't turn out to be his daily player, he just wanted one made from "his" tree. But I'm doing my best to make it a good blade.

[Paul F Franklin]

Thanks for all the suggestions folks! I have a test glue-up in the bag and will know tomorrow how it came out. I used Steve D.'s suggestion for taping the strips along the edge where it will be trimmed off (Thanks for that Steve!) and the glue up was a lot less nerve racking than I had anticipated. But the proof will be in the paddle....

[Paul F Franklin]

Test glue-up came out of the bag this morning and it turned out great! As flat as I can measure and no gaps or voids visible. Thanks again for all the help folks!

Here are a few pics:

As it came out of the bag:

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After trimming and sanding to final thickness:

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Somewhat out of focus shot of the edge:

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A lot of work for less than a square foot of plywood, yet very satisfying! I have the "real" wood veneer all ready for glue-up later today; hope that goes as smoothly and the results are as good.

[John TenEyck]

Looks good. Making your own plywood is a lot of work compared to buying it, but it's a pretty straight forward once you work out the steps. The benefit is being able to make any thickness plywood you need in any species, or any combination of woods. And with the quality of today's plywood (poor, very poor), I make my own plywood from Baltic birch with whatever species I need for cabinets, tables, etc. that matter.

John