Crossgrain abuse? Anyway to glue 1" thick boards crossgrained to make 3" thick 3 ply

[Dennis Thornton]

Is there anyway to glue 1" thick boards cross grained to make 3" thick 3 ply plywood? Maybe even thicker plies? I know wood moves! And I know this violates that rule big time, but so does thin plies plywood and it works. So thin plies works but what would the limit be for thick plies?

I'm hoping to use air-dried quarter sawn ash 24x84 glue ups with long grain running the lengths of the outer plies and the cross grain in the center. I did have a major supplier of epoxy tell me that theirs would work. I'm still concerned. I do expect to dip soak the finished plywood in an oil finish to hope to stabilized it somewhat.

added day 2:
These will be workbench tops with opening all around the edges to fit appliances. Rather than lots of drilling, I had thought that 3 layers would be an expedient means of creating those voids, but expecting that the cross-grain abuse was just not going to work I've developed a plan B that should work fine. But then I wondered, what is the limit for ply thickness? And motivated by the epoxy maker I thought I'd ask the pros at the front! Initially it seems we are in agreement that 1" thick is truly abusive! But this is also a case where I'd be happy to be wrong! <grin>

Thanks for any thoughts and a real big THANKS to anyone who has seen it or actually successfully done it!


Dennis

[Mel Fulks]

I have seen it tried. I have not seen it stay together free of cracks. You have a guarantee from the glue guy ...now you need one from the lumber guy . If you custom ordered three inch thick plywood it would be made in pretty thin layers ,they engineer that stuff .

[Kent A Bathurst]

Ummmm......

There obviously is a lot of back story missing from your post - along the lines of "Why?"

So - realizing I am missing something key, I will still ask this:

Why not glue 4 pieces of 3/4" plywood, and - if the ash surface is your goal - veneer the outsides?

[George Gyulatyan]

lumbercore

[Mike Cutler]

Stickley, Green & Green, William Morris and Limbert have done it successfully and their furniture has lasted 100 years. It's also done to make ship's knees on smaller water craft. Every piece of architectural flat circular work has to have it done. Maybe not at 90's but at varying degrees. An M&T joint is essentially the same as what you want to do, just smaller. Of course the end grain isn't exposed though.
I just got done gluing three 4/4 boards of Qsawn Padauk doing it. The inner board is at a 30 degree angle for a corbel application on a Limbert 153 reproduction. This particular corbel has to be supportive as well as aesthetic in appearance. It will support 14" of granite overhang.
Using well acclimated Qsawn wood, of the same species, I don't see a problem. I don't know about air dried ash though. You may have to "size" the exposed end grain.
I'm not sure why you need to run cross grain, but it's not my project. In this instance though I would epoxy the glue up using a structural gap filling epoxy, or an epoxy mixed with micro ballons or wood flour. Size the exposed end grain with epoxy and use a compatible epoxy finish. If you are using West's marine products, they have a line of epoxy finishes that will work with their epoxies.
The General Finishes line of wipe on varnishes also work well epoxy and tend to hide any epoxy that "stains" through. I've used them many times with epoxy. Use the Seal-A-Cell first, and then the Arm-R-Seal. You want a nice flood coat.

[Mel Fulks]

Since he hasnt said what he's making it's impossible to say what the specs should be. It's not going to disintegrate,but it probably will crack. SUPPOSE IT'S A BENCH TOP! The air drying is a factor.I guy brought us aload of air dried walnut to be kiln dried .I took a small piece of it 13 inches wide and cut off a piece before putting the rest in the kiln. I marked the kiln piece.After drying in a 25 foot computor controlled kiln I compared them. There is little movement in the kiln pc even when I soak it in water,the air dried pc is moving all the time inside the house. Both pilgrims and doubters may see them. AIR and KILN are the operative words,not "dry".

[Peter Quinn]

I have to ask, why not just run all the grain the same direction? You could overlap seems, make plywood or 2X forms to block out your appliance niches and clamp to these to keep these spaces open. But why the cross grain thing? It's a receipt for failure with no upside I can see. Think of a piece of plywood as a tug of war with 11 different perfectly matched teams all pulling in opposite directions. Nobody wins, nobody moves much, so it's a stabile situation. What you are describing is more like wrestling match where two guys on the outside are beating up on one guy in the middle , sooner or later that guy is going to lose. You could make lumber core plywood, but the variable are completely different than you are describing.

[Richard Coers]

"And I know this violates that rule big time"
I think you already know the answer. Seems like someone always comes along and thinks that wood movement will not affect them. "Maybe I can just bend the rules a little." Personally, I'm not a rule follower, except when Mother Nature writes the rules. Lumber works one way, veneer works another. Don't confuse the two.

[Dennis Thornton]

I have to ask, why not just run all the grain the same direction? You could overlap seems, make plywood or 2X forms to block out your appliance niches and clamp to these to keep these spaces open. But why the cross grain thing? It's a receipt for failure with no upside I can see. Think of a piece of plywood as a tug of war with 11 different perfectly matched teams all pulling in opposite directions. Nobody wins, nobody moves much, so it's a stabile situation. What you are describing is more like wrestling match where two guys on the outside are beating up on one guy in the middle , sooner or later that guy is going to lose. You could make lumber core plywood, but the variable are completely different than you are describing.

There's a few approaches for my project that will certainly work without cross grain issues, but it got me wondering just how far can one push the problem without failure. Just how thick can plywood plies be? While my project could perhaps benefit from 1" thick plies, it certainly isn't dependent upon it. Then a major supplier of epoxy says it will work! I asked him for examples of real life cases and I haven't heard back yet, but his email really got me wondering if making 3" plywood from 1" plies was possible. I've not seen it done. I have trouble believing that it can be done without the outsides cracking. But, again, I thought I would ask the pros!

Dennis Thornton

[Mike Cutler]

Dennis

Let me jump in again and hopefully explain myself more fully.
In your intial post there could have been more info as to the exact nature of your project, which may have given you some different answers.
I answered that wood can be glues cross grain, and that is absolutely true. But,,,, there are caveats.
When gluing cross section, or at an angle, the process has to be thought out. The farther you get from parallel grain, the more dynamic the effects there will be.
If you must have to glue up at angles between layers than the wood speicies, grade, prep, and quality have to be selected. Even then you are going to have to compromise. Again though, what is the most important attribute of the project.
Secondly the ambient environmental condition will have a major effect on success or failure. Subject that glue up to up to radical changes in humidity and it will increase the failure rate and time to failure. Use a more porous open grain wood and it will take even less time.
In my response I pointed out prominent furniture makers and designers have done it. Yes they have done it,and it has survived, but it is usually an aesthetic appearance such as increasing the thickness of a circular table top,or the pedastal feet. Areas where the failure, if it occurs, can be compensated for.
Mel is absolutely spot on with regards to understanding the differences between drying processes. It is major consideration. As is the effect of drying on a species.
As for the epoxy manufacturer and his answer, I understand that also. If I take teak, or mahogany, or lignum vitae, and it is all Q-sawn to 90 degrees. Lay it up in an epoxy glue up then wrap two layers of .5oz, glass at 45 degree angles to the grain and 90 degrees to each other, then vacuum bag an epoxy coat, or gel coat, over the entire structure It will last a long time. Will it crack, eventually, but any glueup can crack and fail. It's just that in this instance I am attempting to control the effects of failure. Of course in this instance a styrafoam blank and fiberglass would probably be easier, lighter and cheaper and just as rigid.
Wood is glued at angles other than parallel all the time. You just can't do it without forethought.

What is that you are actually making by the way?

[George Gyulatyan]

If this is mainly for appearance purposes, can you use crossgrain veneer to get the desired appearance?

[Peter Quinn]

There's a few approaches for my project that will certainly work without cross grain issues, but it got me wondering just how far can one push the problem without failure. Just how thick can plywood plies be? While my project could perhaps benefit from 1" thick plies, it certainly isn't dependent upon it. Then a major supplier of epoxy says it will work! I asked him for examples of real life cases and I haven't heard back yet, but his email really got me wondering if making 3" plywood from 1" plies was possible. I've not seen it done. I have trouble believing that it can be done without the outsides cracking. But, again, I thought I would ask the pros!

Dennis Thornton


I've seen a few tops glued up this way, 3/4" planks laid at 90 degrees to each other. Invariably fails. Even with plywood, 11 ply baltic birch is much more stable than 7 layer cabinet grade plywood. I would not be too comfortable veneering to 7 layer ply though its fine for a carcuss in kitchen cabinets. Ask the epoxy man for a warranty, bet he won't offer that! Wood moves across its width, but not over its length. Anytime you pit two pieces against each other, you get failure. Once the plies get much over 1/8" things get weird. And if the humidity goes way up plywood with thick layers can get weird too. My suggestion would be to glue up a small scale section of your proposed construction and let it hang around in the environment in which it would live for a while, note any changes that occur, see how it performs. Maybe 1 SF, maybe a little more? Might be good science, or at least scientific method?