# Advice? How to fix a messed up table-top panel?



## StillTrying (Aug 25, 2018)

I'd like your advice on how best to fix a messed up table-top panel.

Here are end shots of the panel. These glue joints were perfect when they were made. There was no error either squaring the edges or gluing. The panel looked perfect when it came out of the clamps. It cupped - as a whole - about 1/2 to 3/4 inch up in the middle. As you can see, I've already added cleats - one along each edge - which removed most of the curve, but there look to be a few boards that changed much more than others, and the cleats don't work as well toward their ends. (the little clamp is just holding the straightedge on.)

Boards A,B


















Board C



















I understand this is caused by the wood cupping, which means it either added or lost moisture after the pieces were sized and glued. The panel has had several weeks to equilibrate and is no longer changing. In fact, most of the change happened within 24 hours of the gluing.

MY IDEA: To fix the cupping, my best idea is to select the joints where the most distortion shows, put this on the table saw or band saw, rip it down those glue lines, then square the edges and glue it again. I think 3 joints: both sides of board B and the joint side of Board C. I should add, anything that significantly changes the thickness is completely unworkable, given other pieces already finished.

Suggestions?


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## bilyo (May 20, 2015)

Yes. Assuming that the over all width of the panel is such that you can afford to lose a couple of kerf widths, that is the way to go. You may end up with the situation improved, but with a smaller amount of cupping remaining. If so, you might consider some battens on the bottom to pull it flat, if your project can accommodate that. As you may know, the battens should be attached with screws only through elongated holes with no glue. This will pull a slight amount of cupping flat and hold it and still allow for cross grain expansion and contraction of the panel.

I can't tell from the photos if there is primarily one or two planks in the glue up that is causing the cupping. If so, that is the place to rip. Maybe even rip out the whole plank and replace it.


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## SMP (Aug 29, 2018)

> Yes. Assuming that the over all width of the panel is such that you can afford to lose a couple of kerf widths, that is the way to go. You may end up with the situation improved, but with a smaller amount of cupping remaining. If so, you might consider some battens on the bottom to pull it flat, if your project can accommodate that. As you may know, the battens should be attached with screws only through elongated holes with no glue. This will pull a slight amount of cupping flat and hold it and still allow for cross grain expansion and contraction of the panel.
> 
> I can t tell from the photos if there is primarily one or two planks in the glue up that is causing the cupping. If so, that is the place to rip. Maybe even rip out the whole plank and replace it.
> 
> - bilyo


I also would do some battens, that and if tying into an apron with z clips should pull it pretty flat. If needed surface the top with hand planes.


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## 1thumb (Jun 30, 2012)

Hours of reading pleasure. Enjoy.

https://www.lumberjocks.com/search_results?cx=017914489645407774653%3Agwwk-zif3wk&cof=FORID%3A9&safe=high&q=table+top&sa.x=0&sa.y=0

https://www.lumberjocks.com/search_results?cx=017914489645407774653%3Agwwk-zif3wk&cof=FORID%3A9&safe=high&q=table+top+warped&sa.x=0&sa.y=0


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## PlentyFarmLLC (Aug 25, 2020)

Plain sawn. Pine? Not the best choice for a tabletop. Might be better off to start over with better material. If you can find quarter sawn it won't move like that.


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## corelz125 (Sep 23, 2015)

Like the others mentioned you can pull it flat by adding something underneath. You can use c channel on the bottom. They come in pre made lengths or you can make them yourself.


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## Lazyman (Aug 8, 2014)

Are you storing it so that air can circulate on both sides? If not it won't acclimate evenly and this may be the cause of the problem in the first place. Lean it against a bench or the wall or put some boards under it and turn it over every day. A way to see if you can speed up the process a little is to lay it on the lawn concave side down out in the sun. The lawn will give the concave side a little moisture and the sun will dry out the convex side. It may not take long, especially in the heat of summer, so keep an eye on it. I've waited too long before and actually had it cup in the opposite direction in only about 30 minutes. Afterwards, make sure that air can circulate evenly and see if it warps back.

Also, unless it is sort of wavy, mounting it down to the base may be all that is needed to pull it into flat so ripping it apart is the last resort, IMO. If it doesn't take much clamping pressure to pull it flat, drastic measure may not be necessary.


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## StillTrying (Aug 25, 2018)

Thanks, most all, for the encouragement. Ruscal: not so much there.

Sorry if I wasn't clear; perhaps a vocabulary mismatch. I've already drawn this down against 2 cleats, which you might be calling battens. These are the tapered boards under the panel. Also, thoughts about the apron are on point, but this table won't have one.

Nathan, this took a lot of clamping force to pull it flat to mount the cleats, and as you see the top won out toward the edge. I did indeed make the mistake of laying it, when when it came out of the clamps perfectly flat, on the bench, and next morning found a nice potato chip. However the 3 other panel sections I subsequently made seemed much more stable (although I did not repeat that mistake with them), so I do think the wood had not equilibrated to the shop humidity when I edged and glued the first panel.

I *have* heard of the sunny-lawn effect, and since it takes very little effort, I think it merits a try. Tomorrow is forecast to be sunny and mid 80's here in beautiful SE Pennsylvania, so I'm going to remove the cleats and give it a sun bath, and we'll see. I'll be sure to babysit it and keep a straightedge at hand.

Bilyo, there may be one bad actor board - the one marked B - that has twisted a little. I'm interested to see what happens after the sun bath; whether that will un-twist.

I'll make a follow up post as it progesses.


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## bilyo (May 20, 2015)

The sunny lawn might work, but it won't be permanent. Once you bring it back in, the potato chip will return. If it flattens out, that will give a good opportunity to add more or better battens, however.


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## StillTrying (Aug 25, 2018)

bilyo, I had the same understanding, But in searching about this I find that Bob Flexner, apparently an editor of popular woodworking, has posted about "compression shrinkage" which results from the wetting/expansion followed by drying/shrinkage. He shows an example of a cupped board restored to flat using this phenomenon. It is mostly consistent with the sunny-lawn treatment.

https://www.popularwoodworking.com/editors-blog/a-method-for-correcting-warps/

I think I'm going to lightly wet the top convex surface for a bit before putting it out. If Flexner is right, from the wetting and then sun-drying of that side, the cupping should at least be lessened.

I'm thinking back on the particular experience of these panels (I made four of wood from the same tree) and it seems to me that what happened to this one really cupped panel may be a similar irreversible effect from sitting flat on the bench, which I didn't do to the other 3 didn't. I certainly gave it lots of time standing fully exposed to re-equilibrate and flatten, but the cupping stayed. I don't fully understand but I'm now very curious about it.


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## Unknowncraftsman (Jun 23, 2013)

I would like to wager if you put it out in the sun on the lawn the ends will open up. 
Good Luck


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## Lazyman (Aug 8, 2014)

The PW article is interesting I will have to try adding the water and the compression next time I need to flatten a cupped board.


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## StillTrying (Aug 25, 2018)

drum roll…

After about 1 hr 10 min, my eyeball using a straightedge impressed me as no change, so I took it down to the bench, laid it down concave down, and made the same measurement as last night - the height of the bow above the bench. My eyeball was wrong - there was improvement

End 1: start-0.5 in, 1:10-0.358 in
End 2: start- 0.375 in, 1:10-0.253 in

I should say, after about 40 min au naturale, I lifted the panel and i could see a wet pattern where grass was touching. So I wetted it lightly and evenly with a spray bottle (distilled water) and put it down. When I returned it to the lawn after 1:10, I again wetted the bottom with the spray bottle.

Stay tuned.


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## StillTrying (Aug 25, 2018)

After 2 hrs, 20 min, the main body of the panel looks almost flat. There is some waver in it but nothing frightening. there are still one or two boards that have changed more than the others. these are still making the panel not flat, but this is localized around those boards. I don't want the whole panel reversing the cup just to try to straighten those bad actors.

I took it in, and fully agreed with bilyo to immediately replace the cleats. In place, the panel still makes a left turn at the bad acting board, though better than before. It's the second in from the edge, so I cut a support the same thickness as the cleat, and put them under that edge (the cleats run the other direction). since there is basically a crook in the panel, this raised that up off the bench. I then took a long straight stiff 2×3 and pressed along that high point to force the panel flat ( I think).

I'll let it sit this way. As it is now, it is much improved. The underside is still damp from the sunny lawn treatment (with spray) and who knows what will happen as it dries. The cleats hold it up off the bench so it has air circulation.

Just to clarify, the panel was convex up, so it laid top side up in the sun (wetted and shaded on the concave side), and it's now laying top side up on the bench with cleats underneath.


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## Unknowncraftsman (Jun 23, 2013)

The wide growth rings looks a lot like construction lumber from the borg. Is it Douglas fir from Home Depot or Lowe's.
Good Luck with the experiment


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