Resawn lumber bookmatch glue ups cupping problem

[DavidG95]

I used my bandsaw to resaw 8” wide QS White Oak so that I could bookmatch it and use it for the panels of my cabinet doors. I did about 14 of them earlier in the summer, and they came out really nice. Everything glued up nearly perfect, and I used my Supermax 19-38 to bring them down to about .55 inches rough sanded to about 100. All perfectly flat and square.

Now over the summer and into the winter they sat in the house waiting to be used, piled up in a stack. When I took them out to the shop, I was upset to discover that some of them had taken a cup across the entire width. Most of them not too terrible but two of them are awful. I know that some wood movement is unavoidable but I hadn’t really planned for this.

My plan had been to finish sand them and bring them down a bit more from .55, and rabbet the edges down to 1/4” for the grooves in the door frame.

So a couple of questions on this and need a bit of advice. First, any thoughts as to why? Just the dryness of the air? Perhaps I waited too long to apply finish to them after putting them together?

I have options here. I could, bring them down again to flat, probably .40 or so for most of them, maybe .35 hard to say. I could take them all down to .25 which defeats the purpose of trying to make the doors feel less “flimsy”. I could also take them down to .25 and then instead of a rabbet, glue a piece of QS White Oak Veneer plywood (I have a few sheets of it) to the back of each one to provide some additional stability against further movement.
Thanks!

   

   

[R Clark]

I presume the wood was already stable when you re-sawed it.  

You don't say where you live, but around here (Southwest IA) we have huge changes in humidity between summer and winter.  I can see it in pieces I've done, and even see it in some thin ply panels that I use to cover access panels in the basement.  They lay flat in summer and one of them warps like crazy in winter.

As long as the boards aren't twisting, if it was me, I would consider ripping the cupped boards down the middle of the cupped section, joint those new cuts, and glue them back together.  You are likely to get a decent grain match and it shouldn't be too noticeable, except to you since you've sunk so much work into this already.  Also, I don't think you'd lose near as much stock to get them all flat again.

Like you, I'd be hesitant to start planing and sanding again.

[jteneyck]

It sounds like your wood was at EMC with your shop when you made the panels; otherwise they would have warped right away.  If true, then they aren't at EMC now so they cupped.  I would sticker them so air can circulate around all sides of each piece and let them sit for a week or two.  They should flatten out again when they reach EMC with where they now are, unless the conditions change again.  If some don't flatten out I'd do as WxMan suggested and rip/reglue.  

It's never a good idea to leave glued up panels for a long period of time and expect them to stay flat.  Wood moves when the RH changes.  You can minimize that by keeping the RH constant, or wrapping the panels in sealed plastic.  The best approach, however, is to use the panels right away so that the frame they go into helps hold them flat. 


John

[MichaelMouse]

It's never a good idea to leave glued up panels for a long period of time and expect them to stay flat.  Wood moves when the RH changes.  You can minimize that by keeping the RH constant, or wrapping the panels in sealed plastic.  The best approach, however, is to use the panels right away so that the frame they go into helps hold them flat. 


John

Yup, goes for any wood where one side is open, one closed to air circulation.  Like laying on the bench for a couple weeks.  Get the panel in the frame as soon as you thickness it.  If you can't right away, sticker before thicknessing.

Of course, closer to absolute flat grain or quarter you use, less it changes.

[GeeDub]

I usually mill my lumber not too much prior to using it. If I ever do end up having to abandon the project mid stride and store my milled lumber, I sticker it and either weigh it down on a flat surface like the floor or clamp it if the sizes and shapes will allow me to clamp the whole stack. I clamp over the stickers which should be of a uniform size so that everything is held in state.

[DavidG95]

Yeah when it was in the shop I had it stickered for months, and then when I moved them in the house I didn't. Oh well live and learn

[Stwood_]

When I do panels like that I stack then up and clamp all 4 corners together until I do something with them.

[cputnam]

Panels should always be stickered and clamped/weighed down. I'm not a wood expert, but I've read enough of that from folks who are to accept it. Besides, I left a panel flat on my bench, here is Southern California, and it was rather violently cupped the next morning. Lesson learned.

[BrokenOlMarine]

Remember how we all bought those kmart weight sets and were going to.work out at least every other day, then didnt?  I found good use for the plates from the weight sets.  I used a couple of the ten pounders for kayak anchors.... 
 ... The rest I keep in the shop for weight on glue ups and drying wood stacks. 

[EdL]

I just lean them against the wall, 100% circulation.

Also assemble asap.

Ed