MarkN1975

Walnut cupping after glue up.

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Hi guys,

 

I cut and planed 3 perfectly straight pieces of 3/4" plain cut walnut. I wanted to glue them together to make a small panel.

 

I clamped & planed the edges in pairs to get a quality glue joint, I carefully glued and clamped them together using clamping cawls to match and correct any irregularities along the length as the glue dried and reduce any sanding needed.

 

The day after, I went to make some cuts and noticed that the panel had cupped.

 

Why did this happen?

 

Is there any way to correct it so I can cut a straight miter along the length of the cup.?

 

How do I stop this from happening again in future?

 

Thanks in advance for any help.

 

Mark.

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Mark, had you recently milled the lumber to thickness?

Edit: just read again that you planed it.

After thickness planing, did you happen to lay the panel flat on any surface?

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A few things come to mind..  I'll assume that your material was good on moisture content and acclimated to your shop.

 

Did you alternate your clamps?  In other words, one clamp under and the next one over, repeated for the entire panel.

 

Was your clamping pressure too much?  Lots of people squeeze the clamps as much as humanly possible which will cause the panel to cup.  You only need enough pressure to get a good squeeze out of the glue.

 

Was the panel flat to start with?

 

Did you let the material sit for a day after the milling?  

 

Although a panel glue up is a pretty simple straight forward task, many of us (yep, I've done it too) just do it without remembering the details about a good panel glue up.  The devil is always in the details.

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Did you lay the glue up flat on a table? You need to sticker up off of a surface or the glue moisture can evaporate unevenly.

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Not sure if the OP is coming back, but the other possibility is that his edges were not 90 degrees to the face.  If his jointer fence is off by as a degree, and he did not alternate the face of his boards to the fence, he will end up with a cupped panel (think barrel making).  

 

In my glue ups, I always mark the face next to each edge "F" or "O" so I remember to flip the orientation of the fence, which will offset any errors in the fence.  

 

My guess is his problem is a combination of that and too much clamping pressure.  

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Kind of like when you're sitting at a Black Jack table and some guy comes along and places one bet and leaves.

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Hey, all of us who predate home computer use have likely at one point in time made a simple error. Sign up for a restricted service only to forget how you navigated there and/or which login you used. I admit getting lazy because my phone makes it so easy now.

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Hey, all of us who predate home computer use have likely at one point in time made a simple error. Sign up for a restricted service only to forget how you navigated there and/or which login you used. I admit getting lazy because my phone makes it so easy now.

 

So true.  Even if my early days on this forum, I'd have to google "whispering wood guy", find his page, hit "wood talk", realize that was a podcast (didn't know what a podcast was at the time), fart around on Marc's site for a while, go into the "chat room" and realize that is not where I posted, then finally find the forum.  And that was only 2 years ago.   Before becoming a member of WTO, I had not participated in any online forums (ever) so this was all knew to me.  

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