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Walnut cupping after glue up.

5/4/15       
Mark Newton  Member

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.

5/4/15       #2: Walnut cupping after glue up. ...
Jim Clark

sides not 90 deg. @ glue-up?
Uneven clamping?
Wood not dry enough?
Lots of things can do that.
Was the panel flat when clamped?
I use a straight edge to make sure, just
clamping over and under differently can
draw the panel to either side when tight.
For me, most times it's the sides not
90 deg. I run them opposite on the jointer
to cancel out any error.

5/5/15       #3: Walnut cupping after glue up. ...
Andy

How were they stored overnight?
Ideally they'd have sticks of wood between them so they can breathe evenly. If they were laid flat or stacked flat on a table the sides would typically cup up.
A

5/31/15       #4: Walnut cupping after glue up. ...
Gene Wengert-WoodDoc

All wood movement over time is the result of moisture movement or moisture change. So, it is likely that the wood was a bit too wet for the air in the shop. Did the panels cup toward the side exposed to the shop air?

6/25/15       #5: Walnut cupping after glue up. ...
Jason Member

Did you alternate the clamps on both sides of the panel? I've had issues in the past where I put clamps on only one side and they bowed the wood during glue-up especially if the edges at not perfectly 90 degrees. Now I alternate sides with each clamp and put a straight edge on the wood to make sure it is flat during the clamping.

7/29/15       #6: Walnut cupping after glue up. ...
carmen james Member

Website: zuffahome.com/

I use this idea to make a dining table. now it looks like mid century table.

9/22/15       #7: Walnut cupping after glue up. ...
Ryan Kerber

Website: http://emfurn.com

Make sure you're alternating the clamps otherwise you'll keep having the same issue.

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