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Quick question - it seems as if I've gotten a panel to cup from clamping it too tightly. I'm pretty sure that the cupping is primarily due to clamping pressure, as the pieces were all quarter-sawn, and had been stable prior to the glue-up. The fact that I had brought it indoors while the glue was setting may have contributed to it. Is there benefit in leaving for a few days for it return to its original state, or should I just flatten it again now?
Did it cup when in the clamps or after taking it out? When clamping panels, it can be useful to put clamps on the bottom and top to act against each other.
Also, how have you stored the glued boards , I like to sticker it to allow airflow between the pieces.
It's warped after taking it out. Only slightly, but a straight edge pivots on it. The boards were very dry to start with. Also, the glue-up was done in stages, so the final glue up comprised of gluing up 2 halves. The half glue-ups have been very stable.
This happens to me all the time, SEQ weather is constantly humid one day and dry the next
sticker the board both sides with the bow up and put a lot of weight on it. It may also help to dampen both faces.
I’m getting too old and memory not so good but I remember something about putting cupped boards out on the early morning grass cupped side down.
It would suck up some dew (expand)and the sun would warm up the other side(shrink).:rolleyes:
H.
Were all glued edges completely square to each other?
yeap, dead squareQuote:
Originally Posted by Cal
Quote:
Originally Posted by yoboseyo
It depends what you plan to do with the panel. If the cup is very slight, and the panel will be joined at the ends to another panel, such as with a case, especially if dovetailed, then I would not bother with straightening it. The joinery will hold it flat. If the panel is to stand on its own, then I might try adding breadboard ends to reinforce and flatten the panel. The worst case scenario is to rip all, re-joint and add cauls when glueing.
Regards from Perth
Derek
It's more than useful. It's necessary to avoid putting undue pressure on one side to the boards. If they don't sort themselves out you may need to cut them along the glue lines and re-glue upQuote:
Originally Posted by lewisc
Probably better on the concrete than the grass. Have done it there and it can work.Quote:
Originally Posted by clear out
Also, if the cup side up is the face you could do some relief cuts lengthwise on the underside.
Yeah, I’m feeling it too, just edge joined two sassafrass boards perfectly flat, they cupped in the wet weather here in Perth after I took them out of the clamps and before I could put breadboard ends on. So back in the clamps for a few days, hopefully they will flatten when the weather dries out. Sassafrass always does that, a beautiful timber but behaves badly! The clamps are the “squeeze ‘em both ways” type.
Some time ago I was shocked by how well the leave out on the grass method worked. I cut a 10mm thick slice off a burl and left it flat on my bench overnight, it looked like a potato chip/crisp the next day. Left it out in the sun with the side that was on the bench facing the sun for a few hours and it had cupped in the opposite direction... I flipped it over and left it for another hour and it was almost flat afterwards. I need to cut another slice of that burl and take some photos, the severity of the cupping was crazy.
Edit: If the panel is going to restrained by joinery or be floating in grooves, I wouldn't fret too much about a small cup. If you're cutting dovetails into it for a carcass, you can clamp your slightly cupped board to a backer board to get the cup out. Once assembled, the joinery will constrain and guide the cupped panel.
I just chucked it on the grass as suggested for a couple of hours, worked fine and I managed to fit the breadboards to boot. Thanks for the tips!:2tsup:
I'll give the leaving on the lawn thing a go. Hopefully it actually stays that way!