All –
Need a little bit of help here to remove (or at least minimize) the warp in a glued up panel.
Here’s the situation – I glued up and machined several 3/8″ think raised panels for a blanket chest. I then got distracted, and put the project aside (for about 5 months, which was obviously my first mistake, as it took me from summer to winter). The panels were stored upright, exposed to the air on all sides (except for small portions of 1 edge where they were supported).
I came back to the project today, and of the 6 panels, 4 are fine, but 2 have a pretty good warp (probably 3/8-1/2″ over their width). I _can_ simply bend the panel back to flat to put it in the chest, but would like to get them back to flat if possible. I don’t have any other stock from that project (it was all white oak), so creating new matching panels would be very difficult.
My plan as of now is to finish (poly finish) the concave side of the panels only, and then leave them unfinished on the other side until they (hopefully) move back to closer to flat when they release the additional moisture.
So my questions are: 1) Is this a reasonable idea with some prospect of success? and 2) Are their other methods I should consider first?
Thanks in advance for any help,
Doug
Replies
Doug,
You've got a problem. This kind of thing happens all too much and we try all kinds of things to unwarp the wood. Just about every method you use will only partially work. (Sorry to sound pessimistic).
I assume that the panels have been planed down from their former thickness. I think that you're experiencing the results of improperly kiln-dried wood called case hardening. By working the panels, you've released some of the acquired stress from having had too much moisture escape from the surface layers during drying and they've warped. There is a lot to be said for making panels from stable substrate and finishing them with veneer on both sides. Hard to accomplish with raised panels.
Bending the panels back to flat will only be a temporary fix and they will eventually either bend the frame or split.
You probably will need to redo the set if you want to maintain uniformity. They probably warped soon after you worked them. To tell if new lumber is case hardened, mill a few pieces 1/4" or so in thickness. They will warp if there is case hardening. Which is a good reason to ask for replacement.
R
Doug,
Your question rang a bell with me: I had the same problem with a 22" wide hard maple panel I left lying flat on my work bench Fri night and found cupped the next morning. I fixed it by just leaving it upright for 24 hrs, allowing it to absorb moisture equally on front and back till it straightened out.
What struck me in your question was the thickness of the panels: 3/8". That should allow them to be pressed back flat (as you said) easily and installed in the frames. I don't think that thickness is enough to pull the frames out of flat if they try to warp more. As added precaution, could you use the warped panels in the areas of the chest where the frames will be kept straight by their attachment to other members (front, back and sides of the carcass) and use the straight panels for the lid? GP
All - thanks for the responses - definitely a couple of ideas I hadn't considered!
Luckily (or not, depending on how you look at it), the panels are thin, and will be contained in a fairly heavy (3/4") rail assembly on the front of the chest. So, GP, I am also trying the "expose the other side of the panel" method, and hoping it works, and may end up just bending them back to flat, installing, and hoping for the best. Ians suggestion is my other option at this point, although I'd like to avoid ripping the panels if possible - I can only imagine the headache of trying to get the raised details to line up again...
Stephen - I hadn't considered kerfing, but would be concerned about making the inside of the panel look bad (it is, of course, exposed when you open the lid and look inside) at all the mismatched lines. Other than veneering the inside, how would you cover them?
Another friend of mine suggested wrapping the pieces in damp (not moist) paper towel like material and clamping them flat for a couple of days - I think I may try that before doing anything more radical...
Thanks again for the ideas!
d-
Well, I took my friends advice, and put the warped panel with the concave side down on top of some damp paper towels (ok, not quite what he said to do - he said "wrap it in damp paper towels and clamp it to the table" - close enough).
Anyway, I left the panel overnight, and sure enough, it took the cup out. And introduced a HUGE cup the other direction. Clearly I left in there too long.
So I let it sit, new cup down again for another day, and sure enough, the panel returned to flat.
Soooo, although it wasn't exactly what I had planned, it eventually got the job done...
Thanks again everyone!
d-
Doug
This may be a silly suggestion, but is ripping and regluing the panels an option? In principle it should be possible to rip, rejoint (carefully) and reglue the panel thus removing the warp. Conventional panel glue-up will result in a very thin panel, so a strategy similar to veenering may need to be adopted. It would be a lot of work, but it should be possible to reglue the panel one joint at a time, sandwiching the piece between two heavy flat cauls - made from 50mm MDF, say. The cauls would keep the pieces in alignment and prevent fresh warping.
Alternatively, is it an option for you to rip the two warped panels into strips, resaw the strips into 3/16 veneer, which you then apply either side of a piece of 1/4 or 1/8 ply which is then finished to a thickness of 3/8. You would then end up with six panels all with the grain match you were originally seeking.
I would rate my experience level as weekend hobbiest and have never tried either technique, so I'm open to comment from other more experienced persons.
Ian
If other methods fail, adding moisture to the concave side or placing it on a concrete floor convex side up, overnight there is a more radical method for flattening the panel. You can cut a series of parallel saw kerfs about 1/2 to 2/3rds the thickness of the panel on the backside of the problem panels. If they are about an inch or so apart you should be able to easily flatten them, the frames will hold them flat. For larger panels or table tops (you can't cut all the way to the edge so they are stop kerfs on a table top) after the kerfs are made small wedge shaped shims can be glued into the kerfs (with the panel flat) to hold it flat.
The kerfs releive the tension within the board, you need to take care with raised panels as the kerfs can't be too deep or they will come out on the raised bevel and ruin the work.
Good Luck
Stephen Shepherd
just to be clear, you have a warp (corner-to-corner), not a cup... correct?
Jeff - you are correct, I have a cup (side to side), not a warp.
Darn English language...
Doug
This forum post is now archived. Commenting has been disabled