Really bad warping

[stevekendal]

Well I removed the veneer ok, but the round edge and rebating that the new top would need are a little beyond my joinery expertise, so as a last-ditch shot, the solid wood top, minus its top and bottom veneers is clamped to the bench after wetting the cocave side only. Will report in due course. Steve.

[FRANK.C]

You may need to keep a damp cloth under it to keep the wood wet.
The one I straightened took a few days, but keep a close eye on it as if it's left too long it can warp in the opposite direction

Frank

[mattCRT]

How Annoying!!! How come the rest of the radio didnt warp??

[McMurdo]

Think I'm going to have to bite the bullet here and buy/scrounge a pair of sash clamps

I've never used anything else for holding down warped ply!

Our friends in china make these by the lorry load and those tool stalls at sunday markets usually carry radio-sized ones for less than a fiver.

[Aerodyne]

Steve, I'm very surprised to hear that the top is solid timber beneath the veneer. No wonder it warped. I was bemused at the thought of blockboard warping quite that badly! The rounded edge would require routing if you replace the top, but you might just consider using a ply panel and 'adding' the rounded part with a length of moulding from a DIY store. Stainig or spraying/toning would blend things in, I believe.
Whatever method you choose, you can't makes things worse.
-Tony

[stevekendal]

Originally Posted by Aerodyne

Steve, I'm very surprised to hear that the top is solid timber beneath the veneer. No wonder it warped. I was bemused at the thought of blockboard warping quite that badly! The rounded edge would require routing if you replace the top, but you might just consider using a ply panel and 'adding' the rounded part with a length of moulding from a DIY store. Stainig or spraying/toning would blend things in, I believe.
Whatever method you choose, you can't makes things worse.
-Tony

Thanks for that Tony, though I may be ok now, because after little more than a day wetted and clamped, the released board has only crept back by a couple of mil. Going to re-clamp with a wet cloth in contact, then have another look tomorrow, fingers crossed Steve.

[FRANK.C]

Steve
When it has straightened I would keep it clamped until it is fully dry and replace the wet cloth with dry newspaper to help to dry it out changing the newspaper for dry ones as necessary.

Frank

[stevekendal]

Ok Frank, but should I use multiple sheets, or maybe some of that spongy kitchen roll? Steve.

[Radio_Dave]

Hi Steve, If there's room inside, what about gluing and screwing a piece of plywood to the back of this panel to permanently hold it flat and stable?

[FRANK.C]

Hi Steve
Kitchen paper would be good, really anything that's absorbent will do. I just used multiple sheets of newspaper as it was to hand.

Dave's suggestion is a good one, although I have to say that the panel that I straightened once straight and dry hasn't moved since then.

Frank

[stevekendal]

Originally Posted by FRANK.C

Hi Steve
I had a radio with a badly warped top. The whole cabinet was dissembled though which made it easier to straighten. Thread here.

I straightened it by wetting the concave side only and laying some weights on top. The idea being that the water will swell the wood on the concave side only, and help to straighten it. It took nearly a week in my case. You would need to keep a close eye on it as if you leave it too long it will warp in the opposite direction.

Frank

Well, that was right enough. After 24 hours wet and clamped it , when released started to move back into the warped position again. Now, after a further 24 hours clamped and 4 hours after releasing, it is bowing in the opposite direction. Seems like a game of chance now, so if it doesnt straighten up as it dries, I will be taking bets on which way it will spring next. Steve.

[Aerodyne]

Steve, unfortunately the introduced moisture content will inevitably dry out again, especially in today's central-heated environments, so unless some measure is taken to prevent its return, the warp is almost certain to reappear eventually. I still feel that the tension needs to be taken out of the timber in the manner I suggested in my PM to you - even though what we supposed was blockboard actually isn't. But... I do understand that without a circular saw of any kind it cannot be done.
-Tony

[FRANK.C]

Hi Steve
It is probably best to keep some thing flat and weighted on top as it dries.
I used a piece of plywood, CPC and Maplin catalogues, phone book and a couple of heavy motors etc. You can always wet on the opposite side to straighten.

Frank

[chipp1968]

slots can be cut in the underside using a handsaw I would have thought .

[stevekendal]

Think we're on the home straight now, with the piece dried out and only curling upwards by a couple of mil and is easily held with the sash clamps. This however might change when I re-glue and clamp on the bottom veneer. Why did they veneer both top and lower surfaces? Steve.

[Aerodyne]

The purpose of veneering the underside - a method called counter-veneering - is to eliminate warpage due to uneven shrinkage...
Yes, I know....
It SHOULD work, but seemingly not every time!
-Tony

[stevekendal]

Ok, so I think I'll glue and clamp the bottom veneer first and just maybe that will relieve the slight remaining bow. Then, if I re-attach the top to the set and put the top veneer on last? Who knows? Steve.

[stevekendal]

Well, the tops back on now and quite a snug fit, thanks to the 3 pairs of massive sash cramps that a kind freecycler has loaned me. However, it now extends 2mm too far back as it seems to have permanently expanded depthwise only, at 90 degrees against the grain. Pretty sure this will be a lasting effect as I saw it once before in a near-terminal PB55 that I put back together. That was like a jigsaw that no longer fits and finished up with two substantial fillets in the split sides that would no longer meet due to expansion. Next decision is whether or not to attempt refitting the wanut veneer on top. This now of course, is about 2mm too short and in addition, it appears to actually consist of 2 layers, with opposing grains. The underneath layer lost a couple of chunks when it didnt come away clean, so I may save myself a load of trouble and just sand and stain the timber surface instead. Cant believe how bad this cabinet warped after I just found out it was made by a famous and respected US clock and cabinet maker, but thats a story for the success (or not) section in the New Year Steve.

[Aerodyne]

You've seen what all woodworkers know - that expansion and contraction is cross-grain, not along the grain. This is due to the cellular nature of the timber growth. It seems like too much moisture has been taken up now: if there's any possibility of leaving it in a warm spot for a while, such as an airing cupboard, it should return to size - but some of the warpage is also likely to return.
Could you obtain fresh veneer for the top? there are sources on Ebay and elsewhere. It should be veneered for stability.
-Tony

[Retired]

Hi Steve,

If it was mine I'd turn it into a wonderful project and do a full cabinet restoration.

I agree with Radio Dave in post #20 and think the long term solution is to replace the entire panel with a new piece of veneered plywood.

If you haven't got many woodworking tools and don't feel quite confident enough may I suggest trying the following to see how it works out?

Obtain a piece of decent quality 1/2" thick plywood (perhaps a local timber yard will have an off cut or even be cheeky and visit a local joiner; this has worked for me many times). Cut the plywood perfectly to size but make certain the grain of the plywood runs at 90 degrees to the grain of the finishing veneer.

Buy a cheap veneer for the bottom surface and a suitable veneer for the top. Take a lot of care and glue the veneers watching for grain direction. Trim the veneers to size once the glue dries. You can do this without touching the original panel so if you make a mistake there is little lost apart from a bit of ply and veneer.

With the new panel veneered and cut accurately to size you can once again visit a local joiner and ask if it would be possible for him or her to run a moulding around the panel with a router for you; this is an easy job and only takes a few minutes.

The new moulding could then be carefully painted in to hide the end grain of the plywood. Mat black over a decently sanded undercoat would possibly enhance the look of the cabinet; Done with care the result should look presentable but above all you wouldn't be watching the cabinet all the time in case it started to warp once again.

It's just an idea requiring few tools. Hope it helps and good luck.

Regards, Col.