Thread: door cupping disaster

Can we have a few photos of the job and the problem?

Regan,

Sorry to hear about what happened (the upside: now that it has, at least you know it won't happen again). What might have amplified your issue was that the timber could have already been wetter than usual to begin with. Any environmental change in humidity and temperature, whether is due to aircon, a different house, a fireplace, etc. will affect the timber.

Yep, if you want it to look the same, the only option you have is to re-saw and veneer on both faces. MDF should be fine, perhaps resaw closer to 3 or 4mm rather than 5 or 6 mm if you are using 18mm MDF.

Good luck!

Steven.

Regan, you say you have a cupping problem but you seem to be talking about a shrinkage problem. I would be inclined to wait until the shrinkage has stopped and then remake the doors.

Sounds like the doors are just pieces of wood with hinges attached ? is that right . A solid plank of a door ?
If it is , the best way to do a cheap door like that is to cut the wood into strips and nail them to cleats , with an angled brace . same as the inside of the old outside dunny doors were done . The hinges are screwed to the cleats.

Other wise, a door should be a panel and frame construction , it can be a flat panel , it doesn't have to be raised .

Rob

thanks gents... I have a cupping problem AND a shrinkage problem! I glued cleats to the back of teh doors, but they bowed as well.. yes - they are solid timber doors, and I understand that blackbutt is a bit of a culprit when it comes to wood movement. What alarmed me was how quickly and severely they changed.. My options still seem to be panel doors or veneered doors. Any advantages or disadvantages of either? I estimate that the cupping of teh doors was aat least 10 mm off the flat...

cheers, Regan

Ive been thinking about this all day.

An alternative might be to approach the problem differently. As I don't have a photo to go by (put one up!!) can I suggest a two prong fix.

Firstly, you made them, so perhaps you have scraps. You reduced the width of the doors to make them fit. Find the off cuts and glue them onto the hinge side of the door matching the grain direction and slip matching the grain itself. You might get away with a very fine glue line that if 5mm from the edge might be undetectable. Do the same on both sides and it might be a "feature"....

Second, you could take them off and route a 5mm wide 15mm deep trench down the middle length of the bottom side and epoxy in a steel bar matching the dimensions.... the steel will resist bending like crazy and if you were keen, make it spring steel or add a slight bend that would resist the door from re-cupping.

This diagram shows the trench being full length, but you could stop 20mm from each end so its hidden....

Untitled (491x834).jpg

What was the MC of the timber when you started manufacture, and what is it now?

fireplaces are notorious for drying timber, and what you've just done is the equivalent of sticking it in a kiln for a few weeks, but even then... Cupping like that shouldn't occur if it was drying from say 12% to 6% for example. And particularly not if the timber had been down to 10% first then regained moisture. To me this sounds like the timber wasn't adequately seasoned/KD before you started.

No problem... It is now.

pull the doors off, rip them down, drop them on the jointer to remove the cup, then glue it all back together. Do a good enough job and you'd need to be looking to see it's been done, all you need is an extra piece to cover the gap and the kerf losses.

or

get another piece of timber, stick it by a fireplace and drop the moisture down to the levels the existing ones are at taking care to prevent movement, then replace the doors with your new adequately dried timber. Cuppings always going to be an issue in thin wide boards though... Rip and join has been the solution for the last couple of thousand years.

Well, you can't beat nature! Wood moves with the annual moisture cycles (which are amplified by heating!), and the thicker & denser the wood, the more power it develops when it absorbs or gives off moisture. Cupping is the result of a different amount of swelling or contraction in the radial & tangential planes. Tangential change is often twice that in the radial direction for the same change in MC, and so is most pronounced with 'flat sawn' boards. Quarter-cut slabs shouldn't cup (they will become thinner or thicker towards the 'outside'), but even if you used perfectly quartered slabs in door widths, they would still expand & contract during the year, creating unsightly gaps or binding doors as the year rolls around. Anything you do to try & stop thick, solid-wood doors from warping & moving is likely to be an exercise in frustration, Auscab's suggestion seems to me to be the best solution if you want a door with a simple 'rustic' look that will stay flat & close neatly. It won't stop the wood moving, but it breaks it up into small parcels than are accomodated to a large extent by the small gaps between the individual boards.

Frame & panel construction was invented for some very sound reasons......

Cheers,

Originally Posted by John.G

Rip and join has been the solution for the last couple of thousand years.

Do you think they could be steamed for a few hours and forced back in a jig?

Originally Posted by Evanism

Do you think they could be steamed for a few hours and forced back in a jig?

only steaming I've ever done is wet steaming. There you want the wood at just under FSP, and utilize the moisture content of the wood to convect the heat to soften the lignin. in that instance if the wood is dry it gets throw in a bath to bring the moisture back up... Otherwise it needs steaming forever to get Enough heat in to bend without cracking.

here we'd be trying to "unbend"... Maybe that would take less effort so wouldn't need the higher moisture content. I honestly have no idea. Worst came to worst it could be rehydrated, steamed, bent flat, then dried again I suppose. Two weeks by a fireplace would do it.

If it could be heated enough to soften the lignin then there's no reason why it couldn't be bent back into a flat shape. Then a couple of crosspieces could be screwed into the inside where it's not visible to stiffen it up to prevent reoccurrence of the cupping. If it's cupped once my bet is it'd just do it again if left to its own devices. Leave the cross bracing inside the door and it'd still look clean on the outside.

depends on the piece... lateral bracing might be timber, big old fashion decorative hinges, anything to stiffen it up. I like that concealed steel rod idea.

rip and rejoin just sounds easier.

thanks for all the feedback... my last reply was a quick sneaky one from work, so now have a bit more time to think.. I certainly like the idea of a steel bar routed into the end grain, but feel that I would be needed on both ends, making the top of the door a bit tricky... also, of course, if teh problem is shrinkage (no way around that, of course) then it is less useful. Anyway, I have no idea of the moisture content of the timber to begin with, but it was bought from Anagote in Sydney, so looked after properly in storage, and presumably kiln dried to 12-15% moisture. When doing the joinery (boards were 200 x 22 mm) I made sure that the growth rings were running in opposite directions in each adjacent board. The doors are about 540 wide, 700 high, and, this is the worst part, were made and installed for a paying customer! I am going over to the house to remove the offending articles tomorrow, so will post a photo of the mess after that. This was not rough and ready construction, so they cannot have any of the "rustic" about them!I guess I could rip and rejoin (what width? 100mm??) but am not sure that this would solve the problem. The customer is not a fan of veneer, so have to be careful how I word my solution... ("oh yes, we are just going to use very thin boards to rework these doors..") of course, I am not sure what their house is going to like in summer, whether it is A/C etc... I guess the frame and panel solution accommodates the seasonal movement caused by alterations in moisture and temp, but will look different to the original. I will reiterate, that I glued 25 mm thick blackbutt cleats to the backs of the doors, virtually the entire width, top and bottom, and they were of no assistance - they got bent to buggery along with the doors! so, the things I think are against me are... Environment of cabinets, species of timber, thickness of boards, width of boards and the piece of lard between my ears! Anyway, please keep the ideas coming, I will (try to) post photos, and let you know how my conversation with said client goes!

cheers, Regan

The piece of lard ha ha lol . That cracked me up . A paying client ! Well at least you have a sense of humor about it . One of the most important things you should never do is to glue cleats a cross the grain . That's a disaster waiting to ocour . You could screw them , with slots even , or nail them but not glue the whole thing . It will self destruct .

I mentioned two door types before but thought of another , build a frame for each door and then cover it front and back with ply . Cheap light doors are made this way , you could then drill a hole in the bottom frame member and fill with very dry sand and plug it up . Then they'd feel like quality doors ? Or possibly way to heavy ? Depends on the size and space in between .
Rob

I have in the past few months dealt with about 15 cupped boards and learned the best way to flatten them was to wet the concave side (I used a pump/spray bottle) and put the board concave side down on the floor. Check frequently as I found that sometimes even an hour was sufficient to get rid of the cup totally.

thnanks again for ideas... the clients were pretty unfazed about it all, but I did assure them that it would be fixed... I removed the doors, and have them in my workshop, as observed by auscab, one of the cleats ripped right off the back of one door! will try to post photos when time allows....