'Adjusting' a warped box

[Paul200]

This should have been a post under 'Projects' to show off my wife's nice new Workbox. The box has decided instead that it belongs under this more general heading, complete with an annoying twist.

The box is approx. 70cm x 29cm, dovetailed corners with a ply base rebated into the sides which is reinforced with a small crosspiece. Construction and glue-up all went fine but then I had a couple of weeks off after minor surgery. When I came back to it this week I found that the lid no longer sat happily and further investigation revealed that the body of the box had twisted along the diagonals. In other words the back right corner and the front left corner have pushed upwards (or the other two corners have pushed downwards) by about 3 or 4mm.

I've had this Elm plank for about 5 years and it had been air dried when I bought it. It took quite a bit of work to flatten out the lumps and bumps but I reckoned it had done all its twisting by now. I'm assuming that the recent spell of wonderful (but hot) weather has got something to do with it (24 degrees for nearly 3 weeks and not a drop of rain - in Scotland!!). But could it be my dovetails not being quite right - although it was all flat and level when I put it together.

I suppose what I'm asking is - has anyone else experienced this and is it recoverable? (Please let it be!!). Have I done something (or not done something) to cause it?

All criticism gratefully received!

Paul

 

[custard]

Commiserations Paul, I've been there, I know how dispiriting it is when scores of hours of intense effort doesn't pay off. Here are some random thoughts,

-You've nothing to lose. Leave well alone for a few days and see if it settles back down. Failing that try cramping it down to a flat surface for another few days and seeing if there's any improvement. To be honest the odds are not in your favour, but given where you are in this project it's worth a try.

-If this is a free standing box then incorporate corner feet like these, and adjust these feet to take up the error. This would be my preferred solution.

-The third (and least attractive) option is to plane down the two opposing corners that are causing the rock. It'll look a bit ****-eyed but maybe the casual viewer won't spot it.

-When I've got a commission incorporating drawers I get out the stock for the drawer sides several weeks in advance. I carefully choose bone dry, straight grained, quarter sawn stock and plane it down to final dimensions in multiple small stages, resting it in stick between successive thicknessing operations. The reason I go to all this painstaking trouble is because bitter experience has taught me that if a drawer goes into wind (twist), like your box has done, then there's no clever trade trick to recovering it, I'll have to start again and remake the drawer.

-The next lesson is how painstaking you have to be to when dovetailing. I mentioned in this recent thread that the wood needs to be dead square and true, easy-project-for-dovetail-practice-t112386.html And during the transfer you have to take infinite pains to ensure the pin board and the tail board are perfectly aligned. Dovetailing is as much an exercise in taking care as it is a test of hand tool skills.

-There's a lot to be said for hide glue with projects like this. The opportunity to disassemble the joint and sort out the problem at the component level can be very useful.

-Full credit to you for pausing and reflecting on your options, most people would have run around with their hair on fire, trying dafter and dafter panic remedies, but just making a bad situation worse.

Good luck!

 

[MikeG.]

Custard has about covered it. I'll just add that elm isn't a very stable timber, so although it looks beautiful it may not be the best choice for a box. Secondly, if you were to try to clamp it back into shape I would suggest slightly over-twisting it the other way, rather than just clamping it to something flat, because it will spring back a bit when you take the clamps off.

 

[Phil Pascoe]

That's a point I thought Custard might have mentioned - and the wilder (prettier) the grain the more unstable it often is. I remember a piece in the store when I was at school (50 years ago) 12' x 12" x top side of an inch that was kept purely because one end was at 90 degrees to the other. :shock:

 

[Paul200]

Thanks so much for your responses. I'm trying the reverse clamping option at the moment - time will tell! The various scenarios you have mentioned Custard, are things I have pondered but have no real experience of so wasn't sure. It's very reassuring to be given the benefit of that experience, so I thank you. I had wondered after the event about the swirly grain and burrs having an effect on stability so it's nice to know I was thinking along the right lines Mike and Phil.

I can't honestly take credit for pause and reflection. Normally my default would have been to run around with my hair on fire (a great image!) but I'm not yet firing on all four after hernia surgery and have been banned from anything strenuous - hence my serene acceptance of this disaster :roll: :evil:

I considered planing the bottom but there isn't enough meat below the ply base to do this and the top would still be awry. Ditto with the feet - the lid sits inside the edges of the box and rests on the front so the top of the box has to be flat and square. Apart from a bit of practising these are only the second set of dovetails I have ever cut so there's every chance that something has gone wrong there! I know - more practise :wink:

One thing I considered was to reverse clamp the box until it sat evenly and then rebate steel angle brackets into each corner on the inside in an attempt to stabilise it. These would be covered over when I line the inside (thanks again Custard for your very informative post!) but there's only 16mm of depth to screw into so probably won't be very effective. Epoxy adhesive? Dunno but I may try it if the clamping doesn't work.

The only other alternative is to scrap it and re-use the timber in smaller boxes. Shame about the lost hours but at least I can put it down as experience (and dovetail practise!). I've got some nice steamed Pear that I could use for a replacement - hopefully that's stable enough!

Thanks again for your help guys. It is always very much appreciated.

Paul

 

[profchris]

If it's the unusually low humidity it will move back to pretty much where it was once humidity rises. Unfortunately it will move again when humidity changes.

If there were internal stresses in the wood, released when you planed it, then it may have done all it's moving. Clamping, maybe with some heat from a hot air gun (to "Ouch" hot, without scorching, and heated all through) might help- guitar necks can be straightened this way and sometimes stay straight. Only heat the warped parts and your glue will probably release and reglue as it looks so be prepared for that.

 

[custard]

maybe with some heat from a hot air gun

Worth a go. If you used regular PVA, and you have a beefy hot air gun, you're in with a chance of the glue releasing, then you can examine each side separately for twist and attempt to rectify.

Another option might be a 1" tall skirt all around the base, but if it's in wind you may not get away with straightforward 45 degree mitres.

For only a second go at dovetailing you've done pretty well!

 

[Jacob]

I'd be wary of clamping, bending, heating, metal work etc - too unpredictable and might carry on moving.
I'd take the joiners way out which would be to make it look straight even if it isn't
i.e. by careful planing edges which clearly visibly don't line up. Perhaps even consider gluing on an extra bit to one or more edges and then planing off.
Whatever way you take I'd leave it somewhere warm and dry week or so until it has finished moving.
A lot of creative bodging goes on out there - a good joiner covers his tracks!

 

[Paul200]

Some more great suggestions - thank you. I considered heat and/or steaming. We'll see.

Another thought I had was to clamp the thing straight, apply the suede lining material to 6mm ply and glue this in place with Titebond. I needed to use ply on each end to support the tray I've made so it would just mean using it at the back and front as well. This would hopefully mean the box material becomes an extra layer of the plywood and stays put. Worth a try?

 

[custard]

Paul, I did a WIP last year on how to line drawers and boxes,

how-to-line-boxes-drawers-t106375.html

I wouldn't recommend the ply liner idea; Copydex/double sided tape are the better choice for attaching suede or fabrics (see the WIP), the ply will arrest seasonal movement in the box causing splits, and it will take up internal space plus add weight for no benefit.

 

[Paul200]

Saw your WIP thanks Custard. Saved it to my Favourites. I see what you mean about movement in the wood. I'll stick to the clamps and see what happens.

Thanks again

 

[Paul200]

I'm taking my box out of traction today. I'll let you know what happens :roll:

 

[Paul200]

Hmm? After 48 hours out of the clamps I'm not exactly overjoyed with the results but things are looking better. The box made some attempt to resume it's 'wind' but nowhere near as bad as previously. I'm quite encouraged by this and have put it back in the clamps (probably for another week) to see if it can be reduced further. I may try the heat gun trick but I'm a wee bit wary as it's had two coats of Danish oil and I'm not keen on the solution being too final!

I'm now pretty sure that the instability of the wood and the very warm weather we've been enjoying for the last month could be the culprits. Humidity has been at the high 70's mark for most of the time but has now dropped to 50%. My workshop was shut up with the box inside for about a month and must have been stiflingly hot inside during the day (which is about 20 hours in Scotland at this time of year!). So I'm hoping that another week in the clamps and a return to more seasonal weather may straighten things out. (We could do with some rain - our small burn has virtually run dry in the last couple of days - never seen it this bad).

Paul

 

[profchris]

That's encouraging ... up to a point.

If normal humidity does return its shape, it will move again when it's dry (I guess in Scotland this could be a few years off ).

There's nothing you can do to stop this, short of dipping the whole thing in plastic, and even that might not work.

Your best option is to find a place for it to live where humidity doesn't change much, ie certainly not next to a radiator. If it will keep its shape there, you've won!

 

[Paul200]

I kept the box in clamps for the last 2 days and attacked it with a heat gun for about half an hour on each day. It's now been sitting on a plate of glass (unmolested by clamps) since yesterday eve and hasn't budged an inch.

I'm now convinced that humidity is a main factor here - now the seriously warm and humid weather of the last few weeks seems to have passed the problem has gone away. Whether the heat gun had anything to do with it I couldn't say but I'm keen to finish the thing now (wife's birthday is very imminent!).

By a strange coincidence we've been monitoring the humidity in our house on behalf of a neighbour, who's building a house to Passive House standards and was concerned about the humidity levels indoors. He was using our readings as a very unscientific 'norm'. The upshot is that our house is remarkably un-humid (much to our neighbours' disgust!) and, as that is where the box will live, I'm hoping it will be OK.

Next step is to fit the internal linings. The two end pieces were always going to be on thin plywood to provide a base for a tray to sit on so I'll ensure these are a very tight, square fit and with any luck they will resist any future attempts to 'wind'.

Thanks for the helpful suggestions. I'll keep you informed of progress (or otherwise).

Paul

 

[Paul200]

After the trials and tribulations of this workbox going into 'wind' recently I thought I should post a few pictures of the finished article.

A few days of 'reverse' clamping, threatening it with a heat gun and shaving about 1mm off the diagonally opposite bottom corners it seems to have stabilised itself. After about a week of suspicious glances in it's direction I decided it wasn't going to twist any more and it was time to finish it. Five coats of Danish Oil, a wax polish and lining out the inside with suede and - well - here 'tis.

Missed SWMBO's birthday by a few days but she's chuffed to bits with it - and so am I. I've learned a lot from this one and couldn't have done it without the helpful advice given so freely on here. Thanks guys - very much!

Paul

 

[thetyreman]

what a beautiful box! looks immaculate =D>

 

[Paul200]

what a beautiful box! looks immaculate =D>

Wow - thanks! Appreciated

 

[Fitzroy]

That’s gorgeous, love it!

F.

 

[Racers]

Very nice use of a cracking piece of wood.

Pete