Thread: In a stroke of stupidity....

OOPS!

Originally Posted by dave_in_gva

Do people here think this is the best approach to fix the problem? I'm concerned of course that even after gluing the assembly could separate in the future. I've invested an incredible amount of time and energy (very enjoyable mind you) in planing those Sipo boards by hand and want to get the look I originally wanted for this piece.

I'd try flattening the slabs as you are, which will work to a degree... but I'm guessing you'll either have to finishing flattening by hand or - if you're lucky - the gap may be reduced enough to pull in with clamps.

Nevertheless, any flattening you can do without removing material is a bonus.

The glue joint shouldn't fail, over that expanse it's almost certain to be stronger than the wood!

Any reason you didn't simply drive some coach-bolts up through the bottom slab in the first place? (Which is still an alternative)

do you think you could coachbolt a length of angle iron each end of the bottom slab just inside the box it is sitting on then when it has been straightened glue and screw the top slab to the bottom slab from underneath the slab which has the metal strengtheners under it then the angles would act as locators for the top of table and stop warping as well............................bob hope you understand what i mean

Turn the slabs so the grain is 90' to each other, then screw them together at close centres from the bottom face, if they wont pull together fully, re-tension screws in a few weeks or months.
regards inter

Originally Posted by dave_in_gva

Do people here think this is the best approach to fix the problem? I'm concerned of course that even after gluing the assembly could separate in the future. I've invested an incredible amount of time and energy (very enjoyable mind you) in planing those Sipo boards by hand and want to get the look I originally wanted for this piece.

Best,

Dave M

Sorry Dave I don't think that will work but.....do you know the moisture content before you started and now.

I'm no expert but I suspect the slabs will move around seasonally because of the way they are cut, you have some big hunks there and it is interesting that the growth ring orientation on the top and bottom slabs is the same yet the warp occurred in opposing plane which points to moisture movement from the exposed surfaces as you say.

FWIW I would suggest small spacers between the slabs to leave a permanent air gap assuming they straighten OK.

Good luck
Mike

Right gents, thanks all. I'll combine most of your suggestions and go ahead. This basically means doing what I thought I would do, although in addition I will strap on around 5 heavy duty bars under the bottom slab oriented across the grain and screw bolts through these up into the bottom 2/3 or so of the top slab.

One question on that....I don't usually try and immobilize my work (in general I just accept wood movement and try and allow it in the design). Which ironically is what screwed me on this one....I overlooked that there would be air exchange passing in between the slabs and the two pieces being able to move independently was a recipe for disaster. But it seems to me I can bolt up through the slabs with two possible types of bolts. One is thickish bolts with a wood screw thread going into some smaller pilot holes.....or I can bolt up with thick machine bolts that are threading into T-nuts (at least that's what we call them in Canada) - basically nuts with an internal thread to receive the bolt and an external thread to allow them to be securely screwed into the wood. Any feelings here on which of those two options would be best?

Also any other opinions about my plan for flattening these out....I am toying with the idea of not only placing them concave faces down but if the bow doesn't come out entirely I may place a few spacers above them and the floor and spread a few damp towels on the floor to get humidity going back into the concave face. I really don't want to work these faces again apart from lightly sanding off the tung oil to get a better glue bond. Someone asked starting humidity etc. I picked up the wood about a year ago and it was 13% but it's been in my workshop and rough cut for most of that time....RH in the workshop ranges from about 45%-70% and inside its around 35%.

Oh...and BTW in case any of you are wondering why a Canadian living in Switzerland is posting on an Australian board....well it goes down to two things. First I did actually live in WA (just outside Perth) when I was a kid and secondly quite honestly I sussed out the various wood forums and as far as I could see this one seemed to have the most active, pleasant exchange of good advice. I don't often get into trouble with my woodwork and can usually turn things around but wanted a good set of second opinions on this particular cock up so thanks all of you for that.

Best,

Dave M

Thats quite a problem you have there and will be interesting to see how it turns out. Keep us posted and good luck with it.

Never too late to respond.
If you did not apply finish equally to both sides of the table, it'll cup.
In future, or with this table, simply apply equal amounts of finish to both sides - no cupping.
I once built about twenty tables for a restaurant. All of them cupped severly!
I took them off of their stands and back to the shop. I finished the underside and in about ten days they were flat as could be! - I was saved.

They're finished identically on all sides. The issue is tung oil doesn't act as much of a barrier to vapour exchange so these may as well be raw pieces of wood. The fact that they were in equilibrium with a higher relative humidity and brought into a place with lower RH means they are now giving up moisture. And that moisture can come from 4 faces but is coming out much more easily from the top and bottom of the pile.

My expectation when I get the bow out and glue them up with some metal bars to support is that I'll remove vapour exchange occurring from the two inner faces and any further vapour exchange will keep the 2 slabs moving in unison with much less - hopefully no visible - bowing.

Of course, now my wife is saying she likes the bowing....says it gives a Japanese look.

Anyway, we've got guests this weekend but after that its off with the slabs and hopefully I'll see some wood movement in the other direction with both of them.

Dave

Good move with the idea to give both slabs the same 'breathing room'.
Great wife for giving you the same - breathing room!
By the way. You're brave to show such pics of your nice work that has gone wrong for you. But, of course you know that if the slabs were once flat, flat they will be again.
Also I didin't compliment the design. That is one nice coffee table!
I keep trying to leave this post and then I scroll up and read more!
With such huge pieces of timber I would wait. I would leave them equally coated, and apart, on both sides and in the same R.H.(as is the room they are to inhabit) I would take measurements that indicate that they are moving back to flat - this might take some time.
Inexorable movement is the habit of large chunks of wood.
If you try to 'peg' them together, the glue joints may split.
Wait them out and wait for flat.
This started out as two lines! -see above.

So gents,

I am resurrecting this thread to give an update.

Took the table apart and laid the two slabs concave face down. Also removed the tung oil finish from the interior faces. After about 1 month they were both flat.

This morning I glued them together with a polyurethane glue and supplemented with some lag bolts. Time will tell whether the top cracks but I've a feeling it'll all hold up fine.

Will report back in 6 months or so with some pics if all goes well......sooner if it doesn't.

Best,

Dave M

Dave whats them speakers in the background

Those are Gallo Reference 3.1 loudspeakers....fantastic bit of kit in every way.

http://www.6moons.com/audioreviews/gallo5/ref31.html

Dave

Originally Posted by dave_in_gva

Will report back in 6 months or so with some pics if all goes well......sooner if it doesn't.

Will keep my fingers crossed for you. Well... mentally, anyway.