Thick Boards warping

[mikejohn]

I think this is the right thread for this question
I am making some furniture using 12" (30cm) wide boards, 1 1/2" (38mm) thick.
I have read in another forum that routing out u shaped channels along the length of the piece, and then having cross pieces for strength, will greatly reduce the chances of warping.
Apparently 'square' saw kerfs stress in the angles, hence the round nosed bit.
I can well imaging going 1 1/4" (31mm) deep, when you could probably bend the piece, would stop warping once braced, but how deep do you go just to releve the stress?
Has anyone done this, or do you have other solutions?
I know I am supposed to rip my planks in 4" (100mm) strips and join them, but I want to recreate the look of old board furniture.
Along the same lines, anyone breadboarding with the shopbot?
....................Mike

[gene_marshall]

Mike,
I have had some success with this.

I know it's a twilight zone method, but I have saved a few projects this way.

Sunny day, sprinkle the grass with the hose, lay the peice cup down on a couple 3/4" boards.
Keep an eye on the thing... It happens pretty quick, about 20 minutes or a half hour.
The sun will bake the back and draw the moisture thru the block.

When it flattens out I rush the peice to a flat table and clamp it down thoroughly.Sometimes I might shim the middle to over bend the board.
Cover the "wetted side" with some dry rags so it dries slowly.

We try to make glueups for wide projects but those wide planks do have a much nicer look for classic projects.

as far as the "fluted method" with the back knotches goes... This weakens the board quite a bit, and The depth is only part of theprocess.
Proper spacing and placement of those notches will help the bending a whole bunch.

i hope you find this helpful.
Gene Marshall

[waynelocke]

Warping and bowing are most likely moisture content issues. I have never been a believer in the rip to 4" and glue school. If the boards are dried properly and dealt with properly in the design and construction of the project, you should not have problems. I have just purchased a $2" X 16' X 2"piece of Bubinga for a conference table and the rough board is straight and true.

If the boards are too wide for your jointer why not use the Shopbot to give you a true surface before planing the other face. I think that the kerfing technique for warped boards is mainly for antiques where you are trying to preseve as much of the original as posible. If you have to do that on new work you are probably going to have more problems with the piece down the line.
Wayne

[mikejohn]

Gene and Wayne
Thanks for the replies.
I have the boards true now.
What I would like to know is if there is a way to minimise the chances of warping and cracking in the years to come.
It took us some time to achieve rocking horses that overcome wood movement over time, but as these are painted we can take a different attitude than in waxed and polished wood.
I have used wide board construction in the past with no problems, but I'm seeking out more experienced heads than mine to advise me on this problem.

....................Mike

[beacon14]

Mike,

What species of wood, what cut (flatsawn, quartersawn, or combination), what is the current moisture content, was it kiln-dried or air-dried, and what are you using it for? Wood that thick unless it's improperly dried or already warped is likely to stay pretty stable in my experience. Your design and joinery must allow for the wood to move across the grain more than along the grain, as I'm sure you know. The method you described would be be a good idea for thinner boards which would be more likely to move and crack if not supported, but at 1 1/2" your pieces are beefy enough to support themselves.

I use my Shopbot routinely to surface wide boards before planing. I'm currently making some furniture for my kids out of 8" to 12" wide boards from a tree that fell on my house several years ago. The nicer boards were fairly straight, but cupped down the middle so the section looked V-shaped. I ripped each board at the center of the "V", jointed all the edges, and glued the boards back together - the joints virtually dissapear, but now the boards are flat across. I was able to make a 3/4" thick x 48" wide panel out of four 1" thick boards, and it's dead flat - I'll try to get a picture posted when it's done.

David B.

[mikejohn]

Dave
Its Beech, air dried to 10%, stored inside my workshop for the past 6 months.
Its straight and true at the moment.
I want it to stay that way.
Ill photograph the pieces as I complete them.
....................Mike

[waynelocke]

As you describe the boards, you should not have to worry as long as you allow for seasonal movement as David described.
Wayne

[ron brown]

David's comment on grain should be taken seriously.

I have noticed older wood does mill differenty than "fresh from the kiln" stuff and air-dried works differently than kiln dried.

Ron

[gerald_d]

Growth rings, as they dry, want to flatten out into straight lines. Movement in later life relates to these rings flattening and curving - that's why vertical grain is stable for curving and everything else isn't, unless the moisture content is absolutely stable. That's the little that I know about wood and that's why I stick to metal.

[beacon14]

Its Beech, air dried to 10%, stored inside my workshop for the past 6 months.
Its straight and true at the moment.

Sounds like dream lumber to me - I wouldn't be too worried about warping. In fact my supplier has been importing your European Beech as a maple substitute. It's a little coarse for maple IMO but it's beautiful wood, and strong as anything.

We await pictures...and I'm curious about what furniture has 1 1/2" x 12" members?