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?

[john_shiel]

Mike,
All wood reaches equilibrium with the ambient relative humidity value,eventually.Having done so it will move up or down the scale ,following humidity changes as they occur over time.Even up to 2% variance in moisture content will have very little effect on beech if your 10% is accurate in the first place. 10% appears to be very low , unless your climate is very dry.It is very important to apply whatever finish you are using to the unseen back of the work ,as well as well as the face ,or it will behave as Gene has
said above.Rogue planks usually show their colours when you have left them lying about for a while.'The kiln drier's handbook'is a mine of information if you lay hold of a copy. John

[rhfurniture]

Hate to say this but beech is one of the most mobile European hardwoods (experience + figures from trada handbook of hardwoods), and personally I tend to stick to smaller sections. They do make woodwork benchtops out of massive thicknesses and butcher block type tabletops out of small widths and lengths well dried, but that is mainly because it is very close grained and tough. If quartersawn may well be fine (but tell the owners not to store it in a damp garage). Basically you must allow it to move. Maybe a heavy stretcher with a dovetail slide underneath, or clamped ends fixed at the outside with loose tongues to the inner joints if a table top.

[mikejohn]

The problem with all timber is change the humidity and temperature, the wood moves.
Get Hani to make you a piece of his great outdoor 'screens' and try putting it outside in New Orleans, or get Paco to send a table to Arizona.
Such major climate changes cause problems in 200 year old furniture which have remained perfect up to that time.
I read on Google (but can not now find it) about a removal firm who were unsuccessfully sued because an ancient table top cracked in such a north south move.
Using dovetailed slides, bread boarding, and firm fixing means the piece will leave the shop OK, but how will it fare once it ends up in an air conditioned house?
Solving this problem with the horses was difficult enough!
Anyone want a genuine Tudor refectory table made of MDF and Ply?
.....................Mike

[rhfurniture]

If it is "genuine tudor" then the boards will be warped and cupped! Just design in movement and it will be fine. ie dont glue them up into one board 3ft wide and fully fix at the outsides - it will bow or split.
Cupping results because the radial and circumferential movements are different. The closer the two figures the more "stable" the wood. It is also why quarter sawn wood is more stable, plus radial is usually less than circumferential. If you want I can look up the figures in trada tonight when I get home. Mind you they are only figures.
As far as grooves underneath are concerned it may work under some circumstances, but I've never tried it and would be very wary.
r.

[rhfurniture]

Traditionally of course tops were fixed with buttons - small wood blocks with a tongue on one side that went into a groove in the rails between the leg tops.

[bleeth]

Mike: It is unfortunate that many of today's clients do not understand the natural movement of wood as being a direct result of it's reality and expect their solid furniture to act like a piece of plastic. The best solution for a plank table is for your buyer to understand that a it will not look or act like a piece of glass and if that is his desires then you will have to build it out of a laminated substrate. If you are going to move a large object like that from Romania's hills to England's climate the best you can hope for is to coat it very well with an oil and wax build up so you get some good saturation and elasticity in the finish as there is absolutely no way that the planks are not going to move. We have a large oak table in our family with breadboard ends and between winter and spring the planks move a good 3/4" (19mm). This table was made of appalachian trees in the mountains of North Carolina and has never left it's "home" environment.
To answer your question "Anyone want a genuine Tudor refectory table made of MDF and Ply?" The real answer is too often yes.

Dave

[rhfurniture]

Actually I think the Tudors would have loved a refectory table made of mdf and ply - it would have stayed flat and cost tuppence.
We have a romantic notion of craftsmen with a twinkle in their eye who spent months lovingly created masterpieces, and we buy it to attach ourselves to that notion. Most of it was the result of a rather squalid class system and short lives - Sheraton died a pauper (afaicr).
r.