How to keep wood from warping?

[dcohenour]

Hi all,

In my reading of various builder blogs, I note that wood stored and machined inside (basement, heated workshop, etc) warps quite often when taken outside for assembly. I was planning to do the same, but am wondering if there is a simple way to prevent this.

If the wood is kept outside under cover (temporary boat shed, barn, unheated garage), worked outside under cover, and assembled outside under cover, is it less likely to warp? Seems like a simple solution to me, but I may be over looking something.

Anyone have any experience with this? Thanks, in advance.

[Mrleft8]

Subjecting wood to extreme changes in temp. and humidity will increase your chances of warping, but there are other factors as well, such as stresses built into the lumber from growth habit, sawing, and storage. Even milling (planing) unevenly can cause warping.

[gibetheridge]

Sounds like the best approach to me. Like Lefty says, it's the change (especially uneven change) that does it. Vertical grain lumber is less likely to warp, twist and crack than flat grain, in the event that you haven't acquired the lumber yet.

[David G]

Yes... the word is 'acclimate'. Ideally - one brings in the wood to the space where it'll be worked, stacks and stickers it, and allows it to adjust to its surroundings. Only then can you begin machining it and expect it to stay where it is with no appreciable movement.

One then machines it to thickness by first flattening one face then running the board through the planer using the flattened face as a reference. As Mr. Left suggests, one needs to take more-or-less equal amounts of of each face during this process, or you can create an 'unbalanced' stick which will tend to warp. Once the desired thickness is achieved, in a balanced stick, one can cut to width and length.

I would fully expect that you could do all your machining inside, with no warping problems - if you kept the boat wood stored most of the time in a basic covered unconditioned space (no heat, no a/c, no baking attic conditions, no moist cellar conditions).

[schoor]

You can’t persuade wood when it comes down to warping. If the wood I’m working with has the tendency to warp, I like it to have done so before I make anything nice out of it. So I like to buy my wood seasoned and long before I actual need it.
Most tension in the tree is in the center so to cut the center out helps to reduce the tendency to warp. Actually I cut every board over the centerline(of the tree) before doing anything else and after ripping I give it time to warp.
Good luck

[dcohenour]

And what does one do for plywood? It looks like some of the stuff used on Bolger boats (and others) has a tendency to curl.

[amish rob]

Nothing will keep cheap plywood from warping, except better plywood. Seriously, it is just a straightened out peel glued to other straightened out peel. You need more than three mediocre peels to make a good board.

So what you do is cut your panels so the curl suits the boat; try to have them curl in.

To try and keep it flat, though, lay it down flat and weight it; leaning plywood will almost always warp.

I wonder if any planking stock has ever warped to the exact twist a garboard needed?

[dcohenour]

Nothing will keep cheap plywood from warping, except better plywood. Seriously, it is just a straightened out peel glued to other straightened out peel. You need more than three mediocre peels to make a good board.

Right now I have several board feet of white oak, maple, cherry, & walnut that I was planning on using for my boat. They are stored in the basement.

I have negotiated space for the boat on the porch of our barn. Concrete slab with an overhang, about 22 ft of space. I was going to enclose it with framed walls & plastic, as a temporary "boat yard".

I suppose that I should move the wood out to the yard about a month before construction, and bring the tools out to the wood rather than trying to cut in the basement shop & move the pieces outside for assembly.

Am I thinking about this right?

[gibetheridge]

That's what I would do, the sooner the better.

[Michael D. Storey]

I have had success removing warp from planks and plywood by placing the concave surface down on damp grass in the sun. Keep an eye, however, because it will continue to correct itself until you have a warp in the opposite direction.