Been air driying some red oak in the garage for a few months. . The boards are just shy of being 4/4 and 6 to 9 inches wide. In the process of moving it to a new area I noticed that many of the boards are cupped. was this caused by uneven drying between the top and bottom of the boads? if so will the cupped boards eventually stringhten our as they continue to dry? I'm assuming their pretty dry now since they have been stickered for quite a while now.. Would it help to go through the stack again and turn all the boards so the convex (wetter) side it up? How about storing it unstickered now, would that help un-cup them? Mike in Arkansas
I takes a year per inch of thickness, on the average, to become "air dry." As wood dries, it cups, wanes, twists--that's just what happens. It is difficult to tell if wood is dry without some kind of test. I would probably turn the boards around to dry them as evenly as possible, but there's no guarantee what will happen. Drying wood is part science and part art.
I have found that the best chance of reducing cupping is when the wood is still "wet", i.e. the first few months. So I am afraid there may not be much that can be done for your wood now that it has "set". Force required to straighten would likely end up with cracking the wood.
The ideal way to dry wood is with consistent stickers and lots of weight. Wood at the bottom of my stacks always comes out better than at the top. I use concrete cinder blocks on top, but have started using those nylon web cargo straps as well to get more pressure on the top pieces. The worst cupping will be the flatsawn pieces near the bark as JGS states. if you look, you may find that ripping down the center or "pith line" will yeild two pretty flat peices that won't require much jointing. This works best as you work with cupped boards nearer the center of the tree. the edges will be more quartersawn or riftsawn and as result will be nearly flat.
I have air dried quite a bit of wood (for hobby, not pro) over the last few years, include two cherrybark logs about 23" in diameter. I get a lot of satisfaction out of taking a live tree all the way to furniture. I get others to do the sawmill work, but I'm always there to watch and help. Air drying is a big investment in time and space. but after a few years, you end up with a steady supply ready to work with. Watching the roughsawn peices come out of the planer is like Christmas. The cost sounds real advantageous, but it probably isn't unless you count your effort at zero cost and you have plenty of space for stacks of wood, which I did. But a dollar per board ft is typical. But by the time you add up all the wasted wood due to drying defects and just plain undesirable parts, I have found there is usually 20% waste on average. Cherry, walnut and Oak in that order are well behaved. Cypress is great too and drys quick, but I've only found use for it in outdoor funiture. Sycamore twists badly, and sweetgum is very cool but twists with enormous force. I'm not sure what it would take to keep it flat. I suffered maybe 50% loss on that, but I love the wood.
Anyway, enjoy and good luck. Where in Arkansas? I lived in Jonesboro the past few years but have moved to St. Louis this past summer. Moving the shop and wood was fun. . .not.
Nope, turning will do no good. It's not present differential moisture but past which causes cup and bow. Sapwood started with more than the heartwood, so it loses more volume when drying.
The oft-referenced "inch per year" is valid for 17th century New England and outdoor sheltered storage. If your garage has had the same conditions as your home, your wood's probably good to use. If the house has lower humidity due to air conditioning, bring the boards in, sticker for exchange, and let them accommodate a couple of weeks before planing.
So much for my free advice. These guys know all the answers.
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