Flattening Bowed Plywood?
Issue: Issue 358
Posted Date: 8/18/2014
After cutting 3/4" plywood and storing it for a chest, when I was ready to work it, the pieces had a bow lengthwise. Is there a procedure I can use to remove it? - Joeseph Labrie
Tim Inman: You can try storing the pieces lying flat, possibly weighted. Is the plywood veneer cored or solid wood cored? Solid wood cored plywood is more prone to distortion. Either way, I'm guessing that if you can pull the pieces into place when you assemble your chest, you'll be good to go. Be sure your plywood can have air circulation both above and below the wood if you try flattening before you assemble. Your plywood will have a bit of a memory, and will want to return to the flat condition it was in when you started.
Chris Marshall: If you have the space for it, lay the warped pieces down horizontally on several spacers with their bows oriented convex-side up so air can circulate all around each piece. There’s a chance this bow may have developed because humidity absorbed into one face of the plywood more than the other, and it warped. You could weigh the top of the panels down with illed, 5-gallon buckets, sand bags or bricks to help speed the flattening process along, too. Even if the components don’t flatten out completely, it may not be that big of a deal in the end. They may flatten out just by fastening to the other carcass components or to one another. Good luck with the project!