I am building a modular L-shaped layout, and altho my thread in the Layout design forum has taught me much, I ran into a problem last night. The modules I am building are 18x48", 1x4 frames, and 1/2"OSB screwed/ glued w/ liquid nails. I have a problem, tho. I ran into a few that had cupped wood, so when I screwed/glued them together, they are warped. As in, the won't sit flush on all 4 corners on the sawhorses. The other ones do. Can I internally diagonally brace it to get it plumb? The plywood didn't plumb it up enough. It is glued, and screwed to the frame. Any ideas anyone? I hate to tear them up, and rebuild a few more to replace the ones I screwed up...
Not a rare problem. It would be difficult to fix if glued. One method would be to place it on a level surface and add weight to the module. Concrete blocks would propbably do. You would have to leave it thatt way for a week or two. Best thing to do is check your wood beforehand and never glue modules (screws are sufficient unless you want to throw them around) Be sure to seal the wood from moisture.
If you have NOT sealed the wood yet, you can wet the wood good with a garden hose, then lay blocks and slats of 1x4 or 2x4 on your driveway, then stack the blocks or bricks on. Watch and stack until the wood begins to bow down flat. (It does not have to go all the way right now, you might break a glue joint loose.) Add weight as needed over the next day or so until the wood relaxes flat. Because it is too large to steam it, you may have to add water over a day or so to get it soaked enough to warp back. The air can circulate all around because of the slats. Leave it until dry. I have had to wait a month or more sometimes. If you did NOT use Marine grade water proof plywood and, If you can NOT remove the plywood top, it may start separating the plies. They "can" be re-glued and clamped down flat again later, but it is a JOB to get any kind of nice looking surface, like on desks and shelves. (It may not matter so much on the layout.) The ground is not flat, so just glue the edges and clamp it. Make certain the plywood is dry first though. Go to a hardware store and buy a large hypo shringe, and the longest glue needle they have, about a BX-4 size. Try to get 3 to 5" long. If you have to get one from a drug store, besude to grind the point off, and clean the burrs out of the bore. A Vetinary supply will have some huge ones! They are good for all sorts of things when doing scenery too. Just wash the glue out each time you stop! (Take it apart, needle off, and store it under water in a pan until you are finished with this job, then clean it GOOD!) Stand the edge up you are to work on so the 'leaves' of the plies open up vertically to let gravity help the glue to go deep. Start about the middle of that side and work out to the corner. Start with the gap closest to the 1x4 frame, and work out to the surface. Place your "C" clamps on 1x4 blocks to spread out the clamping area. Position the clamp so the solid jaw is on the frame edge and the screw jaw is on the block. When you tighten, allow the glue to squeeze out and just wipe it off. Leave this a couple of days before removing clamps, unless you are using Gorilla (Polyurethene) quick setting glue. For up to 3/4" plywood, plan on using 4 clamps per foot. Buy good clamps, Jorgensen, Pony, Proto, even Buffalo, but not cheapo sheat metal ones. You will need some serious pressure here. Slip a screwdriver down in to open the crack but not break the wood. Slip another in about four inches away. Place the needle down in the crack as far as you can and run a bead of about 1/8" diameter glue along the bottom. Use a scrap piece of sheet metal, or plastic to push the glue farther down into the crack. Do not worry about the sides, when you start clamping, the glue will paint the sides on the way up. It does not take any more glue film than they had to begin with, see? Yellow wood glue will work OK. Yes you can glue all the layers at one time if the glue does not set up before you get the clamps on, so only work an area one foot long max at a time. Yes it is a job, but worth the effort on furniture and cabinetwork. You will have to judge if it is worth it on the modules. Email me if you try a corner and have any trouble.
I thought of that, and I used Liquid nails to glue the joints, and used 3 #6x1 5/8" screws to hold everything on. The 1/2" OSB top is glued, and screwed the same way. Would the water/blocks method work?
I used Liquid Nails once and got violently sick from the fuems. (I can't work with Liquid Polyurethanes because the catalyst is Polyisocynnate, a cyannide derivative I am sensative to.) As I recall, it is slightly flexible, so probably wont break the bond. I think it will "give" a little so the wood can warp back straight ok. However, I am not so sure you can salvage the oriented strand board as easily. It will come apart if wet for a couple of hours or so, unless you got a water-proof type. I told you how to repair it if the edges do delaminate. It is a job to do. Sorry. You may just have to saw down to the plywood in several places, lay the plywood down flat, then fasten cleats over the cuts inside to hold the structure flat. Let the wood stay warped, and glue the cleats to hold shape. Do this dry without any water.
