I am getting close to the benchwork construction phase and am considering plywood as the material to be used vs. 3/4" lumber. At the local building supply store they have 3/4" AC cabinet grade plywood at a price that is lower than the BCX grade plywood. The AC stuff has at least 9 plies( so many that is is hard to count ) against the BCX which has 5 plies. The AC looks great but I have the concern that there may be issues with that I don’t know about. Any voices of experience want to weigh in on this. The lumber is price competetive with the AC plywood.
AC is good quality. I wouldn’t hesitate to use it.
It depends on how big your tables are. I use 1/4" good quality plywood on my layout, braced with 1 x 2 or 1 x 4 stock to keep the surface from sagging.
If you’ve got a long distance between supports, even 3/4" plywood will sag. Also, 3/4" sheets of 4 x 8 plywood are a real bear to move around.
Why plywood instead of 2" foam? Unless you are going to rip it and use in 3" or 4" strips. Then the only issue is that Ply wood spits a little easier than solid pine when you screw into the plys. It takes great care either way.
GO with the Cabinet grade 3/4"
I use 3/4" (strong) cabinet grade (less warp) Birch ply, and @ $35 sheet it’s still cheaper than anything else you will put on that layout. My Biggest carpentry problem is getting uniformitry at the joint’s where two different sheet’s join and ‘warpage’ show’s up. I’ve planed and sanded my A** off, trying to correct.
On a 4X8 (single piece) layout most ‘warpage’ is uniform, so greater STREGNTH becomes more beneficial. SOTA* layout’s today add foam to the TOP of good ply., to carve reaistic topography such as stream bank’s, and culvert’s , and even canyon’s - with thicker foam. Beginner’s generally dont think if that.
*SOTA -State Of The Art.
3/4 inch is a bit beefy, but stronger, having joint problems if you have peices end for end or side to side becomes a problem with using mid grade plywood. To prevent the crack from growing or pushing at there ends, use construction adhesive and nail the plywood with ring shank nails, I learned this years ago being a self employed contactor. OSI makes PL400 and PL100 grade adhesive that comes in a caulk type tube. I used the same treatment on my layout and sanded the joints and put joint compound on the joints, so they hade held great over the past 3 years. To prevent sagging I built everything 12 inch on center, cost more but it might be worth the extra wood for support.
I used 5/8" GIS and have it supported with three pony walls 36" apart. Zero sag eight months later.
There is one possible pitfall with cabinet-grade plywood - the facing plies are so thin that they might not provide a good solid bond if someting is glued to them (the top ply will separate, splintering from the lower layers, especially if you are working at a cut edge). At least that’s my limited experience. But I used the same tools I use on BC plywood - same coarse table saw blade, circular saw blade, and sabre saw.
Is there a secret to avoiding this splintering?
Use the ply only as support and build on the foam. Or add a few braces and eliminate the ply altogether. Ply has its problems and the don’t go away. If there are humidity issues, the problems can be impossible. We used to use ply because there was no foam. I used ply in the cookie cutter sections but have foam road bed on top, and I contol the humidity with great effort. As I add things they will be on foam.
One thing to keep in mind: I saw the cheap cabinet grade plywood last week at my local Home Depot. It was stamped “made in China” all over the place. I have no idea about the quality of Chinese plywood, but I’d experiment with a piece before sinking a lot of money into the product in bulk.
9-ply is good, but I’ve been wondering about using MDF instead of plywood, just because of it’s ridgity, and there’s no risk of splitting or splintering. It drills clean and cuts smooth too.
Greg
Ten minutes working MDF was enough to convince me I never wanted the stuff near my tools again. Unfortunately the butler’s pantry I was making out of it took 15 hours to complete. Talk about a mess. Extremely fine grained sawdust that sticks to everything like glue, packing every nook and cranny of every tool that got near it, so dense that cutting a straight line required the sharpest of blades, and they didn’t stay sharp in that mess very long.
If I was starting benchwork all over again, I’d build L girder open frame benchwork only for the places where I needed below ballast grade terrain, and the rest would be standard framing with plywood decking. I’d use half inch plywood for the roadbed, and cork on top for noise reduction, and I wouldn’t hesitate to use plywood for the structural members in the L girder construction. Delaminate? Only if your layout’s outside, in the basement, or in a garage. It can delaminate all it wants and won’t put bumps in half inch plywood roadbed. If you’re worried about the half inch roadbed itself delaminating, finish it. All your kitchen cabinets are made of AC plywood, and they don’t come apart often.
There’s no need for open benchwork unless you have need for below rail terrain planned. Elsewhere, save the time and effort, lay the slabs of plywood, and use the extra time where it will do you some good. Don’t use luan, it isn’t quite strong enough, and the thickness varies too much from manufacturer to manufacturer. Get all your half inch at one time, so any variances in thickness won’t affect you.
I use 3/4" AC plywood ripped to 3 1/2" instead of 1x4s for benchwork. (I have a woodshop and can do this easily). Given the quality of 1x at the local HD, I’ll never go back. The trick to using plywood is to use glue and an air nailer (not screws) to hold the joints together.
Nick
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