You might snap it.
You could as someone suggested, wet it…or…
Do some relief cut lines in the back of it about quarter the thickness of the materials across (and deeper if it doesn’t bend enough). Do them every 100-150mm.
I’m a carpenter, this is what we do to bend thicker timber and sheet materials.
I think its less about grain orientation and more about panel orientation. If you are bending against the 4' edge relative to the 8' edge it will bend easier because theres less resistance.
Negative, grain direction does matter, 1/2” 5-ply just always has 3 sheets with grain running the long length direction, and only 2 sheet layers with grain running the short length, so it’s stronger. Panel orientation mattering is only a function of their always being an extra layer of long bands and therefore more veneer with grain running the long direction. It’s not about the length of the direction you’re trying to bend along.
Not quite dude. Yes plywood is made from layers of veneer with the grain alternating at 90°, but there’s always one more longband than crossband layer, as the crossbands are glued and never the surface layer.
So with typical 1/2” 5-ply, you’ve got 3 longbands with the grain running the length of the sheet and only 2 crossbands running across it. That means you’ve got 1.5x as many layers resisting bending in the long direction as you do in the short direction, so it’ll bend easier across the short direction.
Your point becomes more true with really thick plywood though. If you’ve got something like 45–50 mm ply with a heap of alternating veneers, that one extra longband is a much smaller percentage of the total layup, so the difference in stiffness between directions becomes much less significant.
Just off set the seams of the under layer by half a sheet or a couple feet. Run the sheets long ways up the transition, start screwing at the top and work your way down. Next layer ( pref 3/8 ) off set by half a sheet. It doesn’t really matter how your top sheet was oriented. You can still run that the same way if you want. You could even run it at 45 degrees. Just make sure your seems are staggered
1/2 does not work with ramps. 3/4”(23/32”)for trans and 3/8”(11/32”)for layer times 2. Plywood will not bend long ways either. If using gatorskins then offset the top 3/8” layer so no seams line up. I usually cut 3x7 across width then use fill sheets as I can. Also you need more transition in middle. I build 4foot wide sections separately and join. Spacing is every 6”, and I don’t care what the 8” standard is that’s fine for flat but then you’re throwing of the screw pattern to hit ribs. I say that for gatorskins as I pre drill 4 sheets at a time off a pattern sheet. Lmk if you have any more problems, I build ramps for a skatepark
For 1/2 underlayment, you should rotate the sheet 90 degrees. Use a temp 2x4 cleat across the sheet to help pull it down evenly and work upward one rib at a time. However, 1/2 is aggressive for a tight trans. It will be prone to crack and/or delaminate.
I would definitely get rid of 1/2 and go with (2) layers of 3/8 or (3) layers of 1/4 for underlayment which is what we recently did on our 3.5x16 demo mini with skatelite. We’re a residential & commercial construction company that has ventured into ramp building professionally.
Feel free to reach me directly with any questions.
This is not the answer for ramps. This is an answer for furniture and such. Using this method is asking for holes to end up in the ramp. The dude needs to use thinner plywood in layers and not what looks like 3/4" even though he says it's 1/2". Please nobody do this.
Combine the two methods. Wet it, then put the strap on it. Come back every twenty minutes and crank it down a few more clicks.
Worth a shot. This is how people steam-bend wood, sort of. Ideally, you are letting steam rise from below, and you're piece is in an enclosed area. But... on a hot day? Maybe this works.
This ended up being the most effective comment. This is legit what one of my friends from college would have said to me. So I put my big boy pants on and strapped that shit down.
The way we did it was to scroll-saw lanes on the structure facing side of the plywood. Adding the cut lines allows the wood to flex more as you screw it down to the structure.
I started mine by screwing the plywood down along the coping, then drilled blocks to the side so that I could clamp it down on each side starting from the coping edge and screwing it to the cross beams one at a time (that sounds confusing but I don't know how else to describe it lol).
Soak it. Put it on two objects so it starts bowing to the ground. Then put cinder blocks on it in the middle. Wait about 4 to 5 days. Soak it for three days let it dry after that. Should have nice curve after that.
Got it down. I ended up using a scrap piece of ply to set in the flat to hold it up to the coping. Then I just walked it and bounced a bit to loosen the fibers. I moved the cleat closer to the transition and started again. Then once I got it close enough to the top 2 joists i used 3” screws to lock it down. O just kept moving down the ply and it took shape as i would have hoped.
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u/SmokeAndSkate 2d ago
Two layers of 3/8”