I'm making a book case for my daughter and she wants a curved top. I have made a form over which to do the bending but I am having a problem with the
1/4" plywood splitting. I can not use 3/4" plywood and make cuts in one side as both the top and bottom with be visible so I decided to laminate 3 pieces of 1/4" plywood. I plan to use polyurethane glue to do the lamination but I need to conquer this splitting problem. I would appreciate any help you can offer.TIA.
Dick Snyder
You should get some bending plywood which has all the plys running in the same direction allowing it to bend easily,
Use bending plywood, and cover it with birch veneer.
What about kerfing the interior sides of the 1/4" plywood? The center piece could be kerfed on one or both sides.
May be kind of dumb, but what about wetting it? Like sheetrock for an arch.
Watch the grain direction of the top sheet. You want to orient the grain so it is perpendicular to the direction of the bend.
Also, try bending plywood for at least the middle of the three layers. You may not like it for exposed surfaces. Doug suggested using three layers of this, and veneer for the exposed surfaces, which IMO is the way to go if you have a way to apply the veneer.
"Dick Snyder" wrote in news:SYSdndyZbsIUA6LYnZ2dnUVZ snipped-for-privacy@comcast.com:
So, why do you _need_ to use the poly glue?
Patriarch
Dick Snyder wrote: I can not use 3/4" plywood and make cuts in one side > as both the top and bottom with be visible so I decided to laminate
3 pieces > of 1/4" plywood. I plan to use polyurethane glue to do the lamination but I > need to conquer this splitting problem.Bending plywood and epoxy.
Poly isn't going to cut it.
Lew
Dick, I'm with Lew about the Epoxy. If not that, I'd go with Titebond II or III before the poly.
Steam, soak, or 'local hot towel' if you want to use the stuff you already have.
Cut your pieces 'over length' by a good bit. Re-make the form with a tighter curve then the finished lamination {to allow for 'springback'}. Soak the pieces - in the bathtub if necessary. {If still not long enough . . . lay out a piece of plastic, put hot-water soaked bath towels on it, lay the strips of ply on the towels and roll them up, wrapping the plastic around all.}
Take out the ply strips, and clamp to form, piece by piece. Either 'square' at one end and let the other 'stairstep', or let both ends 'stairstep'. DO NOT glue and use LOTS of clamps. Let completely dry . . . I'd go at least a week.
When dry, unclamp, apply glue, and re-clamp. After another week, unclamp, sand sides, and trim to square off ends. Do whatever edge treatment you want and trim to final size just before assembly.
Regards & Good Luck, Ron Magen Backyard Boatshop
The problem I think will be that the book case has to be stained to match other furniture in the room that is birch. I'm worried that if I buy bending plywood, it will not match. Thoughts?
Hi Ron,
This seems like it can work. Any particular Epoxy you would recommend? I can get the pieces in a bathtub. I will do as you suggest.
Thanks.
Dick
I didn't read carefully enough before replying a few minutes ago. I see that Boulterplywood has a flexible birch!
How are the splits happpening? Is the plywwod actually cracking or is it delamination? Splitting is a little vague here.
What is the radius of the curve? Perhaps instead of 3 piesces of 1/4" you could try 6 pieces of 1/8" Baltic birch.
I'd follow Ron's advice. I had a question or two on my first bent lamination and his thoughts were right on. As for the wetting I suggested, I know what a piece of ply left out accidentally in the rain looks like!
The wood was splitting in a line parallel to the grain. I am bending with the grain and it was splitting along the grain and not at the lamination. I have gotten lots of great advice from this group (as usual!) and I am going to get some bending birch (it is made using a radial cut so it has a natural bend to it) from Boulter Plywood here in Boston and I am going to use epoxy to do the lamination rather than the polyurethane glue I had planned on using.
Another way to do this is to buy the flexible mdf and cover that with birch veneer.
That, of course will require a veneering vacum bag and pump.....
I would stick with the flexible birch from Boulter.
Glad I could help you...
Dick Snyder wrote:
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