Thread: Bending Tight Radius in Ply

The only thing that I can think of is to saw grooves to allow the plywood to bend. Even heated, plywood is not going to bend very easily. Maybe it would be better to laminate your own steam bent timber to fit the radius needed.

Originally Posted by rrich

The only thing that I can think of is to saw grooves to allow the plywood to bend. Even heated, plywood is not going to bend very easily. Maybe it would be better to laminate your own steam bent timber to fit the radius needed.

Re the steam bent timber, how would I go about that? I'm using 0.8mm ply so its pretty thin. Would I need to get some ripped down on a table saw and laminate up?

Originally Posted by rrich

The only thing that I can think of is to saw grooves to allow the plywood to bend.

Umm....grooves in 0.8mm ply? You're keen

Normal plywood generally doesn't like bending, but I've never used anything that thin.

My old work had 2 type of 3mm bendy ply; one 3-ply for general work that would comfortably bend around a 100mm radius, and one super-flexy 2-ply that was specially done by Plyco for us which you could pretty much fold in half - it'd take a 10mm radius no problem.

Welcome to the forum Andrew.

Originally Posted by old1955

Welcome to the forum Andrew.

Cheers. I'll post in the intros forum now.

An old boatbuilders' trick was to set fire to some metho poured on the ply. Apparently, this softened the glue and allowed the ply to bend. Heard about it but never done it, so no guarantees, and I suspect they weren't terribly tight bends.

Ply is 0.8mm Birch. Don't know if that makes any difference. Radius is about 6-8mm inside.

If I bend along the grain (so the middle ply is across) and cut the top layer with a knife/bend/fill with PVA while on the bending buck for the top layer (there are 4 sheets at 0.8mm) would that work? What have I got to loose really?

I think the key word there is "old".

If I'm not mistaken, pretty much all plywood now is bonded with thermosetting resins, which don't soften with heat.

Originally Posted by 4xsama

If I bend along the grain (so the middle ply is across) and cut the top layer with a knife/bend/fill with PVA while on the bending buck for the top layer (there are 4 sheets at 0.8mm) would that work? What have I got to loose really?

It's most flexible with the 2 outside layers being across the bend, like this:



Honestly, I don't like your chances on such a tight radius but all you have to lose is a sheet of (rather expensive) ply

Originally Posted by 4xsama

Ply is 0.8mm Birch. Don't know if that makes any difference. Radius is about 6-8mm inside.

If I bend along the grain (so the middle ply is across) and cut the top layer with a knife/bend/fill with PVA while on the bending buck for the top layer (there are 4 sheets at 0.8mm) would that work? What have I got to loose really?

Lee Valley sells 0.8 mm ply which they advize will form to a 38 mm diameter. 6 to 8 mm is too small.

I think you should forget about using ply and investigate other options such as using veneer and laminating.
you might be able to steam (or heat bend) 0.6 mm veneer around your form.

I suggest you protect the form with packaging tape.

Originally Posted by ian

Lee Valley sells 0.8 mm ply which they advize will form to a 38 mm diameter. 6 to 8 mm is too small.

I think you should forget about using ply and investigate other options such as using veneer and laminating.
you might be able to steam (or heat bend) 0.6 mm veneer around your form.

I suggest you protect the form with packaging tape.

Cheers Ian. I'll look into the veneers. I think I'll do a bit of a proof of concept exercise and see if I can laminate some similar thickness cardboard (like construction card). I'll have to soften it up so the packaging tape is a good thought.

Andrew

I've not looked at or done it, something that comes to mind that makes me wonder if a similar approach might help or work is like the Luthiers do with a bending iron to form the sides of say a Violin etc

Hi Mick.

I'l look at that too. You Tubing on the weekend for Luthiers techniques.

Have you got a sketch or image of what you are trying to achieve? I have started building ukuleles this year and as part of the process built a bending iron, I have also used a steam iron from the laundry with great success. Luthiers usually bend timber at or around 2mm thick (or less) and no where as tight as you are proposing to do.
I have a few threads in the musical instrument section of the forum if you wish to see what I have done.