Trouble with veneering thin plywood

[Jack Ganssle]

Folks,

I'm making a cocobolo box about a foot square. The top and bottom - being a foot across - can't be solid wood and the configuration doesn't allow for a floating panel. So I want to cut thin (like 3/16") strips of cocobolo, then glue them over 1/8" plywood, both sides. That makes a plywood sandwhich which, I hope, will be stable.

My cocobolo boards are 5" wide, so I need to glue three strips side by side over the ply. But everytime I do this, the layup gets slightly bent by the clamps and other forces, which makes the cocobolo strips separate from each other. That leaves a tiny but, to me, unacceptable break in the glue line. It looks a bit shoddy especially since the pieces are bookmatched.

Any ideas of a better approach? Am I missing something?

Thanks,
Jack

[Scott Mann]

Try gluing the 1/8" strips together first, then lay it down on your substrate. This has worked for me.

[Mike Henderson]

To follow up on what Scott said, lay your strips side by side and tape them together with blue painter's tape. When you put the tape on, try to stretch it slightly so the pieces are pulled together. Finally, run a strip of blue tape all along the joint.

Then turn the pieces over. Raise the joint and put some glue on the edges. Now, put a strip of blue tape on this side along the joint. Then just put something on top of it to hold it flat 'til the glue dries. The reason for the strips of blue tape is so that the pieces don't get glued to the surfaces you use to hold them flat (like your benchtop and a heavy chunk of wood). They also help to keep the glue off the front surfaces of the wood.

When the glue is dry, scrape or sand to make sure it's flat, then glue like a single piece of wood.

Mike

[John Lucas]

Yes to Mikes instructions but an add: remove the blue tape from the side that you will be gluing down to the substrate (1/8" ply). Tear off as much as you can and scrape the rest.

[Mike Henderson]

Yes to Mikes instructions but an add: remove the blue tape from the side that you will be gluing down to the substrate (1/8" ply). Tear off as much as you can and scrape the rest.
Ah, you're right. I forgot to mention that step! Just assumed he'd know that. But better to be specific.

Mike

[Jack Ganssle]

Thanks, folks. I'll give it a try.

[Frank Drew]

Jack,

You might also examine the method you use to glue your veneer assembly to the substrate; if the panel isn't perfectly flat during glueup, it won't be flat once the glue dries. Do you know anyone with a veneer press, vacuum or otherwise? If not, you'll have to take care to apply enough even pressure all across the panel to ensure good adhesion, while at the same time keeping everything flat in all directions.

[Jesse Cloud]

Agree with Mike's advice. Are you using a vacuum press? If not, what are you using to apply even pressure on the veneer?

If you are not applying veneer to both sides of the ply at once, there's the culprit.

Be sure to apply the veneer so that the grain is 90 degrees to the grain of the top ply.

Hate to say this, but even with all the cautions above, I'm not sure your product will be stable. 3/16 will move with change in humidity (and as the glue dries).

[john bateman]

It seems a leap of faith that this sandwich is any more stable than just edge gluing your boards and planing to the desired thickness.

Maybe just get some real veneer and apply it to a thicker plywood substrate.

[Brad Shipton]

Veeners 3/16" thick. I agree with John and Jesse that this might be a bit of leap of faith that the resulting sandwich is more stable.

Before switching to a vacuum press I was making stave core door stiles with clamps and my biggest problem seemed to be getting all the clamps in place and tightened equally without the veneers shifting. At that time I was using 3/16" thick veneers and since working with the thin veneers I have found they are less likely to float around.

Another option is to glue the 3/16" sheets prior to applying to the substrate. Clamps to hold them to a flat surface and a few Besse's to hold them togther. I have done this before. You might want to use a glue that sets up pretty quick to avoid the glue absorbing into the veneer sheet as it is clamped to the surface.

Brad