laminating purple heart to plywood question?

[Stephen Edwards]

I'm working on a new project and need advice about laminating purple heart to plywood.

The particular piece I'm working on is appx. 11 x 18 inches. Only one side will be exposed. I have glued up two pieces of PH into a rough size of 12 x 20 x 3/4. The glue up is perfectly flat and the glue joint is undetectable. The finished piece of PH will be set into a rabbet or a dado in a "picture frame" so to speak. This will be the background of this piece.

I was considering resawing the PH on the bandsaw into two 1/4 inch thick pieces (then I'd have two pieces, one for a future project). If I decide to go this route and laminate one of the pieces of PH to a piece of 1/2 or 3/4 birch plywood is seasonal movement of the PH apt to be a concern, causing it to split? Keep in mind that the whole thing will be "floating" in a rabbet or a dado so there will be space provided for movement there. My concern is the movement of the PH after it's glued to the birch plywood. What's the best way to glue this PH to the plywood to avoid a future split in the PH?

Thanks for your thoughts and input.

[Doug Shepard]

I'd resaw it thinner so it behaves more like veneer and less like solid wood. 1/8" max, and 1/16" preferably. I personally experienced the effects of laminating plywood and too-thick wood and it aint purty.

[Stephen Edwards]

I'd resaw it thinner so it behaves more like veneer and less like solid wood. 1/8" max, and 1/16" preferably. I personally experienced the effects of laminating plywood and too-thick wood and it aint purty.

Thanks Doug....I had experienced that too. However in my case I hadn't allowed for any movement at all.....a frame glued up on all 4 sides to the plywood with a 3/4 piece of another species glued up to it. You're right, that ain't purty when the solid wood moves! Live and learn!

I haven't done any veneer work before....thin material I mean. Why is less likely to split? Does less thickness = less stress?

[Doug Shepard]

I dunno why it acts like that. There are sure to be those here that probably know the science behind it. I only know that when you glue wood that wants to move to ply that doesn't, it will start speaking to you very loudly when the furnace starts running in the fall. At one point it sounded like an M80 firecracker went off in the house and the result was a very large split in the wood.

[Stephen Edwards]

I reckon I'll just stick to using the solid piece of PH for this project, allowing for seasonal movement, and forget the plywood backing. Thanks again for your input.