Flat Material for a "Jupe" Table

Thoughts on flat, stable material for constructing a table with multiple segments and leaves. September 30, 2009

I am making a historical Jupe style table - 8 pie-shaped sections on a round table that simultaneously open for 8 dart shaped leaves. I will not be using MDF. I need the flattest plywood available that supports its own weight (unlike MDF). Honeycomb is not an option - top cannot exceed 1" thick. Baltic birch I've received in the past has been badly bowed. In my research I see all Baltic birch is not the same. Apple ply used to be considered the best, but now it's hard to find. What is the truest/stiffest plywood I can use? Can I veneer directly to it or do I need a 1/4 MDF layer underlayment?

Forum Responses
(Furniture Making Forum)
From contributor R:
Consider bamboo plywood. Very flat and stiff, very consistent in thickness.

From contributor C:
Here in the California Bay Area apple ply is very common. Try plywood and lumber sales (website worth mentioning is earthsource.com). You might be able to get an answer directly from a major plywood and panel manufacturing company such as Columbia. Another interesting thing to look at would be companies that manufacture panels for the aviation industry and NASA such as Paneltech (I think this is one company). Otherwise I agree with the bamboo, as I have worked with too much of it to ever want to see it again. It is very flat, though. I have worked with Kirei brand bamboo and Plyboo. The Plyboo seemed a better quality.

From contributor M:
I believe there is a lumber core sheet with a thin layer of MDF just under the finished veneer. I do not know how it holds under its own weight, but 95% of the sheet is solid wood. Fine Homebuilding or Woodworking had an article on different kinds of sheet goods that ran within the last few years.

From contributor W:
We encountered the same problem when we made a Jupe table last year. We solved it by making our own substrate from 1 piece of 1/2" Truepan sandwiched between 2 pieces of 1/4" finbirch. We laminated up each leaf individually, edged them with solid material (English brown oak) and then cross-banded and face-veneered. A lot of steps but we ended up with 12 perfectly stable leaves that continue to align accurately after being in service for over a year.

Coincidently we are doing some work now using Plyboo and while it is stiff and strong, it seems to have some rather powerful internal tensions that make it bow when cut. I would be nervous using it as a substrate for anything with an irregular shape like a Jupe table leaf.

Roberts Plywood on Long Island sold a 3-ply lumber core veneer substrate that would be good for flat cabinet work but I still would like to find a source for a decent quality 5-ply basswood lumber core panel. There are certain things that are so much easier to make using lumber core plywood with or without veneer. Does anyone know of a source?

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