Particle board / plywood desktop


I'm building a desktop that will have about an 8" overhang on the front as well as an unsupported span of about 30" in the kneehole area. The material for the desktop is 3/4" quartersawn white oak plywood. I considered a torsion box (per Niall Barrett's Desk book) but am afraid that the desktop will become too thick. I'm considering laminating the 3/4" plywood to some 3/4" particleboard then banding the edges with some 5/4 stock bicuited into the sides. But something makes me think this is a bad idea. I fear the plywood and particleboard, while both pretty stable, may nonetheless react a bit differently and cause me some problems down the line.
I've scoured the net and this board but haven't found anything quite on point. Has anyone tried this successfully? Would laminating the bottom with 1/4" plywood be good insurance against warpage? I'd really like to keep the thickness around 1 1/2" if possible.
Thanks,
Steve Polaski
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On Mon, 30 Jan 2006 15:51:58 -0800, polaski.steve wrote:

Steve,
I've successfully made torsion box tabletops of about 1 1/4" thick using 1/4 inch material. I also made a platform bed using 1/2" plywood with 1 1/2" webbing (pretty beefy). You could use 1/2" material for the tops and bottoms with 3/4" material for the web. I've successfully used foam insulation as the core material. Just an idea.
DGA
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snipped-for-privacy@gmail.com wrote:

All you need is the 3/4" plywood for the top. Put 3/4" x 1-1/2 squirt, band, edge or whatever you call it all the way around. And you don't need the biscuits. Don't know what your fear of the banding is unless you make a 10 foot desk. There should be no warpage if you make sure you add finish to all surfaces. I made a desk with a similar top about 30"x48" in 1974. No problems yet.
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Real problem will be keeping your pen from digging in to a plywood top. Use a blotter.
If you want reinforcement, make it part of your design. Rabbet and drop an inch and a half of solid 3/4 stock all around, with perhaps a couple of fully glued lengths of three quarter longitudinally where you won't see them.
Other, and better technique to my thinking is to laminate a 1" piece to a 1 3/4" piece of 3/4 oak stock (other piece need not be oak) to use as edging so you can have a good 5/8 or even 3/4 radius roundover to keep from marking your forearms.
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Exactly. Make it more like a funky H-beam than a slab. Ditto that on pen digging in, unless OP goes for some close-grained hardwood-laminated ply.
J
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Just to close the loop on this. I built the top with 1 1/2" thick 5/4 stock around the edges of the plywood. The desktop came out plenty stiff. My concern was the overhang but I can barely get it to flex even putting my 230 pound frame on it. I put 5 coats of poly on the top so it should hold up as long as my kids don't attack it.
Thanks again everyone,
Steve
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You will do fine leaving out the particle board.
--
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Thank you all so much for your replies. I think I'll take Swingman's and George Cawthon's advice and skip the particleboard substrate. Since the desk is in my own house, I can always go back later and stiffen if should it not work out.
And per George's "Real problem will be keeping your pen from digging in to a plywood top. Use a blotter. "
Absolutely.
Thanks again everyone - your input is very much appreciated.
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