Will TS Extension Warp?

I am making an extension wing for a tablsaw using MDF. I gluing Formica to the surface using contact cement. It will be screwed to a frame made of 3/4" x 2 1/2" maple boards. If I don't seal the bottom of the MDF, will it warp? My basement shop keeps pretty dry. I know the MDF will absorb moisture faster on the unsealed bottom making it warp, but the question is, will the frame boards be stiff enough to overcome that tendency?
Thanks,
Bill
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Bill Calbert writes:

I did one like that about 4 years ago. A friend has it now and there has been no warping, 2 different shops, fairly humid area in summer (central VA), neither shop with AC.
Charlie Self "Take care of the luxuries and the necessities will take care of themselves." Dorothy Parker
http://hometown.aol.com/charliediy/myhomepage/business.html
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Seal the edges and both sides. Even if you don't have enough material (Formica) to do the edges and bottom, seal them with poly or some shellac or an enamel paint (use oil primer first though).
Whether the maple boards will keep it from warping is not the question. The frame is to keep the top flat and rigid as a work surface, the Formica or other surface sealant will keep the moisture out so the MDF does not swell and cause the top to distort - especially along the edges.
Bob S.

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I don't know if your top will warp but my Delta extension table warped pretty bad. I am not sure of the exact model of the table but it came with a Unisaw with 50" Biesmeyer fence. It had a pronounce crown where it met the saw. I had to sand the laminate off in a fairly large area get it flat. Now I have to wax the table to insure that wood slides without too much friction.
Bob McBreen - Yarrow Point, WA
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"Bill" wrote ...

Nope. My table saw's side extension is made like that and it's 10 years old and has lived in both dry and very humid locations around the continent. Still flat.
--
Cheers,
Howard
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Howard Ruttan wrote:

I'm on my third extension in 7 years. The first two I made out of particle board. The first I just laminated the top. The second I laminated every side. Both warped. The third one I made out of birch plywood a few months ago. I'm hoping that stays stable. In defense of the particle board, I live in a suburb of New Orleans. It gets a little humid here ;).
Andrew Robinson
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