Don Stephan
Posts: 825
Joined: 2003-07-18
Location: Cincinnati, Ohio
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Bob:
I hope lots of people will contribute their thoughts.
When I build a pedestal table, I like to outline of the base to be within ten inches of the outline of the top, so if your top is 8' long and 3' wide, the base would be at least 6'4" long and at least 16" wide. This width seems too narrow, so I'd be more comfortable with a base width of 24". A base 3" thick MDF will be heavy, but I'd still not be comfortable with a smaller base.
Veneering both sides of a surface is recommended because drying adhesive adds stress. However, four layers of 3/4" MDF will be able to resist such stress - I don't think it's necessary to veneer the bottom of the base.
I think I'd first make the curved sides of the top, gluing several layers of 1/4" or 1/8" plywood with a rigid adhesive such as epoxy or urea formaldelyde over a bending form. A cabinet shop supplier will have 10' sheets of MDF. They are very heavy, but you can rip strips and with a pattern router bit make a form.
The cleanest appearance, for joining the base and pedestal to the top, would be to imbed a piece of 3/4" plywood in the torsion box. The easiest way to do this would be to use 3/4" paper honeycomb around the plywood. If you have a sub-top capping your column, you could screw from the underside of the sub-top into the imbedded 3/4" plywood.
In small quantities, resin coated paper honeycomb is only available in 1/2, 3/4, and 1" thicknesses, so you'd have to build up the total thickness in several layers. My understanding of torsion boxes is that the rigidity is strongly related to the total gluing surface. If you use basswood strips 3 1/2" tall with 1/4" skins, you'll only have two gluing surfaces, and I don't know if that would be rigid enough for your use. But it's a big project for a full sized test panel . . .
Don Stephan
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