Replies

1. 
   JohnWW | May 03, 2010 04:36pm | #1

   For the Ladies

   1/4" plywood will be strong enough, though a bit flexible, birch plywood only be marginally stiffer than luan or DF.  The best way to stiffen the top with minimum weight would be to make a pair of diagonal crosspieces from something like 1/2" by 2" pine.

2. 
   PSeverin | May 03, 2010 06:48pm | #2

   How about a hollow core door.

   If weight and stiffness are your concern, why not use part of a hollow core door.   You can buy them as seconds from some lumber yards for practically nothing, cut them to the size you need and insert a new edge board after clearing a path through the cardboard spacers.   I've made bookshelf standards, desk tops and even a conference table from hollow core doors.  

   But as I think about your question I realize it will probably be difficult to find a door quite wide enough.  Still you could make one.  I learned to call these things stressed skin structures, which seems a better term than torsion box.  Anyway, whatever you call them the doors have probably 3/16 or 1/8" thick skins held apart with corrugated cardboard spacers and a wood edge frame.  I wonder if anyone has tried gluing two sheets of plywood glued either side of rigid insulation and using it as the spacer.  All that stuff in the middle other than holding the sheets a constant distance apart is relatively inconsequential structurally...  So if weight and stiffness is a concern, do less with more and use a given material in its most efficient manner.  

   Peter

3. 
   DonStephan | May 03, 2010 07:32pm | #3

   Assuming the leather will be glued, there may be tremendous pull on the surface causing it to curl up.  Depending on the glue, even applying the leather to one side of 3/4" ply would probably result in curling.

   My expectation is that the card players would find a 33" square of 1/4" material flimsy and "tinny."  The material would constantly be flexing, which would constantly weaken the attachment to the cherry edging.

   My suggestion is to make a 3/4" torsion box, and ideally apply leather to both sides so any stresses are balanced.  You could try to use styrofoam for the core, but the stiffness of the torsion box, as I understand it, is determined primarily by the strength and surface area of the glue bond between the skins and the core.  Not sure how firmly any adhesive would bond ply and foam, and produce a smooth flat surface.