SIPS - Structural Insulating Panels and DIY Cheap HoneyComb
SIPS aka (stressed skin panels) are sandwich panels used in the construction industry. They are typically EPS (styrofoam) or rigid polyurethane foam sandwiched between two or OSB (oriented strand board) sheets. For more info check out www.sips.org. Depending on your size and anticipated loads, for a router table you would probably want to use a thick 6+" SIP, and perhaps laminate formica or bond-on a thin steel or aluminum facings to provide some additional structure and moisture resistance. You would also cut/route out foam along the edges of the panel and glue and screw in edge boards. And then there is the DIY foam-in-place option in which you could make a hybrid torsion box / SIP with whatever internal structure you desire.
Now, for the "out-of-the-box" DIY Honeycomb panel using low-cost, readily available, precision formed, lightweight, corrosion resistant, aluminum alloy components for the honeycomb cells. Start saving you beer and soda cans! :cheers: Simply stated..Bond the cans to the bottom skin (or better yet have someone route shallow positioning rings directly into the skin), make a little dam around the bottom skin and then flood it with thin layer of epoxy. Flip the panel over and bond on the other skin. And to maximize strength you could also bond the cans along their contacting edges. For a big panel larger diameter (ie coffee cans) might be more manageable.
I'll be using a more proven traditional construction methods in building my router table, but I thought I would share these thoughts. :)