On Sat, 22 Jan 2005 16:28:08 -0800, Evan Gatehouse
wrote:

Hi all,

I'm building an 8' x 12' formica toppped mold table.
//

2) I'm thinking of building a "bridge" (for lack of a better word) to
get to the middle of the panel more easily. Any construction hints?
Maybe some 2x8's with ply top and bottom to form a box beam. It has
to span 9'+ and have 220 lbs in the middle.
///
Evan Gatehouse

I made a double take on your bridge suggestion.
I made a strong beam 18 feet long supported either end on perimeter
walls, to support a wide ceiling with screw rod hangers, whose rafters
were sagging a little.

This could easily take me jumping up and down on the middle.
With me aboard, the static deflection was less than 0.45 inch.
It was an upper and lower member of 18 ft X 2 X 4in,
with 1/4 in ply webs of 12in X 18 feet to make a stiff box beam. I
used internal struts ot 2 X 4 X 8.5 in on 2 ft centers.
External dimensions 12 X 4in X 18 ft. The longer cross section was
vertical, of course.

Use two beams like this, with a ply platform between.
Or if you choose another structural plan, put the meat of the
structure vertically spaced as two spars, and use ply just for the
sides as a compression/shear web.....

Brian W
p.s. For table heights, higher is ofter better.... how about waist
high?