Lenny,
If I were to use 1/4", I'd use a small perimeter flange (aka eurobrace), maybe 1.5" wide to keep deflection down to an absolute minimum. 3/8" could be used without the flange but may bow *a little*. Personally, I'd use 1/2" and not think about a flange at all. At that size, I wouldn't use a crossbrace at all.
Being cast acrylic is not enough IMO, use a good name brand acrylic such as Polycast, Acrylite GP, or Plexi-Glas G. If someone tells you they have the "equivalent", don't buy it, again IMO, it should *only* be one of these brands. Look in your local yellow pages in the plastics section to see who sells acrylic sheets in your area, there should be a section that reads "plastics, distributors, sheet, rod, tube" or something to this effect, or possibly glass shops as some carry acrylic. There may be some online vendors as well, I don't use them so can't make recommendations in this regard.
HTH,
James
If I were to use 1/4", I'd use a small perimeter flange (aka eurobrace), maybe 1.5" wide to keep deflection down to an absolute minimum. 3/8" could be used without the flange but may bow *a little*. Personally, I'd use 1/2" and not think about a flange at all. At that size, I wouldn't use a crossbrace at all.
Being cast acrylic is not enough IMO, use a good name brand acrylic such as Polycast, Acrylite GP, or Plexi-Glas G. If someone tells you they have the "equivalent", don't buy it, again IMO, it should *only* be one of these brands. Look in your local yellow pages in the plastics section to see who sells acrylic sheets in your area, there should be a section that reads "plastics, distributors, sheet, rod, tube" or something to this effect, or possibly glass shops as some carry acrylic. There may be some online vendors as well, I don't use them so can't make recommendations in this regard.
HTH,
James