I think that level is not as important as flat.
An out of level condition can change the pressures on the glass by only a little bit. A stand that is not flat will cause the tank to have to distort to conform to the stand causing strain on the glass. Did the crack start near a corner and propagate toward the center of a face? I think that's caused by twisting the tank some way. I made a scale model of my tank out of paper to demontrate this. Twisting causes two planes to put a shear on the third plane. Try it. I think a bowed base would cause a horizontal crack in the center of a face.
Also, 1/8 inch on one end and 1/16 non the other implies a twist. Check the top of the base with a six foot straight edge (not necessarily a level). I can let you borrow an 8 foot long 1 inch square aluminum extrusion that's pretty straight. PM me if you want.
I went through this. I'm on my third 240. The first was an obvious manufacturers defect. The second, I think I cracked with my base being twisted, maybe .03 inches (half of your 1/16 inch). I replaced the cracked panel and reworked the base and everything seems to be fine, so far. Yes I used 3/4 inch foam on each attempt.
Good luck,
Jack
Jack
Last edited by rocketeer; Sat, 12th Apr 2008 at 02:49 PM.
Big whorls have little whorls, Which feed on their velocity;
And little whorls have lesser whorls, And so on to viscosity
Lewis Richardson in 1922
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