[ATM] Break Strength of Glass

["Bob Walker" <tac@i1.net>]

Here's one for all of you structural engineers out there.  I'm thinking of
vacuum flexing a large, thin mirror just for the heck of it.  I did a PLOP
analysis and figured that with a 36" x 3/8" disc of plate glass, about 5 psi
of vacuum would produce about 5 1/5 mm of sag (and sagitta, too), resulting
in an f/10 mirror.  Probably nothing but an ant-burner, but what else am I
going to do with 3/8" glass?  The question, which has resisted all my
efforts to research it via Google, is: can such a piece of glass bend that
much without breaking?  When I built my bridge, I had no trouble finding
tables and equations for beam strength of any species of wood you care to
name, but no dice for glass. As I recall, even Schmidt himself broke a plate
or two with his vacuum pan, but still I'd rather not.

 *  Best regards, Bob
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