[quote author=GreshamH link=topic=2013.msg19639#msg19639 date=1177695220]
[quote author=sfsuphysics link=topic=2013.msg19624#msg19624 date=1177680327]
Some might say you'll create a weak point, however I don't buy the idea that an inch or large piece of acrylic can bend in the plane of the acrylic (ie the hard way to bend a piece) under the pressures our tanks are creating unless of course you had a 400watt lamp really close to it. Now it could possible outright snap, but I don't see that happening either due to the acrylic pane that's attached to it, so I wouldn't see any possible deflection.
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Being plexi is elastic IMO and IME your wrong
It starts with crazing, moves into larger cracks, then, BANG, you have a broken tank and a mess to clean up.
I have seen 55g tanks brake from having the rear section made smaller, as well as having the brace cut out. I have seen 55g tanks brake from a whole being cut into the rear (far too fast - created too much heat) for a bulkhead. It took 5 weeks, but it finally did brake. The entire rear panel cracked in half, then delaminated from the glue joints.
Tank manufactureres make the tanks the way they do for a reason. If you ever have then chance to talk to Scott at TruVu, he'll explain it a lot better then I do.
BTW, 20KK lamps are VERY bad for acrylic glue joints and will lead to eventual failure of the glue joint over time.
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Yup, profit motive being what it is, I doubt many tank manufacturers put "extra" material on their tanks. I even try not to drill in the same plane any more than necessary. Good reminder about bulkhead drilling. And it's true that the uv from the lamps will effect the binders in any plastic so I bet it's not just the joints that are getting more brittle. I'd be very reluctant to do what you're proposing, but then again, I live in earthquake country.