Replace 12mm Glass bottom from 4ft tank with GRP?

[Agouti]

I have a 4ftx2ft Reefsys 326 tank which has had the base crack during transport. It looks like it cracked from one of the through holes. I believe the factory glass is 12mm thick.

Is replacing the 12mm untempered glass with fibreglass and option to save weight and add some impact resistance? Napkin math says it will come out at about the same cost compared with getting the piece made up by a glass shop.

I have experience with hand layup and vacuum infusion of fibreglass and carbon fibre, including marine structural, so I am confident I can lay it correctly, but I'm not sure about how thick it should be or if there are any other issues with mixing glass and GRP panels in the design.

Structural glass fibre (biaxial, not chopped strand) is stiffer than float glass but a lot is lost in the resin. Good lean 70% unwoven cloth/30% epoxy has about 2/3rds elastic modulus of float glass, I believe, which suggests something like 9mm marine ply with 6x600g biaxial cloth each side would be about right?

I'm also not sure the best way to tie it into the glass sides, I assume building it separately and then silicone in would be preferable to epoxying in in case a side panel needs to be replaced?


Or am I just making extra work for no reason, and should just replace like for like and be more careful if I move it again?

 

[threebuoys]

If it's a crack and not the actual loss of glass, what's the possibility of just laying a fiberglass mat on top of the existing bottom rather than removing the bottom? Perhaps the strength of the glass is still there, but just not water tight?