Hi Rupe,
Yes, I like the HDPE food grade plastics and when I mentioned safe FG, I was sort of inferring Structurally safe. As you know, there has been a bit of discussion about what resins, gel coats and the like to use in FG, in this thread in fact.
The acrylic windows I'm putting into my Megabin are 6mm thick food grade Perspex (Used for aquaria etc) and will handle the static head OK. The wall of the Megabin where I am placing the windows, is twin HDPE skins at about 4mm each, no gap. I am not disrupting the structural integrity of the purpose installed wall thickenings or the like. Using SS blind pop rivets at 50mm centres around the perimeter (250 wide x 300 high openings), through a 3mm thick aluminium flat bar as a continuous anti-pull out washer, through the skins of the tank and sealed with Gold Label food grade sealant from the inside, will ensure water tightness. As far as the structural integrity goes, I am also insulating the tank with 75mm thick, double sided, colorbond steel faced EPS panel with a surround angle of 75x50x3mm. This extra reinforcing will allow the megabin sides to be restrained in situ and will negate any loss of "membrane" tension. The top of the tank will also be restrained by a 75x38 Hardwood fitted perimeter batten to fix the top flashing and provide a "hoop" brace for any tank distortion. The base of the tank and the EPS panels will be restrained by a 150x50 HW fender fascia, all fixed with SS bolts and corner brackets. I think I have pretty well allowed for any abnormal stresses that may occur, statically and dynamically, for the tank to be a sturdy solution. Have a look at the section drawing attached. I would be interested in your thoughts.
I have been fiddling and futzing about for 18 months now, and am finally putting the little system together, ready for fish next summer. I will start a thread later when it is up and running to show what I have done.
Cheers IanK
