Plywood DIY questions on glass thickness...

[Chicxulub]

OK guys, I have a quick question for the DIY gurus.

I'm soon going to be getting a 180 as a growout stepping stone for my fish until I (someday) get around to finishing the 510 that I'm working on. Work stalled on that thanks to the logistics of moving that monstrosity if I was to finish it by adding a ~500 pound sheet of glass, among other things, when I get out of the army in a few months.

But, the new 180 has opened up an interesting opportunity for me. I am planning on cannibalizing the glass in my 150 to make a pair of DIY plywood tanks that would be an intermediate step between the 180 and the 510- a pair of 72 x 30 x 30 inch, 280 gallon growouts. My 150 has 1/2" glass. I see no reason why this wouldn't be sufficient to hold the water volume, and the calculators seem to agree. What are the thoughts of the experts on this one?

I would REALLY like to utilize resources I already have in order to get those two tanks for the cost of a few sheets of plywood.

LMK guys, thanks!

 

[David R]

The glass thickness calculations used in most online calculators are based on a standard all-glass aquarium, in which case you'd have a safety factor of 2 with those dimensions and 1/2" glass, which isn't fantastic but still double [in theory] what is needed to support the weight of the water. However, when the glass is supported evenly around its perimeter by a solid frame then I think you would find (and I'm no genius/engineer/mathematician!) that the safety factor would increase for a "window" the same size as the all glass tank.

What are the actual dimensions of the window you'll have with the DIY 280g tanks? How high will the water level be above the bottom of the window?

 

[Chicxulub]

The glass thickness calculations used in most online calculators are based on a standard all-glass aquarium, in which case you'd have a safety factor of 2 with those dimensions and 1/2" glass, which isn't fantastic but still double [in theory] what is needed to support the weight of the water. However, when the glass is supported evenly around its perimeter by a solid frame then I think you would find (and I'm no genius/engineer/mathematician!) that the safety factor would increase for a "window" the same size as the all glass tank.

What are the actual dimensions of the window you'll have with the DIY 280g tanks? How high will the water level be above the bottom of the window?

My plan is to use the entire 72 x 30 inch piece of glass from the 150. The wood part of the tank is going to be fully framed in 3/4" oak cabinet grade plywood with an approximately 66 x 24 inch window in the front piece of wood. This would give me 3" all around the edge of the glass. I plan to run the water to within an inch or so of the top.

The inside of the tank would be fiberglassed, the glass siliconed in place and then the inside would be coated in pond liner.

 

[David R]

Given that you have only 24" height of unsupported glass, and the depth above the bottom of the window will be ~26" I'd say you'll be pelnty safe with that glass thickness. I've seen tanks taller than that built entirely out of glass, so if it is supported by ply around the edge I'd say you're good to go!

 

[Muni]

I built my tank at about the same dimensions and used 1/2" glass. Supported with a full frame it worked great. You can check out my thread for details.

I think mine was 72" x 36" x 30" so you calculate for an approximate water depth of 28" or so. Seems like I was getting 2.7 for my safety factor but I may be mistaken as its been a few years.