large tank construction

[zkt]

I posted this in another forum and it didnt get vary far, hopefully this is a better place. I have 2 insulated glass panels. They are each about 36x80x1 and consist of (2) 1/4 inch tempered glass panels seperated by an air space. Tempered glass is about 4 to 6 times stronger than regular glass. According to the chart I saw somewhere a tank this size should be made of 20 mm thick glass. I`m thinking that with 3 verticle supports spaced along the length and banded along the top and bottom it would be just fine. Does anyone have any experience with this sort of thing?

 

[Anonymous]

I don't have any experience building large tanks. But I do know that 1/4" glass is pretty far from 20mm. You need the extra thickness to compensate for the extra pressure from that much water.

I would think you would need to brace it every foot or so, and that would look pretty bad imo.

B

 

[zkt]

Yea for sure, every foot would mess up the view so much it wouldnt be worth doing. But I could live with one from top to bottom at the center and equidistantly form each. Basically its looking like a framework around the top and bottom, all 4 corner edges and 3 along each face. The largest unsupported space would be about 3Vx2.5H.I think 1/4 tempered would gp that far.
1/4x1/2 inch steel wouldnt be too hard to cut out and weld up and would be the least noticeable.
See:http://saltaquarium.about.com/cs/aquariumdiy/l/blcustomtank.htm

 

[Anonymous]

Temper glass is more difficult to work with, e.g., when you need to cut or drill it. You are planning to use one of the two panel that contains two pieces? Or you are going to use all four pieces and make the tank out of them entirely?

I feel it is a waste to use a insulated glass for aquarium, unless it will be smashed and dumped as landfill.

1/4 inch is too thin without supports. Not too sure about the claim that tampered is 6X stronger. It is probably for busting strength or something. You need to read the "stronger" metric very carefully.

Personally, I would go for a smaller tank if I have no better use for the glass. Again, tempered glass is very difficult to work with unless it is pre-cut to exact dimension.

 

[zkt]

Yea, since double pane glass isnt any stronger than single pane it makes sense to take it apart. A piece weighs about 200 lbs. anyway. Then make the front and back out of the 2 pieces and cut the ends from 1/4 plain old plate annealed. I think it would be a lot simpler in the long run to sit the glass on a fiberglassed plywood base rather than make the bottom out of glass. I just measured the panels ; seems they`re actually 83x40. I wondering now if a single verticle support at the center wouldnt do it . The problems involved in cutting and drilling tempered glass shouldnt be a problem since I`m building the whole thing built to fit the glass. One nice thing about tempered glass is that if it does fail, it breaks into small relatively harmless pieces rather than long sharp shards. Did a little more reading an it seems that fully tempered glasss has about 4 times the strength as the same size ordinary (annealed) glass. Just which parameter theyre talking about is still somewhat of a mystery. I think its sheer strength- which is what important here. So then, tempered would support 4 times the weight of water as untempered. But how to translate that into thickness substitution for a given size is another story all together. I vaguly remember from calculus a million years ago determining the force of a quanity of water in the face of a dam wall. But i`m afraid the details escape me. Any civil engineers out there ?

 

[zkt]

Google hit the jackpot !
How to calculate glass thickness for any size tank:
Anyone who even Thinks about building a tank should read this.
http://www.fnzas.org.nz/articles/technical/glass_complete/
I crunched the numbers using the tensile strength of heat treated glass. Heat treating , as I understand it, increases the tensile strength also- but not as much as full tempering. So I`m probably using a lower than actual strength figure. Anyway, for a 40x83 tank with a safety factor of 2 the thickness comes out to be 6.43 mm. I checked the actual thickness of the pieces and theyre 5.56 mm. Solving the equation for the safety factor gives a safety factor of 1.7 . With no bracing. I can live with that alrite.
There is another calculation for maximum deflection which i havent done yet. That`ll prolly put the brace back in the center.
If anyone could check my calculations sure would appreciate it.