How big with 1/4" Glass?

[Fluxion]

I have two pieces of glass laying around the shop that are 32"x74"x1/4"

I would like to build a tank but I am unsure of the maximum size for 1/4 glass. I tried the calculator on GARF and after playing around I came up with 18x18x48. I was wondering if it would be safe to change the dimensions to something like 18"x24"x48" if I was to weld up a steel frame to for the top of the tank which would be hidden by the canopy.

[Ghoti]

It's the height of the glass that is the critical factor. I believe a height of 18" or 19" is the maximum for 1/4" glass. GARF explains this somewhere. You can use all 72" in length but it will require cross braces. It is the weight of the water from top to bottom pushing out on the glass that will cause the glass to fail if you go too high.

[DeFeKt]

as soon as you get to 24" high you need 3/8 or more.

[Fluxion]

So do you guys think that 20" tall is feasable? I have another question, in the instructions from the GARF website it says to space the bottom up 1/4". Is this the best way to do this? I understand why you need to support the tank from the sides but will the silicone joint support 700-800 pounds of rock, sand and water?

Thanks for all the help. I love this place!

[bigsky]

my tank is 48x24x24 but is only filled to 22" deep and has been up for 3years 8 months with no problems. It is made of .25" glass and silicone only and the only bracing is around the top just inside and is 1.5" strip of .25 glass siliconed to front and rear panes and both ends with one across the middle making 2-2ft squares.

plate glass has a tensil strength of 10k psi so keep the tensil stress below 5k psi simply supported on all edges and you'll be floating your boat with a happy 100% safety margin.

build the tank with the bottom lying flat and the back glued onto the bottom then the two ends and then the front and then the bracing around the inside top. when I'm done with that I clean it all up and then run a fat bead of silicone alone each joint dressing them with a spoon creating a perfectly smooth curved wide seam. make sure glass is extremely clean with alchahol and dry.

when you put it on you stand, I put a 3/4" plywood panel ontop of the stand and then a layer of 1/2" closed cell foam them the tank. the foam (like a bed roll for camping) will not crush all the way and absourb any minute warpage and lumpiness and vibrations coming from the floor.

[DeFeKt]

in the instructions from the GARF website it says to space the bottom up 1/4".

personally i dont like that idea, like you said,
a 48x18x20 will hold around 250L of water, being 250kgs
800lbs of rock is around 360kgs
not to mention sand bead, driftwood and whatever other stuff you put into it..
ultimatly thats a 1/4" piece of glass supporting 3/4 a tonne of weight..
There is no way in heck i'd have that in my house, especially running off a 6 outlet power board which will be either directly underneath it or next to it..
Personally I don't like the garf standards they use, I don't think they thought about it very well.
Even the stand they descrive has the potential to warp twist, and crack or shatter the tank.
I'd recommend people stay away from GARF, but thats my personal opinion mate..
[acronym:3ee07e2ad6="Hope this helps (or) Happy to help"]HTH[/acronym:3ee07e2ad6]

[JProx]

garf isn't that bad, i agree their aquarium building is a little lackluster, and i probably wouldn't trust it completely, their stand design is perfect though. i have built one about 2.5yrs ago, and have had it in use just as long and nothing has warped, twisted, etc and i have never heard anyone on the forum complaining about a garf stand failing.

warping is a defect caused by humidty and excess water being present as well as how the board was cut to begin with at the mill. if the right wood is picked out, and the stand is built and coated to resist water you will never have problems.

[greenmaji]

the idea behind the gap.. well commersial tanks have it with trim or just like garfs design.. and the reason is the glass has to have room to flex on the bottom..
when someone is having trouble with there all glass tank in posts on the internet.. well they didnt put the gap under the bottom glass... just a thought..

[bigsky]

You don't want the bottom of your tank to flex that is how they break.

build your tank with the bottom down flat and all the sides glued on top.
just besure to put a sheet of 3/4" plywood down and then a sheet of cork or styrofoam or closed cell foam down for your tank to sit on.

I use a 1/2" thick sheet of military bed roll it is dense closed cell foam.
the foam sheet is there to absorb and irregularities in your stand or spec of sand that might have gotten under the tank or any vibrations that come up from the floor.

I have build three tanks this way and have never had a problem even after moving from one house to another (I only have one in my possesion now and the other two are at my parents house).

I have a british book that talks about building a fish tank and it says that you should not build any thank with just glass and silicone bigger than 500 liters (about 125 gals.) and my calculator says not to go deeper than 22" with 1/4" plate to maintain a 100% safety margin (5,000 psi tinsel stress-plate glass rated at 10,000 psi tensel strength) I got this info and formulas from a mechanical engineer's handbook.

[bigsky]

oh yeah, that gap on the commercial tanks is there to replace the foam sheet.
the glass is raised so irregularities of your stand don't interfere with the bottom glass but it is supported by all edges with the frame were as Garf's are not. I would not trust garf's design either.