Cantilevered Tank

[YHSublime]

Hey WAMAS!

 

Not looking for any guarantees here, but want to know if my suspicions are alright. 

 

If I took a 3' tank and placed it 4-5" off the side, but it was fully supported on all other sides (3 of them) would I need to be concerned? I'm guessing it should be fine.

 

Thoughts? Do I need more information? 

[dpassar12]

Glass or Acrylic tank?

[YHSublime]

1 minute ago, dpassar12 said:

Glass or Acrylic tank?

 

Glass

[dpassar12]

I think you would be ok with glass, just my opinion. Acrylic no. 

[YHSublime]

4 minutes ago, dpassar12 said:

I think you would be ok with glass, just my opinion. Acrylic no. 

 

I agree. Do you think it would help if it was eurobraced?

[epleeds]

Upgrade??

[epleeds]

And I would brace the inside of the tank as well. My custom builds all are braced on the inside of the tank. Similar to a eurobrace for the inside. 

[YHSublime]

8 minutes ago, epleeds said:

Upgrade??

 

Nothing crazy, but exploring. 

[Origami]

I'm having trouble with this. Are you saying that you want a 3-foot glass tank to extend 4-6 inches out into open space without support underneath? My guess would be there would be stresses that ultimately opens the bottom seam, creating a leak. Heck, I had an old 55 that I was using as a frag tank that leaked after a few years of being on one of those really heavy duty shelves. The shelf sagged less than a quarter inch and eventually opened up a small leak. When I reinforced the shelf, pulling it back up, the leak was sealed. 

[YHSublime]

25 minutes ago, Origami said:

I'm having trouble with this. Are you saying that you want a 3-foot glass tank to extend 4-6 inches out into open space without support underneath? My guess would be there would be stresses that ultimately opens the bottom seam, creating a leak. Heck, I had an old 55 that I was using as a frag tank that leaked after a few years of being on one of those really heavy duty shelves. The shelf sagged less than a quarter inch and eventually opened up a small leak. When I reinforced the shelf, pulling it back up, the leak was sealed. 

 

Here is a terrible exaggerated drawing to illustrate what I’m curious about!

 

 

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[flooddc]

I have seen someone with a 55G (4 feet) sat on a 3 feet stand. but that just a disaster waiting to happen. Could you build a well support platform that stick out 4-6" and place the tank on that instead? 

[YHSublime]

10 minutes ago, flooddc said:

I have seen someone with a 55G (4 feet) sat on a 3 feet stand. but that just a disaster waiting to happen. Could you build a well support platform that stick out 4-6" and place the tank on that instead? 

 

Honestly, I don't think I'll have to, have about 4.5" of wiggle room, but wanted to lay out a "what if" scenario. Like, would .5" make a big deal? 2"? Or is anything over one out of the 4 edges probably not OK.

 

[Origami]

The glass tank has a frame that shifts the load to the outside edges. So, by hanging it over the edge like that, you introduce a sagging load that runs parallel to the table edge. That sag will tend to pull the bottom away from the parallel edge and pull on the front and back panes as well, causing those seams to see stresses that they weren't designed to sustain. Even if it were frameless, I wouldn't cantilever it out any more than the thickness of the bottom pane. That means, 3/8" for a frameless glass tank that had a 3/8" bottom. If you could put a support under the tank, you should plan for at least a 45-degree load transfer. In other words, if the tank were hanging over an inch, it could be safely done so with a 1" thick table surface extending the full length under it (or angled supports under the full length of the cantilever). You need this because you don't want / can't have the glass bearing the load of the moment that you'd be creating with the cantilever.

[YHSublime]

The glass tank has a frame that shifts the load to the outside edges. So, by hanging it over the edge like that, you introduce a sagging load that runs parallel to the table edge. That sag will tend to pull the bottom away from the parallel edge and pull on the front and back panes as well, causing those seams to see stresses that they weren't designed to sustain. Even if it were frameless, I wouldn't cantilever it out any more than the thickness of the bottom pane. That means, 3/8" for a frameless glass tank that had a 3/8" bottom. If you could put a support under the tank, you should plan for at least a 45-degree load transfer. In other words, if the tank were hanging over an inch, it could be safely done so with a 1" thick table surface extending the full length under it (or angled supports under the full length of the cantilever). You need this because you don't want / can't have the glass bearing the load of the moment that you'd be creating with the cantilever.

That makes sense, thanks for explaining. I’m dreaming of putting together a larger tank, but using the same stand. I think I’ve unknowingly planned ahead when I had the stand built.


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[GraffitiSpotCorals]

You could use a 1" thick piece of mdf board, maybe it would support a 6" overhang? Not sure but I know that stuff is strong.

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[dpassar12]

6 minutes ago, Piper27 said:

You could use a 1" thick piece of mdf board, maybe it would support a 6" overhang? Not sure but I know that stuff is strong.

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MDF is not a good product to use around water.it gets warped very easy. What about a steel plate that ran the length of the tank. You would need to calculate the thickness vs inches of overhang. I am guessing a 3/8 to 1/2 plate would support a few inches of overhang without bending. You might not even notice it if you got it cut to size. Only issue is rusting, you would need it powder coated or sealed in some way.

[Origami]

3 minutes ago, Piper27 said:

You could use a 1" thick piece of mdf board, maybe it would support a 6" overhang? Not sure but I know that stuff is strong.

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I'd be wary. Let's say that the tank is 40 gallons, fully loaded (water, rock, etc) weighs 500# (this is on the higher end to be safe). Let's assume that this weight is distributed equally on the load-bearing perimeter of a tank that's 36" wide x 15" front to back (for a total of 102 linear inches). A  6-inch cantilever leaves 27 inches, or over 25%, of the load bearing surface unsupported. Now, think of putting 125# on a 6-inch overhang and measuring the deflection. You want to constrain this deflection to no more than a sixteenth of an inch (my guess) over such a short run. And that deflection limit would have to last over time - no fatiguing or warping, you know? You could safely get there with a six-inch wood beam with lots of margin. You could probably even get there with a 4-inch wood beam. But 1-inch? Maybe steel. 

[YHSublime]

What if I did it the other way around? What if it ran the full 3', but evenly hung over 1" on the left and the right? 

 

Would a 1" board underneath be enough that I could rest the tank on top? 

[Origami]

37 minutes ago, YHSublime said:

What if I did it the other way around? What if it ran the full 3', but evenly hung over 1" on the left and the right? 

 

Would a 1" board underneath be enough that I could rest the tank on top? 

Yes, that should work. The length of the front pane on my in-wall 210 overhangs its load-bearing frame by the 1/2" width of the drywall. It sits on a 3/4" plywood top that cantilevers out from the frame by that half inch (similar to what you're describing) so that it's flush with the tank frame on all sides.