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How much overhang is ok


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I have a 10 gallon that I am cycling and I want to move and this is the spot I chose but I want to know if this is ok the thing I am putting it on is solid oak and I could stand on it so I have no worries about that this Obviously isn’t the tank but this is how it would look about 2.5 inches on either side 

image.jpg

Edited by Angelfishlover
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3 minutes ago, Chris said:

Glass tanks are usually supported on the corners - I absolutely would not trust the setup you've shown a picture of for any size tank.

You can test this by sliding a piece of paper under a tank on a flat surface. I can easily slide a sheet under the center of my tanks, but the corners are tight to the surface.

Definitely find a different surface for your new tank.

Edited by Schwack
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25 minutes ago, Schwack said:

You can test this by sliding a piece of paper under a tank on a flat surface. I can easily slide a sheet under the center of my tanks, but the corners are tight to the surface.

Definitely find a different surface for your new tank.

Thanks! I will make sure to find a new place or   
just leave it where it is currently even though I don’t like the spot it’s better than having a broken tank 

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8 hours ago, Koi said:

You can use plywood or anything that will cover the bottom frame of your tank if you want it on that stand. That way the pressure is distributed evenly.

It's possible the plywood would still flex enough over time to stress the tank seams (have you seen bookshelves sag over time?). I personally wouldn't risk it or recommend it to others.

Edited by ererer
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10 hours ago, Angelfishlover said:

I have a 10 gallon that I am cycling and I want to move and this is the spot I chose but I why to know if this is ok the thing I am putting it on is solid oak and I could stand on it so I have no worries about that this Obviously isn’t the tank but this is how it would look about 2.5 inches on either side 

image.jpg

If you want to put your tank here, you can build a stand fairly cheaply out of just 2x4s. Most big box hardware stores will even cut lumber to specified lengths if you don't have access to a saw. All you need would be a drill. Just be sure to support the edges and corners properly, wood screws aren't designed for much shear strength.

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Beam analysis may be a good guide here. Since we know a 10g can be supported on its ends in a simple span condition and we can approximate overage with a cantilever beam condition.

Thinking moment governs and equating simple span to cantilever span and solving.

w*lx^2/8 = w*ly^2/2

lx = 2*ly

Supporting on ends is the same moment as half the tank hanging off the table and arguably better since the bottom will be braced in compression and arguably not since this is glass and not the governing mode of failure. ¯\_(ツ)_/¯

In a nutshell though you are probably just fine as shown in the picture.

Edited by TheDukeAnumber1
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2 hours ago, ererer said:

It's possible the plywood would still flex enough over time to stress the tank seams (have you seen bookshelves sag over time?). I personally wouldn't risk it or recommend it to others.

It would depend greatly on the thickness and quality of the plywood--1/2"-3/4" marine grade plywood would be safe in my experience. Bookshelves are made most often of particle board. It is NOT the same. 2 lengths of 2x4 running the full length of the tank would also be safe in my opinion. I have a 40 breeder sitting on the floor that I wanted boosted up just a bit to keep the roomba from smacking it, and it is sitting on flat 2x4s painted black.

My bigger concern here would be that it is right next to the bed, and you are creating a top heavy cabinet with a narrow base. Knocking into that at night, you could potentially tip the whole thing over. 

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52 minutes ago, TheDukeAnumber1 said:

Beam analysis may be a good guide here. Since we know a 10g can be supported on its ends in a simple span condition and we can approximate overage with a cantilever beam condition.

Thinking moment governs and equating simple span to cantilever span and solving.

w*lx^2/8 = w*ly^2/2

lx = 2*ly

Supporting on ends is the same moment as half the tank hanging off the table and arguably better since the bottom will be braced in compression and arguably not since this is glass and not the governing mode of failure. ¯\_(ツ)_/¯

In a nutshell though you are probably just fine as shown in the picture.

You probably know more about the application of these formulas than I do. However I am curious whether the plastic frame and glass plane construction is really the same as a solid beam. Does this formula apply in the same way? Red Sea had a handful of documented tank failures a couple years back on their XXL750 series because a small gap formed between the tank and the stand in the middle due to lack of a center support. 

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42 minutes ago, Brandy said:

It would depend greatly on the thickness and quality of the plywood--1/2"-3/4" marine grade plywood would be safe in my experience. Bookshelves are made most often of particle board. It is NOT the same. 2 lengths of 2x4 running the full length of the tank would also be safe in my opinion. I have a 40 breeder sitting on the floor that I wanted boosted up just a bit to keep the roomba from smacking it, and it is sitting on flat 2x4s painted black.

My bigger concern here would be that it is right next to the bed, and you are creating a top heavy cabinet with a narrow base. Knocking into that at night, you could potentially tip the whole thing over. 

I haven't worked much with marine grade plywood. I have seen 3/4" plywood shelving (not mdf) visibly sag, though this is after 20+ years of use. 2x4s properly secured **should** work, but they would need to have their longer side placed vertically, not flat, and they would need to be secured properly, and checked for cupping/twisting, etc. If I were going to do it, I'd make a rectangle out of 2x4s and screw plywood to the top and bottom of the rectangle and screw that into the table top unit. I wouldn't do this however, as it wouldn't look very nice, and as you said, it wouldn't be the most stable. I was going to suggest it in my earlier comment but then removed it, as I wouldn't recommend something like that unless someone was experienced enough to know what they were doing.

Also, your 40 breeder on 2x4s on the floor is a different situation, as I'm assuming that they are supported their entire length by being in contact directly with the floor.

Edited by ererer
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2 hours ago, ererer said:

It's possible the plywood would still flex enough over time to stress the tank seams (have you seen bookshelves sag over time?).

The point of the framing on glass tank is to distribute the weight evenly. A fish tank can't decide if it wants to put pressure on the corner of the tanks only, this would only be possible if it wasn't level. The same theory applies to your bookshelf analogy because weight isn't being evenly distributed along the shelf, all the weight is coming down the center. Book shelvings are often held on the razors edge of the board with very small pins, but that aside you could even circumvent that issue by putting another board on top of it. In that scenario the only point of concern would be the pins itself.

Even when you look at fishtanks wether built solely with wood or the use of cinderblocks the main focus is to support the 4 corners not the glass (besides rimless tanks). The point of plywood is not to support any pressure from overhang but take the pressure from the perimeter of the frame and spread it evenly. When building stands the fundamentals are all the same.

This is a 65 gallon tank

IMG_1319.jpeg.866dd8fa26434c36b26b9c5e5ac29283.jpeg

IMG_1315.jpg.3f80b8f87f3b62c8e28c1f3dc81ea09a.jpgYou can even zoom in if you'd like to see the level

IMG_1316.jpeg.f5ed65e93eb66adcb6e81702a1b74af2.jpeg I'm not looking to argue but I felt like I should have clarified my point since I got shamed.

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Alright, so my bookshelf analogy wasn't the best. I still don't believe that the plywood adds *a lot* of structural support, unless it too is properly supported. There's an important difference as to whether the plywood is supported at the edges or whether it overhangs, and by how much. I'm sure there's a point at which overhang is too much for a given thickness and quality of plywood, and I don't personally know what it is. An inch or two is likely fine, I doubt that 6 inches is. Is 3 inches okay? I would be interested if someone could provide that information. It would also be useful to know the allowable deflection for an aquarium with a given volume and thickness of glass.

  

21 minutes ago, Koi said:

I'm not looking to argue but I felt like I should have clarified my point since I got shamed.


Also @Koi, I wasn't trying to shame you, and not interested in arguing either. Sorry if it came off that way.

Edited by ererer
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17 minutes ago, ererer said:

You probably know more about the application of these formulas than I do. However I am curious whether the plastic frame and glass plane construction is really the same as a solid beam. Does this formula apply in the same way? Red Sea had a handful of documented tank failures a couple years back on their XXL750 series because a small gap formed between the tank and the stand in the middle due to lack of a center support. 

If a horizontal member is carrying a vertical load over a span then it's likely acting as a beam. The formulas are idealized for calculating the load on things acting as a beams regardless of construction type. Looks like the XXL750 is on a much different size scale and would not apply in this case, especially since we know supporting a 10g only on it's corners is safe.. The beam formulas may not govern here either but they do show bending overhang stresses will be lower than if it was only supported on the corners.

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3 minutes ago, TheDukeAnumber1 said:

If a horizontal member is carrying a vertical load over a span then it's likely acting as a beam. The formulas are idealized for calculating the load on things acting as a beams regardless of construction type. Looks like the XXL750 is on a much different size scale and would not apply in this case, especially since we know supporting a 10g only on it's corners is safe.. The beam formulas may not govern here either but they do show bending overhang stresses will be lower than if it was only supported on the corners.

 

Beams do flex though, and I think it's more likely a failure will occur due to flexing at a seam causing a leak than from a glass panel breaking. I've personally never tried supporting an aquarium only by the corners, so I'm not personally suggesting that either. Will a failure take years to show up if it ever happens? Probably. We don't know how old this aquarium is or what shape the seams are in already though either.

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37 minutes ago, ererer said:

Also, your 40 breeder on 2x4s on the floor is a different situation, as I'm assuming that they are supported their entire length by being in contact directly with the floor.

True. However, my 2x4 are just supporting the frame, which was my point. Sorry that was not clear, and I think most of us understand that the frame is the major structural component of these type of tanks, so that may have been a pointless distinction.

If a 10g is 100lb filled, each length of 2x4 is really supporting a fraction of that, and across a very small distance, and the weight is also being redistributed by the frame of the tank. While 2x4's vary in quality, any (flat/straight/true) 2x4 should be able to manage a 3" cantiliever, even laid on its side, as should a 1/2" piece of ply, when supported along the majority of its length. 

However, excellent catch on the broken frame. I did miss that.

 

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@ererer all good brother. To address your question if you use something to cover the entire bottom of the tank there technically is no overhang. The plywood isn't really used as structural support, that job would be allocated more to the legs or frame of the stand.

Not to say that there is no such thing as too much overhang but in most cases the failure point becomes the structure itself that is holding the tank up. The structural integrity of the frame of the stand is more at question than what is on top of the frame. The plastic framing makes it so that equal weight is pushing down towards the ground.Neither the center nor the corners are applying more downward weight than the other unless you are purposely trying to push it to drastic extremes.

Here is a great video of this technique being applied in a sleek way. Although this is the inverse of the method I use, it still supports the idea that you support the 4 corners of the tank.

@Brandy I was gonna say the same thing but OP mentions that this is just for visual purposes

Edited by Koi
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42 minutes ago, ererer said:

Also, I just noticed that the black bottom rim is missing on about 1/4 of the aquarium in the original post. That's probably an issue that should be addressed as well.

Yeah that’s just a trash tank I have laying around the mfg. date on that tank is 1981 so I doubt it holds water I was just using it to mock up what it would look like I never plan on using it for anything 

Edited by Angelfishlover
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2 minutes ago, Angelfishlover said:

Yeah that’s just a trash tank I have laying around the mfg. date on that tank is 1981 so I doubt it holds water I was just using it to mock up what it would look like 

Ah, I didn't understand that from the initial post.

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