Water (bubble wall) DIY

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keithd

Feeder Fish
MFK Member
Apr 4, 2007
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austin, tx
I'm interested in building a series of water filled bubble walls using acrylic paired with a small frame. Essentially a very thin, tall aquarium (without the fish).

I've read a lot on the forums as well as worked with acrylic for a lot of other projects (non water related). However, I have two issues I can't quite get my head wrapped around.

First, most of the acrylic thickness calculators I've seen out there take only height and width into account. It seems to me this is a flawed way of calculating, based on an assumption that the depth of any aquarium must be more than a few inches thick. Thus I understand the height becomes a "damning" factor when calculating the thickness necessary for a sturdy tank. However, in this case, I only want the entire project to be about 4 inches thick. And surely something that is only a few inches thick does not require the same thickness as something ten feet wide with the same height and length. Right? So, what is the best way to go about calculating the necessary thickness needed?

Second, I will be using an air pump to add the bubbles (of course). I see many of these things in stores that appear to be completely sealed. Obviously this is not possible as the air I'll be pumping in (from the outside) must be able to escape. So, what is the best way to allow the air to escape while minimizing evaporation and, more importantly, moisture or odor building up around the decoration?

I know the second question is teetering on the edge of the scope of these forums; but I'm hoping some people out there have extensive experience working with the acrylic and may have had to deal with issues like this before.

Thanks so much for any and all help.
Keith
 
Drill small holes at the top so air can escape. Better yet make a custom lid.




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So you're saying that, even with a frame, I cannot build a water wall that is 6-8 feet tall unless I use 1.5" or even 2" acrylic. This does not seem logical, but is what the "calculators" gave me. I have seen larger walls in hotels and such that have been made out of either .5" or .75" acrylic and look perfectly stable.

Not to mention it doesn't seem logical (assuming I want the entire wall to be only around 4 inches thick) that I need 1.5 inches of acrylic on each side of only 1-2 inches of water?

There has to be more to this equation than just the vertical force on the seems from the water.
 
It may not seem logical but it's true.
All the tall and thin ones I've seen have some sort of bracing between the front and back, making individual chambers that are no more than a few inches wide or having peg style braces every few inches to prevent bowing.
 
Water exerts pressure of .036 psi per Inch of height. Force equals pressure times area. The force on the wall has nothing to do with thickness of the water layer.

The only reason you see tall water bubblers like that at malls without 2" acrylic is they have bracing every few inches.


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Ok, so the height is the major factor, but the "braces" will displace enough of the water pressure to make it negligible? That makes more sense.

What would be the best way to make an educated guess as to how thick the acrylic would need to be for a 5-6' tall wall with braces every say 3 inches as well as a frame?

I know I could probably just build one with 1/4 inch and see how it holds up, but adding the extra acrylic for the braces is going to make that much less attractive.

Thanks again for the input guys, I know this is a different application than most people on this board normally deal with.
 
1) Atmospheric press + weight of water = Hydrostatic press. Something similar, I cant remember the mathematical formula off the top of my head and normally have to consult my notes for it... sorry, it shouldn't be too hard to find on line though. Then you will need to figure out the shear strength of the weakest point which will be your joint seam if using the 2 part stuff which (which is normally far greater than you will ever reach).

Also look at the deflection rate of the material otherwise know as modulus of elasticity. This data can be obtained from the MFG. It will tell you how much the material will bow in relation to the ammount of pressure exerted. Once you know this you can determine how much bowing to expect at the point of greatest pressure (max depth). You will then need to figure out the shear strength of your joints to determine if they can handle the pressure. This is often why you see crazing along the seams of acrylic tanks over time.

Solvent may be best for this project depending on thickness which is dependent on height. How tall is this tank anyhow? If too thin it will bow like crazy so... essentially if you were to build a 4x4 ft tank that holds back a 4 wide section of water it would need to be around 8" thick (front to back using at least 2" thick material min). Strange I know but Im assuming you are building it to last awhile. For purposes of aquarium construction the length and depth (height) of the body of water is miniscule when determining the thickness of material. Hydrostatic pressure is almost entirely related to the height, density and atmospheric pressure exerted on the water column.

2) Provide an access cover with vents, you will need it to fill the tank due to evaporation anyhow. Or use a closed loop system with an inlet and outlet for the air. You could also pump in the water from these points, then when filled elevate the airpump above the water level and pump air in thru the bottom horizontal manifold.
 
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