Your tank is TOO SAFE! Yeah, I said it - it's TOO SAFE!

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Desdinova

Feeder Fish
MFK Member
Oct 1, 2010
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Kentucky
So, I figured I'd cause another uproar with the following reference to the hydrostatic paradox:

Given the fact that pressure upon the sides of the tank is dependent upon the height of the water column and NOT the total amount of water contained, why do people go to such great lengths to secure the sides of their tanks?

For example, consider this 2700 gallon vldesign tank. This guy built up the sides of the tank by layering dimensional lumber flat against the bottom and then attaching plywood to it. Did he really need to do that? If the tank is 36" high, it would not appear to exert that much pressure upon the sides of the tank.

I'm led to believe that all we ever really need to do is build Rivermud's Test Tank on whatever scale we need. You would add some basic framing if the sides were larger than one continuous sheet of plywood, but nothing like the vldesign tank.

It would seem important to focus on the bottom of the tank, due to the sheer weight of the volume, as well as the bracing at the top, but the sides appear to be of least concern (unless they're over 3 feet high...).

So, am I going wrong somewhere, or is building up the sides too much an exercise in futility?
 
The force isn't just exerted on the bottom, it is exerted outward on the side as well. A simple sheet of plywood on a 36" tall tank would not last very long.
 
Maybe I wasn't clear enough. I was trying to say that the bottom of the tank, which needs to hold up the weight (maybe more-so the stand?) needs extensive attention, but the sides need much less. As the volume of water increases, the tank will weigh more and need more support beneath. However, as the volume of water increases, the force exerted on the sides doesn't change at all. The force exerted on the sides is a calculation based on the height of the water column, exclusively.
 
Think of it this way, a 6 ft stick is easy to break in half, a 3inch stick not so much. The longer the tank the better built the sides need to be because the length 'weakens' it for lack of a better word.
 
Yes, it's true Cich, take a look at my link in the first post. This is why it's referred to as a "paradox"

Are above ground swimming pools made of different material for their walls, depending on volume of the pool? Nope. Same height = same material and thickness.
 
I totally agree! I didn't want to be the first guy to bring it up for fear of being flamed. But yes finally somebody with some sense! The stacked lumber is a total waste of time and money. If I were to build a 6ft high tank all I would have is 3/4 inch ply with 2x4 support every 12 inches and maybe some fiberglass in corners and seams. That's it. That's all that's required. Why do people go overkill? It's basically because they don't know any better and rather err on too much than too little.

My 36" high 650g tank has only 3/4 ply unsupported other than 4 layers of fiberglass and it's solid as a rock. No bowing, flexing or distortion whatsoever. My rational is simply observing other tanks with thin little 3/8" or 1/2" thick glass for 4-500 tanks 36" high or more. The only support they have is a ring of plastic around the top perimeter to hold the edge together. So I can't believe 3/4 ply with 2x4 support has less strength than 1/2" untempered glass? Please...

Desdinova, thank you very much for starting the thread you are a braver man than I. LOL But I do support your thinking.

p.s. I do have a Mechanical Engineering degree.:p
 
Personally, if I am going to build a tank that hold a very large volume I am going to overkill on the structural integrity of it. I will pay no regard to anyone who has a minimalistic view on what is the requirement.

I have always said it takes an expert to complicate the simple so they can simplify the complex!

The reality is that when dealing with water, all it takes is for a little wee hole or stress fracture to cause a huge issue.

Also, my philosophy is that the person building should be the one who gets the finished product they want.
 
chefjamesscott said:
Personally, if I am going to build a tank that hold a very large volume I am going to overkill on the structural integrity of it. I will pay no regard to anyone who has a minimalistic view on what is the requirement.

I have always said it takes an expert to complicate the simple so they can simplify the complex!

The reality is that when dealing with water, all it takes is for a little wee hole or stress fracture to cause a huge issue.

Also, my philosophy is that the person building should be the one who gets the finished product they want.
Click to expand...
Tottally agreed.
 
Does one hold water better then the other, no? Who cares, to each their own. If your gonna built a tank and need to feel secure with it, so what if it is overbuilt.
 
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