Potential Acrylic Tank

[rdbrown]

So I'm still in the talk-myself-into-it stage but contemplating an acrylic tank dimensions 8' x 3' x 18" (269 gal). Not hard to guess what might be destined for a tank with those dimensions (think large and flat).

First thing is I want to check that the $$ numbers I'm coming up with aren't totally wrong. Using this pricing tool: http://www.interstateplastics.com/Clear-Acrylic-Cast-Paper-Sheet-ACRCLCP.php I come out with the following numbers:

[FONT=Courier New]Base        1 @ 0.375" x 36" x 96"   $248.47
Long sides  2 @ 0.375" x 18" x 96"   $250.48
Short sides 2 @ 0.375" x 18" x 36"   $ 96.42
Top         1 @ 0.236" x 36" x 96"   $175.36
                                     -------
                                     $770.73
[/FONT]

Do these numbers look about right? What am I missing? Am I right in guessing that the top can be thinner acrylic than the rest of the materials because it's only being used to brace? I also realize that the bracing need not be a single piece - I've priced it out this way to have a worst-case ballpark figure.

The thought beyond this is to also hook a 125 gal into the system for additional water volume and a DIY sump (probably a 55 gal).

Go with .25 on the bottom. The bottom is supported by the stand, you must use a solid base stand on acrylic. Use .375 on the top. The top is what takes all of the stress off of the sides. You are fine on .375 at only 18" in height. Tenecor makes some of there 180 gallons out of .375 at 24" tall.

If you want to make sure just use some square acrylic rod in all of your joints to add some strength to the joints.

 

[Pharaoh]

Thanks for the replies and no, I don't mind the minor hijack either

Interestingly enough I found the calculator you linked to Pharoah, although after I'd started this thread. I was basing the 3/8" thickness on pages like this: http://www.cichlid-forum.com/articles/diy_acrylic_aquarium.php and this: http://www.duboisi.com/diy/BNdiytank/bndiytank.htm which say 3/8" for 18" height. That calculator is saying .514" thick acrylic for the tank and I guess you'd figure to believe the pros but does that really mean the advice on CF and Dub.com are just totally whack?

You run into all kinds of different opinions on thickness required. The difference comes from safety factor associated with building. The ones linked on C-F are a generalization. It is up to you to make an educated decision based on all of the information that you have received.

 

[Noto]

It's not just the height of the wall- the length and bracing strongly affect how thick the acrylic needs to be.

You'll notice the chart on the first site says "only for tanks eight feet or less in length" and that 18" is where the break from a 3/8" recommendation goes to a 1/2" recommendation, so you're right on the very cusp of the 3/8" recommendation. The second site is similar but places the break at 19".

I'm just mentioning this as something to think about. I haven't built a tank of that size and have no engineering background, so I won't make any positive recommendations of my own. I think if it were my tank I'd go for the overbuild and step up to 1/2", but that's just me.

In any case I look forward to seeing this project progress!

 

[rdbrown]

Here is a 72x24x24" Tenecor made of 3/8" sides and top, 1/4" bottom. Although I would prefer to have it made of 1/2", I bought it used and I have had it in service myself for 4 years without any reason to doubt the strength. I agree, if it were going to be some sort of show piece I would use 1/2" to construct it, but if he is looking a budget I know for certain he would have no problem with 3/8" acrylic.