Acrylic Thickness


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I keep seeing Questions about the appropriate acrylic thickness to use for construction of tanks. I have come across a couple of calculators. One is put out by Cyro, an acrylic manufacturer. I am not an engineer but it seems that they are "heavily" weighting it towards safety (read no liability) They recommend only using Cell Cast acrylic and a two part polymerizable cement and do not recommend solvent welding. It seems to be giving some pretty hefty thicknesses. The other is on GARF and gives a cut list, instructions and recommended thicknesses. These are "more inline" with what I see commercial tank manufacturers using. They also say that solvent welding is OK..

Cyro Acrylic aquarium Thickness Calculator - Excel Spreadsheet

Cyro Acrylic Knowledge Base

GARF Build Your Own Aquarium Calculator

My question is which one is real. If the GARF recommendations are practical it represents a substantial savings. What are the experiences you have had with tank thicknesses. What is the proper size thickness from and experience AND and engineering standpoint?
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I sure wish someone with engineering and or experience would have responded to your post. From my standpoint, if manufactureres do it, we can too. Although you know different mfg. do vary slightly in thickness. I think I would err slightly on the thicker side, but use garf's. I know this doesn't answer your post, just my .02
If you look at manufactured tanks, sumps, etc. a good majority are made with 1/4" to 1/2" material. Most of the sumps are made of 1/4" material. They will tell you to use thicker material for several reasons: (1) this has a larger margin for error when glueing up the pieces [more space], (2) they have experienced personnel that have been doing this type of work and know what they are doing [cannot say what the average DIY'er would have], and (3) they want you to look at the materials and then look at their product and see almost no cost difference ;) .

I can't say that they are wrong for all of it but it is a good way to scare people by saying, "do you want to rely on your abilities when it comes to 20 gallons of water on the floor?" The thoughts of our loved ones saying. "I told you so" booms in our heads and we go and buy it without attempting to do the project. In fact, most projects I have seen done are more than twice as strong as necessarry for the application intended.

Understand that acrylic does bow... That is part of the specification for the product. Deal with it or use glass.. plain and simple.:cool:

I would easily use 1/4" for anything under 55 gallons dependant upon height and method of build. I would use 1/2" up to about 125 gallons dependant upon size and build. It's ultimately up to you...
I suppose an acrylic manufacturer like Cyro )manufacturer of Acrylite) has to consider "all possible uses and requirements" like public aquariums when putting a calculator like this out. I can imagine they have very stringent guidelines and the is why it is Cyro so select in thickness and welding methods. I was curious because the Cyro site mentioned "crazing" under hydraulic pressure after long periods (many months or years) . In your opinion and experience would you use standard acrylic sheet (like Acrylite, Plexiglass, etc), or should it be cell cast acrylic (like Acrylite GP, Plexiglass G, etc).
I'd guess they err on the side of caution as well, since they don't know how you will be reinforcing the box (cross-bracing, etc...).

Let's put it this way, I have a sump made out of Lexan 1/4" that is 30" L x 18" W x 18" T with a 2" lip around the top. I don't have any bows because of the baffels in there help support the weight also. I am not worried about it leaking because I filled it up out in the garage for a solid week with a spare MAG 5 pump running water through it at a high rate :D

If it would have broken, I would have known. Lexan acrylic is optically clear stuff and that didn't bother me since I picked up a 4x8 sheet for $20!! Don't ask, they were going out of business.;)