Acrylic Thickness Question

[HighestOlive]

For those of you who have worked with building your own acrylic tanks before could you help me get and idea for roughly how thick the acrylic would need to be for a tank that had the dimension of approximately 24x36x12. That is in the ball park of 50 gallons or so. Could I get away with using 1/8" acrylic or would I need to go with the 1/4" of maybe even more. How do you make this determination.

[ScubaTC]

http://www.garf.org/

Select DIY Pages on the left to expand and click on Tank Building.

[BOKER420]

If you just want to have a eurobrace then I'd go with 3/8" With 1/4" You would need a full top with 2 small access holes. But I wouldn't suggest anything less than 3/8" either way.

[BOKER420]

The garf websites says you can use 1/2" acrylic to build a tank that is 8 feet x 8 feet by 30" high. With a pieced together 2" top. 1,197 gallons That is crazy. I wouldn't go by what they say forsure.

[woz9683]

The GARF calculator is based solely on the height of the tank. For oversized and abnormally shaped tanks it is definitely not the best resource to use for sizing (or construction methods). However, for the tank in question it will recommend 1/4" material which is acceptable. However, it's going to be rather difficult to make perfect seams with such thin material (more flex requiring perfectly level bracing during the gluing phase). For this reason I'd agree with Boker and say that if you go up to 3/8" material I think you will have a much better experience. Plus, with 3/8" material, even if your joints aren't perfect you should get enough bond surface to insure the structural integrity of the tank.

[woz9683]

Also, HighestOlive make sure you draw the cuts out on a piece of paper a couple of times. I think you'll find that the cheapest way to buy the material is by purchasing a full sheet, and you're definitely under-utilizing a sheet with that tank size. Just a thought but if you're building your own tank and you've already purchased a sheet of material (assuming this is cheaper for you) you might as well build the tank to use as much of the material as possible. If you find a nice acrylic shop they will make the basic cuts for you for just a couple dollars a cut.

[checkinhawk]

IMO 3/8" would be best but you could go with 1/4"

[GARFVolunteer]

Originally posted by BOKER420
The garf websites says you can use 1/2" acrylic to build a tank that is 8 feet x 8 feet by 30" high. With a pieced together 2" top. 1,197 gallons That is crazy. I wouldn't go by what they say forsure.

And why not? Water is a liquid therefore not compressible so the depth of the tank is what determines the thickness of the acrylic. With proper bracing, 1/2" thick acrylic 30" high could hold back the ocean...

A little common sense needs to be used when building any tank.

Thanks,

Scott

[woz9683]

The depth of the tank is not the only factor that comes into play. In most of your basic (smaller) tank sizes the length does not play a significant role in determining the thickness of the sheet used, however it is still a factor. When you get to larger tanks the effect of the length and width is more important.

Let's be perfectly honest here, the GARF "calculator" isn't even a calculator. The only reason you enter length and width at all is so that it can spit out cut sizes. To determine thickness it's recommendation is based solely on the height you enter. Like I said before it's a good general guideline but not realistic for abnormal situations. You're very right, common sense does come in to play here. There is a real calculator at www.cyro.com (the maker's of Acrylite GP). I can't give the exact link because you have to create a log in ID, but it's free so if you do that log in, then run a search for aquarium thickness calculation, it should pop up as the first link (or one of the first few). They have the equation used under that link. There's also an excel file somewhere that will run the equation for you if you enter your dimensions (although I believe James has been debating part of that equation with them because of one of the constants used in the rimless calculation). Either way though, you can see how length and width come into play.

[BeanAnimal]

Scott, the width of the panels also come into play and is a significant factor.

The longer the panel, the more it will deflect at a given head height.

I would use 1/2", but that is me. I have many "high end" acrylic tanks that have a bulge around their waists!

I don't think the thinner stuff will fail, I just think it looked like hell Then again the more the panel deflects, the more it stresses the joints. The thicker the panel, the thicker the glueing surface.

[BeanAnimal]

doh woz... you beat me to it while I wasy typing. And who said beer doesn't slow a person down!

[Acrylics]

Originally posted by woz9683
although I believe James has been debating part of that equation with them because of one of the constants used in the rimless calculation.

Actually to be clear, there's more than one thing in that equation that I would debate but they are considered "safety factors"
The points you made above are correct though, while span doesn't change the water pressure, it does play a role in deflection and therefore overall stress on the material. And every material does in fact have a breaking point.

hold back the ocean, yeah - try it sometime

BTW, cheers

James

[BOKER420]

Garf either needs to retify their calculator or take it away completely. I'm not trying to be an *** but those calculations could end up with someone flooding their house or even worse.

[woz9683]

Thanks for chiming in James. So, you think the safety factor is too low on the rimless version, and maybe a little too high on the rimmed version? Or is there another factor, I really didn't go look at the equation in depth just remembered you were talking about the rimless version before and that particular safety factor being too low to avoid significant deflection.

And Bean, every once in a while I get lucky.

Boker, I think it still has its uses, the cut list for one thing is nice. I really don't think many (if any) people building a tank 8'x4'x3' or anything else in that ballpark are going primarily to GARF and using that calculator as their only reference. If they are and they have an issue, well it's at least partially their own fault for trusting a single source for such a major application. Again, in standard situations that most people would encounter while using that calculator the results will be perfectly legitimate.

[BOKER420]

That's very true I guess I wasn't thinking that all people have common sense.

[GARFVolunteer]

I will try to get ahold of Leroy and see if he will let me make changes and add limits...

Thanks,

Scott