Confused on acrylic thickness please help!

stempy

stempy

Dovii
MFK Member
Sep 8, 2011
901
302
102
Galloway, OH
Hey guys, i am currently building a 530ish gallon plywood aquarium following http://www.monsterfishkeepers.com/forums/showthread.php?181445-600-Gallon-Plywood-and-glass layout. the inner dimensions of the tank is 72"x48"x36" tall with a viewing window of 68"x30". Getting a solid answer on thickness is impossible, calculators are giving me over an inch thickness needed, usually 1.3", though i've seen bigger tanks using thinner. I am using a cross brace on it as well. I was planning on using 3/4" cell cast but am now really unsure, and the cost increase from 3/4" - 1" has my wife glaring at me :) Do you guys believe 3/4" would be fine?
 
G

gilberbt

Feeder Fish
MFK Member
Mar 16, 2010
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Indianapolis, IN
I have seen several 3' high tanks (including the 2600 gallon project on here now) with 1" thick acrylic, but I cannot remember seeing any using 3/4". The 3/4" acrylic may hold but it would bow significantly more than 1" and possibly not last as long and a much higher chance of a catastrophic failure as its all about the safety factor. If I where you I would either reduce the height to possibly 30" or spend the extra $$ to make sure its done right.
 
K

karak

Gambusia
MFK Member
Jan 21, 2011
181
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Australia
wat.jpg

The green arrows are the force the water pushes on the front of the tank, as the water depth increases, as does the force linearly.
If you say the wood to be considerably more rigid then the acrylic, which it is in an overbuilt style tank, then the bottom arrow has no(little) effect on the bowing. Its the total amount of arrows on the open spaced acrylic that causes the bowing/failure, it is this depth that needs to be considered when choosing the right thickness.

Ofc this is quite simplified of whats actual happening, but gives you quite a good idea.

As far as if 3/4" will work, im not sure, youll have to ask one of the more experienced tank builders

wat.jpg
 
E

epond83

Plecostomus
MFK Member
Nov 10, 2009
801
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Duvall, WA
As the the pictures shows, yes it's height of water that determines how thick the acrylic needs to be. Also as the picture shows if the acrylic doesn't go to the bottom you can have a deeper tank without having to go as thick.
 
S

sross

Gambusia
MFK Member
Apr 18, 2011
251
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Ohio
I agree if you want to stick with 3/4 you should raise it up off of the bottom so the pressure on the window is reduced. I built a plywood tank with a water height of about 33.5 inches. I raised the window up so the water height for the window is about 27 inches so I could use 1/2 glass instead of 3/4. and it worked great.
 
V

VLDesign

Silver Tier VIP
MFK Member
Mar 20, 2007
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30" tall with 3/4" acrylic will be fine as long as there is enough support around the edge of the window. At least a 1" lip for support will be good. Your actual viewing area will be 28".

Anything taller than 30" has been done with 3/4" without issues, for me though I would go 1".

Also you might want to check glasscages.com and see what a piece of 3/4" starfire glass will cost you.

It might actually be cheaper than the acrylic.
 
stempy

stempy

Dovii
MFK Member
Sep 8, 2011
901
302
102
Galloway, OH
There will be 2 inches of overlap by the acrylic on the wood on all sides. Basically the tank is 36" tall with 2 2x4's along the top and bottom which totals 6" leaving me with the 2" overlap of support along the top and bottm and a 30" viewing area. The peice of acrylic I plan to buy will be 72"x36".
 
stempy

stempy

Dovii
MFK Member
Sep 8, 2011
901
302
102
Galloway, OH
Also forgot to mention I checked glasscages and a 3/4 starphire of those dimensions is gonna run about $576 about the same as a 1" thick acrylic :/ The 3/4" cell cast I got quoted was for $417.
 
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