Will my plywood tank bow out?

[danielz]

I would like to build an aquarium but this will be my firstever attempt at fishkeeping. Since I am a cabinet maker by trade I have plentyof ¾” (1.90 cm) plywood lying around. So I plan on building it out of plywoodlined with epoxy. I think I will make it 4’ by 4’ and 3’ deep with windows on three sides and build a stand for it. Since I plan to glueand screw all the edges at about every six inches I feel pretty confident thatthe joints will hold back the water pressure
My only concern is the lateral pressure on the sides of thetank causing the top to bow out. Is there a simple formula (I am not very goodat math or engineering) that I can determine how much pressure is pushing outon the tank? Will the plywood hold upand not bow out and if it does how much? I was thinking that if the pressurewould be too great on the plywood I could weld a band out of angle iron thatcould be powder coated to slip down over the top of the tank and give it extrasupport to keep the bow in check. Or, I could glue and screw a piece of woodalong the top.
I would appreciate any advice anyone may have.

 

[Tiller11]

I would do the wppd idea on top... Thats in my plan whenever i start... Im jus gonna put like a t through the middle so it kinda holds the front back and both sides.

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[808_fairladyz]

Wow, I've been going back and forth with few people currently building plywood aquarium about our own experience, may as well jump on board. First off, with your cabinetry experience, your already a step ahead of most. Second, if you're going to be just using plywood, 48 inches is to tall. To much pressure unless you're building a frame around it. I'm building an aquarium that's 96Lx34.50Wx30H. I'm building it with a full top, 3 layers of fiberglass cloth and laminating resin. First layer is 7.5 oz cloth with additional 2 layer of chop mat and resin. My front viewing glass is 90x24 inches. Check it out, I hope I can help in any way. By the way, if you haven't seen them yet, everything that I've done has been base on Uaru Joey's YouTube videos. Check em out if you can. FYI, this is my first build also.

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[danielz]

I am new to fish keeping. What is wwpd?
The tank above looks a lot like what I have in mind. It is only going to be a bout 32 to 36 inches tall and not 48 inches so that would be less lateral pressure than 48 inches. The plywood top you put on it is a good idea to keep it from bowing out. I wonder if the angle iron idea I had would work as well. Anyone know how much water pressure in pounds will be on the top of the tank walls?

 

[808_fairladyz]

Originally I was going with 36 inches high, but seeing 30 inches in person, I'm happy with the change.

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[CJH]

There are free standing fiberglass rectangular aquaculture tanks so in theory you don't even need the plywood to minimize bowing. But the extra fiberglass and epoxy costs a heck of a lot more than adding support to the outside, even powder coated steel.

Looking forward to seeing this one. I love the "more or less" cube shape of your plan.

 

[808_fairladyz]

There are free standing fiberglass rectangular aquaculture tanks so in theory you don't even need the plywood to minimize bowing. But the extra fiberglass and epoxy costs a heck of a lot more than adding support to the outside, even powder coated steel.

Looking forward to seeing this one. I love the "more or less" cube shape of your plan.

Yes, I agree. As much money as I've already spent on my fiberglass and resins, it would've probably been cheaper to just build a frame around it instead, but the aquarium would've been quite bulkier. Space was already a concern for me. My original plan was 96x36x36, but now it's 96x34.50x30. Looking at my aquarium in person to me is still quite large for where it'll be put.

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