Minimum requirements for plywood build?

[nikirushka]

I know there's a plywood tank compilation thread, I'm just about to read through it!

I just wondered if anyone could suggest the minimum requirements for a build please? I'm working out what I'll need. So minimum number of vertical supports say, minimum ply thickness, that sort of thing.

Now this isn't a tank with a viewing window, this is going to be a tropical pond, but when I look into it from that angle everything is crazy over-engineered and I know from plywood tanks that it doesn't need to be.

Pond will be 2x1x0.8m high, or possibly 2.5x1x0.8m (depends where I put it). 2000-2500 litres. Using pond liner for simplicity and cost, but still using plywood for support.

Ideally I'd like to build it with 2x3 CLS as that's affordable for me (super tight budget) but if I have to go bigger, I will. I've built stands so I have some experience and the tools I need. I just haven't built the water holding bit before!

 

[tlindsey]

I know there's a plywood tank compilation thread, I'm just about to read through it!

I just wondered if anyone could suggest the minimum requirements for a build please? I'm working out what I'll need. So minimum number of vertical supports say, minimum ply thickness, that sort of thing.

Now this isn't a tank with a viewing window, this is going to be a tropical pond, but when I look into it from that angle everything is crazy over-engineered and I know from plywood tanks that it doesn't need to be.

Pond will be 2x1x0.8m high, or possibly 2.5x1x0.8m (depends where I put it). 2000-2500 litres. Using pond liner for simplicity and cost, but still using plywood for support.

Ideally I'd like to build it with 2x3 CLS as that's affordable for me (super tight budget) but if I have to go bigger, I will. I've built stands so I have some experience and the tools I need. I just haven't built the water holding bit before!

jjohnwm

 

[Backfromthedead]

My advice for plywood aquariums: stop thinking "minimum". If anything, overbuild.

 

[nikirushka]

Absolutely. But if I don't know the minimum, how do I know if I'm overbuilding? I'm not going to take silly risks, it's a lot of water, but I also don't want to go absurdly OTT or cost myself way more than I need to!

 

[M1A1]

No one can really tell you what the minimum is unless they do some finite element analysis and calculate it. That's why we overbuild - there's less math involved.

So you do what the rest of us do and look at all the other tanks you can find that are similar in size, figure out what they used for plywood and framing - if any - and which tanks have failed - if any.

For what it's worth, 2x3 framing seems fine for a 0.8m tall tank as that's only like 31.5 inches. Your build is going to be the same as any 8ft by 4ft build. Some of these are done successfully without any framing at all and just plywood (maybe multiple layers) and fiberglass (strongly recommended along joints).

 

[nikirushka]

That's good to know, thank you.

 

[jjohnwm]

i've built a bunch of plywood tanks but nothing exceeding 24-inch water depth. I got the idea originally from a couple sets of plans that appeared a few decades ago in FAMA and The Marine Aquarium magazines.

My tanks are all epoxy lined with a single viewing window of glass. If I were doing no window like your plan, I would definitely go with the liner as you mentioned. I use a single layer of good-one-side 3/4-inch exterior grade plywood. Minimum vertical supports? Zero! A simple plywood box with a completely Euro-braced top opening, assembled with both screws and glue. No fiberglass, no exterior reinforcements of any kind. My 8-foot builds incorporate one or sometimes two 6 or 8inch center braces across the top from front to back/

I have had very few problems (none of them structural) with this construction, and some of the tanks are well into their second decade of useful life. One is well over twenty years old and has had a grand total of one complete facelift which included recoating the interior with a fresh epoxy seal. Several were cut apart when moving (new home owners didn't want an aquarium...what's up with that?) and were still very solid and tight.

I'm cheap, patient and careful when building a tank. I have no idea if this construction will work for a water depth 8 inches more than my tanks, and frankly don't care to experiment. I know it works, and if I were doing your project I would likely reduce the height to 24 inches just so that I could build it more easily and cheaply.

By the way, if you are planning on sitting on the pond edge...I have no idea if this would work, and certainly wouldn't advise it.

 

[fishdance]

For a DIY build, I would look into a steel frame support as this will be cheaper, lighter and stronger than a wood frame.
If you can't weld, screwed would still be strong enough. Steel coating expoxies (paints) against rust have hugely improved with technology.

Having a structurally solid frame allows you to use thinner plywood walls. And to go deeper with water depth if temperature fluctuations are an issue.

 

[Dovii kid]

I likely overbuilt mine but somewhat allows me to sleep better at night ?. It's 10x4.5x36" tall

12" OC 2x4 exterior bracing, 12" OC 2x6 base, 3/4" plywood, biaxial 1708 fibgerglassed corners, 12oz fiberglass cloth entire inside with epoxy resin, then topcoat with interseal 670hs epoxy paint

If I were to do a smaller, shorter aquarium I will use simply 3/4 plywood, polyester resin and the same interseal top coat.

 

[Jack Daniels]

Polyester Resin does not adhere to wood all that well. Epoxy is the resin of choice for wood. Epoxy will absorb approx 2% water over time. Polyester absorbs much more over time and the gel coat blisters when under constant water immersion - ask me how I know ;-)