proof that design ( not 2x4's) are key to stand integrity.

[biodegraded]

Thanks for the clarification. I would argue that you can't count on the aquarium to provide much stiffness. The walls of the tank will certainly not deform as they are on edge. The problem comes with the flat bottom. That will flex far more than the sides and can either crack or cause failure of the silicone seals.

I agree the bottom sheet in isolation wouldn't cut it. I just did a calc for the 180 g tank, guessed at the bottom sheet being 3/4" non-tempered glass (modulus 10 Mpsi) and got a deflection of 0.8" (span 66", total weight 1800 lb). The maximum stress is right at the 50% probability of breakage (6600 psi) for annealed soda lime float glass. Get a decent scratch in a surface and "she's gonna blow fer sure".

However, the sides do add stiffness, I suspect a lot, as they're glued to the bottom. This is in the realm of needing FEA, at least for me. Maybe I'll see if I can wheedle a run from one of our MEs who have licenses to SolidWorks.

 

[Flanders]

Most people build the stands out of 2x4's then skin them in plywood so it ends up costing more than just buying the plywood. Not to mention from my experience you have to buy more 2x4s then you actually need because many times you end up with bowed or crooked pieces.

Skinning a stand is purely cosmetic. From the standpoint of being able to hold up a fish tank, 2x4's are far cheaper, and you won't end up with crooked ones if you just kind of look at them first.

Obviously either works but this weird argument about which is better seems pretty foolish.

 

[sfsuphysics]

Most people build the stands out of 2x4's then skin them in plywood so it ends up costing more than just buying the plywood.

Only if you're silly enough to skin your stand with 3/4" plywood.

 

[James77]

Skinning a stand is purely cosmetic..

No, its not. While it serves a cosmetic purpose, it also ties all those 2x4s together. Someone above gave an example of a cheap bookshelf. Without that thin backing I can easily destroy it by twisting the frame. 1/4" plywood over a 2x4 frame will add a tremendous amount of strength.

 

[Flanders]

No. its not. While it serves a cosmetic purpose, it also ties all those 2x4s together. Someone above gave an example of a cheap bookshelf. Without that thin backing I can easily destroy it by twisting the frame. 1/4" plywood over a 2x4 frame will add a tremendous amount of strength.

It depends how you attach the plywood. I throw a couple of nails in each trim piece which does basically nothing structurally, because I don't have incredible forces trying to twist my already ridiculously overbuilt stand.

 

[James77]

Right, its ideal to glue it on....but either does add strength. Not that we are in the habit of falling into the sides of our tanks, it only takes several drinks though

 

[trinity1012]

they build houses out of 2x4 and plywood for cryin out loud.:headwally:

 

[James77]

Does anyone know of any threads where some ones stand actually collapsed or failed?

 

[sswells]

I think more people would enjoy having a true cabinet; it's a piece of furniture that compliments all the work that happens on top of it. Having a cabinet shop rip out a plywood cut list of 4 or 5 panels and a few strips should be about as easy as having glass cut, plus then the lists of woods and veneers to choose from becomes only as limited as your funds. In the end people could still have all the fun of screwing it together and trimming it out.

Here is my current project and it's trim schedule:

Interested to see this when finished...

 

[jayinh]

Does anyone know of any threads where some ones stand actually collapsed or failed?

yeah...i want to see those threads. like a car crash, cant look away!:hmm3:

 

[Wills612]

I'm designing a new stand and material cost, weight, and inside room are playing a huge factor in my design. Yes I am a carpenter but I am a metal framer and welder. woodworking is not really my thing but I like to build and I LOVE aquariums so I naturally build my own stands. recently I've been working with an engineer buddy of mine who actually does fine woodwork as a hobby and we ran into these at the lowes and I saw the load capacity and called bull crap but he quickly threw some numbers out there about tensile strength and bridges and blah blah blah blah blah lol and I felt the need to share ( minus the boring calculations). that's all

So your a welder but choose to use wood? Seems like your could get away with a lot less material, and weight with a tube steel stand or even sheet metal stand skinned with a thin veneer, rather then ply.

 

[Jodah]

At first I was like hmmm, then I was like f it. Not worth my time debating.

 

[Drae]

So your a welder but choose to use wood? Seems like your could get away with a lot less material, and weight with a tube steel stand or even sheet metal stand skinned with a thin veneer, rather then ply.

my design is a non "skinned" type of design. 3/4 ply is the support. the plywood box will bethe exact dimensions of my tank ( length and width) with trim going from 1.5" down the box to just past tank trim. so simple with modern style doors with NO DETAIL. big square doors that cover the entire front panel almost. hard to explain. 12" pulls in a modern anodized color with matching anodized sunpower fixtur hanging via a single metal bracket coming from the left side of the tank over to the right ( single leg). I'm just trying to do something a little less common. although I have seen this. plus I'm union! they supply my welder on site. I don't even own one anymore due to last year's money woes ( had to sell it).I won't be doing any metal stand for anything under 400 gallons. ply works well

 

[Drae]

plus I'm not the best at it honestly. Lol I do small stuff like weld up clips for 40' 16 gauge red iron studs when I'm exterior framing out here in Vegas. I specialize in metal stud framing. ceilings and sofets, shaft walls, radius ceilings and domes and such. cast product, doors and hardware, and I've dabbled on the commercial industrial side but hated it. I'm a real carpenter.

 

[Drae]

10 yrs strong.

 

[Drae]

double postage.

 

[barjam]

It depends how you attach the plywood. I throw a couple of nails in each trim piece which does basically nothing structurally, because I don't have incredible forces trying to twist my already ridiculously overbuilt stand.

3/4 ply with as little as four screws on a side panel adds ridiculous amount of strength. Glue it and you have built a tank.

My first in wall tank stand was 2x4 and if you slammed the door on the connected wall the stand was hooked into you could see the water in the tank ripple a tiny bit. Adding two side panels (screwed/glued) prevented that entirely.

 

[barjam]

Either way works. I built one decades ago out of 2x's, then skinned with T&G bead board to match the kitchen it is in. Still there, still looks good, sister is still happy. A properly built plywood stand will hold the weight of a tank no problem. Lots of people don't have the skill or tools needed to work with large sheets. Go look at any factory stands at your LFS.. I have never seen one with a 2x substructure.. But I do see plenty made of MDF and such.. those scare me way more than ply.. because if they get wet... well we all know what happens then.. and we all know "wet" is going to happen. They are often reinforced in the corners with a second piece of MDF for strength, because they don't have long fibers in them to hold up the weight.

Now.. real story about "plywood and tank" (well almost a "tank") I have personally seen, and worked on a Bradley Fighting Vehicle that had its complete suspension system removed, and it was supported by only 4 plywood "boxes" about 2 foot square and cross braced in one direction. Those boxes weighed less than 40lbs each.

I have also worked on M60 series tanks that were in the same status, but sitting on 4 oak cubes, about 18" on a side. Now those blocks weighed about 175 pounds, but they were supporting around 50 TONS.

I am a carpenter and artist who works with wood.. so I have access to a great cabinet saw and lay up table.. my display stands I built are done with plywood and solid wood face frames. I build my own doors, but many people buy them built...

Current 70 in dining room, built to match the other furniture in there..

Underneath with lots of room.. (not a great pic.. but you can see how open it can be..)

And sometime.. 2x's ARE the right choice..

sump in basement..

I think the OP's point was that many stands are overbuilt for no reason.. he didn't maybe articulate it well though. I know I have seen stands on here built with 2x6's, then skinned in 3/4 ply.. I am sorry.. but I do get a chuckle out of those. The biggest stand I ever built is for a 380.. it's all plywood, been up about 8 years now, no problems.

The facts are that many feel comfortable with working with 2x's, and they do work. But 2x's are not as dimensionally stable as ply, by a long shot. All is good if it has an aquarium on it

It is funny that in this thread about 2x4 vs ply you show the wrong way to create a 2x4 stand for a tank (your sump). Obviously this is well built for your purpose though.

He probably knows this but for anyone else reading this I am talking about the lag screws carrying the weight of the top. It is better to out the 2x4 top frame over the 2x4 posts so the relatively week screws aren't carrying the weight. It looks like he used lag screws so he was likely aware if this and compensated.

 

[Fish_Hobby]

Interesting...

 

[BeanAnimal]

Interesting...

Now that is a very deep thought!

You do realize that as soon as a moderator sees that you are post padding just to get to 50 posts (or whatever it is) that you need for the selling forum... they are going to knock you back to 0.