10 ft. Long Stand, Double Tank Advice

[imeridian]

Originally Posted by intermediate_noob

Did you use 2x4s for your setup?

Yes, I used 2x4's and then "skinned" it with oak and 1/4" oak plywood. Here's an example of one of the pocket screw applications. The pocket screws are on the outside, but the pocket is in the vertical support and connects to the horizontal member, while screws also go through the horizontal member into the front to back middle support.



This photo shows some of the overall construction, including my triple 2x4 corners. The over-construction of the corners should, I believe, greatly lessen any twisting potential, whereas the central downward supports are more limited in the strength side to side.

I don't know if any of that is actually helpful for this particular stand, but there it is anyway.

FWIW, If I were to buy the Kreg Jig again, I'd have bought the 2 hole version. Clamping the 1 hole version in place was always a bit too tricky for my tastes. It was great for joining the mitered frames of my stand doors though.

[Sponsors]

[swylie]

Here's a link to a template that's based on actual engineering calculations and has been used by a number of people successfully.

If you build two of those or modify the design into a double-wide it will be plenty strong enough to support your tanks. The design doesn't appear to resist twisting very well though, which is why it should be skinned in plywood. Virtually any thickness of plywood would be sufficient, even the very thinnest.

If you read through that thread you'll see that a number of people ask about 4x4s and are repeatedly told that it's a bad idea. For vertical members they're just not necessary, and for horizontal members a 2x6 will give you more strength anyway. Worse, they're apparently prone to warping, dunno why. If you follow those plans and use two perpendicular 2x4s at each corner and attach them at a couple of points they'll never warp.

I built something based on those plans, but it's only for a 10g tank, so I used the scrap I had in the barn which happened to be 1x4. I used glue and screws instead of clamping, and the damn thing is strong enough I could jump up and down on it all day and not break it.

[imeridian]

Oh, wow, that template actually shows how I constructed my stand! I'd never seen it before. The only difference is that I have the purple members in the center also, in addition to a center brace across the bottom like the top. The top & bottom of my stand is sheathed in 3/4" outdoor ply. The center brace at the bottom helps keep any spilled water on the "wet side" (shown in the photo above) too.

[swylie]

Originally Posted by indiboi

Oh, wow, that template actually shows how I constructed my stand! I'd never seen it before. The only difference is that I have the purple members in the center also, in addition to a center brace across the bottom like the top.

Yeah man, that's why I linked to it, to show how little is really necessary. Even that design is significantly stronger than commercial stands, and massively stronger if you add a skin. Most people overbuild, IMO. Why build something heavy, ponderous, and expensive when you could build something light, engineered, and efficient? Maybe I've just helped too many of my friends move recently...

[imeridian]

Hehe, that was kind of exciting, to see that someone else had the same stand plan and made a nice color coded diagram.

While apparently not necessary, the center vertical supports gave me something to attach my thin bookmatched veneer plywood to. The 3/4" stuff had horrible rotary cut veneer, in addition to being twice as expensive and 3X heavier.

My stand is still obnoxiously heavy, but probably no more than the aquarium itself (empty of course, lol).

[jinx©]

Great linkage swylie!

That's a well done thread with an easy to understand diagram & explanantions.

[n00dl3]

I built my 180 gal stand made out of 2x4's and angle braces and it is study and very strong. It works great! Metal stand is great if you know to wield. Here are a couple pictures of the stand and hood.

[lauraleellbp]

WTG- awesome job!

[kornphlake]

You can bolt steel or aluminum together and it will be just fine, you should design the stand so that your joints, rather wood or metal are loaded in compression rather than shear. In simple english that means that the weight of the tank pushes the joints together rather than trying to rip them apart. Fasteners should serve only to hold things together when you're moving it around and keep pieces from slipping off of each other. That's the idea anyway, some times there are situations where it's just not possible, I've found nuts and bolts to be remarkably strong, the best would be socket head cap screws (google knows what they look like if you don't) a 1/4-20 SHCS is rated for minimum 5730 pounds tensile strength, that's a lot of water on one bolt. Stay away from stainless fasteners, I know they look nice and it sounds like a good idea for a something intended to be used near water but they are a bad idea. Stainless fasteners are usually not graded and not rated for structural applications, many "stainless" fastners will rust as well.

Drywall or deck screws are not very strong, if you've got to use them make sure they are just holding things together, not being loaded in shear or tension.

I've heard that 2x4's are less likely to warp and twist than 4x4s if you must use 4x4s consider a pair of 2x4s side by side instead, or better yet use a 2x6, it will be much stronger than a 4x4.

Wood has grain, you have to take that into consideration when designing and building a stand, end grain is not very good for holding fasteners, end grain is not good for gluing, wood will split in the direction of the grain, wood swells more across the grain than along the length (a 2x4 will swell more in width than in length). Plywood adresses some of these issues by combining several layers of wood with the grain running in different directions, plywood does not hold fasteners well when driven into the edge, it may be worse than trying to drive fasteners into the end grain of solid wood. A superior design uses both plywood and solid wood strategically to take advantages of the benefits of each.

People like to claim they have over engineered their stand design when in fact they haven't engineered a thing, they just built something heavy, expensive and unlikely to break because of the amount of material in the stand. An engineered stand looks a lot like what some people are uncomfortable with. Good construction, quality materials and a sound design will hold a tremendous amount of weight.

Any guesses how thick the shaft of a screwdriver needs to be to resist breaking under the force of a human wrist turning a screw? It's something like the diameter of a thin coat hanger, obviously they are made to withstand abuse like being used as a pry bar, a chisel, a hammer, a lawn dart, or whatever uses people can come up with. This is a case of overengineering, because the tool has a potential for uses aside from the intended use it was designed to be much stronger than it needs to be, I can't think of many ways a tank stand could be misused, overengineering is really not necessary.

[jinx©]

The stands I'm uncomfortable with are the ones that may very well be engineered to hold weight and sell to the masses but have very little lateral strength whatsoever. (The knock-down stands quickly come to mind)

The one stand pictured earlier that I commented on as causing me concern may be engineered and work fine for holding weight, but once you factor in possible unlevel floors and bumps from the side by adults or children it's pretty much the same as using an underengineered screwdriver as a prybar IMO.
There's just nothing there to give it much lateral strength if it's ever needed.

[swylie]

Originally Posted by jinx©

The stands I'm uncomfortable with are the ones that may very well be engineered to hold weight and sell to the masses but have very little lateral strength whatsoever. (The knock-down stands quickly come to mind)

The one stand pictured earlier that I commented on as causing me concern may be engineered and work fine for holding weight, but once you factor in possible unlevel floors and bumps from the side by adults or children it's pretty much the same as using an underengineered screwdriver as a prybar IMO.
There's just nothing there to give it much lateral strength if it's ever needed.

Such stands could be easily corrected though. I'm not an engineer and I haven't run the numbers, so don't take my word for it though. This is just my opinion. If those stands had braces glued into the corners they'd have more than enough lateral strength. I'm thinking of something like triangles cut out of 3/4" plywood or 2x6 or something. A 5.5" per side wedge should do it, right? Finishing the cabinet with a skin would work too.

[jinx©]

Originally Posted by swylie

Such stands could be easily corrected though. I'm not an engineer and I haven't run the numbers, so don't take my word for it though. This is just my opinion. If those stands had braces glued into the corners they'd have more than enough lateral strength. I'm thinking of something like triangles cut out of 3/4" plywood or 2x6 or something. A 5.5" per side wedge should do it, right? Finishing the cabinet with a skin would work too.

I completely agree.

Such stands could easily be beefed up by skinning and/or framing to add lateral support, but seeing that we're talking building stands I'd be more inclined to build something better to begin with like the example shown in your link.

[kornphlake]

I totally agree that this stand looks underbuilt for the purpose, I'd have framed the vertical corners with 2x4s and either used a few triangle gussets or a diagonal 2x4 across the back. From the picture I'm not sure the cabinet is finished yet, as it is shown it's not a very good representation of a well engineered stand.

A good engineer understands that while a design may be strong enough on paper consumers demand a certain look or feel, extra reinforcements while often unnecessary are often added to make a product look more industrial, or give a sense of quality. As an example I worked with a folding table manufacturer as part of my senior project, the company we worked with uses a small triangle shaped bracket at the joint on one of the legs. They straight up told us that the triangle bracket was not structural at all, in fact the hole required to attach the bracket reduced the overall strength slightly, but it was needed to satisfy customers who thought the table didn't look "strong" without it. In this example the engineer added a piece of material that was tastefully sculpted to give the illusion of strength without adding unnecessary weight or cost to the product. The addition was made after an engineering analysis and testing, not an off the cuff attempt to solve a hypothetical problem.

I understand that carpenters are not engineers, I understand that framers are not engineers, I understand that most people who own a keyboard are not engineers, which is why I don't understand where people who aren't engineers get the idea that they are qualified to make an engineering assessment of a product based on a feeling. Would it surprise anyone if a stand that seemed flimsy when the tank was not filled with water could be very rigid when loaded with nearly a ton of water? It wouldn't surprise me.