How much weight could this stand hold?

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I'm building an aquarium stand for my reef tank. The lighter brown in the mock-ups is bubinga. The top would be solid bubinga along with all the rails and legs. The bottom shelf would be a bubinga veneered (or maybe just plain) plywood. The darker one is wenge, except on the sides where it would be wenge veneered plywood. The light support pieces are probably going to be maple. There is going to be a tank on top, as well as one inside the cabinet. Net weight is conservatively 350lbs not including other equipment. I'd feel comfortable if weight support estimates were around 500lbs or greater.


Here's the full mock-up, The stand is about 45" tall (I may knock the cabinet height down so there's a total of 40" high), and the cabinet is 42" wide and 20" deep. The legs underneath it are 4" long if it matters.








Here it is with the top and doors stripped off, this would be the structure that would support all the weight. All the bubinga rails and legs would be 2" x 2"  (these may be made larger to extend out further on the sides for design purposes) and the plywood, between 1/2" and 3/4", would sit in dados cut into the legs and rails to help provide rigidity. The maple support pieces are 3/4" x 1".




The bottom piece of plywood has the same supports as the top. This is the frame of the cabinet.




The legs and rails would be joined with mortises and tenons. One question I have with this is how should I size the tenons because I have two going into the leg and the same height.









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How thick is the top?  


Since the top is solid hardwood, you've got to plan for wood movement, so it will be floating on top of the rails and aprons.  Using a veneer/plywood top, glued and screwed to the rails and aprons, would give you more strength, because the combined unit would be effectively thicker.


The weight is transmitted to the floor through the four vertical posts.  The mortise and tenon joints you have are strong enough, I think, because most of the weight will be on the top, which is resting directly on the posts.  Especially if you make the top plywood as i suggested above.


If you make the back and sides veneered plywood, and glue them along all four edges, that will do a good job of preventing racking.

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The top is around 3/4"-1" thick depending on what kind of stock I can find. I wasn't entirely sure yet how I would attach the top to the frame, I had thought about just screwing it on in a few spots. I'd prefer to keep the top solid hardwood if it isn't going to compromise the structure.  


And about most the weight being straight down the legs, the bottom piece would be holding a tank potentially as heavy as the one on top, so this one would be supported by the mortise and tenons. What would be the way to size these tenons?

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I meant that the legs--one single piece from top to floor--extend 4" past the bottom shelf. 


One other thing I had forgotten to mention, and that is basically impossible to see from the mock ups, is that the plywood for the bottom shelf would sit in a 1/2 lip in the bottom frame such that it would be flush with the top of the bottom frame.

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I would suggest dropping the height to 40" like you said you were considering. What size is the tank? I had a 210g reef that was 24" deep. If the stand gets too high you may have trouble getting your hands to the bottom of the tank. As far as the weight goes,  just wanted to make sure you're taking into account the additional weight of sand and live rock. That can really add up. Please post pictures as you get it all set up. You're combining my two favorite hobbies. I may have to do this sometime. Good luck!

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Yeah I factored in sand and rock. Its a 20L on top with, currently, a 15g sump, but I've made the stand such that it could accomodate a 29 for both.


I'm thinking about modifying the design a bit, construction wise, its not going to change much of anything other than the legs getting larger at the bottom and the rails getting wider and a curve getting cut into them. Through mortises might be considered as well. This piece really caught my eye and I've been thinking this little mock up is pretty plain anyway.



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I would be leery of just screwing the top on, as you indicated above. A 20" wide by 1" thick solid bubinga top will need to be attached so that it can expand and contract across the grain. I would consider cleats or at least make sure you elongate the holes the screws go through to allow for the expansion/contraction.  I like BC's idea of using glued plywood side and back panels to add structural strength to prevent racking, rather than relying solely on the m&t joints.

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I once had a 10 gallon tank on an old piano bench, with a 3/4 inch top and slightly flared legs that weren't more than an inch square.  Maybe a two inch apron, with micro stubs of a tenon.  The bench still exists, but the fish and aquarium don't.  I'd say you shouldn't have much worry, but I don't know the weight I had.


My uncle used to have two massive salt water aquariums in an over/under arrangement like what you're talking about.  If I remember right, he just used construction lumber and steel frames, and laid plywood across the tops of them.  (Last time I saw the arrangement was over 30 years ago; he's moved four times since, and the tanks have been reassembled into different configurations.)


My worry about the rail set-up is that it might weaken the support with the dados/holes for the cross rails: you should be able to get similar support with just two or three underneath your top.  As for the tenons going into the leg at the same location, that's not really much of an issue.  There are a couple different ways of doing an interlocked tenon, such as mitered ends or half lap ends.  It comes down to practice in getting the layout right, so I'd grab a stack of scrap and try out a couple options before working on the live projects.

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JHop makes a good point. Make a test joint to understand what is involved and see if your faith in the joint you propose is gonna work.

I have made several aquarium stands over the years and I would at least have a back panel between the legs to stiffen things up. Back and both sides if it was going in my house.

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