Need help design stand - The Planted Tank Forum
 
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post #1 of 13 (permalink) Old 01-20-2008, 12:36 PM Thread Starter
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Need help design stand

Hi,

I'm unable to choose between the two designs. Currently I'm leaning toward having 2x 26" work area (Drawing #1) vs 1x 36" work area (Drawing #2).
Could you help me select which is better structural wise, also can the designs handle a 72x30x25 tank.

Stand dimensions are: 72x30x28"H, Height is still undecided atm.

Top down drawing:
#1 - 2x 26"


#2 - 1x 36"


I needed these work area because I'm going to have a full pentair double module setup, going horizontally from back to front.

Thanks.
Khoi


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post #2 of 13 (permalink) Old 01-20-2008, 04:37 PM
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It's hard to say really without knowing what work area means, but maybe this site can help you decide.


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post #3 of 13 (permalink) Old 01-20-2008, 08:39 PM Thread Starter
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What I meant by work area is the area this open for me to access from the front. This is because I want to ease maintainence of the pentair modules. I plan to have them all face outward so I can easily unscrew the cap to replace filter media, uv bulbs, and heaters.


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post #4 of 13 (permalink) Old 01-20-2008, 09:31 PM
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In #1, I don't see what the 4 4x4's clustered so close together in the middle buys you. Since it looks like you're planning on using framing lumber, 2 4x4's in the middle (one on the front, one on the back) would be OK. Although with a 36" span between 4x4's, it's probably better to use 2x6's for the horizontal front and back members, rather than 2x4's.
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post #5 of 13 (permalink) Old 01-20-2008, 11:30 PM
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Wow it took me a long time to figure out what I was actually looking at there. What size tank is this for? Glass or Acrylic? Are you putting something like MDF or plywood on top of the stand or will the tank rest directly on the lumber?

With a glass tank all the support you need is in the 4 corners of the tank, you don't necessarily need anything in the middle because there's no load there but it can help stabilize the stand. I'd use 2x4s in the middle and 4x4s in the corners or better yet use pairs of 2x4s to make 4x4 pieces for the corners, 2x4 lumber is less prone to twisting and warping than 4x4.
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post #6 of 13 (permalink) Old 01-21-2008, 05:17 AM Thread Starter
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The tank is to be made out of glass. I didn't know 4x4 is more prone to warping.. I'll revise the design to use 2x4s and 2x6s.

Also I went to Lowe today and they sell Fir and Redwood. Redwood is more expensive, but the sale guy said they warp less than Fir. Is redwood OK for this stand?

Thanks.


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post #7 of 13 (permalink) Old 01-21-2008, 04:49 PM
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Quote:
Originally Posted by kornphlake View Post
With a glass tank all the support you need is in the 4 corners of the tank, you don't necessarily need anything in the middle because there's no load there but it can help stabilize the stand.
That's not true. With a glass tank you need to support the perimeter, but not the interior. With an acrylic you need to support the interior as well.

Supporting a loaded glass tank at just four points, one in each corner, is asking for trouble. You put a bending load on the bottom, and shear stresses on the side panels.
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post #8 of 13 (permalink) Old 01-21-2008, 08:46 PM Thread Starter
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Final? Design

Here's a pretty much final design.



Comments?


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post #9 of 13 (permalink) Old 01-21-2008, 09:03 PM
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ok, better safe than sorry and coincidentally I design my stands with full perimeter support but I've heard it's not necessary. Logically I can see how the tank walls act as an i-beam structure to reinforce the bottom and I know people who have had 20 and 30 gallon tanks on breeder racks for years without full perimeter support but that doesn't really prove or disprove anything.

I could model a tank and run FEA on it, but its really irrelevant as the OP's design includes perimeter support by the 2x6s which when set on edge should be sufficently strong to cover a 72" span without bracing in the center. I'd recommend something for stability though.

personally I'd use option 2 with 2x4 supports in the center and doubled 2x4s in the corners. I'd add a couple of diagonal pieces on 3 sides to reduce the twisting as well or skin the stand with plywood.
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post #10 of 13 (permalink) Old 01-21-2008, 09:19 PM Thread Starter
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The reason there's no support in the center for #2 is because I needed the open access space from the front for my pentair modules. I needed space for at least 4 modules connected together, each module has a width of 7" so 7x4 = 28" minimum open front accessable space.

What do you think about my latest design? I include the holes placement to explain the reason why those beams are where they are. The top of the stand will be a some sort of wood board (pine?) and then a 1" compression foam, then the tank, hopefully this will be adequate.


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post #11 of 13 (permalink) Old 01-21-2008, 09:34 PM
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What do the black outlined holes represent in your last diagram? Are they the actual hole size or the outer diameter of the bulkhead? They are awfully close to some of your crossmembers and just want to make sure you have room to thread the bulkhead on.



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post #12 of 13 (permalink) Old 01-21-2008, 09:39 PM Thread Starter
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Oh sorry I didn't explain that. They are "work area" that I plan to have so I could work on the bulkheads. The colored holes are actual bulkheads holes. The outline are the area I plan to cut on the top pine wood board and compression foam.


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post #13 of 13 (permalink) Old 01-21-2008, 10:19 PM
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Cool, just checking.

For the top, I'd just use 3/4" plywood or mdf. Cheap and easy.



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