Stand Design question: lumber for span

[Js.Aqua.Project]

I am in the planning stages of building a stand for my 265 gallon aquarium (85" x 24" x 30") and plan on using the standard Rocket Engineer design for the subframe.

My question is this, what dimension of lumber do I need to span the length in order to have it not need a center support? Will a 2x6 be sufficient or should I use 2x8?

 

[xaflatoonx]

i would go with a 2x8

 

[anit77]

Are you going with a framed tank or rimless?

 

[Js.Aqua.Project]

Are you going with a framed tank or rimless?

The tank is rimmed. I would like to not use a plywood deck as well to make access to bulk heads easier.

 

[anit77]

You can do it two ways. Build a RE stand and skin it with plywood, if your going for a finished look. Or make the whole thing from plywood. Which ever way you go increase the length and width by 3/4". The dimensions of the tank don't include the frame.

With the RE stand I would use plywood to make the entire upper portion. With one 3/4" 4x8' sheet and five cuts you will have six 8"x96" pieces (less the blade width) to build that part. Home Depot or Lowe's will do those rips for you too.

Then cut four pieces 85-3/4" and four pieces 21-3/4" and with 1-1/4" wood screws and Titebond III make two pairs of each laminated together. Once you have that done you need to make the box. I like to use a kreg jig and 2-1-2" screws with Titebond in the seam. Remember it's the glue that gives the joints strength not the screws.
This is strong as hell, won't sag or need middle supports.

If you're interested in making the entire stand out of plywood I can explain that too. Even show you how to get a complete cut list together so all the major cuts can be made in the store when you get the sheets. Then you just need to cut whatever openings you want for any or all sides. Depending on the size of some of those openings you can use the scrap pieces to make doors for the smaller openings.

 

[Js.Aqua.Project]

So I finally have sometime to come back to this design.

I think I would be more comfortable using this RE frame and skinning it (haven't decided between skinning it with plywood or 1" lumber similar to https://www.reef2reef.com/ams/how-to-building-an-aquarium-stand.203/ )

I just want to verify that this frame is going to be structurally sound. The pieces highlighted in blue are going to be made from 2x8 and the rest from 2x6.

 

[don_chuwish]

Definitely skin it, best with plywood. You'll want something to brace against racking.
2x8 seems like it should be enough. It's basically a 6' span once you factor in the width of your corner posts. Just make sure you get kiln dried 2x8s that are as straight as possible. Then make them even straighter in the shop - usually means removing about 1/4" - 1/2" on the table saw or jointer.

 

[jsker]

So I finally have sometime to come back to this design.

I think I would be more comfortable using this RE frame and skinning it (haven't decided between skinning it with plywood or 1" lumber similar to https://www.reef2reef.com/ams/how-to-building-an-aquarium-stand.203/ )

I just want to verify that this frame is going to be structurally sound. The pieces highlighted in blue are going to be made from 2x8 and the rest from 2x6.

That is a solid plan, with the 2x8's. I would suggest running a 2x4 inside on your corner for more corner bracing instead of just stacking and pocket holing.

I would suggest if you are going to us the door hinges that you referred to in the link, use 3/4 ply to skin. Find a cabinet supply place (Kelly's) by you and use cabinet grade birch or pine for the skin and trim the skin with molding. You are looking for a 9 to 11 layered ply;) The big box store usually sell 5 layer ply with all kinds of gaps in the gluing.

 

[davocean]

Having a rimmed tank gives you added tolerance, that was the key question.
Anytime I build a stand for 240 or bigger my concern is that is remains flat, it's a big footprint, so keep in mind most 2x8's may have a slight crown, crown up is best to keep from sagging over time, and this is when I will probably hard fasten the skin to also help lock that in place.

I do agree this is about the length where I would prefer sandwiched ply over 2x if that is an option for you, and if you were rimless I would even more so go that route to maintain a a true coplanar surface.

 

[Js.Aqua.Project]

Having a rimmed tank gives you added tolerance, that was the key question.
Anytime I build a stand for 240 or bigger my concern is that is remains flat, it's a big footprint, so keep in mind most 2x8's may have a slight crown, crown up is best to keep from sagging over time, and this is when I will probably hard fasten the skin to also help lock that in place.

I do agree this is about the length where I would prefer sandwiched ply over 2x if that is an option for you, and if you were rimless I would even more so go that route to maintain a a true coplanar surface.

I have never built a sandwich ply structure before, I am just more familiar with 2x construction. If there is a video/picture based tutorial using that method that you recommend I will watch it and see if I can get my confidence up to try it.

I was looking to skin it prior to the tank being on it to help keep it from racking or sagging (hopefully).

 

[davocean]

2x and skin attached will do just fine w/ what you are looking to do on that tank, as in keeping it open.
I often build 2x frames and make the skins stand alone/removable, but w/ that span the ply will help secure and add shear strength.

Ripping ply is more precise, but you should be fine, a trimmed tank is more forgiving, you usually only need support at 4 corners compared to flat glass on tank stand like a non trimmed tank.

Mine are mostly like rockets design, but I do a couple extra steps on mine, a flat 2x cap on top of frame, and 3/4" ply on top of that, lots of glue, gold colored/zinc coated screws, tightbond 3 for the glue.

I am however known to be a little overkill though, but I think these things do help ride minor deviations and keeps pretty darn solid long term.

 

[davocean]

This is my standard frame as I build them.
There is a center brace on this, my own personal tank, it could have been skipped, but I have doors landing on something there anyway so I added it, and it is removable, 2 screws at top and bottom, should I ever need to really get in there.

 

[Js.Aqua.Project]

This is my standard frame as I build them.
There is a center brace on this, my own personal tank, it could have been skipped, but I have doors landing on something there anyway so I added it, and it is removable, 2 screws at top and bottom, should I ever need to really get in there.

I have seen your tanks before in the stand show off thread, unfortunately you and I are on opposite coasts...