Please survey my 300g stand

[HenryC]

My 300g is pretty much finished! While waiting for the silicone to finish curing, I wanted to see what people think of my stand. It's made with 20 2x4's, triple on the corners and doubles on the center legs. I think I will be ok, but as I live in earthquake area, I was wondering if anyone has any advice on how to reinforce it even furtuer (if needed). I am kinda uneasy on the smaaaaall wobble that remains when I push it a bit (can be seen in the video at the end).

I was thinking on putting more 2x4's across the center, uniting the center legs with each other. Kind of like "bridges"

Like so:
|     |                      |     |
|  o |---------------| o  |  <-------- horizontal lines: 2x4 "bridge" connecting center legs on both sides
|  o |---------------| o  |                 vertical lines: center legs
|     |                      |     |                 o: screws

Any suggestions:

 

Edited July 22, 2022 by HenryC

[Pepere]

Plywood panels on the sides glued and scewed into the 2x4s would add tons of rigidity and bracing and would be my choice.

Alternatively you want diagonal bracing to make triangles.  The bigger the triangles the better from a structural standpoint.  Aesthetically I prefer plywood.

 

and there is plywood and there is plywood…. Ie there is low grade rotary cut fir, and there is high grade veneered plywood…

case in point, here is a sailboat I built for a client that is completely built with high end plywood.  Zoom in on the plywood on the deck for the wow factor.

[HenryC]

On 7/21/2022 at 6:25 PM, Pepere said:

Plywood panels on the sides glued and scewed into the 2x4s would add tons of rigidity and bracing and would be my choice.

Alternatively you want diagonal bracing to make triangles.  The bigger the triangles the better from a structural standpoint.  Aesthetically I prefer plywood.

 

and there is plywood and there is plywood…. Ie there is low grade rotary cut fir, and there is high grade veneered plywood…

case in point, here is a sailboat I built for a client that is completely built with high end plywood.  Zoom in on the plywood on the deck for the wow factor.

Aw it can't be zoomed in, but that looks real pretty even from afar. Love the color.

Yes I forgot to mention I will put plywood! Do you think my stand is ok structurally? Someone told me 2x6's would have been better.

Gonna go look for high quality plywood. Bet it can save a lot of staining time and effort lol.

[Pepere]

And I would without question want to significantly increase rigidity before adding north of 3,000 pounds.

 

With plywood glued and screwed to the 2x4s significant strength will be added to the 2x4s.  You are in essence creating I beams bonding the top horizontal 2x4 to the bottom.  Tremendous bearing strength.  I would use3/4 ply.

The boat gets nearly all of its strength and rigidity from the plywood and not the framing members in the above picture..

 

you want to ensure all of the dimension lumber is flush to adjacent pieces so the plywood mates to all dimension lumber well with good gluing surfaces.

Dont scimp on the glue….  Squeeze out is good….

[HenryC]

On 7/21/2022 at 6:39 PM, Pepere said:

And I would without question want to significantly increase rigidity before adding north of 3,000 pounds.

 

With plywood glued and screwed to the 2x4s significant strength will be added to the 2x4s.  You are in essence creating I beams bonding the top horizontal 2x4 to the bottom.  Tremendous bearing strength.  I would use3/4 ply.

The boat gets nearly all of its strength and rigidity from the plywood and not the framing members in the above picture..

 

you want to ensure all of the dimension lumber is flush to adjacent pieces so the plywood mates to all dimension lumber well with good gluing surfaces.

Dont scimp on the glue….  Squeeze out is good….

Thanks a lot! Will do exactly that.

[Pepere]

Bear in mind he importance of the glue.  The screw are used primarily to provide clamping pressure for the glue.  They are somewhat superfluous once the glue sets up.

I would not rely on screws without glue.

[nabokovfan87]

This is the part that concerns me.  The gaps here.  I also saw them when looking down the length of the stand on all of the supports.  If the floor isn't flat, the base was assembled on the floor, the question is how "flat" is flat.

If you can, try to detail the hardware placement and people can chime in on how the construction is attaching the vertical supports to the horizontal panels.

 

Red = no gap or less of a gap
blue = slightly bigger gap.

[ScottieB]

I’m certainly not qualified to give you engineering advice but I (ok my Dad) build my stand for the same tank dimensions. We opted with mostly 2x6’s and a nice furniture grade wood to skin the whole thing. I’ll just include some pictures that I took along the way and hope that helps. 
 

 

 

 

 

 

Edited July 22, 2022 by ScottieB

[Brandon p]

I think it will be good. 2x6 is over kill. Your spacing looks good it should me great.

[Odd Duck]

Hubs and I once built a stand for our 70 gallon reef tank and we used 4 x 4’s at the corners.  We did a lot of things wrong at the time (that you are not doing wrong) but it was sturdy and didn’t fail for over a decade until we finally sold the tank.  As far as I know, the stand is still serving well but it’s “lost to follow up” as we say in the medical field.  If I was building now, I would follow exactly everything that @Pepereis saying because I came here to say the same thing and found they were already very well stated.

Get some glue between all your doubled up 2 x 4’s and screw them all together so the legs are much stronger and more rigid.  Use the strong, high grade plywood as suggested since it provides loads more rigidity against diagonal flexing, essentially acting like all the diagonal bracing you see in the Eiffel Tower.  The plywood doesn’t have to physically hold weight up, it is more about bracing the stand against flexure in this case.

@ScottieB, that stand looks like it could hold a couple stacked elephants!  No worries for that dude giving way and still looks good!  Nice job!