My DIY stand design. Is THIS safe?

[sikorskys]

The stand is made of 3,9 x 1,9" pine wood (100x50mm). It's typical DIY 43x20x35" stand my for 70g build, https://www.reef2reef.com/threads/70g-diy-peninsula-40x20x20.390761 .

The only difference is that my tank is sitting between vertical supports, not directly above them:

I do understand this stand is way overbuild, compared to MDF cabinets sold everywhere. I realize that horizontal rails purpose is to distribute weight between vertical supports and nothing much else. I know two 4 feet long 2x4s should hold equally distributed weight of 70g tank with ease.

Still, I really need someone to convince me this is absolutely 100% safe So, сan I sleep soundly or should be worried?

 

[Redleg]

You should probably reinforce this with by adding another vertical framing member. As it sits now it appears that your tank is being held up by 3 screws on the left side of the line. That is assuming there is a framing member under the end of the tank.

 

[Sierra_Bravo]

You're fine. As long as the load is transfered to a vertical support member and down you are good. I would agree with Redleg if the horizontial member was screwed in to the leg with a butt joint rather than sitting on top, but it doesn't appear to be.

You may not win any woodworking contests , but for a 70 gallon tank you are just fine.

 

[Erica-Renee]

what does it look like from the end..

 

[Skep18]

The photo below was taken from the linked thread. Added for reference to others.

Bottom line, you're structurally fine IMO. (mechanical engineer FWIW)

Since you have the front and back headers sitting on top of your vertical studs, the load should transfer fine completely through the vertical stud. The offset shouldn't make a difference, especially as you're quite close. Deflection would be nonexistant or negligible as again, the offset it very small. I can't tell but I'm going to guess the lower sheet of plywood is screwed into the boards as well? That actually adds a lot of strength also if screwed in. It makes half of what is called a "torsion box" which is commonly used in building workbenches and stuff among other things.

If you're concerned the wood will shear since the tank corner isn't directly above the upright, don't be. I'm struggling to find numbers online but wood has a listed shear force limit when applied perpendicular to the grain, as is here. Those numbers I'm sure will be quite higher than the weight that you're tank might be.

Now, in regards to the cross members in the depth direction, tieing them into the upright studs like that isn't ideal. Ideally you want cross members to sit on top of uprights. This utilizes the compression strength of the wood instead of the shear strength of the screws. As you have it, the load to the ground goes through the screws which wouldn't be ideal. That said, the four studs carrying the front and back headers will alone be enough. The extra four uprights only add to strengthen the situation no matter how their done.

All in all, you're fine. The stand should hold whatever size water box you're planning to fit on it.

EDIT: Also note, screwing through the front header into the end grain of your depth headers isn't ideal either. Screwing into end grain in general is not as strong. Something light metal joist hangers or even a Kreg pocket hole might be better suited in a situation like this.

 

[sikorskys]

Thank you very much guys!

I made my stand this way, because additional vertical supports require some space I don't want to waste. From what I've read, vertical side supports are optional and this design will work. Not the best one for sure, though good enough. So I did it.

Can't get rid of this anxious feeling I'm missing something since then

Bottom line, you're structurally fine IMO. (mechanical engineer FWIW)

Thank you!

Since you have the front and back headers sitting on top of your vertical studs, the load should transfer fine completely through the vertical stud. The offset shouldn't make a difference, especially as you're quite close. Deflection would be nonexistant or negligible as again, the offset it very small.

That's good

I can't tell but I'm going to guess the lower sheet of plywood is screwed into the boards as well? That actually adds a lot of strength also if screwed in. It makes half of what is called a "torsion box" which is commonly used in building workbenches and stuff among other things.

Plywood sheets are glued together and then to both front and back headers with PVA. No screws.

If you're concerned the wood will shear since the tank corner isn't directly above the upright, don't be. I'm struggling to find numbers online but wood has a listed shear force limit when applied perpendicular to the grain, as is here. Those numbers I'm sure will be quite higher than the weight that you're tank might be.

Glad to know, thank you again!

Now, in regards to the cross members in the depth direction, tieing them into the upright studs like that isn't ideal. Ideally you want cross members to sit on top of uprights. This utilizes the compression strength of the wood instead of the shear strength of the screws. As you have it, the load to the ground goes through the screws which wouldn't be ideal. That said, the four studs carrying the front and back headers will alone be enough. The extra four uprights only add to strengthen the situation no matter how their done.

Yes, I knew that it's better to have cross members sitting on top of uprights. But all these stands I've seen usually have center cross member with no vertical support at all. I started to ask myself why so and it turned out that cross members are used more likely to hold front and back frames together, but not for distributing weight between vertical supports. So I decided it's fine to go without additional uprights to save some space.

All in all, you're fine. The stand should hold whatever size water box you're planning to fit on it.

Thank you

Also note, screwing through the front header into the end grain of your depth headers isn't ideal either. Screwing into end grain in general is not as strong. Something light metal joist hangers or even a Kreg pocket hole might be better suited in a situation like this.

Thank you, I will take it into account next time I dare to make a stand on my own