DIY stand strength question

[Alex27]

Here are a few pics

 

[Alex27]

The first pic held a 200DD marineland and the second pic is the inside.It was made from 2x6 no center brace.
The third pic is a current stand I'm building for a 45 cube. It will be skinned in 1/2" plywood and topped and bottomed with 3/4" plywood.

 

[jtgordon20]

Here an improved design from what you guys have suggested.

Same skeleton but the red top is overhanging 1/2" on the sides and front to go over the side plywood pieces.
The front, and side pieces are 1/2" instead of 1/4"

 

[redfishbluefish]

I hope you're putting a full piece of plywood on the back.

 

[jtgordon20]

I wasn't really planning it due to air flow but when I build it, if it needs it then I could.

 

[fragmatic]

In my opinion, for what it is worth. You do not have anything to keep the frame from going out of square from left to right, without at the least a half sized rear piece on the back or two short pieces front and rear. When the tank is full there will be horizontal forces as water sloshes back and forth or the tank is bumped or you lean on it while working. These small forces will be plenty to bust your glued joints while under load, because of the short distance they span and the wear and tear of cyclic forces. With a glued on back or two additional shorter faces at the rear and front you expand that joint and form large gussets which brace those joints and buffer those cyclic forces. If you look at professional built wood stands you will find wide boards at the top and bottom. These are there because of what these forces. However, if you attach the stand to the wall you can use the wall to provide this stability.

 

[jtgordon20]

I'll have to add a piece of plywood along the back then. Will a 12.5" tall piece across the back be strong enough? I'd like it not to be taller than my sump and probably a 6" piece up top to attach a future reactor to.

All joints will have screws and glue, not just glue.

 

[fragmatic]

I'll have to add a piece of plywood along the back then. Will a 12.5" tall piece across the back be strong enough? I'd like it not to be taller than my sump and probably a 6" piece up top to attach a future reactor to.

All joints will have screws and glue, not just glue.

I think so. I just looked at my commercial built stand and it has 4" top and bottom horizontal boards at the back, and 4" at the bottom in the front with 3" at the front top. So that sheds some light on the subject, and my sump and refugium set in nicely. Plus the vertical members are 4" wide in the rear and 3" in the front.

However, the joints at the back are lap joints. This is where they gained that buffer strength. By lap joints I mean the vertical members are indented inside enough that the horizontal members are outside of them which allows them to be glued as over lapping joints. This lets you put glue on the whole lap joint, then put screws through holes in the horizontal members into the vertical members sucking them together in a forever tight joint.

If you make sure that you completely seal all the wood, inside, outside, bottom, and top. That will work. The reason for this is you have wood going different directions in the joints. If it can get changing amounts of moisture it will swell in different directions. This weakens and or loosens joints. By sealing the complete unit you can do a reasonable job of preventing most of that from ever happening.

This should help you get your open format back. :smile:

 

[Alex27]

Here’s a dimensional lumber plan:

If you are using pocket screws and skinning the stand, you should be able to eliminate that light green piece.


For a 40B, 2 x 3’s should be more than enough. I would also top the stand with a minimum of ½ plywood. And ¼ ply would be enough for the skin.

If you follow the stand above as a map, you will not need to have any coverings in the back. you can see that the above stand has two wood pieces at every corner in additiong the blue piece at the top frame provides stability. even if you did not cover the tank with anything it will be stable.

 

[Alex27]

Here an improved design from what you guys have suggested.

Same skeleton but the red top is overhanging 1/2" on the sides and front to go over the side plywood pieces.
The front, and side pieces are 1/2" instead of 1/4"

This is what I call a frame. In this case the wood stand isn't as sturdy as you'd like it to be, only one piece of wood at the corner, all in the same place and direction will fail. If you take the previous colored stand and placed this frame around it you will have no problems. most people do this so that they can have full access to the bottom of the tank as a sump area.