Threshold for solid contact between a stand and the tank

  • We are currently upgrading MFK. thanks! -neo
Well styrofoam mat would be better than discreet shims. The whole idea is that whatever you use should provide continuous uniform bearing.

I know that shimming directly under the tank would be a bad idea, though in the case of the stand I've put shims in all the way around with no gaps.
 
The cheapest Dap painters caulk works OK & dries fast.

Also I have used wood dough, on wood then flat-sanded. Some stands, I just got a big board and flat-sanded them.

I have used Sikaflex concrete adhesive, but it is 6x as permanent.

Almost any caulk which dries will work.
 
So I took a look behind the stand, and there's a bad warp along the back that I didn't notice, and while I believe there's solid contact at the very corners, I am 100% not comfortable with this.


Tank_Problem.jpg




While there's a bit of forced perspective going on because of how I had to contort myself to get this picture, the gap along the back is around 1/16" at the thickest. Will I be able to fix this with wood dough, or do I have to pretty much get a whole new stand? The gigantic rim on this tank doesn't really help when it comes to shopping around for new stands.
 
Wood dough is fine if just 1/16" thick or so.

I did one 29 years ago and it has been moved 4 times without issue.
 
Wood dough is fine if just 1/16" thick or so.

I did one 29 years ago and it has been moved 4 times without issue.

Honestly, replacing the top piece of plywood doesn't actually sound so hard after all, so I'm planning on doing that and adding some additional reinforcement.
 
You can re-sheet the stand 10 times, but you can't make it mate up with the tank 100% unless you bed the tank. The bedding insures it fits, as neither the tank or plywood are 100% perfect.
 
By the way, if the tank in that photograph is full of water I would shim it up with plastic bits temporarily.

Vertically, the front and back of the tank act solid, and when the middle of the bottom is not supported, it tries to pull those side straight down. This puts enormous shearing stresses on the silicone at the corners. It will make the top of the tank try to "bag open", putting a lot of strain on the cross braces.

Shimming it up temporarily would relieve a lot of those stresses. Be careful because by forcing shims into that tapered gap, you can lift the corners off the stand.

This allows you to put some shims in the middle that you might not quite be able to get in place. Then pull the ones that are holding the corners up and allow the tank to drop to compress the shims slightly.
 
By the way, if the tank in that photograph is full of water I would shim it up with plastic bits temporarily.

Vertically, the front and back of the tank act solid, and when the middle of the bottom is not supported, it tries to pull those side straight down. This puts enormous shearing stresses on the silicone at the corners. It will make the top of the tank try to "bag open", putting a lot of strain on the cross braces.

Shimming it up temporarily would relieve a lot of those stresses. Be careful because by forcing shims into that tapered gap, you can lift the corners off the stand.

This allows you to put some shims in the middle that you might not quite be able to get in place. Then pull the ones that are holding the corners up and allow the tank to drop to compress the shims slightly.


Don't worry, I've longs since drained the tank. I'm probably lucky that this tank was built like a tank though, because I see now how it could've gotten extremely ugly upon filling. It's all 1/2" glass AFAIK despite being a 120 (and the bottom pane is tempered), and there's a sheet of glass about a foot wide serving as the cross-brace rather than the more conventional plastic cross brace.

I see your point about the importance of bedding the tank to the stand, but I still like the idea of having a neoprene mat cut out to match the rim, that seems less permanent than bedding compound, and I might have to break down this tank at some point in the next few years.
 
If you put a coat of wax on the bottom of the tank it won't stick to the bedding compound and that will remain on the stand when you lift your tank.

If you use a styrofoam or elastomeric mat you will probably achieve full contact.

Yet that contact will not be equal as far as pressure on the tank goes.

You need to set it in something that will flow a little bit and then stiffen up, to get equal pressure everywhere.

Now depending on your stand and what your stand is standing on, that may not be the ideal situation from a structural standpoint; but I'm assuming that all things are nominal
 
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