How flat is flat?

Fiziksgeek

New member
I've been working on finishing the basement of my townhouse which will included an in-wall AGA 210. I thought I had done a decent job of building the stand. Its a 2x6 frame with 3/4" plywood supported front and back with a beefed up wall section.

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The other day, I placed a piece of paper on the back on the stand (its about 30" deep, tank is 24" of course). I pushed the paper, and it actually was able to go under the edge of the tank.

Getting to the point, how flat does the top of the stand need to be?? I can slip a piece of paper or two under some areas of the tank, but not others. Anyone else have a similar experience?? Is foam the solution? should I take the tank down and put down some self leveling cement? Looking for thoughts and ideas here.

Thanks.
Ken
 
Yes buy foamboard from lowes or HD to place under your tank. It is in the insulation section and is pink.
 
I've seen foam used under every acrylic tank, but almost never under glass tanks. So either I just havent been paying close enough attention and it is a common practice, or everyone else is a much better builder then I am :-p
 
Does your tank have trim?

I have a atandard AGA 210. The glass will never touch the stand anyway, its supported around the outside endge and has a couple of corss supports through the middle.
 
Just an idea - since the tank isn't filled yet and you are only talking the thickness of a piece of paper - why not mark the high spots (where the paper won't slide under) and knock them down a tad with medium grit on a random orbital sander? You are probably only dealing with the variation in the top ply of the wood but it wouldn't take to long to clean up.
 
the tank will sink some as it fills....however, the foam is the solution. Just sit the tank on it, fill the tank then trim the front edge after the tank has settled down.

You will probably be fine with ply, but for $10...why risk it?

Paul.
 
MrZ. Thats a good idea, though I have a feeling it isnt as easy as it sounds. And there will be some clean up, and then repainting. I'd also like to move the tank around as little as possible, because its heavy! I envision a couple of trial fits and some additional sanding. Sounds like atleast a couple of days to get that done.

Foam sounds like the way to go here. Only have to move the tank once, no repainting, no waiting!
 
I'm going to have to agree with MrZ. Foam is the "PERCEPTION" of a fix. It's not filling the gaps truly, and it's not truly supporting the tank. I could have a half inch gap, and with the right foam, it would LOOK as though it was flat, even though the support doesn't exist. If the tank was flexible, you would see the foam collapse further in that low section, but it's rigid so it appears to somehow support it.

Just remember foam is foam. It compacts to the same size and density if same size and density pressure is applied.

Hopefully that made sense ;)

If you do some searches, it is very highly recommended that foam is not placed under glass tanks with an edge. It causes more issues than it fixes. Flat bottom acrylic is a completely different item.

FYI, I had the same type of issue with my 180 I just built. I could NOT get my plywood on top of my 4x4 frame to truly flatten out. In ended up putting it straight down on the 4x4's which were almost perfect.
 
hmm...thats an interesting perspective, and a very valid one. Hmmm...tough decisions. This is not something I want to take a risk with. So I guess I am back to either trying to sand the plywood to take out any tiny variations, or putting down a layer of self leveling cement....hmmmm....
 
The purpose of the foam is to distribute point loads. It is true that the foam does not flatten everything out, but is does distribute the load over a larger area. It's kind of like trying to support yourself on your finger tip vs your hand. Same load, but a difference in area and pressure on a single point. Believe it or not glass also flexes a bit and after you start filling your tank the stand it also going to "settle" slightly.

I personally would go with the foam, but you have to do what you feel is best. I used all sorts of straight edges, sanding and epoxy to get my stand flat and still used foam because the manufacturer recommended the use of foam under my glass 300.

I hope that helped.
 
It has a very thin trim that was placed on the tank to prevent it from gettting scratched or chipped during shipping. It is more decorative than structural and can be removed.
 
It is safe to say the tank sits on the bottom panel. I can pull the trip right off if I want. granted it would take a little effort.
 
From what I understand you use foam to avoid point pressure (from say a knot in the wood that sticks up 1/16"), not to fill gaps. Most tanks can flex some, but they will crack if there is a lot of pressure on one spot.
The trim on tanks with it does the exact same thing by crushing in spots with high points.
 
If you use foam, make sure it is thin enough that when the tank is on and filled the glass will not touch the foam. I have heard that will cause pressure spots on the bottom pane and could cause it to crack. Glass tanks are designed and built so that the weight of the whole tank rests just on the outer edge where they put that plastic trim. Cloudancer is right about the plastic trim absorbing pressure points. Once you fill it with water and corals there won't be a gap (unless you start out with a huge gap, a few thousandths of an inch would be eliminated.)

Jeff
 
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