Foam under a SeaStar tank?

[Borderjumper]

Originally Posted by Aquattro

so far my story is that it's a leaking bulkhead, accumulating water in the bottom trim. It's dripping back into the sump, so that's a good thing. Right?

I read your first post and just went OMG! It's contagious ! I'm glad it's "just" a bulkhead. Sounds like if it's leaking into the sump you haven't lost any water, so that's a good thing.

[Borderjumper]

I've googled all morning, and what I am finding is.. Never put foam under a rimmed tank. A rimmed tank is designed so that the weight of the tank sits on the rim, which displaces the weight up the sides vertically. makes sense, as glass it strong vertically and weak horizontally. IF you put a rimmed tank on styrofoam, the weight bearing edge will compress into the foam until the glass is being pushed down onto the foam, your now messing with the design intent and instead of all the force of the weight being transferred vertically up the sides, it's also pressing up on the glass bottom which eventually cause it to flex, and as I know only too well, horizontal glass doesn't flex well when the corners are being pinned down by over a 1000lbs of water and rock.

[MitchM]

Originally Posted by Aquattro

so far my story is that it's a leaking bulkhead, accumulating water in the bottom trim. It's dripping back into the sump, so that's a good thing. Right?

Um no, Brad, any leak is a bad thing - otherwise Borderjumper would be overjoyed right now...

I don't get how the styrofoam under the tank would be a bad thing. If the glass is supported, then it's supported and should be stronger.
I can see if the supporting structure is uneven or warped, then you would have a problem.

Mitch

[Borderjumper]

Originally Posted by MitchM

Um no, Brad, any leak is a bad thing - otherwise Borderjumper would be overjoyed right now...

I don't get how the styrofoam under the tank would be a bad thing. If the glass is supported, then it's supported and should be stronger.
I can see if the supporting structure is uneven or warped, then you would have a problem.

Mitch

I think it's a very fine line between the bottom glass being supported, and the bottom glass being pushed up by the foam as the edges compress down.

[MitchM]

It shouldn't be that fine of a line. I've had 6' pieces of glass bow out 1/4" with no ill effects. Pink foam doesn't compress that much, does it?
A couple thousand pounds of water and rock pressure on the bottom glass should balance out the downward pressure from the edges. That would result in less pressure on the edges.
(just trying to wrap my head around the physics of the foam problem)

Mitch

[Doug]

Shelley, although not much help now, sorry, but I agree with no foam under a framed tank. We had many threads on RC in regards to it. One builder even said it voids there warranty if foam is used under a frame.

Any tank thats custom made, with no frame, where the complete bottom sits on the foam is usually fine.

[Borderjumper]

Originally Posted by MitchM

It shouldn't be that fine of a line. I've had 6' pieces of glass bow out 1/4" with no ill effects. Pink foam doesn't compress that much, does it?
A couple thousand pounds of water and rock pressure on the bottom glass should balance out the downward pressure from the edges. That would result in less pressure on the edges.
(just trying to wrap my head around the physics of the foam problem)

Mitch

If you look at the picture I posted above, the foam WAS compressed visibly along the edges. My theory is it compressed as much as it could until it made the bottom so tight it popped.

We just popped a piece of the trim off, and this tank is bottom glass with the sides all on top of the bottom glass.

[Borderjumper]

Originally Posted by Doug

Shelley, although not much help now, sorry, but I agree with no foam under a framed tank. We had many threads on RC in regards to it. One builder even said it voids there warranty if foam is used under a frame.

Any tank thats custom made, with no frame, where the complete bottom sits on the foam is usually fine.

Thanks Doug.. I'm just trying to come to a conclusion as to why this tank failed.. I'm prolly going to have a new one built and I don't want this happening again.

I think there is some confusion as to what foam I used. It's not spongy carpet underlay type foam. I have other tanks sitting on very thin open cell black actual foam.. Spongy foam.. I think that's ok as it can totally compress.
This pink building insulation sheet foam is over 1/2 thick and will not hardly compress even if you stand on it. IMO it's so rigid that once the tank edge settles IN to the foam the whole middle of the tank has an upward force pushing against it.

I won't use it again,, I'm going back to the thin open cell spongy foam, if any foam at all.

[Madreefer]

Originally Posted by Borderjumper

IMO it's so rigid that once the tank edge settles IN to the foam the whole middle of the tank has an upward force pushing against it.

Makes perfect sense to me. I agree. If tanks were designed to have any foam under the tank than why do they not come that way? Or why do they not sell the correct sized precut peices? Good money maker especially for odd shaped tanks? Someone posted about glass bowing out. Maybe there is supposed to a little bit of bowing out underneath.

[MitchM]

At any rate, sorry to hear about your tank break.
Not a nice thing to have happen at any time of the year.

Mitch