Hehehe......let me just add a little food for thought for you all to ponder on, and thats that, do what you like.
1. Topic du jour: Interesting place to put it, adds elevation for viewing, gets is off the rock. It would be super cool to have a drain there. My concern: Most of the hearths though built in rock and stone are usually just laminates with minor jointing. I would be concerned with these jointed, discountinued sections of rock being able to hold the wait without cracking. At most a minor visual irritation. How about below it? How is the platform those rocks built upon constructed. Below that, Its likely due to the size of the tank and its proximity to the corner of the foundation as is seems to be, not an issue.
2. I thought building up the surface a better mode as well. However, I had envisioned more of a 1" wire reinforced pad, rather than thinset. I am picturing a thin layer of leveling thinset to eventually become brittle and crack away.
3. Foam............WarrenG debated this to some length a few months ago. Prior to that discussion the subject had been on my mind, during the discussion over those couple of days, and ever since.
As I said last time, foam under a tank is a much debated concept, some say yes, others no. Though the concept sounds very sound, something raises the hairs on my neck about. Which is why I recended my stance before to relegate for more information before comming to a conclusion.
It is even split down the lines of manufacturers, with the Engineer's at Aqueon (All-glass) saying not to. And then you have the others that claim "I have always placed foam under my tank and its been fine" This is just plain poor logic, and one who's tank did not crack and spill water all over the floor can not tell what effect and to what degree the foam helped or hindered.
One of the main logical fallacies we as Reefers are prone to is the over utilization of observation through sight only. Cause and Effect, A=B, 1+2=3..........we draw observational inferences from limited statistical data through observation only and try to come up with catch all/stead fast rules to be governed by.
Most of the time, because of the scale and the degree of error to which we are working in we are safe, but as we get into larger and larger models (tanks), we begin to see our logic break down as the things we did not think to consider have an effect on the system. This is EXACTLY why we see so many people who are setting up their second or third tanks and have problems selecting the wrong pumps. As the stakes get larger, the circumstances are greater, and our delinquencies shown. This would be main point here. In small scale tanks, you can get away with murder as far as placement orientation, equipment selection you name it........on a bigger tank, if you don't select the right pump that is operating within its BEP range, you can end up with a poor preforming, expensive pump because we were using the same "rule of thumb" for a smaller tank than a big one or designing the system after buying the pump rather before. This is how I will comment on using foam underneath a tank.
In my research before, during and since the last discussion on the subject, I dug through each of my Mechanical Engineering textbooks looking for a similar application, researched hours of articles on the subject, even consulted with my peers who are also Mechanical Engineers on the subject, even going as far as to ask the wife of a friend who is a Materials Engineer with Lockheed Martin. All had the same response I have, "Maybe, but I wouldn't risk it."
Why? For the basic statics of the situation, most have a basic understanding of the subject, but there is a lot that is overlooked and brought into the equation when this material is introduced. The main problem with this discussion is: Nobody can really tell until it tested. You see, foam is a semi-rigid body and varies with different compositions. Its at the point that it is settled and compressed that concerns me. Discussions of dynamic loading, sheer strength of the two planes, a failure due to fatique have never been considered, especially factors of safety.
True, you may lessen a stress point or a discontinuity eliminating some of the stress on the bottom pane, but that may open up another set of problems that you may have not considered.
I found this quote in a preview of a journal article I that uses words other than my own.
"On the Crushing Stress of Open Cell Foams
The compressive response of many foams is characterized by an initial linearly elastic regime which is terminated by instability. For open cell foams instability leads to localized buckling and collapse of zones of cells. Local collapse in these zones is terminated by contact between cell ligaments. "
Of course, remember I have not defined which tanks we are speaking of. It seems to be current thought that it is accetable practice to place foam under acrylic tanks to ensure distributed loading. I could agree with this provided that the thickness was not extreme so as to bring about other problems. Think of the princess and the pea. Once she couldn't feel that pea under all those materess which compressed and took in all the feel of the pea, how stable do you think it was to shear loading? I digress.
In reefing the stakes get higher the farther you climb be it with livestock, expensive fish or larger tanks. There is always less room for error, and what applied before may not apply now. This is my main concern of the catch all of using "foam" and makes me nervous. Thicknesses, densities, sizes change which change all of the rules. For instance is a chart I made up quickly to illustrate the loading on the rims of glass tanks. As you can see, the psi increase with tank size.
It shows the stakes get larger as the tank gets bigger, so one "catch all" rule has the potential for mistake, it is up to the individual to make that call for themselves and what makes them more comfortable.
My answer on foam......I don't know as semi-rigid bodies are unpredictable, especially when the application for the material can not be found elsewhere.
Water pushes in all directions, not just down which is why spheres are best in high pressure depths. The Normal force is force that is straight down. In your tank, the water is always pushing out in every direction, trying to split the joints to "find its lowest point".
This is what I have discovered in my research on the subject and thought I would share it with you guys. This is my .02, please use it to ponder to make your own decision.
