Styrofoam Under the Tank

[bladeruner143]

Does anyone do this? I've heard it could help keep things level if your stand was a DIY that maybe shouldn't have been a DIY project! Just wondering if anyone has tired this before.

[bored4long]

from my research: Acrylic tank = use foam; Glass tank with trim = no foam.

[yoboyjdizz]

i have 1/2inch i believe under my tank...but its an acrylic, not sure if glass tanks need it or not.

[bladeruner143]

Oh, I did not know that. By "trim" you mean that black plastic stuff at the bottom of the tank? Does that itself help with leveling? You couldn't you still use the Styrofoam on a glass tank?

[yoboyjdizz]

Yes the black plastic stuff, i believe that it doesn't help with glass tanks just puts more pressure on the uneven sides. If i were you i would ask this in one of the glass tank manufactures forum.

[bladeruner143]

Hhhmmm, good idea. Thanks Yoboy!

[WarrenG]

If you didn't have the foam under a glass tank ALL of the pressure would be on the trim.

With the foam in place, the load is more evenly distributed across a slightly uneven surface (wood) that may be the top of your stand.

For example, if you had a small ridge of wood hitting the bottom of the tank there would be tremendous pressure applied to the tank (and wood) in that place. With the foam, that extra pressure from the wood would simply compress the foam slightly more in that area.

And remember, the actual weight/pressure per square inch is less than a pound per square inch IF the entire bottom of the tank is in contact with the stand.

[bladeruner143]

So wait, are you saying that styrofoam CAN be used under a glass tank?

[Underwaterparadise]

I use it under all my glass tanks at home and in the store!

[bladeruner143]

Really? Is there a certain thickness or type you have to use? Does it have to extent past the tank? Basically, I'm thinking of doing this because I'm making a stand, but I don't consider myself a master carpenter, so I'd like some security with it. So if you could go into more details with you setup, I'd really appreciate it. Pictures would also help!

[yoboyjdizz]

I would still double check with someone who makes glass tanks. I swear with trim no foam without then you could.. Better be safe and double check.

[bladeruner143]

Hey Yoboy, I can't find a Tank Manufacturer in the vendor forum. Can you give me the name of one?

[bored4long]

From the research I did, glass tanks with trim are DESIGNED to have all the weight supported by the trim. Styrofoam just isn't necessary. Whether it CAN be used or is even good or bad is unknown to me.

Let us know what you find out.

[yoboyjdizz]

http://www.reefcentral.com/forums/fo...s=&forumid=434

[philter4]

The glass doesn't need the styrofoam under it, but it will not cause any problem using it. The trim keeps the glass off of the stand or whatever you are using as a base so there is no single pressure point. For example if you lay a piece of glass out and put evenly distributed weight on it it will not break, but put weight on a single point and the glass shatters. The same is true of the acrylic, except the acrylic wont shatter it would crack, the styrofoam just protects it from a single point of pressure.

[WarrenG]

I agree that the weight of a glass tank without foam would go to its trim as intended, but spreading the load instead to the entire bottom of the tank and the entire top of the stand could be helpful too.

The glass in the tank bottom will flex a little too. I dunno if dropping a rock on the bottom would matter less if there was foam under the bottom, but it might.

Styrofoam is a pretty good insulator for the water temperature and sound/vibration.

I'd go with foam of 3/8" to 1/2" thick. It's at Lowes and HD. Maybe it will compress by 1/16".

In the back of my mind I always wonder what the tank will do in an earthquake. If the load is only carried by the trim around the tank, what happens if the tank moves an inch?

[D&KSac]

so you should use this stuff under acrylic tanks too? I thought they were designed to give a little to pad the weight?

[WarrenG]

Originally posted by D&KSac
so you should use this stuff under acrylic tanks too? I thought they were designed to give a little to pad the weight?

"Pad the weight"? I dunno. I've used it under my tanks for the other reasons people have mentioned here. It costs less than $12 so I don't see a downside to using it.

[dots]

Styrofoam is mostly air, at the weights we are speaking of, it would be compressed to the point of being worthless. Its best application is as an insulator.

I would be learly of using this as over time it will just catch moisture and become a great mold breeding ground.

Essentially, foam rubber would be an good choice as a gasket material to fill the voids between the disimimalar surfaces to distribute the loads evenly like a gasket, but I think too much emphasis is placed on this topic and should not be used to compensate for poor craftsmanship.

However, if the top of the stand is made of plywood, when it is loaded, the sheet will flatten. Plywood is made of layers of wood in alternating directions to give it shear strength. Plywood is often "twisted" when not installed. A low weight structure like a stand could easily twist until the downforce from the tank is applied.

If the surface is flat and the rest of the stand is accuratly and precisely built, shimming it like a door to accomodate for flooring unevenness is all that would be needed.

But as you can see, I am guessing on what the stand looks like......hint, hint, hint......

[BodiBuilt]

Especially with reguard's to fabricating your own stand, I would always recomend the use of foam to take up any imperfections

[WarrenG]

Dots wrote: "Styrofoam is mostly air, at the weights we are speaking of, it would be compressed to the point of being worthless. Its best application is as an insulator."

For a tank 24" deep there is about 1 pound of pressure on each square inch of the foam. The foam will not compress like you say from one pound of weight. And if the air was compressed to the point of being worthless there would be virtually no insulating value since it is trapped air that is the insulator. The material other than the air actually conducts thermal energy.

Styrofoam does not catch moisture very well, especially from a tank, at least not on the two I've had it under for around 15 years. No mold at all, even though it gets splashed occasionally.Foam rubber that can offset the imperfection of a nail/screw head or ridge in the wood is too flexible and doesn't provide a stable platform unless the stand constrained the perimeter of the tank. Many of the foam rubbers and neoprenes will absorb far more water than styrofoam.

If water gets under the tank I'd much rather have a sheet of styrofoam there to block/contain it's movement instead of wood that will absorb the water. And since there will not be even a 1/128" gap between the bottom of the tank and the foam the water won't move anywhere-it won't even get there to begin with.

[dots]

I was thinking about this a lot last night and this morning, the picture above got me thinking more. There is little information available to be readily found because foam is not used primarily to transfer loading evenly, which is the main purpose of this application, to correct the voids in the surface that could cause stress concentrations and failure.

Some considerations:
Glass tanks need even distribution on the edges primarily
Acrylic needs it all across

Foam is historically used in impact force force instances, once compressed it is in a plastic state (won't spring back to it original shape)

Polymers such as this come in two flavors:
open cell and closed cell, both have different mechanical properties.

When one says "styrofoam" I think of blown polystyrene which is a closed cell type, (which is mostly air, as can be shown when a styrofoam cup was placed on an ROV on a dive). However, what the ability to transfer loads and characteristics when compressed is what I am looking for.

Open extruded polystyrene as seen in the picture above is used in building applications.

Historically, polystyrenes are used in thremal applications and sandwiched between stronger materials.....like steel doors, I am unsure if it trasfers the loads through these void areas or low spots and solves the problem or just covers it up.

And if under compression, it does fill the void and tranfers the load, what about the places that were fine before?

In the case of a foam gasket under a home window, the foam is mearly a means to stop air flow.

After thinking more, I am unsure about if it does any good at all to redistribute stress concentrations, and may even create some, which may be the wrong application for the material.

Regardless, my main point was not to use this as a replacement for construction quality and will have to do some more research on foams and the mechanical properties while in compression.

Reminds me of the old cartoon gag when the guy takes off his jacket for the lady and they walk arcoss, but when the villan steps onto it, falls in.

[WarrenG]

dots,

The purpose of the foam IS NOT to transfer the load evenly, it is to spread the load evenly. It is to overcome any irregularities/projections in the surface of the stand under the tank, to dampen noise and vibration, and to insulate.

Get a piece of wood that has 8 square inches. Put a nail through it that protrudes 1/4" inch. Now put a gallon of liquid (8 pounds) on top of the board and hold you hand flat under the board. The nail punctures your skin because the entire 8 pounds is applied to the nail and into your hand. Take the nail out and it doesn't hurt to support that load because it is distributed evenly across the board.

Put a nail into a piece of plywood but let the head of the nail protrude 1/16" or so. Take a piece of styrofoam 3/8" or thicker and apply one pound of force per square inch across the entire surface (you can use a gallon of liquid on top of 8 square inches of wood). This is the same amount of pressure a 24" deep tank will apply. The top surface of the foam will be perfectly flat and the underside will have the indentation of the nail head. A softer foam could do the same, but when you try that you'll see that the board on top of the softer material can move laterally.

The reason there is a localized indentation is because the pressure is greater at that location (the entire 8 pounds is applied only to the nail head) until the foam compresses enough in that local area to redistribute the eight pounds to the entire area under the weight.

The same will apply to a glass tank. The area on the underside of the frame will carry the entire load of the tank, and this is probably enough pressure to crush the foam in that local area. But once the foam crushes the thickness of the frame's protrusion, the entire load of the tank will be carried equally by the frame and the bottom of the tank (glass). When this happens there will be about one pound of pressure on EACH square inch of foam under the 24" tall tank.

Your styrofoam cup underwater analogy is greatly flawed. The aquarium applies ONE psi to styrofoam that is 3/8"+ thick. The underwater ROV at a depth of 240 feet applies ONE HUNDRED psi to a cup (foam) that is 1/8" thick. 1psi is not enough to push all the air out of styrofoam so its original characteristics will remain.

Get your own piece of foam, measure its thickness very carefully, apply ONE pound of weight evenly to each square inch of surface area and measure the foams' thickness again.

[kevin95695]

Words, words, words.

After about 6 lines of text the avg RC surfer loses their

Huh? What were they saying?

So what did you science guys decide after the arguing?

[WarrenG]

Originally posted by kevin95695
Words, words, words.

After about 6 lines of text the avg RC surfer loses their

Huh? What were they saying?

So what did you science guys decide after the arguing?

Are you saying we should just let incorrect information sit out there, or do you think people who do care about the topic will appreciate accuracy? Do you think illustrative examples are worth including in a post?