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Old 12-22-2015, 09:29 PM   #11
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Then when they are the same, I'll transfer it to its permanent home

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Old 12-23-2015, 12:22 AM   #12
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Can you post results? Would love to see what it does if possible.
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Old 12-26-2015, 10:43 PM   #13
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Boss level.


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Old 01-08-2016, 11:19 AM   #14
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Ran into a little bit of a snag...never underestimate the buoyancy of styrofoam. I have a large tote that I am trying to presoak this structure in, and it is doing its best boat impression. I know that there is a LOT of styrofoam involved in this piece, but I thought that 4 layers of cement would weigh it down. I was wrong.

The good news is that I never used cement on the bottom of the structure, as I wanted to see how it worked in the tank with gravel or sand. Hope this makes it simpler to modify to work. I am trying to find some type of buoyancy calculator to see if it would be more beneficial to simply hollow out as much of the structure as possible, or carve holes out and fill them with cement or rocks. Suggestions?
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Old 01-08-2016, 12:02 PM   #15
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*Update

I am currently at work, but have rough dimensions of my structure, and estimate it to be ~1 cubic foot of styrofoam. Which from what I have looked up is that I will need 64 lbs to make it sink. The volume of the structure does not include the areas that are hollowed out for the caves or bowl. I think that I am going to carve out areas underneath the structure and fill them with concrete that I have laying around. I may be wrong, but my logic says that if I am able to remove styrofoam (essentially trapped air) and replace the area it used to occupy with something like concrete, I should be able to double the effects on its buoyancy.
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Old 01-08-2016, 01:00 PM   #16
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So I looked this up and this is what I found. Buoyancy is the force of a floating object. First you have to know how many square feet of water are displaced after placing the object in the tank. Then, you have to multiply this number by the weight of sea water (64 lbs per square foot). That will give you the buoyancy force of the object.

Buoyancy Force = Volume of Water Displaced x 64 lbs per square foot (Weight of Sea Water).

F=VW
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Old 01-08-2016, 03:19 PM   #17
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That's what I found too. So with the volume of my structure being ~1ft3, it would need to weigh 64 lbs to sink, or at least be neutral. So by hollowing out unnecessary styrofoam on the bottom, I would reduce volume, thus require less weight, correct?

I was also going to fill the space that I vacated the styrofoam from with pure concrete, to add weight. My biggest question is...will I benefit as much as I think I will by replacing styrofoam with concrete? Per the equation, I will reduce weight needed by reducing volume. But by adding concrete, I am increasing volume again, thus requiring more weight. I would imagine the weight addition would outweigh the additional buoyant force

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Old 01-08-2016, 04:08 PM   #18
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Looks like concrete is about 150lbs/ft3. I am going to say it would definitely be beneficial
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Old 01-08-2016, 04:09 PM   #19
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In my opinion, the theory sounds good. I would imagine that eliminating the buoyant styrofoam for the heavy and sinking concrete should provide enough balance to sink it down. I would only change a little at a time so as not to make it so heavy that it cracks the bottom. You should be able to tell how much more you have to do based on the force you have to put on it when you push it under the water. The less force, the less you have to remove and replace. Good luck
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Old 01-08-2016, 04:13 PM   #20
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Definitely a good school of thought. Thanks for the help!
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