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Ferrocement sphere

Home Forums Research Engineering Ferrocement sphere

This topic contains 16 replies, has 6 voices, and was last updated by Avatar of Elwar Elwar 1 year, 11 months ago.

Viewing 15 posts - 1 through 15 (of 17 total)
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  • #1716
    Avatar of Elwar
    Elwar
    Participant

    I started testing a ferrocement sphere and have a few questions.

    When doing your layers, how long between layers do you wait? I have the first layer on and it is hardened. Was I supposed to put another layer on while it was still moist? I do have it under a damp cloth.

    Also, I was trying to test out the idea of filling the sphere with foam but the can of foam I bought from Walmart did not even come close to filling it. I checked into styrofoam spheres online and anything of any decent size is pretty expensive. I would rather keep the cost down as much as possible.

    My initial plan was to use hardware cloth as the frame but trying to turn square hardware cloth into a sphere was quite the daunting task. What if I did a wire mesh around the sphere instead, using like a thin roll of wire? Would it provide enough strength, or would I need to get some bands of wire welded together?

    I realize at this point in the process that I will need to go with a mold to make things easier. Trying to put ferrocement on a sphere is not very easy.

    #16570
    Avatar of Elwar
    Elwar
    Participant

    Here is a picture of my first ferrocement sphere:

    #16573
    Avatar of Elwar
    Elwar
    Participant

    I found this sphere mold online:

    http://www.gardenponds.com/spheres.htm

    #16578
    Avatar of wohl1917
    wohl1917
    Participant

    These molds are for producing solid concrete spheres not hollow balls unless you you use them and male molds. You could build your own male mold for much cheaper than they are selling these for…

    < http://ocr.wikia.com/wiki/Oceanic_Citizens_Republic_Wiki>

    Avatar of captainradon
    captainradon
    Participant

    I haven’t tried this myself yet, but how about using an inflatable exercise ball as a form? I always find good second hand ones in op shops for around $5.

    #16592
    Avatar of Elwar
    Elwar
    Participant

    I used a $2.50 Walmart ball as the form. Wrapped it in mesh drywall tape and smoothed the cement on by hand.

    It was messy and not easy.

    I need to do a mold. I will just use the same $2.50 ball since they are cheap and plentiful. But trying to get the cement on without it falling off was difficult, especially when getting the bottom. With a mold I could just pour it in over the ball.

    My concern is the frame. Would wrapping it in loose wire give it enough durability or will I need a fixed wire frame?

    #16593
    Avatar of shredder7753
    shredder7753
    Participant

    what is the objective? when this exercise is complete, what will you know then that you want to know now?

    ____________

    My Work II

    “Leadership and do-ership are not the same thing”

    #16594
    Avatar of OCEANOPOLIS
    OCEANOPOLIS
    Participant

    Why a sphere for flotation? You do as you wish, it is your time and money. And I am not telling you what to do. Just voicing an oppinion. But after 25 years floating around on few boats here and there, I don’t see how a sphere could possibly do better than a barge like structure for any seasteading projects. Otherwise, I am sure that thay would have used spheres for the last 5000 years of sailing around.

    #16596
    Avatar of elspru
    elspru
    Participant

    Elwar wrote:

    I started testing a ferrocement sphere and have a few questions.

    When doing your layers, how long between layers do you wait? I have the first layer on and it is hardened. Was I supposed to put another layer on while it was still moist? I do have it under a damp cloth.

    For the new layer to stick to the old layer,

    they have to have similar levels of humidity.

    You can

    a) apply while first-layer is still damp

    b) make it wet before applying second layer

    Also, I was trying to test out the idea of filling the sphere with foam but the can of foam I bought from Walmart did not even come close to filling it. I checked into styrofoam spheres online and anything of any decent size is pretty expensive. I would rather keep the cost down as much as possible.

    an option is to get styrofoam insulation, and brake it up into smaller pieces to stuff in your sphere.

    There is also the option of having multiple compartments in your sphere, though that would be more relevant for larger designs.

    My initial plan was to use hardware cloth as the frame but trying to turn square hardware cloth into a sphere was quite the daunting task. What if I did a wire mesh around the sphere instead, using like a thin roll of wire? Would it provide enough strength, or would I need to get some bands of wire welded together?

    they would best be twisted together, you could make a sphere grid, if the wire was strong enough wouldn’t need additional reinforcement, though you could also have a strong icosohedron frame, and then simply tighten some mesh around it.

    I realize at this point in the process that I will need to go with a mold to make things easier. Trying to put ferrocement on a sphere is not very easy.

    no easier than on a boat.

    Elwar wrote:

    Here is a picture of my first ferrocement sphere:

    Congratulations!

    We with You are a Network, our goal to become technologically-enabled reproducible family communities. http://weyounet.info

    Elwar wrote:

    I used a $2.50 Walmart ball as the form. Wrapped it in mesh drywall tape and smoothed the cement on by hand.

    It was messy and not easy.

    ouch, I hope you used some gloves at least. cement is rather corrosive.

    I need to do a mold. I will just use the same $2.50 ball since they are cheap and plentiful. But trying to get the cement on without it falling off was difficult, especially when getting the bottom. With a mold I could just pour it in over the ball.

    My concern is the frame. Would wrapping it in loose wire give it enough durability or will I need a fixed wire frame?

    when there is a wire-frame such as a wire tightened triple-layered hexagonal-mesh it’ll stick to it even upside down. remember to let the mesh and wire oxidize (become dull colored) before applying so it has some traction.

    Though of course for the cement to be sticky has to have a low water content.

    If you have a thin rebar skeleton, then don’t need a mold either, simply apply directly onto your sphere, I’d highly recommend having a drainage hole, also for the fact that some cement might fall into the sphere while applying.

    We with You are a Network, our goal to become technologically-enabled reproducible family communities. http://weyounet.info

    #16597
    Avatar of Elwar
    Elwar
    Participant

    OCEANOPOLIS wrote:

    Why a sphere for flotation? You do as you wish, it is your time and money. And I am not telling you what to do. Just voicing an oppinion. But after 25 years floating around on few boats here and there, I don’t see how a sphere could possibly do better than a barge like structure for any seasteading projects. Otherwise, I am sure that thay would have used spheres for the last 5000 years of sailing around.

    Incrementalism. I do not plan on sailing around.

    I laid out the general idea here:

    http://www.seasteading.org/interact/forums/research/engineering/an-island-built-floating-cement-balls

    An island made of floating cement spheres.

    #16598
    Avatar of Elwar
    Elwar
    Participant

    shredder7753 wrote:

    what is the objective? when this exercise is complete, what will you know then that you want to know now?

    The objective for this initial sphere is to figure out cost, ease of creation and how bouyant it is (focussing on durability with later models).

    1. Cost

    My goal is to be able to make a sphere for under $10 each. That way you can have a 10′ x 10′ “island” for $1000 in material.

    The Walmart ball was $2.50, The 95lb bag of cement was only $8 of which I barely made a dent so I would say $1 worth of cement. I did use Home Depot sand which cost $3.50, again I probably used about 50 cents worth at the most. And the tape was about $2.50 and I used half.

    So for what I have now it would cost about $5.25 per sphere.

    2. Ease

    It was certainly not easy. Of course, this was my first time working with ferrocement. I think I had just a tad too much water. The cement was the consistency of slightly melted soft serve ice-cream and I hear it should be the consistency of peanut butter. So a lot of bits started falling off as I turned the ball. Putting the tape on was easy. I attempted hardware cloth but that would have been far too difficult. I covered the sphere in tape in about 5 minutes. Between mixing the cement and coating the sphere, I would say that took between 30 minutes to an hour.

    So an hour of unskilled labor at most (though the quality shows my lack of experience).

    3. How bouyant

    I will test the bouyancy this weekend, but from picking it up while I was putting the cement on, it was still fairly light. I would venture to guess that it will float with over half of the sphere out of the water.

    #16599
    Avatar of Elwar
    Elwar
    Participant

    elspru wrote:

    For the new layer to stick to the old layer,

    they have to have similar levels of humidity.

    Thank you for the input, and yes I did use some decent gloves. I will try a second layer with less water content to see how much easier it is and try the wire mesh.

    #16600
    Avatar of Elwar
    Elwar
    Participant

    My initial goal for this project will be a practical use. A small “beach island” that I can take out on the weekends pulled behind either a jetski or small boat. The initial size will be just wide enough to anchor and lie down on with a beach towel. I plan on setting down some flexible material, a tarp or rubber or plastic or a combination. Then fill it with beach sand.

    I can see pulling this out about half a mile from the coast and just pack a picnic and swim or play on the jet ski and enjoy a nice afternoon. And on a nice night my wife and I can sleep under the stars. No mosquitos and nice waves to bob up and down with.

    And when I do not have it out on the gulf I can use it as a floating dock next to my sea wall.

    I am looking at different solutions though for the sphere. I would love to test out some foam cement.

    #16602
    Avatar of shredder7753
    shredder7753
    Participant

    when it comes to the bouyancy, you can calculate exactly where it will sit on the water. find the total weight of the sphere, lets say for example it weighs 70lbs. water weighs 8.33 lbs per gallon. therefore you would displace 8.4 gallons of water (8.33 x 8.4 = 70). looking at the sphere, you need to understand where a cross-section of the sphere would have a volume of 8.4 gallons. thats where the water line will be. its a lot harder with a sphere than my Bergs. but thats the idea of it

    ____________

    My Work II

    “Leadership and do-ership are not the same thing”

    #16610
    Avatar of OCEANOPOLIS
    OCEANOPOLIS
    Participant

    If your goal is to built a 10′x10′ small floating island, fill it up with sand and tow it to the sandbar, then using ferro spheres will be expensive compared to other methods of achiveing your goal. You will have to built 25 sphere of 2′ in diameter. Then, you will have to raft them up somehow. Then, you will have to build and secure the sandbox on top of it. Then you will have to buy a small boat to tow it to the chosen location. So far, you are looking at a good $5k+ and the labor, since you need at least a 20′-22′ LOA boat with a 100 HP outboard to tow your 10′x10′ island behind. (being of ferro, will be heavy)

    The easiest way out, is to buy a small used houseboat with a running engine for that money, and use it for your purpose. You will save on all that labor, plus you will have living amenities onboard (fresh water, a small galley with fridge, stove, a head, a small stateroom with a couch to get out of the elements when needed, a VHF radio, lifevests, flares in case of emergency, etc). The “sand beach” can be easily built on top of the cabin.

    Also, keep in mind that towing “anything” its a bitch, no matter what. Also, keep in mind that you will be required to register that island with the Florida State. Since it’s a “new boat construction”, the Coast Guard will have to inspect it DURING construction to give you a safe flotation ok. Now you opened a can of worms, my friend, since this guys are picky, picky, picky…I dealt with them for years,…

    Another way to save money and labor would be to built your island as one hull, on a 10′x10′ float, your choice of shape, out of marine plywood, and then just ferrocement the bottom and the topsides. Then do the towing thing. IMHO.

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