Sunday, May 30, 2010

Re: [papercreters] dome ideas / discussion



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On 5/29/2010 9:52 PM, stick0boy wrote:

ok in the grand some day plan i want to move to mexico and make a huge dome PC of course. like a supported second floor sleeping area.   
Don't move anywhere near Juarez, the murder capital of the world. Mexico is in the midst of an internal war between the drug cartels and everybody else. I can see Mexico from where I'm sitting, but I don't go over there any more, you can be shot for just walking down the street. A couple of days ago gunmen opened fire on people buying food from a roach coach, killing several of them. Last month one of my students was off work due to a broken arm and visited a bar in Juarez. Gunmen came in and ordered everyone to hit the floor. He was slow due to the new cast on his arm, so they shot and killed him. Have you considered Belize?
 i was thinking about a spray application over hardware cloth near the interior (and possibly exterior somehow) to prevent cracking. this brings support issues to keep it upright long enough to apply PC ... any ideas will be appreciated. i was thinking a actual half round dome i can pivot a form of wood metal or fiberglass set off from the centerpoint with a triangular frame.   
Haven't tried hardware cloth, but expanded metal stucco mesh works well. Getting flat material to fit on a curved surface can be a challenge, especially without generating a lot of waste. One advantage of geodesics is that there are no curved surfaces.

An airform would be easier than a rotating wooden form, and spraying could cover it in short order. Someone on this list was making a sprayed pc dome on an airform, but never updated his photo album or posted results after the first bit. The album is still in the group photo section.
 or seeing spaceman's dome i was reminded of the PC fence where 'flat' panels were capped with what appeared to be steel/aluminum framing.. i could very well make traingles of thin ~2 inch edge capped with steel studs. then to assemble by quickly tack welding on the inside of the dome where geometry would place the edges close enough to make it possible.   
This would require a lot of precision to have the studs fit well enough to weld. Also studs are generally thin metal that would need MIG/TIG welding. Do you weld? Harbor Freight sells a wire welder that works fairly well and is less than $200. My large dome is screwed together, a much easier and cheaper way to go.
  this brings me to the dis-simmular expantion rates of steel and PC. will this create problems?   
On my 33' dome the expansion of the metal is less than 1/4" in the circumference, within a normal range of livable temperatures. PC is compressible, so absorbs this small expansion without a problem.
then i can fill out the structure of the dome by stapling chicken wire and placing wire condiuts and pex water lines and spraying PC and finish coats on either side. bringing the total thickness to what 18-24 at the base and thinner at the top.   
Hot air rises so your greatest heat loss through the skin would be near the top. You need more insulation at the top than at the base.
 also i am wondering what the 'open' time on papercrete is like if i was to spray 2 inches in a pass to allow the initial drainage to happen. how long will i have when the PC is set or initial drainage has occured and when the chemicial reaction has slowed or stopped. making for the maximum bond   
Portland cement's hydration continues for a long time, but for practical purposes is pretty much done in a month. Papercrete is different from concrete, and the processes are not completely documented yet.

I have slipformed and sprayed pc onto surfaces that have set for months. No problems.
 i am also also wondering about any possible density difference between sprayed and block. as in strength and insulation properties   
Sprayed pc seems to be a bit lighter, but that's a subjective opinion. I have not measured. As far as insulation goes, there is some debate over whether compressed heavy pc has as much or more value than light pc. IIRC someone was about to do some definitive testing.
 thanks for any input 
Welcome to the group. Be sure to let us know how your project(s) turn out, and send lots of pictures : )

http://www.starship-enterprises.net/Papercrete/Workshop/index.html

spaceman  All opinions expressed or implied are subject to change without notice upon receipt of new information.



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