(in progress)
Walls and Roof
- quick-and-dirty units fabbed directly from materials from home
depot or lowes. That's what we did at strong angel. Basically we're talking about Tuff R and Super Tuff R.
- same materials but precision cutting of angles for tighter
assembly. that means a table saw. ideally we'd find a local wood shop and have them cut for us because I'm, er, not the guy to be doing that work and keeping my fingers.
- higher spec materials (see Dow Thermax HD) which may need some
wrangling to obtain. Two or three inches thick, better foil facing, generally much more like what you'd use in an American disaster.
- hexacomb cardboard (http://hexacomb.com/) which can be
manufactured on site from flat pack core materials, so the 1"x4'x8' board is made from a core about two inches by six feet by one inch, and a couple of rolls of foil. Hard to explain, see the "Rapid Deployment Concept" page on http://howtolivewiki.com/hexayurt/
- Weyerhauser has a really good waterproofed triplewall cardboard, as
used in the Global Village Shelters. We're trying to source some but having problems, but of all the materials, it's probably the one closest to spec for developing world use if somebody wanted to start making units ASAP.
Plywood / OSB
http://openfarmtech.org/weblog/?p=340 - $132 plus paint for 166 square feet. Unbeatable.
and there's a ton of unedited video and pictures here:
http://www.files.howtolivewiki.com/open_source_ecology_plywood_hexayurt_build/
I think there's scope for an approach here where there is no flashing used, but (for example) the roof triangles over-lap a few inches at the center of each triangle and screws hold the boards together, and at the roof edges, the roof goes over the lower of the two boards comprising the roof triangle, and is screwed directly into place.
Could be hell to waterproof, could have structural problems, but my intuition is that there's an approach here which does plywood with no fasteners beside screws/nails which might be very useful for some circumstances.
Corrugated Plastic
This is generally not a recommended approach because for most applications, polyisocyanurate boards with aluminum facing are a better bet for long life and insulation properties. However, should you wish, here's how to do it.
I had a little think about coroplast again, and spotted two things I have missed the first time we looked at coroplast.
We can now offer a pre-fab or field-fab hexayurt which folds up very much like the existing folding units. The mechanism might change just a little on the roof.
As a bonus, the coroplast hexayurts can be fastened with pop-rivets rather than tape, which cuts the price even more. Pop rivets are five cents each, and we'd use one about every six inches. They go in with a cheap manual tool or a power tool.
The trick for strength is that for the roof, where two panels come together, you take about four inches of each panel and make a crease. The panels are put side by side, with the 4" strip bent up at 90 degrees to each panel, forming a fin.
Those fins then re-enforce the roof from wind loads.
That fin - that vertical ridge - is then folded over in half, forming a 2" fin - and pop-riveted in that position. This connects the two panels, and and produces a structural reinforcing fin which is also watertight because there is no route for water to enter the building's roof, except by going up the fin, through the tight folds, and into the building.
A similar approach can be taken at the roof edge, incidentally producing a rainwater harvesting gutter if done right.
Taking down the hexayurt would be a matter of using bolt cutters on the rivet (light ones, maybe even tin snips) or just ripping the rivets through the material - note the holes would only be in the fins.
With a little additional work, I'm also pretty sure we could make this entire assembly fold. There might be some fiddly little cuts or creases in the coroplast to make it work, but nothing you couldn't do with a craft knife or a hack saw. We could also spec an 8' roof pole to go into the center of the space, which removes all and any structural issues about the coroplast permanetly by putting it in tension, and it will simply never tear in that configuration (*very* strong in tension). I should have thought of that before.
Or consider the IcosaPod direction, and use ?triangular? box girders on the structure. They could, for example, be fabbed on the edge of each panel, or possibly done as separate items. Might be a good way of getting the roof pole also.
Tape
- 3M bidirectional filament tape, 6" wide.
- Ideally we need a one stop tape; a duct style waterproof, bidirectional filament tape with a foil face.