I came across Chuck Henderson's Conic Shelters information a couple of years ago (maybe three? time is slipping on me...) and got quite excited about it. Subsequent life events have interfered with getting anything built yet, but this is one that is definitely On My List. Here's a little information on them:
Conic shelters/structures are what they sound like: shelters that have a conical shape. Score one for Captain Obvious, right?
What is less obvious is that conics have some properties that offer the possibility of building decent living spaces both cheaper and more durably. For instance, the conic can serve as both roof and walls, to a large extent. The curvature gives it a lot of strength. That same curvature reduces the need for strength, since wind can flow around it easier; possibly good news for tornado prone areas (like mine...).
One property unique to conics (as opposed to hypars, domes, and other thin-shell shelter types) is that the conic shelter really is a flat plane wrapped around to make the curves. You can see that for yourself with a piece of paper; when you twist it around into a cone shape, you don't have to actually stretch or rip anything; the plane curves into that shape quite handily.
Now image using many plywood sheets bolted together to make a quite large sheet of plywood instead of paper, and you have a pretty good idea of how some of Chuck Henderson's early Conic Shelters were actually built. He recommends a different order of operations today, but there were some in the past that were actually built by just bolting together a large plywood sheet with appropriate bits left out (to facilitate mating without unnecessary overlap), then winching it up and around into itself with a gin pole and come-a-longs.
He has come up with multiple designs, including 'multi-conics' which intermingle different conic sections to form larger shelters, but the Umbra Cone (simple conic), in particular, strikes me as the most elegantly simple solution to basic shelter durability out of all the conic designs.
He has also been experimenting with smaller shelters that turn the cones over onto their sides and mate them together like a clamshell standing upright, sort of. Interesting look, and he shows how easily they can be assembled (after the two halves have been pre-built as flat pieces) here:
Now for a few cons:
The multi-conics are interesting, and pretty, but I'm not convinced they would necessarily show the same resistance to high winds that a simple cone would. If I build anything, it's probably going to be a plain Umbra Cone, or some slight variation thereof, but still a plain cone; no inter-mingled partials.
The smaller refuge patterns share a similiar con; they look interesting, but I would not consider them to be as strongly proven as a durable shelter as the plain conic.
The little refuge patterns also have a moderately greater complexity in their cut patterns. The big conics use almost entirely one size plywood square; the little ones have nearly every piece cut differently. Granted, he may have changed that by now; it has been a while since I looked at the preliminary plans, which Chuck was kind enough to send me for preview way back when I ordered the plans for the conics and multi-conics.
That leads me right back out of the cons into a pro: Chuck is very helpful, very willing to talk to you and get feedback on how to make the design instructions clearer. He is also clearly continuing to experiment and work on improving these ideas. I was quite pleased to be able to actually get the originator of a nifty idea on the telephone and ask him questions directly.
Chuck's site appears to have multiple copies and/or entry points; here are a few:
http://conicshelter.com/
http://www.fishrock.com/conics/default.html
refuge assembly
multi-conic flexibility demo
Avi Rotem's take on conics is described on this page, after the overview of Chuck's Conic Shelters:
http://www.greenhomebuilding.com/conics.htm
