The Plywood Hexayurt

[Vinay Gupta]

(note: reply all includes mailing lists, be aware.)

Actually OSB , but it's a very similar material. 

I'll let the Open Farm Tech blog entry speak for itself: http://openfarmtech.org/weblog/?p=340

Bottom line: basic materials, $132, plus paint. Fairly slow construction time due to panel weight and ground preparation issues. Unbeatable for some contingencies, and clearly SOUTHCOM might want to be looking at this kind of tech for South America - metal roof flashing as the fasteners rather than tape. The logistical issue for disaster relief is weight - these things are *heavy* and *time* - slow to construct relative to the prefabricated folding hexayurt technology. That's likely, in the long run, to be the distinction between improvised hexayurts, which are largely built in place, and the deploy-and-redeploy fast-up fast-down folding models which need some factory details.

I think we could be pushing these out in Haiti now, though. Time to show some local builders the plans and have them take a crack at a local unit?

Vinay

Hexayurt building went well - a 7/16″ Oriented Strand Board (OSB) structure with 4 inch wide, 32 gage galvanized flashing as the ‘tape’ to hold it together. Being familiar with standard construction methods, I had my doubts concerning the structural integrity of a tension srtucture. I have been converted after this project.

The opposing walls gave strength to each other and to the roof. Once all panels were in place they could support people walking on top. Using minimal resources we were able to construct a space of 166 sq feet in two full days - at a cost of $132 for panels and flashing- not considering paint, tar, screws, nails, and 2×4s used in the walls.

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Vinay Gupta

Free Science and Engineering in the Global Public Interest

http://hexayurt.com - free/open next generation human sheltering

http://hexayurt.com/plan - the whole systems, big picture vision

Gizmo Project VOIP : (USA) 775-743-1851

Skype/Gizmo/Gtalk  : hexayurt

Icelandic Cell     : (+354) 869-4605

"If it doesn't fit, force it."

[Troy Jones]

If anyone else out there has experience building more permanent structures, I'd be interested in hearing from you.  I've been looking closely at combing the hexayurt design with a Grancrete coating.  See the first video on this page for an example of their building technique:
 
http://www.grancrete.net/videos/index.cfm

Grancrete is noticeably stronger and lighter than concrete, doesn't expand or contract, is waterproof and fireproof, has a much better environmental footprint than concrete, and acts as a radiation shield (hopefully that last attribute won't be needed).  Applies using most traditional concrete techniques, including spraying, and cures within 15-30 minutes.
 
-Troy-

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From: hexa...@gmail.com
Subject: [hexayurt] The Plywood Hexayurt
Date: Mon, 29 Sep 2008 21:00:36 +0000

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[Caroline Tigeress]

On Sep 29, 2:00 pm, Vinay Gupta <hexay...@gmail.com> wrote:
> (note: reply all includes mailing lists, be aware.)
>
> Actually OSB , but it's a very similar material.

> between improvised hexayurts, which are largely built in place, and
> the deploy-and-redeploy fast-up fast-down folding models which need
> some factory details.
>

> Vinay
>
> Hexayurt building went well - a 7/16″ Oriented Strand Board (OSB)
> structure with 4 inch wide, 32 gage galvanized flashing as the
> 'tape' to hold it together. Being familiar with standard
> construction methods, I had my doubts concerning the structural
> integrity of a tension srtucture. I have been converted after this
> project.
>

> The opposing walls gave strength to each other and to the roof. Once
> all panels were in place they could support people walking on top.
> Using minimal resources we were able to construct a space of 166 sq
> feet in two full days - at a cost of $132 for panels and flashing-
> not considering paint, tar, screws, nails, and 2×4s used in the walls.

Very cool. I was thinking about using this concept in Eastern
Washington - but we have some healthy snow loads there. Do you think
this could take such things? I'd be going with 8' wide (4 x 8) type
dimensions. Can you also elaborate a little bit more about the 2 x
4's in the walls?

Thanks,
Caroline

[Vinay Gupta]

Marcin Jakubowski - joseph....@gmail.com - is the point of
contact I have for the team that built it but I think they're hard at
work on other things right now :-)

I'm hopeful we'll get more pictures and notes soon.

In general - and I can't stress this too much - you have to check
this stuff with qualified professionals before putting anybody's life
on the line. Including your own, please.

At Burning Man building in Tuff-R if the building fails you might get
hit by a 5lb roof board or your stuff might all blow away, but it's
quite unlikely anybody is going to get seriously injured by a
hexayurt failure. The only risk we saw was fire, and we've got big
notices on the site advising on best practices for reducing fire risk
and disclaiming responsibility.

So, on to plywood. A plywood roof cone is going to weight something
in the region of 180 - 300 lbs. On the other hand, a moderate to
heavy snow load (10 lbs per foot) would add 1660 lbs to the weight on
the roof cone. At that point, if it *does* fail, it's going to be bad.

My guess - and this is purely a guess, based on my engineering
intuition, is that 1" marine ply with very strong metal fasteners and
beveled board edges to ensure full contact between the edges of all
the boards - will be more than good enough to sustain that kind of
snow load. But we'd need to do some engineering drawings and have a
chartered engineer or something similar compute snow loads and rubber
stamp the plans as "this will not fall over" before I'd feel
comfortable saying "you can build it's reasonably safe."

Because snow is *very* heavy, and buildings designed to withstand big
snow have to be engineered.

Other things that might help - the Pentayurt has a much steeper roof
angle, so will accumulate less snow, although it's obviously a little
smaller. Same amount of headroom over the 6' line, interestingly -
the steeper roof helps.

http://vinay.howtolivewiki.com/blog/index.php?s=pentayurt&submit=Search

Really, though, by the time we start talking plywood, we're at the
limits of my engineering capability. From here on in it needs people
who actually know *buildings* to do some analysis and offer an opinion.

Sorry I can't be more help, but hopefully the Power of Free/Open
Source will get us some analysis, and then people can build these
everywhere.

Vinay

--
Vinay Gupta
Free Science and Engineering in the Global Public Interest

http://hexayurt.com - free/open next generation human sheltering
http://hexayurt.com/plan - the whole systems, big picture vision

Gizmo Project VOIP : (USA) 775-743-1851
Skype/Gizmo/Gtalk : hexayurt
Icelandic Cell : (+354) 869-4605

"If it doesn't fit, force it."