PE - re: PVC for Gers?

[Todric]

At 09:03 PM 08/24/2000 -0400, "Thumpa" wrote:
>
>  I have been having trouble with my yurt project snapping as I pull the
>hannas out to set them up.  I choose a poor wood source.  Has anyone used
>pvc for thier hannas?  Do y'all think it would bow to much when the weight
>of the roof was applied or just not look as good as wood?  Im begining to
>think a few weeks of extra shifts so I can buy one is a better idea but i
>love the idea of working on this myself.

        Structurally, there's nothing at all wrong with using pvc for wall.
I've seen at least one ger with khana made from 1/2" white pvc pipe, and it
stood perfectly well. It works okay for wall because of the "co-support"
each "slat" gives the others, but it's not so good for roof poles. Each roof
pole is generally long enough that the "modulus of elasticity" (how much it
bends sideways versus the length) is way too great for any reasonable
diameter. Remember, the total weight of your roof is divided between the
poles, and each one is under end-to-end compression. If it bows a lot when
you push it end-to-end, it's too flexible for roof poles.

        The thing is, if you look at any individual slat in a wall, each and
every one of them has to be able to "bow" _slightly_. I strongly recommend
rectangular cross-section, like lath, rather than square cross-section for
this reason. Likewise, a long run like a roof pole has to be more rigid to
prevent twist and maintain support for it's share of the roof load.

        That being said, pcv is light, strong, easy to work, okay for walls
but not roof, and generally ugly as hell on a bad day.

        Go with wood; you'll be happier with it when you're finished.  :-)

        Oh! And if you're on a budget, don't be afraid to pay extra for wood
without knots. You _can_ overcome weak wood by using more of it, but pieces
with knots are just broken pieces waiting to happen, IMO.

        Todric

        PS: If you looked at the picture of my original ring, take a look at
<http://web.raex.com/~sburnell/36-16.gif> . 16ft diameter, 36" O-D ring, 32
poles. This is the one I camp in at Pennsic.


       "Slat breakage? What's that?"

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	Singing Horse Designs	http://web.raex.com/~yurts
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