PE - Structure tents

[Corun MacAnndra]

Todric wrote:
>
>         BTW, there's a non-period (as far as I can tell) modification which
> greatly increases the high-wind stability of gers; I add a loop which passes
> thru the roof poles near the ring.
>         What can happen in very high wind is that a strong gust can push a
> ger into an oval-shape. When this happens, the roof poles in the long axis
> unplug from the ring, which upsets the dynamic stability (and can drop the
> roof).

Yes, absolutely out of period as this extra cord is only necessary in yurt
designs that use 1x2 flat roof poles as opposed to the period (to this
day) round roole poles, or even the Kazakh style round poles that are made
square on the roof ring end and fit into a tight hole. The problem stems
more from the slop in the roof ring design for the 1x2 type poles. Often
more than one pole is fitted into a single hole and stability relies on a
tight fit which you just don't get with this design.

With round poles you have no room for the pole to move laterally. Thus in
a high wind you don't get the roof ring swaying. Further, a good, tight
belly band around the outside of the ger will not only hold the roof
canvas down, but add such considerable stability to the structure that you
don't get the ovaling effect. When there's slop in the walls and roof
ring, the whole structure is unsound and can easily come crashing down.
I've seen such yurts sete up on uneven groun, and given the nature of a
ger, it will pantograph and cause the roof ring to screw itself into the
ground. The belly band will also lock the poles into place much better.
And it's period.

I've used 1.25 inch round closet poles in all my yurts, and I've had one
that lasted ten years before the roof ring gave up the ghost, and it never
showed any slop in the fit og the poles nor any tendency to sway or oval
in high winds.

Remember that the nomads who still live in gers today have been doing so
for many hundreds of years. They had to A) use the materials to hand as
efficiently as possible, and B) utilize a design that conformed to nature
as well as possible. The fact that they are using round poles, not flat
one is a testament to that.

The only real advantage to flat poles over round closet poles is price.
1x2 boards are cheap and easy to produce. But I always tell my students
that when stability of structure and personal safety are an issue 
(afterall, who wants a yurt crashing down on them in a high wind) don't
sacrifice doing it right for doing it cheap.

Corun



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