On Friday, March 7, 2014 4:25:32 PM UTC+1, Alexander Griffin wrote:
>
> I don't see why there needs to be a tension band at the top of the walls
> ("eaves"). The walls are held together firmly in a circle by a combination
> of hinges and velcro seals. It is not going to expand apart on its own any
> more than a fully taped yurt. The roof cone itself is held together with
> the same tension points as any traditional taped yurt. Can you explain to
> me why you think a constant ring of unbroken tape is needed to keep a yurt
> erect? I'm not saying you're wrong, I just don't see why from an
> intuitive perspective or in practice.
>
As I understood it, the "tension band" is the fundamental engineering
centrepiece of yurt design in general (not just hexayurts.)
>From http://www.appropedia.org/Hexayurt_H13
"...however a door that size will cut into the tape tension ring that also
creates major stability in the hexayurt."
The way I intuit the whole thing works is that your tape anchors' or rope
halo's tendency to pull the roof down is kept in check by the tension ring
of tape around the top of the walls (which also incidentally seals the roof
on.) Without the unbroken tension ring, you will have stress points at the
top corners of the wall panels and they will tend to want to split,
especially if the yurt comes under a lateral load (wind.) The tension band
evenly distributes this load around the whole structure.
Vinay (or someone who's actually a structural engineer) might be able to
provide a better reference, or correct me?
> I don't ever want velcro seals at the bottom of the roof cone. If water
> runs down the roof it will get under the velcro seal and then into the yurt.
>
I guess. You could add some kind of flashing (a tape flap or something) to
avoid this though. Or maybe a ratchet strap tightened over the cordura at
the top of the wall might make a good tension band, reinforcing your velcro
arrangement.
> Also, your roof folds into six separate "chunks"?
>>
> No, two separate sections. Each section is made of six triangles, which
> include a combination of standard and bifolded beveled hinges using BiDi
> tape. There are only two velcro seams attaching the roof cone sections to
> each other, as seen in blue in the photos.
>
Oh right, there aren't any "camp danger loose hinges" in a standard bifi
roof cone are there—what about the walls then, two separate sections or
three? I guess the extra wall seam to tape wouldn't be a big deal with the
re-usable velcro seals—which gives me an idea for a H4 design which will
pack flat into a standard 4x8 plywood sandwich...
Cheers, Robert.
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