polytunnel construction questi

[featherstick]

Hello all

I'm in Kyrgyzstan putting a project together to help people with food security and income issues. Does anyone know whether there is an ideal ratio between the height and the length of a polytunnel, when it comes to stability and wind resistance? We are looking at polytunnels that are 3.5m high and were initially planned at 30metres long, but we are thinking of reducing to 15m. Anyone know whether that would be stable enough in high winds?

Thanks

Featherstick

[rik_uk3]

Put together right and they are stronger than you'd think

https://www.youtube.com/watch?v=TZ7Gg_vV6mc

[Devonian]

From a structural point of view, the length of the tunnel is unlikely to have any real affect on the stability/integrity of the structure.

[adrian007]

My understanding is that the most crucial thing is getting the polythene tight. - if that flaps, it rips.

Next, those bars that go across strengthen the tunnel - you can see them in that video link

[featherstick]

Hello folks

My worry was that with a large sail area at the end for the wind to push on, then there wouldn't be enough strength to resist or hold it up in a shorter tunnel, but I don't think it will be an issue.

Cheers for helping with thinking.

This is an interesting place - many people lead lives that are already post-SHTF. Under the Soviet Union, everyone had some sort of income (albeit small), there was a medical point in every village, all the kids went to school and got their jabs and looked after, and there was enough to eat, especially if you had a bit of land.

Not any more. I've met families of four that are living on one pension of 30GBP a month. There's no work for many people, no facilities, prices for everything are out of reach for a large minority, there are border conflicts and ethnic tensions, and the world is a scary place.

Feathers

[grenfell]

I seem to vaguely recall that getting to angle to the prevailing wind plays a part. The shape of the tunnel allows air to pass over it harmlessly but damage can occur if the tunnel entrance faces the prevailing wind allowing air inside to push from the inside or something like that.