Homemade Polytunnel!

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Iain
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Homemade Polytunnel!

Postby Iain » Thu Dec 08, 2005 8:12 pm

Have just come across a recipe for a homemade polytunnel. Seems ingenious, and I'm sure it would work. This is the url:
www.overthegardengate.net/UserPages/pp_ ... nel&Page=1

If that fails, try:

www.overthegardengate.net
Click on "Constructional Features"
On resulting page scroll down to "New! AlanP shows us how to build a Polytunnel." Click on that.

Could have saved myself a fortune!
Gardener

Great site.

Postby Gardener » Sun Dec 11, 2005 6:43 pm

Great site, good Forum. Cheers.Iain.
Allan
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Homemade polytunnel

Postby Allan » Wed Dec 14, 2005 8:06 am

This is virtually the same as a commercial polytunnel except to the best of my knowledge there is no commercial tunnel that uses blue plastic waterpipe even of the larger size for good reasons of rigidity. Even with steel tubing is the material of the necessary quality and how do you produce a smooth hoop without the right machinery. Most important of all, do make sure of the 4 braces. Now finish it off and wait and see what the winter gales do to it!.
Allan
Iain
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Homemade Polytunnel.

Postby Iain » Wed Dec 14, 2005 4:46 pm

The main difference is that it's about half the price. I agree that you'd think the first decent storm would totally mollicate it, but the chap says it, and-I think- others withstood the Spring gales of 2005 without a problem! Isn't that the way Geoff Hamilton made cloches? The tubing was sleeved onto upright dowels which were glued into holes drilled in a timber base frame?
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Postby Allan » Fri Dec 23, 2005 5:37 pm

Geoff Hamilton's construction was omly 3 foot high, if that. I presume you intend a walk-in tunnel which is totally different. I have several times made a Geoff Hamilton type structure just to cover my extra early runner beans, each time a mdest wind has flattened it, the plastic pipes of small diameter haven't got the stiffnes required and when you see ityou get the impression of a lot of blue snakes .
My large tunnels are now 2 inch steelpipe professionally formed to the right curvature and come with a lifetime guarantee against wind damage.
Tom Parsons

Polly tunnel

Postby Tom Parsons » Fri Dec 23, 2005 7:02 pm

As a Polly tunnel gardener for many a year now I think you should stick to the well established tunnels that are well built and designed - save you all your money that you spend on a second rate job - in the end
Iain
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Homemade Polytunnel.

Postby Iain » Fri Dec 23, 2005 7:48 pm

It appears that I have been misunderstood.
Howard B

FAO Allen

Postby Howard B » Sat Dec 24, 2005 10:30 pm

I have several times made a Geoff Hamilton type structure just to cover my extra early runner beans, each time a mdest wind has flattened it


Just because you couldn't do it successfully does not mean that others can't. It sounds to me as though you were using the wrong materials for a start, either that or you live in the Antarctic :oops:
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QED

Postby Allan » Sun Dec 25, 2005 9:08 am

That's just the point I was making. You can't expect the small, relatively cheap, polythene pipe to be suitable for a large, all weather structure, no matter who uses it. That pipe is for supplying water for which purpose its flexibility is an asset but not the ideal material for any rigid structure.As they say, horses for courses.
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pigletwillie
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homemade polytunnel!

Postby pigletwillie » Sun Dec 25, 2005 10:49 am

I am in the process of building one of these tunnels and can say that it is more strength in it than my neighbours bought tunnel.

Firstly the sides are made from 8ft long scaffolding pipe driven 3ft into the ground leaving me with 8ft sides before the curve of the roof. The plastic is not "domestic " size. It has an internal diameter of 50mm (2 inch) and when linked together with stiffeners (just like on a bought tunnel) is extremely rigid. Only the curve of the roof is pipe only, the downrights are pipe covered scaffolding poles which are about 100 times stronger than the monkey metal that polytunnels are normally made of and are going nowhere. My tunnel is situated side on to the prevailing wind so there shouldnt be an issue

To be honest, the whole polytunnel thing depends on whether or not you have the thing and especially its plastic cover nailed to the ground sufficiently to sustain high winds, whether its home made or not. I will post pictures when its finished and update if it gets "blown away".

David
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Postby sue-the-recycler » Sun Dec 25, 2005 1:17 pm

I came across a good length of underfloor heating pipe in a skip and have used the same construction method with it and bamboo canes in place of the scaffolding tubes to make very generous (3 feet at higherst point) fleece cloches and they have so far prooved to be very efficient, withstanding gales well. The diameter of the tubing was perfect to use ordinary domestic clothes pegs to hold the covering on. So I think the construction method would be fine but I guess its the scale thing again - would the larger structure survive. I think if the construction principles are sound these poly tunnels sound as if they would be a realistic alternative for a gardener on a tight budget.
Guest

Postby Guest » Sun Dec 25, 2005 9:44 pm

Having re-read the minutia of the original link there is a good chance of that working but you first have to have the material which you may not get free and I imagine that there wouldn't be much difference in price between scaffolding poles bought new and similar tubing bought ready shaped for polytunnels. What is described is totally different in scale from Geoff Hamilton's specification and indeed could be better than some of the cost-cutting tunnels often sold. I am still not happy about the apparent lack of diagonal bracing on the tunnel shown. My tubes are onto ground tubes which are set in concrete blocks, I would expect the bare tube to tip in the soil when the ground is wet.
Several years ago we commenced replacing the mud in the trenches with pea grabel which is much better for drainage and has perforated land drain inside it to collect the rain water. It is also far easier to replace the cover.
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re."Guest"

Postby Allan » Sun Dec 25, 2005 9:50 pm

just to say the entry above was from me
Allan
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pigletwillie
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Homemade Polytunnel

Postby pigletwillie » Mon Dec 26, 2005 6:33 pm

Allan,

I too was a little concerned about the bracing but will brace the uprights with scaffolding tube putlocked together. the posts are driven into the ground 3ft, the bottom 18" of which is very nasty blue marl clay which doesnt move as it is consistently wet through the water table height. I will post piccies when completed.

David

ps, the first hoop is in and I can assure you that the finished article will be much more solid than you can imagine. the scaffolding posts are all secured together close to the ground but the sheer strength of the blue pipe and its good rigidity are supprising. It is much stronger than the aluminium bought jobs.

David
Last edited by pigletwillie on Wed Jan 04, 2006 11:53 am, edited 1 time in total.
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Postby Beccy » Sun Jan 01, 2006 5:16 pm

I don't know about polytunnels, but in other contexts a degree of flexibility can confer strength. I recall a very windy night spent in a dome tent on a campsite near Ullapool. It was so windy that the tent was half flattened at times. When we got up the following morning it was to find all the campers who'd had rigid poles in their tents sitting in their cars, with the remains of their tents strewn around the site. We did feel rather smug!

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