[Goldfinger]

I'm hoping to construct my own polytunnel soon, as I have aquired a roll of water pipe (32mm dia') and some scaff bars. I'll have to have wooded bracing added too, because of the size pipe.

This size pipe does work, as I've seen others use this size with bracing.

My problem is the, (MY) measurements. 

The size I'm going for (hopefully) is, 72ft long, 8ft wide and 6ft high. But I'm hoping to have the first 4ft from the ground straight sided (if possible).

I've worked it out on firsttunnels web site and they say I need a 7.3mX26m sheet.

Is this right for my tunnel, with me hoping to have straight sides, and which cover do you recommend (clear or anti-fog)??

Oh, and due to the ground conditions it's going on, I think it'll have to be the 'base-rail' system.
(Tons of roots!  )

[grinling]

People on our lottie use the foggy one as it gets very hot inside the polytunnel.
If this is on a lottie, do you require planning permission as neighbour housing can complain to the council as they did for a guy at ours. Also how are you going to water inside? It can take alot of watering, one guy pumps it from a nearby stream (poly huge) as it would not be cost effective to have the water from the tap.
Also you will need to think how to protect the sheeting from the building construction as it moves a bit when hot and cold.

[Goldfinger]

I've just re-read my post  72ft!!?? I mean't 22ft long. There's a guy in the other allotments next to us, and he has what's roughly a 14x50ft poly. All he does is show stuff though. 

I've never heard of needing planning permission though. As for watering, I'm going to fit guttering and I've got plenty blue barrels to collect the water over the year to soften the use of the tap.