I have used plumber's Barrier Pipe - plastic 15mm water pipe - a substitute for copper - to construct a hoop house system over my raised beds in the garden - covered, not that it matters with horticultural fleece. The diameter is about 48" so the rdaius is about 600mm. The end fixings are just a half inch hole in the wooden frame of the raised bed. I did not need to heat the pipe to bend it because it's flexible. When I remove it from the bed the bends remain much as they were. A heavy fall of snow collapses the hoop house but as the snow melts it quickly returns to its original profile.
Consider Barrier Pipe - I bought 50M for about £35 from Screwfix.
Good luck...
Peccavi
January 2010
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