Despite using a 100mm pipe to slightly gable the top, I returned from overseas to find that the tarpaulin had collected gallons of water and sagged the roof in, bending the pipe in the process. So, James and I set about making five arches out of thin steel strip pulled together at the bases by cord to properly arch the top. The tarpaulin now arches well, also protecting the top and most of the sides from the worst of the UV exposure.
