[sheeny (Al)]

We had a similar idea of "flexing" corrugated iron for a job at work. We just wanted to put a 50mm crown in it over 3-4 metres. Forget it! The forces involved are too high, and if you do manage to do it, it will crease. If you really want a curved corrugated roof, get it rolled.


A tropical roof, is basically a radiation shield. If you look up the performance of a radiation shield you will see that 50% of the incident radiation re-radiated from the bottom. For it to work best though, air flow needs to be able to move through underneath it in any direction, so don't just bang up some timber across your van and expect good results. Spend a bit of time making frames to support the iron so the air can flow in any and all directions.


Do not use any sort of polycarbonate as GlenD suggests. Yes, it's easy to bend, but it only blocks IR radiation and maybe some UV if treated to do so. The amount of visible spectrum blocking is limited to the amount of tint in the polycarbonate only. This is why polycarbonate is used to make green houses instead of glass these days.


At my last house I decided to put clear polycarbonate over the pergola. I figured I wanted as much light as possible and the warming effect wouldn't hurt in a cool/cold climate like Oberon. It turned out to be a great place under the pergola in winter and cooler weather but summer was unbearable. Without the polycarbonate under the pergola would've been perfect in summer, so I guess I needed some amount of tint rather than clear. The reason polycarbonate works so well for green houses is it lets in all radiation except the IR, which is then mostly absorbed and turned into heat. The heat in turn re-radiates as IR, but it can't escape through the poly carb.


So my advice is use corrugated iron. Build frames so air can flow in any direction. And if you want the Rolls Royce version, insulate the bottom of the iron to reduce the temperature at the bottom surface - this will increase the temperature of the iron when in the sun (increasing its IR radiation back up) but the insulation will drop the temperature of the bottom surface of the insulation so the IR radiating down to the van is minimised.


Good luck.


Al.