Solar hot air collectors DIY - Condor collector

Last year I build a few collectors. A 9 m2 gaze collector, a 6 m2 condor collector, a 5 m2 and a 10 m2 solarduct style collector. They all work well, but the condor collector stands out when the sun is faint.

See my projects on: https://people.zeelandnet.nl/a....dhouse/Zonnekachels/

I like large collectors, the small ones are nice for learning and trying. But in the Netherlands you need to catch every sunbeam you can.
I did some experimenting with beercans, but those collectors are a pain to build (cans crease easily). But the idea of thin aluminium is good. I chose used offset printing plates as base material. You can paint them, cut them with a scissor, staple them, drill holes in, rivet them etc. Those plates are only 0.006 to 0.012 inch thick, so they heat up fast.