Today I permanently removed the Kammback.
The immediate reason I removed it is that this week Svieta is due for the annual technical exam, which cannot be passed with homemade additions like this. The reason it will not go back on is that it is old. It was built in mid-2009 and I did not expect it to survive the winter, max 1 whole year. It stood up quite well for over 6 full years, but the sun and the cold have taken their tolls: it now sags:
it is very brittle, flaking away at a mere touch:
or even breaking without touching:
This makes the FE gains smaller, and its safety (for example during strong winds) questionable.
Svieta's butt looks so naked now. I'll miss the fact that it kept both sun and snow off the rear glass. She looks more or less stock, except for the lack of roof rails. Over the winter I'll see how noticeable the FE impact will be, then maybe I'll find enough time to concoct a new Kamm.
I'm open to ideas for improvements: materials, technique, dimensions. I'd like to round it (compound curve?) instead of the straight fold, hopefully reducing some vortexes. I'd love to put the window on the end, even make it a permanent part of the rear hatch, but let's not get carried away: unless I can get the hatch legalized, I'll need to be able to remove it on the roadside. I still have the original piece of PP coroplast in the garage, hopefully it is still worth using. If I could find someone with the know-how and willing to assist, it could be fiberglass or whatever other material. Maybe I'll make two at the same time - the second for Theodor?