Thanks a lot for your great comments my friends, you're all quite heart warming :)
to do Homemade photoetch, you need a few things:
-first being fluent enough in some computer drawing software to be able to design the plate: mine looked like that

messing up with those softwares is a fair part of my day job, so no real problem there -but it could be for anybody who cannot do this!
-then you photocopy the drawing on some transparent plastic sheet -any photocopy shop can do that
-then you must buy some brass sheet that has been treated with photoresist material, I found mine at a French mail order specialized in trains, it's not that expensive really -i paid 8€ for a 25cmx12cm plate, and you can do quite a few tanks with that.
-then the trick is to expose the treated brass a few minutes to the sun, on each side with the transparent plastic sheet as a mask. (3mn if the sun hits hard!)
-then you must dip the plate in this liquid photographers use to reveal their pictures (not very expensive too). And eventually you get a "printed" plate with in black, the exact drawing you made.
-then you put this in a bath of FeCl3 -easy to find ain electronic shops as it's an acid that is used to create some printed circuits.
-after a few hours, you have what i hold in my hands above :)
So you see, the thing is to invest, because none of the ingredients are expensive, but you need quite a few stuff. but then after that.. did you notice all the nuts and bolts and stuff I have been cramming on my plate?!!
I could write pages and pages about this as what i have been writing is the theory, now i failed quite a number of times on stupid issues, and I will eventually post here the dos and don't about the whole thing, but not before a few months, when i write the article for that specific diorama :)
more litterature about the subject
here[edit] woops Blackheart, i forgot to answer your question! here's a Sokol

the parts I have been modelling are the 5 meters after the first 5!