Also what is the yellow material on the pictures labelled crack 2006 and crack 3? Is it primer or adhesive?
yes primer for alu
I also note the "stop" drills on German crack 2007. Someone actually flew this after stop drilling?
As you can see clearly, yes
I am being fasetious; I have yet to see an exampe where a stop drill actually worked!
Actually I have seen few glider canopys where this was efective solution. But probably becouse is aka plastic material, the crack dont spread any more. But agree with you in case of metal .....