Today I started the drilling, dimpling & final fixing of the stringers to the top surface of the left wing.
Inside the stringers closest to the spars, I also ran 8 feet lengths of 3/4 X 3/4 X 1/16 6061 T6 backing angles starting from the rib at the fuel tank.
This is something that the Aeronautical Engineer also advised that would be a good idea, provided that I was happy about the added weight.
After drilling, I then removed the angles for countersinking the holes and to dimple the stringers.
Before final installation, the backing angles were etch primed.
Fixing stringers for final time
Typ. fixing using 3/32 flush rivets where ribs have cuts