Made the flapper door to keep fuel from moving back into the 2nd bay during some aerobatic maneuvers. I had to make the top piece over; the first one's rivet holes were skewed.
The instructions don't say anything about the hinge pin. I put a slight bend in the end that goes against the rear baffle (to the left in the photos). Once the rib is installed, there's no way for that pin to ever get out.
It's funny that we spend time making this flapper, but right above it is a 1-1/2" hole on the rib! So I riveted a piece of .025 over it to keep fuel from getting through. The other ribs don't have the hole.
