As temperatures drop quickly in Belgium, it's bad timing to drill in plexi so the canopy work will have to go on the side for a while.

After a winter stop, I started working on the plane a bit and was looking for some open tasks to do.

This reminded me of a strange sound I keep on hearing in the rudder. When I tilt over the rudder in certain directions, a here a ticking sound.
At first I was thinking of a cleco  or a washer or something that was left behind when I closed the top rib of the rudder many years ago.

As there is no way to look inside, the only option was to remove the top rib again and carefully drill out each rivet.
Fortunatly I have become an expert in drilling out rivets and so the result was very satisfying. None of the holes got enlarged and could be reset later with regular size rivets without any problem.
The procedure I use for drilling out rivets is always:

- first centerpunch the rivet. There is a little notch in the rivet that indicates the center. Using the centerpunch gently enlarges this point.
- use a very small size drill to make an initial hole straight down as shown in the image below.
- then drill #40 until deep enough to crack it of using a center punch.
- gently tap it out without using excessive force.

Half way through.
I never had to remove a pop rivet and the rib attaches to the main spar of the rudder with 2 poprivets so this was a first timer.
Here also, piece of cake. It's actually even easier than a solid rivet.

I removed the rib and almost got a hearth attack.
This is the view I got when taking out the top rib !

Djeezes Christ !
No idea how this could have happened. Certainly because I was being freaking anal at the time trying to do everything perfect.
It's another proof that you have to continuously stay very focused when performing a task.

Leaving this in might have given some serious issues with balance of the rudder.
Fortunately I heared it in advance and took action.

Note to self: "In case of doubt, re-open the piece and inspect. It might save you life one day..."