Today I cut out the pitot mast hole in the left wing bottom skin, dimples the pitot tube bottom skin holes, and countersunk the rib angle holes.
The longest job was cutting out the hole for the mast in the bottom skin. I started by removing the bottom skin from the wing, then drilled the #19 holes in the skin. These are where the screws will pass through the skin and into the mast’s flange. These holes were a pain to locate because I had dimples the backing plate. That enlarges the holes, and leaves a lot of slop when match drilling. I managed to get it pretty accurate, so then I moved on to cutting out the mast slot.
I drilled and then step drilled holes at each end. Then I used a hand nibbler to cut the material away. With a rough cut in place, I switched to running a grinding bit on my drill and cut away more material. Then I finished it up with a file, and checked the mast’s clearance frequently. By being fairly careful I ended up with a good looking hole that seems square and symmetrical.
I deburred the holes I made in the skin, and then dimples them all. I was anxious to get that done without cracking anything, and was successful. Then I dimpled the backing plate and countersunk the holes on the angle.
The pitot tube mast is basically ready to install now. I need to powder coat the mast, which I’m hoping to accomplish this week, then this is ready to be riveted together when the bottom skin is installed.