Month: December 2019

Tonight I scuffed the trim tab skins and spar with some 150 grit sandpaper. I did this where the foam ribs will be glued down, and along the trailing edge where the wedge will be taped into position. The scuffing helps the glue adhere to the metal.

I started by masking the areas I needed to scuff, then carefully scuffing with sandpaper. Because I had already primed the spar, I needed to remove the primer in the areas where the ribs will be glued to the spar. Just a small dab of acetone on a terry towel was enough to break down the primer. With a few careful wipes the primer was gone and I was able to scuff the spar.

I used some more acetone to clean the sanded areas, then removed the tape. Finally I dimpled all the remaining holes in the skins, and they are now ready for riveting and glueing.

I countersunk the trim tab trailing edge wedge, and the trim tab spar, then dimpled the bottom side of the trim tab spar.

I was able to quickly complete the trailing edge wedge countersinking tonight, since I set up the drill press last night.

With that done, I switched countersinks and calibrated it back to a depth of 0.007 inches below flush. Then I spent some time figuring out the best way to countersink the trim tab spar. I ended up drilling a series of holes along an edge of particle board, so that the clecos could sit inside, slowing the spar to sit flush on the board. It also helped to lock the spar in position. It was then easy to countersink, with great results.

Then I dimpled the bottom flange of the trim tab spar. But before I could do that I needed to find my narrow diameter male and female dimple set. I knew I had them yesterday, but just couldn’t find them anywhere. Eventually I decided to check the trash bin, and sure enough I found the male dimple die in amongst some old rags! Digging deeper I found the female die. I need to take care not to do stupid things like throwing away my expensive tools 🙂

Today I worked on the elevator trim access doubler and the trim pushrod arm.

After dimpling several nutplates, I riveted them to the access plate doubler. I squeezed the rivets, but in hindsight it might have been better to back rivet these. The very thin material means that it twists very easily, and i had a couple of less than perfect rivets, one of which I ended up drilling and removing.

Then it was on to the pushrod arm. This is made of 3 pieces of aluminum riveted together. The internal piece is shorter than the two outside pieces forming an attach point in each end. At one end, the outside pieces are also pre-bent to provide a wider opening for a wider part to attach.

The outside pieces need to be countersunk, and then flush riveted. This is quite straight forward except for the one hole closest to the bent parts. The bends mean that the part doesn’t sit flat, and the countersink cage contacts the surface unevenly. I used some scrap and made a couple of shims to use to accommodate the bends, and to support the opening at the end.

Riveting was fairly easy, I squeezed the 3-3.5 rivets, while being careful to only squeeze the rivet and not the material. The shop head is small inside the countersink, but wide enough to form a very strong bond. I’ll touch up the prime on this part again before wrapping up the elevators.

Next it was on to the elevator trim tab. I dimpled the closeout tabs, clecoed it together, drilled the close out tabs, marked the trailing edge wedge and skins, put a break in the skin trailing edges, then trimmed the trailing edge wedge. I set up the drill press for countersinking the trailing edge, then decided to stop for the night.