Riveting the vertical stabilizer5h
May 10, 2022
Today I started riveting the vertical stabilizer.
It was less than 12 hours since I primed the parts, but scratching my test coupon showed that primer is very hard already. I am very pleased with Stewart Systems EkoPoxy so far (not that I have anything to compare it to, but it definitely exceeded my expectations).
The first thing to do was to rivet together the rear spar, the rear spar doubler, and the brackets.
I started with the flat rivets on the bottom, thinking they will be easier to set. Wrong!
First, when squeezing flat rivets you have to be careful to make sure the squeezer is exactly straight or it could bend the rivet (and those rivets are long). Second, rivets on the bottom brackets are very close to the corner of the bracket, so you cannot put them straight in the middle of the flat die. Which also makes them fold over instead of squashing.
It took me several attempts, and many drilled out rivets and in the end, it turned out to be okay. Disassembling the practice kit was definitely the right call -- I did not damage a single hole! I did chip a bit of the paint from the bracket, though, but this could be easily fixed by applying a dab of a primer with a brush.
What I did not realize at the time is that all these rivets could be set with a back rivet set and a backing plate. Might have been worked better 🤷🏻♂️.
Then I squeezed all the universal head rivets. Those were much easier to squeeze because you can "lock" die on a round head, then press the trigger. Sometimes my squeezer would get "stuck" for some reason, as it does not have enough force (I have it connected to 90 PSI). Weird. Not sure what that is.
Then I moved to the front spar assembly.
This one did not go as well as the rear spar. Even though it has very few rivets, those rivets are located such that accessing them with the squeezer is a bit awkward. Few rivets I had to drill out multiple times until I got them somewhat acceptable. In the end, the rib flanges did not look very tight to the spar (but were not loose either). Also, they curled a bit. In the case of the top rib, I should have put the rivet in the opposite direction. This would have made it both easier to set and also would put the factory head on the flange side, which should help with the curling.
One mistake I made with the squeezer was that I tried to "sneak" up to the rivet by gently pressing the trigger until the anvil moves close to the rivet and therefore could be centered on the domed dimple die. This technique works when it works, but if you make a slight mistake (press trigger a bit too tight), it immediately destroys the rivet and leaves all kinds of marks. Ouch.
Later I adjusted this technique: I would remove the return spring, pull the movable anvil and position it on the rivet dome, then press the trigger. This worked much better. However, again, the better solution would have been to reverse the rivet.
Finally, I made the worst mistake. I wanted to flatten the flange on the root rib (VS-704) with the flat squeezer set, but when I did it, the squeezer slipped and chopped a piece from the rib flange and squashed the flange of the opposite nose rib (VS-705). Also, it might have damaged the front spar, too, by leaving a dent there.
Asked Van's support about what can I do here. Since I have not riveted skin yet, I might just rebuild the front spar assembly (and use the current one for more training!). However, I've already dimpled the skin, so I am not sure how to match drill new parts. Probably, could just hope that factory holes are close enough. For now, I am setting it aside and moving on to the horizontal stabilizer.
Few lessons learned:
- Don't fix what is not broken.
- Learn to be comfortable with the rivet gun. On my practice kit, I had no issues with back riveting stiffeners and riveting skins to the assembly with the rivet gun. However, I am not precise enough with the universal rivet set, so I get smiles when I buck rivets. Also, I have never used an offset rivet set which could have helped with the front spar assembly.
- Maybe, get a manual squeezer, for the cases where I need some extra precision?