Finished Horizontal Stabilizer

I received the Torque Seal to finish off the rear spar. I opted for orange (many colors available). This stuff can make a mess if not careful, so I was careful.

The next order of business was riveting on the nose rib, HS-707, to the top of the left skin. The skin really needs to be pulled into a curved shape for the rib to sit fully flush against the skin, so I came up with my string method. I simply tight a single piece of string around the center of the skin to pull it into the optimal position. I used cardboard to help spread the point-load where the string contacted the skin (maybe not even needed). I wanted to leave it as open as I could to provide maximum working space. While the photo shows this vertically, I did this with it lying on the bench.

Before attempting to rivet, I made up a test piece that I could do a fair amount of practice on. My swivel flush set did an excellent job. Once I felt good on that, I went to work on the real thing. I feel the rivets came out very well.

Once the nose rib is riveted to the top of the skin, the instructions have you rivet the bottom of that same rib to the skin. I clecoed the end rib, HS-706, as well as the center-rear rib, HS-708, into place, then clecoed them all to the bottom of the skin. Riveting this portion was tough, I can’t lie. Even with my small arms I had trouble getting the bucking bar into place and still see what I was doing. To add to the difficulty, the forward most rib flange was slightly pulled away from the skin once I removed the cleco. I utilized a trick I learned from another builder and used a small piece of rubber tubing to help push the tab back against the skin while I was riveting (see my Tips and Tricks page for more about this). It worked! I was able to get all these set without issue, thankfully.

Next, the front spare + ribs was put into place. The first step here is to blind rivet HS-708 to the nose rib, HS-707, using LP4-3 rivets. Unfortunately, I could not make this work with the pop rivet gun I had, so ordered a new one with a rotating head. I also ordered the wedge tool from Cleaveland that provides a 10 degree angle to pull against. The combination of the two allowed me to pull these rivets successfully. The space is pretty tight though, so it was still hard to see what I was doing. While I was waiting for the new tools to arrive, I went ahead and worked on the right side, getting the right front nose rib bucked top and bottom, then attached it all to the front spar. Now I could work on both sides at once. This worked really well through the end.

After that, I went to town bucking AN426AD3-3.5 flush rivets, though starting with a AD3-4 rivet where the HS-708 rib joins with the front spar.

I made good use of the awesome word forms another builder had loaned me. While these were originally designed to be mounted to a single long board, I opted to utilize them “loose”. This gave me a lot of flexibility to be able to work on the left/right sides independently until I was ready to join them. When I needed to flip the whole assembly, I removed all but two supports, which I could then grab and move myself.

There sure seemed like a LOT of rivets. Reading build logs sure does NOT give you a true understanding of just how many rivets are here, and I realize this is just a fraction of what’s used in the entire build. Just wow!

I kept at it, over a couple days time I was able to knock them all out, with the final pop rivets saved for last.

Done! (for now…)

Thoughts after having finished this:

While I primed everything, going forward, I may attempt to NOT prime anything that is exterior facing. Knowing that I do intend to paint when finished and not having a clue what that paint will be, any primer on the exterior surfaces would need to be removed or at very minimum, abraded and re-primed. So, it’s probably best to avoid that altogether and only prime the internal structure.

Another issue I’ve noticed is the slight dishing around the rivets. At the right angles it can be seen. I was certain my dimples were great. I had a nice witness “ring” around each dimple and it looked flat using the light reflection trick. My DRDT2 had been preloaded with an additional 1/4 turn, plus a little extra. However, it is very clear to me there is room for improvement. I suspected at first it may be my bucking. However, the dishing can be seen around even the hand-squeezed rivets, so my riveting process can’t be entirely to blame (if at all). I’ll work on improving this before continuing.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.