Sonex 1404

Posts Tagged ‘vertical stabilizer

I got the new clecoes so I completed the final assembly and up drilling of the vertical stabilizer.

There was still the small matter of cutting the new vertical tip and fitting it into place which was by far the most unenjoyable part of the entire build to date. A lot of patience later, this was the end result.

Next step was to remove everything, debur and rivet the frame.

After that, I deburred the skin, applied ACF-50 on it to prevent corrosion (no more priming for me) and riveted it to the frame. My wife helped with removing the clecoes and also with some of the riveting which made it go quickly.

I had drilled three holes on the left side of the rear spar which were slightly off. I had to make those holes bigger and put bigger rivets in them. I got CCP-54 rivets from Wick’s for this (and for future goof-ups like this which is bound to happen). This photo shows the bottom most one.

The final product.

I can now get to the horizontal stabilizer. I have ordered a bending brake from Harbor Freight which should make bending the channel stock ends easier. That should give me a lot cleaner set of bends than the ones I had for the vertical stabilizer.


With the vertical stabilizer skin clecoed, I thought I’d try fitting the new fiberglass tip between the skin and the frame as the plans showed. I was not able to wrap the skin around with the tip in place, but funnily with the whole thing clecoed in place, I could now get the tip in with not too much trouble.

This meant that I did not need to do any “mods” to attach the tip, which was great. I put the tip in, drilled and clecoed it in place and marked the notch to cut for the rudder.

The only problem I see is that the leading edge skin does not sit flush with the tip.

I’ll have to think of something to fill that up, but otherwise this is one big headache that is gone.

I also decided to start updrilling the holes to 1/8″ at this time. I wanted a break from messing around with the fiberglass tip and this seemed like a relaxing, therapeutic thing to do. Which was all great until I ran out of copper clecoes. Here’s the result as of now.

I ordered some more from the Yard Store, but until then I think I’ll get started with the horizontal stabilizer/elevator. I think I’ll work on the elevator horn today.

The vertical stabilizer has a fiberglass tip that has to be sandwiched between the frame and the skin. The tail kit plan comes with an additional sheet that explains how this is done.

I started by making the notch for the rudder. The dremel tool with a rotary cutter did a quick job of this on the fiberglass.

Next was attaching the rib into the tip and drilling/clecoing the whole assembly.

With this done, it was time to start putting the skin onto the frame.

The starboard surface went on without a hitch. I was very happy to see that all the pilot holes on the skin aligned perfectly with the ribs on the frame.

The problem started after this stage. I wanted to wrap the skin around to the port side and get it aligned to the aft edge of the main spar with the vertical tip on. Unfortunately, the tip is quite thick and the skin didn’t quite make it to the edge of the spar. I had my neighbor come over and help me with holding down the skin while I drilled and clecoed some of the holes. The result wasn’t very good; the tip was just too thick.

I had my first Tech Counselor visit at this time. Dale Severs of EAA 414 came by and took a look at my project. We discussed the problem and I told him about some of the things I wanted to try to solve this issue. My first option was to sand the tip edge (the part that sandwiches between the skin and the frame) to make it thinner. The second option and the one that I learned from the Sonextalk group was to insert a strip of metal instead of the tip, and rivet the tip to the strip rather than through the skin. I saw some pictures of another builder who had done this successfully. The third option (also from Sonextalk) was to buy another tip rib and rivet it upside down to the existing tip rib. The fiberglass tip would then be riveted to this rib.

I first sanded the edge down to the bare fiberglass.

I clecoed the tip back on and tried to pull the skin all the way to the aft edge. No luck. It was still too thick. I then removed it and tried it without the tip, and it lined up almost perfectly. The skin was flush with the edge at the top of the tail, while it was less than 1/32″ short on the bottom edge. It looked like I would have to go with either option 2 or 3. 2 was already out since it was clear that the best option for aligning the skin was to have nothing between it and the frame. I therefore decided to order another tip rib (and a new tip just in case) from Sonex.

While I waited for these to arrive, I closed up the vertical stabilizer and drilled the remaining holes. A few holes on the port side were misaligned due to the misadventure with the tip on. I have to figure out what to do with them. I might just drill them out to a bigger size and put in bigger rivets. The rest of the holes were drilled and clecoed.

One quick and easy way to ensure that the surface is flat is to see if all the clecoes are touching the workbench surface. This is by no means accurate, but is a quick check while you are working. I checked the surfaces with a spirit level later on and found that both of them were absolutely flat. Woohoo!

I also drilled the rudder hinge into the aft main spar and I was happy with the result. The hinge is straight and the pin went in without much resistance at all.

The final product, for now.

Next step is to attach the fiberglass tip using the new rib.

At this time I have all the parts needed to start assembling the vertical stabilizer. I was a little bit worried about two things

1. If all the parts would align and at the correct dimensions

2. Whether I could assemble them true without any bends or twists

1 didn’t turn out to be an issue. I had to trim a few things, but nothing was a concern. I decided that the best way to do it was to start attaching things to the spars independently and then put them together, align them, and drill them all into place.

I first attached the nose rib which was rather straightforward. Next went the top rib on the front spar. I then removed the top rib from the front spar and aligned and drilled it into the rear spar. I now had the top part of the vertical stabilizer aligned, and clecoed. The other ribs then were put in their places, and one of the ends of each of them was drilled to the corresponding spar. The clecoes went in, and the other end was similarly drilled and clecoed. The trickiest part was the bottom rib since there wasn’t enough room for my pneumatic drill between the middle and bottom rib. This is because the clip with the pilot holes actually goes on the outside of the bottom rib. The solution on the front spar side was to clamp the rib with the clip on the inside, drill the pilot holes, remove the rib, clamp it into place the correct way (with the clip on the outside of the channel) and then updrill to #30. The other end was a bit of a pain though. I ended up making marks through the pilot holes, removing the rib and making the pilot holes on the Sharpie marks that I had made. Luckily for me, it turned out that these holes aligned perfectly with the ones on the rear spar clip.

Making sure that the whole thing was assembled without twists or bends was not as easy as I thought since the spars are not of uniform width. This means that when they are laid on their sides on my flat workbench, they are not true in the first place. The bottom part of each spar is wider than the top.

The solution was to put a 10 lbs bag of rice on the top rib with the bottom (wider part) hanging over the edge of my workbench. After this, it went together quickly. I measured the distance from the rear spar to the bottom of the front spar. The distance is exactly what it should be according to the plans. I am happy.

Next, I have to disassemble the whole thing, deburr and primer the ribs and put the skin on. The skin is still in the box Sonex shipped it in and I haven’t even taken it out to look at it.