Sonex 1404

Posts Tagged ‘fiberglass tip

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.