Weeks 113-130: Engine/Cowling

It has been a long time since the last update but I have been making progress, although slower than I would like. After getting the engine mounted I started working on the connections to it. This was all fairly straightforward. I attached the intercooler to the air intake with the hoses cut per the instructions.

The only issue I ran into was getting the rubber air intake shroud attached. The instructions said to use an adhesive to glue it together, but any regular adhesive was not holding it at all. I ended up using rivets to attach the rubber to the composite intercooler mount (with metal backing strips to hold the rivet) and superglue to seal the rubber corners together. This worked very well. I also found that the cowling air intake for the air filter had to be shortened to get everything to fit properly.

Completing the firewall forward fuel system was also straightforward. The only issue I ran into was that the barbed fitting I received for the vent line on the fuel pressure sender was not the correct size. I just ordered a replacement for this (and then ordered a stainless steel version after the brass one broke). I also decided to use a hose clamp to secure it to the pressure sender instead of the OET crimp clamp called out in the instructions, the engine side of that hose was already called out to use a hose clamp.

I attached the oil lines from the oil tank to the engine, but I am waiting until after I paint before I install the oil filter and connect those lines. I am also waiting to do the engine cooling system since the radiator will need to attach to the cowling as well.

I also worked on some of the systems on the fuselage side. I planned to finish the fuel system (except for the tank connections), but found that the selector valve I received has the wrong size fittings. The factory is sending me a replacement, but I am still waiting on that.

I spent way too much time working on the brake system. I had struggled to get the plastic brake lines installed so I decided to use metal lines instead. My first attempt was to just bend the metal lines to go from the gear legs to the fuselage, but I quickly decided that would be impossible as well. Then I opted to add a coupling between the gear and the fuselage. That worked pretty well using a tubing bender to make nice bends.

I did the left side first and it came out very well, but when I did the right side I bent the tubing in a way that made a big air trap at the joint. I spent several weeks trying to get the brakes properly bled, eventually I closed the parking brake valve and was able to get good pressure on the brake cylinder. I decided the big air-trap I accidentally put in was keeping me from getting the lines bled properly, so I redid that part. After fixing this I was finally able to get all the air out of the lines so that the brakes work properly.

I also attached the propeller hub to the engine. This went pretty well, with the only issue I ran into was that I could not get all of the bolts installed with the mounting bushings in place. I had to remove them, then reinstall them with the bolts. I am going to wait until final assembly to attach the properly blades to protect them as well as keep them from being in the way.

The next big project that needed to be done before painting was the cowling. The initial fitting was a little challenging since I was doing it by myself. I did finally manage to get it lined up correctly. To mark where it needed to be cut I put masking tape lined up with the edge of the fuselage skin, then after getting the cowling in place I put on another strip to mark where the cowling edge should be. I used that to make the initial cut, but cutting outside that line so I could file it to be exact. I went a little too far filing on part of the top cowling, but I was able to correct it later.

Getting the camlock fasteners installed was easier than I expected. I marked the holes I could get to with the cowling clamped in place, then used masking tape to transfer the location of the other holes with the cowling removed. I drilled small holes to start with, then re-mounted the cowling to get them lined up exactly with the attachment strip holes. With all the holes line up adding the actual fasteners was pretty simple.

The next step was to put on the exhaust shroud. When I initially tried this, the exhaust pipe was interfering with it. A review of the instructions showed that I was supposed to modify the exhaust pipe with the angled attachment provided in the kit. I used a grinder to cut off the Rotax factory pipe as instructed and clamped on the Sling version. The larger clamp would not close far enough, so I decided to use a scrap piece of the original pipe to make a spacer. This let the clamp tighten properly.

I was able to get the shroud lined up on my own using a cleco clamp, then drilling and clecoing holes. I epoxied it on to the lower cowling per the instructions. It took several coats to get everything smooth, but I am pretty happy with the final result. This took some time though since I had to wait for the epoxy to cure between each step.

While I was using the epoxy I also added some to the top cowling where I over-sanded it. I made an extension with epoxy and cotton fiber filler material. This worked out very well, but again took several attempts to get it right. I sanded it down to where I don't think it will be noticeable after painting.

I am now working on getting all the seats assembled, since they will need to be painted as well. One big remaining question is if I need to put the windshield/windows in before painting, or after. If I need to do that before paint then that will be one of the next steps.