Composite is Annoying - Cowling Day 6

TLDR

• Installed the 2 inspection doors on cowling
• Installed 2 bottom camlocs
• Installed the top cowling louver

Why I Built It

Throughout the build, I was frustrated on many steps: fuel tank, wiring harness, control tubes fitting.

But working is compoisite is close to the top of my least favorite type of work. It’s not precise, and super duper dusty.

As I started the day thinking: today let me just spent 1 hour to install the inspect doors then I will work on the intercooler, it turned into a properly full day of fiberglass trimming and fitting. The silver lining, by the end of the day, is that I have probably completed 80%-90% of all fiberglass work required on my airplane.

Inspection Doors

There are 2 inspection doors one on each side of the top cowling. Last week I already started to trim one of them (and I thought I was close to fit it perfectly). So today I picked up the work in the morning as I got to the hangar.

The work is the usual.

    while (it_does_not_fit) {
        trim with grinders and sanding papers of various size and grits;
        vacuum the dust;
        test fit;
        Optional<profanity>;
    }

This lasted close to 1.5 hours before the 2 doors were more or less fitted on the cowling.

I then match drilled the piano hinge on both the inspection doors and the cowling, and countersank/shot the rivet on all the holes. Some of the holes were match drilled last week but at least one of them were drilled at the wrong location, so I mixed some superfil to patch the hole.

Lastly for the inspection doors, I installed 2 camlocs on each side. It was trick to get the camloc holes drilled. The overlap between the door and the cowling is just slightly more than 1/2 inch and the camloc hole requires 1/2 inch. So there was almost no buffer for my drill to drift on either side.

Louver

There is a huge hole at the center top of the cowling to get the hot air out. This hole is covered by a louver. Since today turned into a cowling day, I decided to just install the louver.

The hole is cut a little too small on all sides to fit the louver. I first placed the louver center to the hole, then match drilled all holes and clecoed the louver on.

Then I used a marker to draw lines where the louver doesn’t fit perfectly with the hole, that’s about 3/4 of the part in the initial round. Then I took it off the cowling and sat it aside, and shaved off the marked areas from the cowling.

After that, I put the louver back and tested the fitting again, and drew new lines where it didn’t fit, and shaved some more material.

This repeated quite a few times, each time I removed less and less material. Eventually the louver fit into the hole completely. Then I countersank and riveted the two parts together.

Bottom Camlocs

At the center bottom, there is a bracket with pre-drilled holes for 2 camlocs. This is supposed to be the bottom attachment point for the lower cowling.

In some version of Sling’s build instruction the bracket has its flat side facing up. But in newer instructions, the flat side faces down.

I initially installed the bracket flat side up but had to undo the rivets to make it face down. But I was ALWAYS uncertain which is the right way for my engine. So when I took off the rivets last time, I never riveted it back.

Now with my cowling mostly done, I decided to try both orientation and see which side fits better. As it turns out the flat side should be on top, at least for my own engine and cowling combination. This mean my did it right the first time and didn’t have to undo the rivets lol. Oh well.

Knowing which orientation works, the rest is easy. It’s pretty standard drilling, englaring the holes, fitting and installing camlocs.

While I still have the opportunity to take the bracket off, I decided to give it a primer and paint. This is both for anti-chafing, and also match the color of the engine mount.

I gave the bracket a good alcohol clean and scotch-brite scrub

Then shot a layer of self-etching primer/paint combo

I will let it dry overnight, and install it next time.