Cowling

Today I cleaned up the excess filler by using a small chisel to gently scrape it away.

With that done I was able to fit both pieces of the cowling in position and confirm everything lined up as expected. It looks good!

Today I riveted on the bottom cowl hinges. The boe-lube worked well as a release agent, and the clecos came out easily. With the hinges glued in place, I cleaned out the excess resin by running a drill through each hole. Before glueing I inserted the hinge pins, just to help avoid any deformation, and I left them in while riveting.

Progress was swift, and I had the hinges done within half an hour. I went to test fit the cowl, but found I couldn’t get the aft edge hinges to line up with the firewall-mounted hinges. Pushing the cowling back caused the cowling to bend outboard instead of seating into position. I took the cowling off, and realized that I had some excess glue between the hinge eyelets on the left hinge. This happened because I used filler to build up a bed of glue behind the hinge where it interferes with the foam section. I’ll try to clean it up tomorrow somehow.

After clearing the excess resin, I started riveting the hinges on the bottom cowl. Immediately I realized I needed to first glue the hinges on, not just rivet these. On the aft edges, the interference between the hinge flange and the honeycomb meant that riveting the hinge could cause the rivets to tip, and leave a cavity between hinge flange and cowling. I mixed up some resin and glued all of the hinges into place. As a release agent, I used some Boe-lube on the ends of the clecos holding the hinges.

Tonight I riveted the top cowling hinges on. I first cleared excess resin from the holes by running the drill through the holes. Then I clecoed and riveted the hinges on.

One thing I didn’t do on the top cowl was glue the hinges before riveting. The plans didn’t call for using any epoxy, and I decided it wasn’t really necessary.

It didn’t take too long to knock out the riveting. Once done, I mixed up more resin and coated the inside of the bottom cowl.

Today I coated the interior of the top cowling with a layer of resin. This helps seal the cowling and makes cleaning oil and grime easier. I mixed up the resin and brushed it on.

Today we finished the fitting of the top and bottom cowls, and located and drilled the hinges on both the top and bottom cowls.

The only real issue we ran into was on the bottom cowl. On the left side of the cowling the honeycomb material was too far aft, and caused interference with the hinge. We carefully bent the hinge to conform to the shape, and will use some epoxy filler to fill any void between the hinge and the cowling.

Yesterday, and again today we spent time adjusting the cowling. With the top cowl just about perfect, we marked out and drilled holes in the firewall-side top cowl hinges. Then we installed the bottom cowl and used a strap to hold it in place while drilling holes in the air inlets.

Today my Dad and I worked on fitting the cowling.

The first step was getting the top cowl firewall attach hinges to fit nicely. The instructions call for filing the corners of the eyelets on the firewall to allow the cowl-side eyelets to fit nicely in the area where the hinge curves from the top to the side. Then some fluting is needed on the cowl side to ensure a consistent curvature.

With a nice alignment of hinges, we moved onto trimming the cowling. There is a scribe line that shows where the cuts should be made, but it’s important to go through an iterative process of fitting and adjusting, since the scribe line is more of a guide, and certainly not exact. The cowling went on and off many times while dad carefully trimmed away to get a perfect fit.

The prop needs to go on before we can finalize the fitting of the cowling, but the majority of the trimming work was completed today.