Cowling fasteners, Part 3

August 11, 2018 – Well, things are coming along nicely on the cowl.

I drilled the holes to size in the upper cowl. 15/32″ using a Unibit. At the holes at the upper corners where the engine mount is, I had to start them, and then finish the holes with the cowl off the airplane, because the Unibit hit the mount. This step is hard because there’s no solid way to cleco the cowl in place after the holes are drilled. I just had to be careful and make sure things were lined up as best as I could get them.

I mixed up a little bit of resin and flox and filled the cleco holes that I had drilled to get the cowl into position originally.

I riveted the receptacles for the upper cowl into the flanges.


Then I installed the collars into the cowl. These were really a tight fit, and most of them wouldn’t go in by hand. So I used a C-clamp and a socket to squeeze them into place.

I then installed the fasteners using the pliers.

I put the cowl on the airplane, and tightened the fasteners until they sat flush.

Once the fasteners are where you like them, you remove them by using a screwdriver and pressing down and turning to loosen them with a sharp motion. You have to do this because the receptacles are unlocked and will turn. The sharp motion just releases the pins on the fastener without turning the entire receptacle barrel.

To lock the receptacles, you remove the temporary lockpin and then turn the barrel to the 11:00 – 7:00 position. The collar locks into place with a light snap. That’s it.

I repeated the process with the lower cowl. The lower cowl seemed a lot harder to keep lined up and to drill precise holes. As it turns out, only two fasteners on the firewall, one on top, and one on the bottom, don’t quite line up. So I ordered some floating receptacles from Skybolt.

Now it’s time to set up the fasteners that go down the cowl split on the sides.

I decided to lay these flanges out externally, then they will be installed internally later. I drew a line from the lower fastener on the upper cowl, so everything’s in line. I marked the same spacing as on the firewall, 3.25″, and went from there. I positioned each flange centered on the marks I made, and clecoed them at the receptacle rivet locations.

I just carried that line forward until I ran out of room at the front. The flanges will be riveted to the lower cowl, so I laid out that line and went with .9″ for the rivet spacing.

I started on the left side and realized I’m short two flanges, because of my mistake installing them down in the belly where the exhaust fairing of the cowl is.  So I’m going to make a couple.

This cowl is almost done. I’m really happy with how it’s turning out.

Time: 9:00


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