6 hours
Now that all the cowl pieces physically fit together and I have all the holes drilled and cleco'd, it's time to figure out what actual fasteners I'm going to use to attach the upper cowl.
The plans call for simple nutplates but also recommend Southco fasteners as an option. I did not want to use nutplates and screws because I didn't like the idea of having loose hardware that I could potentially drop somewhere in the engine bay and lose. Plus they would take forever to remove or install every time I needed to take the cowl off/on. I'm also not super impressed with Southco after messing around with one on the fuel door. After some research I decided to go with Skybolt Camloc fasteners. These things are more expensive than Soutchco but they're super nice and easy to install.
Skybolt has a LOT of options for fasteners, so it took me some research to figure out what I actually needed. Their PDF catalog is a lot easier to browse than their website, so I found that to be helpful: http://skybolt.com/wp-content/uploads/2019/04/Skybolt-Catalog-v5.1_Print-aerospace-fasteners-1.pdf
Pages 10 and 11 of the PDF pretty much gave me all the info I needed. I ended up going with SK26S51-SET1 for all the cowl fasteners. This one has adjustable depth receptacles so you can use them on a wide range of panel thicknesses. I also bought some extra SK2600-SW washers. Those washers allow the stud part of the fastener to retract when open, which makes the parts easier to disassemble. The washers that come in the fastener set hold the studs in place which only works if you can pull the parts you're fastening straight apart from each other.
Anyway, for each fastener I bought one of each of these parts:
I also bought a couple of drilling templates which turned out to be super handy:
I bought everything directly from Skybolt. Here's the heap of parts I got in the mail:
The rivet pattern for the receptacles is exactly the same as for regular nutplates. The little drilling jig made it real easy to drill the rivet holes in the correct places relative to the fastener holes I already had drilled.
Here's what the recaptacle looks like riveted in place. I used CCC-32 rivets.
The stud part gets inserted into the other part to be fastened. They sell special pliers to compress the spring inside the stud to make it easier to install, but I found I could just use a small open-end wrench and my thumb to install them without any special tools.
Once both parts are installed they go together really nicely. You just line everything up and give them each a quarter turn to lock them in place.
I did several iterations of installing the upper cowl, checking the fit, installing a few fasteners, and repeating, in order to make sure everything was still lining up nicely. Eventually I got them all installed. Due to all the bonus fasteners I had to use along the upper edge, I ended up using a total of 24 fasteners, versus the 15 called for in the plans. So that was pretty expensive! But it turned out really nice so whatever.
Anyway moving on. I also bought one more extra fastener for the fuel door. Way back when I installed the Soutchco fastener for the door, I installed the receptacle 90 degrees off because the windshield blocked me from installing it the correct way. It didn't occur to me that when I did that, it made it so the flat part of the wingnut stud stuck out perpendicular to the airflow. It really bugged me, but I could not find a stud with the wingnut part rotated 90 degrees! However, Skybolt sells one with a wingnut that folds down. So I replaced the Southco with one of these: https://store.skybolt.com/sk2600fw-set1-p3644.aspx
It's way nicer than the Southco anyway, and now it folds down and looks like I meant to do it that way all along.
Oh yeah, I also riveted the three piano hinges on the lower cowl during this time as well.
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