We took some time to finish the edges around the door where the cabin cover was attached to the fuselage - priming, filling, sanding, priming, and finally painting them - with pretty good results that blend in well with the top part:
Priming the bottom cabin cover edge
Cabin cover edge after primer and paint
With this, the next steps on this section are riveting the tailcon top forward skin (which I'm waiting to finish the ground plane extension to do), final-attaching the center cabin brace (which depends on having the panel riveted on, which in turn depends on completing the firewall penetrations), and then the transparencies (those really should be a separate section).
While I was down with COVID, I took the time to 3D print the new case for the AFR sensor controller - it was my first attempt at dual-extrusion printing, which resulted in big failures and a few lessons learned, including that sometimes it's just simpler to go with single extrusion :) eventually, I realized it was only $25 to have it printed professionally using MJF, so I did that instead.
Very poor attempt at printing the new AFR case myself with PC/ASA
Original Spartan3 case (left), my attempt (center), and MJF-printed version (right)
I also took the opportunity to update the Spartan3's firmware, which, annoyingly, requires a Windows device (or VM in my case):
Spartan3 connected to power and USB, for upgrading the firmware
I also made some progress on avionics attachments, including riveting the ECU brackets and then the GTR mount in the tailcone:
EFII ECU angle brackets
GTR20 mount with nutplates riveted on
GTR20 mount riveted in place
With the bracket in place, I used the inspection camera to check that the nutplates were clearing the bottom J channel, and they were - just barely:
Clearance between nutplate and J channel behind the GTR20 mount
I also made the firewall passthru holes for sensor and power wires:
Firewall wire penetrations
Rear side of firewall wire penetration
For the top COM antenna, I needed to expand the tailcone's ground plane a bit, so we marked and carved "slots" to run aluminum tape through as an extension:
Cabin cover marked for the ground plane extension
Carving the cabin cover for ground plane extension
Cabin cover with slots carved in for the ground plane extension
Next we'll install the aluminum tape in those slots and cover it back up with fiberglass strips - with that, we'll finally be able to rivet the tailcone top forward skin from section 43.
After attaching the cabin cover with resin/flox, it quickly became apparent that protecting the aluminum with tape was a bad idea, as some of the tape actually got caught underneath the resin, and it took us many hours to get it removed:
Tape caught between the cabin cover and underlying structure :(
After digging all the out, we then filled the gap around the edge at a right angle to the aluminum, with resin and microballoons/cab-o-sil (this time using just packing tape, which was pretty easy to remove), then sanded it until it was actually at a right angle:
Cabin cover edge, filled with resin/micro
Sanding the cabin cover edge filling
Cabin cover edge, sanded down to a right angle
We then started the finishing of these edges, filling them:
Filling holes in cabin cover edge filling
Next we need more sanding (and filling, and sanding, and filling, and sanding...) to fully finish the edges, then prime and paint them (the tape we used also removed a lot of the cheap rattle-can paint we used on the aluminum, so that needs to be re-covered).
I finished reinstalling the wheel after the fairing bracket, by securing the disk with safety wire:
I received the replacement nose gear leg fairing, and this time marked and cut the top opening in the right place (quadruple-checked before cutting :) ):
Template attached to nose gear leg fairing
Original nose gear leg fairing (top) and new one marked in the correct place (bottom)
The template is quite conservative, so it took many iterations of trimming 1/8" at a time until I got it to fully wrap around the gear leg nutplate brackets. I had to trim both the bottom where it contacts the nose wheel fairing, and the top edges to move it aft by about a 1/2" and up about 1/4":
Nose gear leg fairing clamped in place
Next, I followed the instructions a bit out of order - first, I match-drilled the screw holes to have a fixed position for the fairing. I did that by sanding the gel coat off in the area that the underlying bracket would be, which worked well for sighting the holes. This also allowed me to mark where the brackets were, for aligning and trimming the hinges.
Nose gear leg bracket hole visible through a sanded area of the fairing
I then drilled the hinges by the recommended spacing, clamped them to the fairing, and match-drilled from the inside:
Nose gear leg fairing with hinge match-drilled to it
Finally, I trimmed the hinges to avoid the brackets, and trimmed the bottom edge of the fairing to provide the required 3/16" clearance:
Fully trimmed nose gear leg fairing attached in place
With all that done, I countersunk the attachment holes, then primed the hinges and riveted the nutplates and hinges in place:
Nutplates attached to nose gear leg brackets
Nose gear leg fairing with hinges riveted to it
Slightly related, I noticed the tug was removing the paint (and at some point, would be primer) from the attachment point, so I cut some adhesive foam to protect it - it won't last forever either, but it's easy to replace later as needed:
With this, the only part of this section still left (for later) is the top intersection fairings, which will be better done after the wings are attached.
