Mid-fuselage ribs and bottom skins complete

As the last bit left behind from section 26 (Mid-fuselage ribs and bottom skins), I got a new flap actuator bracket, match-drilled, deburred, primed and riveted it (interleaving those with tasks from section 40, to come in another post):

New flap actuator bracket clecoed in place

New flap actuator bracket and angle riveted in place

I also shortened the heat tee screw to give more clearance to the flap motor:

Heat tee with screwed marked for shortening

Heat tee with shortened screw
and then drilled the TAS antenna holes just below that:

TAS antenna hole on bottom fuselage skin
With this, section 26 is finally complete.

Time lapse:

Total mid-fuselage rib and bottom skin rivets: 1170
Total mid-fuselage rib and bottom skin time: 102.6h

Baggage area O2 tank attachment points and dimpling

As I was getting ready to prime a batch of fuselage parts, I devised the attachment for the O2 tank. I decided that the best way to secure it would be horizontally - there's really not much structure on the tailcone bulkhead or the side skin to attach vertically, and I didn't want to install it in the tailcone because battery fire + O2 tank = death. This does mean losing some baggage space (about 7-8"), but I also added nutplates before the tank area so that I can make a steel cover to isolate and protect the tank, letting us still put baggage on top of it, and preventing the baggage from hitting the tank (or most importantly, the tank head/fittings which are more sensitive).

I used 6 7/8" acrylic disks to get the tank tie-down structure the right size, and measure/mark the bolt holes on the floor. Finding the right position for the bolt holes that wouldn't interfere with the underlying ribs took some trial and error, but I managed it:

O2 tank attachment parts in place for reference
To reinforce the attachment of those bolts, I made some doublers from .064" aluminum, and drilled them for the AN4 bolts and nutplates:

O2 tank attachment doublers under baggage floor

To further make sure that reinforcement would hold, I cut the corners of those and bent them to form flanges, making them stronger in two more axes. The size and folding of the brackets was carefully calculated to avoid the underlying ribs and stiffeners, which is also why one of them faces the other way (notice the line of holes for the rib) and to avoid the overlying side cover, one of them also has more machine-countersunk holes for flush rivets than the others:

O2 tank attachment doubler with the nutplate for drilling and corner removed

O2 tank attachment doublers with flanges bent

Final form of the O2 tank attachment doublers, clecoed to the floor

After priming, then, I dimpled all the parts for this section:

Dimpled baggage area parts

Next comes painting the visible parts, riveting the doublers, and installing the Clickbond attachments for conduit, while I wait for the 5" GripLockTies to come out/arrive so I can secure the conduits before riveting the floors down to the fuselage. (I tried getting a few 8" ties, but they're too wide/tall for the Panduit attachments)

Time lapse:

Total baggage area rivets: 36
Total baggage area time: 33.2h

Vertical stabilizer completed, again

In my first tech counselor visit, quite a while ago, they identified that the rear spar caps in the vertical stabilizer were not properly deburred (not surprising, it was the first part I ever made):

Vertical stabilizer's poor deburring from 2014

After much hesitation, I decided to redo that rear spar and its attached parts, so I had a lot of rivets to remove:

Vertical stabilizer skin rivets to remove

For the 1/8" rivets that attached it to the ribs, I had to remove them through the shop head, but that turned out to work well with exactly the same technique - drill to some depth, break the head off, and then the actual rivet hole is evident to finish drilling:

Vertical stabilizer attachment to middle inspar rib being removed

After just a few minutes (easier than I expected), I had the whole thing off:

Old rear spar removed from the vertical stabilizer
I got the new parts from Van's, and got to work like it was 2014 again:

New rear spar being drilled

Since I already have the completed tailcone, I skipped ahead and final-drilled the VS rear spar into the tailcone now, so I could countersink the bottom holes and prime the whole thing:

Rear spar attached to the tailcone

Rear spar match-drilled and bolted onto the tailcone
Like before, I added a nutplate for the grounding strap, slightly closer to the brackets this time:

Grounding strap nutplate

After primer, I riveted everything back together:

Rear spar riveted together

Vertical stabilizer completely riveted again

The holes that attach to the middle inspar rib got cherry rivets (CR3213-4-2) instead:

Cherry rivets attaching the middle inspar rib to the rear spar
Overall, the results were a lot better than before (who knew, 5 years of building experience makes a difference :) ):

New (left) and old (right) rear spars

Time lapse:

Total vertical stabilizer rivets: 350 (I didn't count repeat rivets again, so no diff from last time)
Total vertical stabilizer time: 76.1h

Experimenting with paint for the interior

Even if I go with one of the many interior cover options, there are several parts that are still exposed in the fuselage's interior, which will need to be painted. I wanted a matte gray tone, and wanted something that I'm likely to be able to buy more of later (e.g. for touch-ups or future mods), so I picked up a few spray cans at Home Depot to test them out (and it's surprisingly hard to find spray paint without primer). I applied them on the bottom part of the baggage floor so it's not visible later:

Various paint types tested on the bottom of the baggage floor. Left to right: Rust-oleum chalked country gray, Rust-oleum chalked aged gray, Rust-oleum pro dark machine gray, Behr Chalk classic noir

I liked the 3rd color (dark machine gray) best, but it's unfortunately quite glossy (notice the reflection of the can on the paint), so I'll likely go with the first one (country gray) instead. The other two were matte but too dark or too light.

Large batch of fuselage primer

We primed quite a few parts from various fuselage sections (and even some from the empennage attachment, and for rebuilding part of the vertical stabilizer):

Various fuselage parts after scrubbing with Prekote

Primed fuselage parts on the floor (ran out of space elsewhere)

Primed fuselage parts on the workbench

Primed fuselage parts on top of the fuselage

This unblocks a ton of work, so expect many more posts in the near future.

Time lapse:

Total time: 6.5h (but I'll count it towards each section instead)

Empennage attachment progress

I'm going back to finish section 11 in order to be done with all the tailcone drilling before attaching it to the fuselage, since it'd be quite a bit harder to do afterwards.

I installed the rod end bearings into the elevators:

Rod end bearing attached to elevator

I then attached the elevators to the horizontal stabilizer to match-drill the bearing into the elevator horns:

Elevator attached to horizontal stabilizer

Both required some adjustment (loosening up a half turn of the rod end bearings) for the bent-edge blind rivets not to catch on the rear spar rivets, but it was fine after that.

I attached both at the same time to drill the pushrod attachment bolt hole at the bottom:

Elevator horns attached to horizontal stabilizer bearing

Both elevators attached to horizontal stabilizer

Drilling the pushrod attachment hole on the elevator horns

I then removed the elevators and match-drilled the horizontal stabilizer to the tailcone:

Horizontal stabilizer aft holes attached to tailcone

Horizontal stabilizer forward holes attached to tailcone

Horizontal stabilizer attached to tailcone

Since I'm also working to rebuilding part of the vertical stabilizer, I also match-drilled the rear spar into the tailcone:

Vertical stabilizer rear spar attached to tailcone

I removed and put away the HS and VS, and will prime the shims on the next primer batch. After that, the next time I come back to this session will likely be for the final attachment.

Time lapse:

Total empennage attach rivets: 40
Total empennage attach time: 20.8h