Step installation mostly done

I started the step installation section by drilling the step attach blocks in the drill press:

Step attach blocks on drill press
I then match-drilled through them into the ribs with the steps in place:

Step under baggage floor, with attach block

Step going through match-drilled attach block

Attach block fully match-drilled and bolted

Both attach blocks secured to ribs
I then actually drilled through the step into the bottom skin, and back into the baggage floor:

Baggage floor hole where the step bolt goes

Step with bolt in place
Finally, to reduce the chance of the steps breaking, I used the bushings from TCW - they go inside the step (with the bolt going through them) to prevent crushing of the step tube. They were slightly oversized for my steps, so I had to grind them down slightly to fit:

Ground-down TCW step bushings

Step bushings fitting into steps
Now the only steps left are to touch up the primer on the steps and actually attach them permanently, which I'll leave for later.

Time lapse:

Total step installation time: 5.4h

Access covers/floor panels started

While waiting for a riveting partner to finish the forward side skins, I started to take tasks from the other sections ahead, so I started section 35 by fitting and drilling the rear floor pans.

The pans don't really go in without some serious deburring - the aft seat rail supports are about 1" wide, and the gap for them in the floor pan was only about 0.9" - I targeted a little slack and widened them to about 1.07", then they fit perfectly:

Trying to fit the rear floor pan
Floor pan gaps around aft seat rail support

I then clecoed them in place, final-drilled the holes to the adjacent ribs and rear spar, then match-drilled the forward holes into the main spar web:

Final-drilling floor pan attach holes

Match-drilling floor pan into main spar
After that, I removed them - which was in itself a challenge, since they go in pretty tightly and "snap" under the rear spar attach bar. I had to use two thin pieces of metal (two chip removing tools) to bring it over that edge, pulling them with clecos (there's also nowhere to grab):

Lifting the floor pan out of the rear spar attach bar

I then final-drilled the other holes (which were already dimpled in floor stiffeners, so no point in final-drilling together), then deburred the holes and edges of the pans, so they'll be primed on the next batch of parts, whenever that is.

Finally, I final-drilled most of the screw holes and deburred holes and edges on a pile of access cover parts:

Final-drilled and deburred access cover parts

Time lapse (now in 4K!):

Total access cover and floor panel rivets: 0
Total access cover and floor panel time: 7.8h

Fuselage side skin riveting continued

I got some new tools to try to get to all those side-skin rivets, and that was immensely helpful:

New riveting sets and bucking bars
We finished riveting both mid fuselage side skins, and the aftmost part of the forward side skin (where it's very annoying to rivet due to the large wing attachment bolts/nuts):

Riveted right mid fuselage-skin

Riveted left mid-fuselage skin

including all the bottom rivets that get done in this section:

Bottom rivets on the right mid-fuselage skin

I installed the rear seat vents:

Rear seat vent installed

Inside view of the rear seat vent

We then installed the mid cabin decks, and for bucking those rivets, we had someone inside the airplane for the first time!

Bucking the mid-cabin deck rivets

Riveted right mid-cabin deck

Riveted left mid-cabin deck

We also performed a bunch of smaller tasks, like riveting the nutplates on the forward cabin floor panels:

Nutplates riveted to forward cabin floor panel

We applied sealant (Firebarrier 2000) between the firewall and the forward side skins before we rivet it in place:

Applying sealant between the firewall bulkhead and the forward side skins

Firewall/side skin joint all sealed up!

Since we were playing with Firebarrier anyway, we also sealed up the gaps in the firewall recess:

Firewall recess corners filled with Firebarrier 2000

Time lapse (now in 4K, starting at 44:48):

Total fuselage side skin rivets: 1040
Total fuselage side skin time: 137.8h