November 15, 2019

Rear Fuselage Progress

I was able to log quite a few hours this past weekend, working mainly on the rear fuselage. First, I finished assembly of the tailcone, which is fairly beefy since the empennage control surfaces attach to it. Some rivets were a little tricky to set due to limited room.

I needed to ream this outside hole slightly, but I needed some help from a flex shaft attachment to get enough clearance
I couldn’t get a 4x10mm rivet to sit flat here, due to a formed rivet already directly behind it, so I decided to modify a rivet a little per the next picture.
I removed about 3 mm from the rivet body to fit in the hole above – that was enough to successfully set the rivet.
All done! Looks interesting

Next, I cleaned and primed parts for the larger rear fuselage ribs, and assembled ribs 2, 3 and 5. Unfortunately I had to skip rib 4 for now, as I discovered a crack in one of the formed parts. Rib 2 didn’t quite come together as nicely as ribs 3 and 5; despite using the template, there’s some twist in the curved top pieces. I’m not sure if this is a problem yet – maybe the twist will get worked out once the rib is supported by the skin.

Lining up rib 3 using the guide provided with the kit
Perfect fit and flat – rib 3
Rib 5 also went together nicely
Unfortunately I discovered this crack in one of the rib 4 pieces as I was prepping for priming. Replacement part is on order!

I moved onto building up the floor of the tailcone, reinforced with several longerons. I vaguely remembered a warning that the orientation of some of the longerons was incorrectly illustrated in the manual – sure enough, after researching for a good half hour, I found confirmation from reading Peter’s blog. Left and right longeron 902 are swapped in the CAD model used for the manual. By the way, this error is still present in the TSi manual as well, so please be careful and pay attention to the part number left/right digit, and take a look at photo below for proper orientation. If you read on in Peter’s blog, you’ll see that having these incorrectly swapped will cause a headache later on during the center/rear fuselage join.

Longerons 902L/R (short ones), shown in the proper orientation, with the c-channel facing towards the centerline

Last thing I decided to work on was the luggage floor skin. Curiously, my fuselage kit included two skins: one for the parachute option, one for without. Also curiously, the skin for the parachute option was missing a few holes for a support channel specific to the parachute option, so I had to mark and drill those holes.

Non-parachute luggage floor skin on left, parachute on right. I wonder why the inspection ports are in different locations?

I’m holding off on riveting the supports in place, since this skin is supposed to have some foam attached to the bottom for insulation. I figure it will be easier to measure & cut the insulation without these supports in place, so I’m holding off on attaching for now. The kit includes foam, but I’m considering using a denser foam like other builders have opted for.

I masked areas to control where primer gets applied. Outside these areas, insulating foam gets applied instead, and I think the adhesive will stick better to the bare metal. The support channel running across the middle of the skin is unique to the parachute option. I had to match-drill a few holes into the skin that were missing.

I’m not sure what to work on next. I don’t want to do too much more with the rear fuselage, since the next step involves attaching the ribs to the floor skin, and will start to become a fairly large assembly. I want to complete assembly of the right wing before I do that, but I’m on hold waiting for a replacement rear spar. I think I’m going to resume working on the right wing’s fuel tank, which I started in March but then set aside to finish up the left wing assembly.

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