Control Stick Mounts

What should have been 5 minutes of work turned into 2 hours! While attaching the control stick brackets (CF-BKT-009-X-C-) per sheet E6 of the manual, a mandrel broke off a rivet in a hard-to-reach location. It took me over an hour to remove it. First I tried drilling it out from the rear, and found that was nearly impossible. I switched to using a Dremel with a small grinding wheel to grind away the rivet face, until enough of the rivet was gone so that I could push it through as if I had drilled it out; that wound up working. All that grinding damaged the foam, so I had to replace the pieces and replace them.

This is the bracket for the control stick – one on each side, seemed simple enough
Though hard to reach (especially in the corners), these rivets went in OK…
… but then this rivet mandrel decided to snap off! I might have been tempted to just cut off the mandrel, but the rivet didn’t form fully on the opposite side, so it needed to come out. Normally it’s really easy to drill out a rivet… except here, there’s no way to get a drill into this space!
Finally after grinding out the old rivet, I put in a new rivet and then replaced the foam

Forward Floor Insulating Foam

There’s an interior skin that goes over the forward floor bottom skin, so I needed to install the insulating foam first.

A reinforcement skin CF-SKN-007-L/R fits between the bottom skin and the stringers/main spar; I just wanted to make sure I have a pic capturing that I installed it correctly
Checking fit of all the foam pieces before I remove the adhesive backing
All of the foam pieces now taped to the skin
CF-SKN-011-C-C- sits above the foam. For some reason I thought I would be attaching the foam to this skin, so I had masked off the areas with painters tape
Oh well, I guess it still looks neat!
Starting to place rivets, using the manual to help identify which holes do NOT get riveted at this step

Forward Floor Stringers

Having completed page E3 (Main Spar and Undercarriage Channel), the next step is to attach the forward floor stringers. The rivets go up through the bottom skin, so I had to rotate the fuselage assembly onto its side. It winds up resting on the forward upright for the main spar carry thru, which I clamped onto my work table. Once I put it back down, I’ll add the insulation foam to the floor.

Hopefully the plane won’t ever bank this hard in flight!
View from the belly side
Not an exciting task, but I filled all the rivet heads now since I’m not sure when I’ll have easy access to the belly again

Main and Rear Spar Carry-Thrus

I’ve been quite busy the last week with family and friends so I only had an hour here or there to make progress on the plane. Most of the work has been on attachment of the spar carry-thrus to the center fuselage. Those are attached now, so I think the next step is to rotate the assembly onto its side to attach the forward floor channels to the bottom skin.

These brackets (CF-BKT-023-L/R) that sit on the main gear channel are quite thick and weren’t perfectly formed. I had to spend some effort with a hammer fixing the flanges to make them flat (see next pic)
The red arrows indicate where these brackets were bulging a bit and needed some hammering to flatten them
After adjustment, the brackets fit better. Still, I had holes that didn’t line up, especially the three holes that go into the upper surface of the main gear channel.
This elevator control stop (CT-STO-001-X-A-) needed some notches cut into it for an adjacent rivet to have room to form properly
CT-STO-001-X-A-: not sure what happened here, but the holes in the bracket don’t match the holes in the skin. One of the parts is a newer revision? I wound up drilling new holes in the skin to line up with the outer holes in the bracket
Aileron control stop CT-STO-003-X-A-. The holes for the bracket were 4.0mm but the holes in the skin were drilled to 3.2mm so I had to open them up with a reamer
Only after I had already riveted these brackets did I realize I needed to leave the red circled holes open – there’s a close out bracket that comes in a later step. The manual really should have a note about this! It was not easy to drill out these rivets, I had to use a right-angle adapter. Also in this pic, the purple circle shows why the notches were needed in the elevator control stop
Main gear uprights riveted in.. lots of rivets. I put these in before attaching the main spar carry-thru, which is not the order the manual states; my thinking was that these rivets would be harder to access once the main spar carrythru is attached (…I was right!)
Installing the rivets for the main spar carry-thru from underneath, not the easiest angle to work from.
Floor ribs riveted into the main spar carry-thru webbing. Pretty tight quarters here to get my rivet tools into!
I attached these support tooling brackets after riveting in the carry-thru. Notice the holes drilled 1-2-3-4-5 into these brackets? Nice thoughtful detail!

Resuming Fuselage Work

I had planned to spend Sunday doing the majority of the sealing work on the right fuel tank, but I discovered a crease in the leading edge of the skin. I spent a bunch of time trying to smooth it out, but I was not satisfied with the result. I have to ask TAF to send me a new skin, so unfortunately that means the wing is on hold for now.

Now I’m back to working on the fuselage. We had good weather today so with the remainder of the day I primed a few more parts that I will probably need this week. Afterward I decided to spend some time putting in the 1/4” “super” insulation foam I recently got from Aircraft Spruce. Like other builders, I opted to get denser & thicker foam than what is supplied with the kit.

At first I cut the material using a standard box cutter, which works ok but tears the material a little, even with a brand new blade. I remembered that I had a nifty rotary cutter made by Fiskars, which cuts this material without tearing and leaves a clean, square edge. I cut pieces to fit underneath the baggage floor and for the center fuselage floor between the seat ribs.

This Fiskars rotary cutter is perfect for cutting the foam
Perfect cut using the cutting wheel
Foam squares attached to the baggage floor, after I attached the channels
Foam pieces cut for the rear seat floor, but not yet set in place with the adhesive backing

Next up will be attaching the main spar carry-through to the mid and front lower floor sections, so this assembly is about to start becoming quite big.


Undercarriage Channel

Fresh back from a week of vacation on Cape Cod, I resumed work on the center fuselage. On Sunday I worked on page E3, which assembles the rear bottom assembly, undercarriage channel, and main spar assembly onto the bottom skins. Quite a few big and substantial assemblies here, but that’s because most of the weight of the aircraft is supported in this area.

Riveting together the rear floor ribs using the nose piece extension for my Milwaukee rivet gun

I spent a lot of time with the flanges on ribs CF-RIB-001-L / R, which were not formed properly and made it impossible to slide the undercarriage channel into place. I had to bang on them with a hammer and shape with a seamer for quite some time; overall I needed to make the opening between the flanges 1.7 mm wider. After some elbow grease and a bunch of swearing, I got the channel in place.

The flanges on Rib 001 that surround the channel weren’t formed to correct dimensions so I had to bend them into shape
Finally got the channel to slide in!
Me and my rivet gun! Unfortunately I also had a use a manual riveter inside the channel since there wasn’t enough room to fit the rivet gun inside
Page E3 step 1 mostly done. I added the support brace too.

Rear Floor Assembly

I started fitting all the ribs I primed this past weekend to the rear spar carry-through assembly and floor skin. The fuselage is beginning to take shape!

I’m fitting the clecos from the top side, even though rivets go through bottom. Seems easier to do it this way rather than working upside down!
Turning the assembly on its side so that I can rivet from the bottom side

Center Fuselage Parts

In and around holiday events this past weekend I was able to put in a few hours on center fuselage parts. Not much to show, other than a bunch of floor ribs that have been cleaned and primed.

Speaking of priming – I found that I spend a lot of time on this step, so I’ve been looking for ways to speed this up. I am still deburring and lightly sanding parts as before, but I’ve switched up the cleaning routine. Rather than using a combo of simple green, water, acetone, and isopropyl alcohol, I’ve started simplifying to a one-step product that’s recommended by the manufacturer of the primer I’m using (SEM self-etching primer). The cleaner is called SEM Solve, which comes in a spray can and wipes off with a clean towel. So far the results are great – the primer is adhering well and the finish looks good. SEM doesn’t give guidance on how much of the cleaner you will need, but I’m finding that I need one can of SEM Solve per 4-5 cans of the self-etching primer at 3 coats of primer.

I switched to the gray primer color for the fuselage, for no other reason other than aesthetics — there are likely to be primed parts that are visible even after putting in the interior, and I think it would be nicer to see a neutral gray color instead of green.

Preparing the rear floor panel
Various ribs to attach to the floor panel
Rear spar carry-through assembly, to which the ribs above will attach to
Attaching an autopilot servo bracket to the main spar carry-through assembly. Access was really tight — I had barely enough room to get this relatively slim rivet gun into place.
Completed autopilot servo bracket

I have to put in an order to Aircraft Spruce soon, among the items I need to buy are:

  • Garmin GMU 11 Magnetometer plus connector kit
  • Garmin GSA 28 servo (x2) plus connector kit
  • Shielded twisted pair wire for the CAN connection to servos and magnetometer, as well as some normal straight wire for power & returns
  • Soundproof insulation for the interior skins (I want something more substantial than what is provided in the kit)

Anyone have guidance on how much length of wire I need to order, especially the shielded wire for the servos & magnetometer? There may be more wire I need at this point, like antenna wire for comms, ELT, etc., but I need to figure that out.

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.

Right Wing Skins and Starting Fuselage Assembly

I consulted TAF about my damaged rear wing spar, and they advised against repairing it so they will send me a new one. That limits how much I can do on right wing assembly for now, but we had some nice weather this weekend so I decided to prime the right wing skins along the rivet lines so that they’re ready to attach. I already have most other components for the right wing primed and ready for assembly.

I occasionally like to make sure the primer is adhering well, so I perform tape pull tests after the primer has been given a day to dry. I wasn’t too happy with primer pulling up on a recent part I was working on, so I made a slight process change – instead of using Scotch Brite to scuff the surface, I’m now using 400 grit sandpaper. I think the plastic protective sheeting that’s applied to the aluminum leaves behind an adhesive residue that the Scotch Brite doesn’t quite release. Wet-sanding with the 400-grit paper and water seems to work pretty well, so that’s what I’m doing going forward.

Sanding and cleaning the skin. I’ve had some mixed results using Scotch Brite pads, so now I use 400 grit sandpaper only and have had much better results with primer adhesion.
Same skin after cleaning off the sanding residue. First I wipe off the wet sanding residue with a clean cloth, then wipe with a clean cloth with a small amount of acetone, finally wipe with a clean cloth with a small amount of isopropyl alcohol.
All primed and ready – I usually get the desired finish with 3 coats of the primer

I decided to start assembling fuselage components, starting with the ribs of the rear fuselage. Assembly of these components was straight-forward.

Rib 8
Completed rib 8 and rib 9; they come together later on in the assembly.