Rivet Filling & Left Wing End Rib

My fuselage kit will be arriving this week, so I spent this weekend finishing up the left wing. Last few steps are to attach the wing tip and control surfaces (aileron, flap). Before taking the jig off the wing tip, I worked on filling in all of the rivets on the bottom side of the wing with Sherwin-Williams Shrink-Free Spackling, as recommended by other kit builders. After injecting the spacking into each rivet using a 10ml syringe, I sand it down with 400-grit sandpaper to a smooth finish, using a little job aid that exposes just the rivet head. The sanding block I use is a detail sanding block kit available at Pep Boys with multiple fine grit sandpapers that stick onto the flexible block. It’s very useful for this task, but I also use this kit for removing scratches.

Sanding block and a job aid to mask off everything but the rivet head. The job aid is made from a scrap piece of aluminum, with a hole drilled to match the size of the rivet head.
Filled and sanded rivet heads

One last task while I had the wing upside down – install rivnuts for the large inspection holes. There are also a number of smaller inspection holes, but I’m not sure how covers are supposed to be attached – there aren’t enough rivnuts included with the kit, so I’m guessing these just get riveted on?

I installed rivnuts on the large inspection hole (right), but there are several smaller inspection holes (left) that I’m guessing will just have covers that are riveted on – probably don’t need to be inspected as often.

With rivet filling complete I flipped the wing back over and removed the end jig, allowing me to attach the end rib. Once riveted in place, I can also attach the composite fairing, but I may hold off on doing that until it’s closer to final assembly time, for a few reasons: (1) I haven’t purchased the wingtip lights yet, (2) I’m considering modifying the tips a little so that the lights will be closer to the trailing edge, similar to the TSi wingtip, and (3) I think the wingtips stand better chance of not getting damaged in transit if I leave them off. I’m planning to store the wings in our friend’s basement, since I don’t have space in my own basement.

End rib attached – still need to feed the wire for the wing tip lights through the small hole in the bottom of the rib
Sling TSi wingtip, as seen at Oshkosh 2018. The upturned edge offers a better place to mount the position/strobe light than the Sling 4 wingtip. I wish I could retrofit these wingtips, but the wing shape on the TSi is different so I don’t think they’ll work on my wing.

I also attached the flap to see how it fits – looks good so far.

Flap fits nicely, and moves freely
Flap held in the ‘up’ position using a little clamp that I improvised out of aluminum angle stock

Next task is to finish up the aileron. I have to figure out how to attach it to the wing such that I can still adjust the fit of the skin, whilst having it held together with clecos. I know from reading other blogs that getting the twist of the skin just right can be tricky.

Clecos getting in the way! But this picture looks cool, the aileron kinda looks like a Fowler flap in the full down position.

Left Flap Finished, Starting Aileron

I finished assembly of the left side flap. All the parts for the right side are prepared, but I’ll wait to assemble it until I see if I run into any fit issues with the left side.

Putting in the last few rivets
All done. I used some old 4″ vinyl post jackets to elevate the flap off the table due to the brackets on the bottom side
Adding the flap to my collection of finished airplane parts

I started preparing the aileron structural parts next. They go through the same process as the flap structural parts – deburring, cleaning, and priming. I also took some time to smooth out the shape of the tabs on the ribs, so that they more closely match the curve of the skin. In some cases, I have to file a small notch before I can bend the tab. A before-and-after picture is shown below for aileron rib # 4. I use an adjustable crescent wrench to make these bends.

You can see how the right-most tab will bump up against the skin, and may cause it to have a bulge
Same rib after I notch the corner a little with a round file, which allows me to bend the edge of the tab, giving it a slight curve. I guess I should sand out those scratches I caused – but they’re pretty superficial.

Building up the Flaps

With most of the left wing complete, I prepped the flap parts today for both left and right sides – it’s just easier to do all at once. I had to pull out the part bath tubs for the first time in a while, as well as my “paint booth” so that I could prime a bunch of parts at once. Ailerons are next, but as I understand it there’s some more work involved with those to get them lined up well with the rest of the wing trailing edge. Here’s a gallery of Friday’s efforts.