Finishing Aileron; Wing Step Skin Try 2

I had a heck of a time getting the aileron to line up properly with the trailing edge of the wing and the flap. I wound up using a technique that involved putting some tape on the skin overlap, twisting the aileron by hand while on the wing, taking the aileron back off, then setting rivets. I had to use a reamer to open up some of the holes so that I could set the rivets with the aileron twisted to match the wing. It was very much a trial-and-error process, since I couldn’t find a way to set alignment once and then rivet the skin.

At first I cleco’d the edge and then used blue painter’s tape to hold the skin in place so that I could remove the clecos and check fit
I needed a stronger tape to hold the skin down, so I switched to strapping tape
I marked some black lines over the skin overlap joint to make it easier to see if the skin was still aligned after taking it off the wing
As you can see from looking closer, the holes don’t line up very well after the aileron has been twisted for alignment. I use a reamer to open these holes up.
I guess it was worth the effort; the aileron alignment looks good

Next, I wanted to install the wing step skin so that I could call this wing finished for now. TAF sent me a replacement skin along with the fuselage kit that I received recently. This skin doesn’t seem to fit either; just like in my earlier post, the holes on the flange don’t line up with the holes on the ribs or lower skin, so I can’t get clecos in.

I decided to try drilling the holes, and as I expected, I ended up having what looks like slots. I am considering just going with this skin as-is; I don’t think this section of skin sees much tensile or sheer loads, but I’m checking with the TAF tech support team to see what they say.

Comparing the new skin (top) with the original skin (bottom). On the original skin, match-drilling to the wing results in holes that are above the CNC-cut holes, while on the new skin match-drilling to the wing results in holes that are below the CNC-cut holes. You can see there are some holes that are less than 2D from the edge, a potential problem.
I decided to match-drill the rest of the holes on the replacement skin, because it lines up better with the flap when installed on the wing. The holes I drilled are the lower set of holes, some of which are marked with black arrows. I used a file to open up and smooth the adjoining holes.

This week I am going to build an EAA wing rack; I need to get this wing off my work tables and off to the side so that I can build the other wing, and then begin the fuselage.

Aileron Alignment

As I’ve posted previously, I’m trying to be proactive about ensuring the aileron trailing edge lines up with the rest of the wing. I decided to re-use the same trick I used for the elevator & horizontal stab: assemble the part in-place, using clamps to set the assembly straight. So, I loosely assembled the aileron with a handful of clecos and blue tape, put in a few rivets (some set, others loose), and then attached the aileron to the wing.

Using clamps to hold the aileron in place while I pop the rivets

After popping a few of the rivets on top and bottom going into the rib flanges, I can say that this process helps, but it appears the final twist is really controlled by how you set the rivets on leading edge of the skin (where the top and bottom skin edges meet). Unfortunately, these rivets are not accessible while the aileron is mounted to the wing! So, I will ponder how to hold the alignment while taking the aileron off the wing to set the remaining rivets.

Alignment still looks good after setting most of the rivets that I can get to

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.

Aileron Parts Prep; Fuselage Kit On Its Way!

I just got back from an amazing European vacation, and prior to that, a weekend trip to NYC, which is why I haven’t had any updates since Easter. I’m back now, excited to get back to work. While I was away on vacation, I also finished all the purchase stuff with TAF for the fuselage kit, so it’s on its way! The kit was picked up from Torrance last week, and should arrive in about 2 weeks.

During my vacation I also had time to think about my progress as many people ask me when the plane will be done. I had originally hoped to complete sometime in late 2020, but my progress over the last year shows that I’m woefully behind that goal! I averaged 21 hours/month over the last year, which would put my completion date somewhere in 2023 based on 1350 hours to complete the kit. I’m re-targeting a new date of late 2021, which means I need to work about 30-35 hrs/month to stay on track. Yes, that’s 1.5x over last year’s average, but I did have some months where I was able to get in 33 hours, so I think it’s achievable. There’s a new side widget on the home page called “Progress” so you can watch how I’m doing. The fuselage will be the biggest sub-project from what I’ve seen on other builders’ blogs, whom recorded 700-800 hours to complete. I’m hoping I’ll be able to go a little faster, taking advantage of their tips and tricks.

Back on subject – I had some time to work on the ailerons on Sunday. I completed cleaning and priming the ribs for both left and right side, and starting assembling the ribs to the skin. Everything seems to fit ok, but I will hold off on riveting the parts together as I’ve seen from Craig’s blog and Peter’s blog that there is some work required to align the trailing edge of the aileron with the flap and wing tip. I don’t have the wing tip attached to the wing yet, so I’m going to have to do that. However, before I attach the wing tip, I will fill in all the rivets on the bottom side of the wing, since I think that will be harder to do once the jig comes off the end of the wing.

Pictures showing the aileron parts coming together:

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.