McRiblets

I spent a few hours today finishing the bend to the new elevator trim tab skins and fabricating small ribs (riblets) to close out the ends of the trim tabs.

I think they came out really well. The first one I did came out fine, but was a bit of a test on exactly where to bend on my marked line to get the proper part width/flange length. I then was able to bang out the 4 riblets that I needed to make. Two outboard and two inboard riblets. The outboard riblets somewhat interfere with trim tab horns, so I made the flanges a bit longer to share holes and ensure proper edge distance.

I took the following pictures to document the process.

Started with a wooden wedge (oak) that I had previously made when trying to bend the tabs per the plans as a template against scrap trim tab skins.
Traced the outline of the wedge, marked the top and bottom cuts, and make a 20/32″ outer mark for the flange width.
Cut along the outer lines with snips.
Marking the position of the spar on the bottom skin and transposing that line to the riblet
Using a punch to locate the hole to be drilled
Drill a hole to serve as the relief for the flange separation
Snip out the metal on the tangent lines of the circle creating a separate flange piece that can be bend in more to accommodate the extra layer of metal of the spar.
Bend along the marked lines with a hand seamer.
First flange bent
Spar flange bent
Done!
Pretty good fit!
All 4 riblets completed. I used a 20/32″ flange for the inboards and a 28/32″ flange for the outboards to allow for hole edge clearance.
Marking out new holes that I will drill in the skins to rivet the riblets in place. 3 new holes will be added between the notches in the skin.

All-in-all, I’m very happy with how they came out. These were really the first true part that I’ve had to fabricate from scratch on my own. It really wasn’t as hard as I had anticipated, and it’s satisfying to see it come together. I can tell already that I’ll be very happy with how this turns out compared to my barely acceptable bending of the tabs.

Upper Tailcone and Elevator Trim Tabs take 3…

Since the last post, I’ve completed putting together the tailcone structure and match drilled everything. I’ve subsequently taken it all apart and deburred all holes and any remaining edges.

Looks like an airplane part!

Rear Seat Belt Anchor Point

 

Pile of deburred parts

In the meantime, I wasn’t completely happy with how my elevator trim tabs came out, so I got new parts to re-do them. The 2nd time went worse than the first.

The goal here is to bend the tabs to close out the ends of the trim tabs. It seems like it should be relatively easy!

elevator-close-outs

I didn’t have trouble bending the tabs on the skins, but these have given me trouble.

After messing up the first bend of my second attempt, I went off to do some reading on VAF. It seems lots of other have also had trouble with these tabs, so I guess it’s not just me. I also realized that I didn’t use any adhesive on the blocks so they moved slightly while attempting to bend the tab. Once I used some double-sided carpet tape, the next attempts went a little bit better. Probably passable, but I had already managed to crack the skin during my first bend.

Badly dented and cracked skin
Another attempt with tape. Better. Probably passable, but not the greatest.
Wavy!

The first set of trim tabs I attempted are shown below.

Bit of a buldge

Below is yet a 3rd set of new skins for the trim tabs. After doing some reading, I’ve decided to do what others have done, and that is to cut off the tabs and fabricate small riblets to put on the ends instead. It might take me a few tries to get those correct, but I have lots of scrap trim tab metal to work with.

3rd set of skins 😦
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Plan to fabricate something like this instead.