HS Skins Riveted

After coming back from a long Memorial Day Weekend trip to Sedona, AZ, I finished riveting the skins on this weekend. About 500 rivets in total.

The trickiest part was (again) getting the holes in the skin lined up just right with the holes in the ribs and channels underneath; several adjustments of the clecos were required, and even then there were still some holes that I needed to ream a bit for better fit.

35 hrs total to build the HS, including all the rework I had to do with the primer (I expect that to go much more smoothly next time!)

With this part done now, I’ll be starting the elevator next.

Skin on HS

After having to slightly modify my priming process yet again (story for another post), I started clecoing the skins onto the HS frame. First side goes on pretty easily…

…But when flipping over to the other side, it’s a tight fit, and initially the holes don’t line up since the skin needs to pull up tight around the nose. I found starting at the outside fwd edge and working my way in was the best way to do this (see the red arrows on the next picture).

I’ll probably start riveting one side, and leave the other side open for inspection. Before I rivet, I need to check that left and right sides are level to each other – I’ll be using a digital level to do this.

It’s exciting to have my first little wing built! The elevator is up next.

Progress on Horizontal Stabilizer

I got most of the horizontal stabilizer assembled this past weekend, save for the skins. Everything went together fine. I learned it’s a little tricky to get holes lined up just right for all the rivets to fit – especially when lining up overlapping parts with many holes, like in sections that are doubled (or tripled). I found that fitting in a bunch of loose rivets before putting in clecos helps get the parts lined up just right. Here’s an example of what I mean, you can see a bunch of loose rivets with the mandrels still sticking out:

Still, I had to use a #30 reamer to open up 2 of the holes a little bit – not too bad, considering I probably put in over 200 rivets so far. Doing quality checks as I go, I only had to drill out one rivet that wasn’t seated right. I’m pretty happy with the finished product:

The vertical stabilizer is next up in the manual, but I’m missing a few parts so I’m skipping ahead to the elevator for this week.

Process Makes Perfect

After about 2 days of drying, my freshly-primed parts for the horizontal stabilizer started showing spider lines in the paint, then flaking off and looking like this horror:

It took me a while to figure out what went wrong, but it looks like I failed to properly clean the parts before priming with SEM Self Etching Primer. I had been using the Simple Green Extreme precision parts cleaner to clean and de-grease, then drying the parts with a clean towel. Here’s where I went wrong – after this step I went right to priming. The important step I missed was to rinse the part off with water, to remove the cleaner from the surface of the part. Going through a Google search, I also learned that a lot of people do a final cleaning with acetone or isopropyl alcohol right before priming.

Check out my Process page for details on my revised priming process – which I can confirm now works successfully.

Mercifully, I’ve been able to fairy easily remove all the primer from the affected parts using the Simple Green cleaner and a Scotch Brite pad – still a lot of work though. I got through about half of the HS parts tonight, will have to finish tomorrow.

After following the 9 steps above, I re-primed one of the parts (a plate) and the finish came out much better. On the left is a part that I stripped back down to the bare metal, and then cleaned with the new process. On the right is a part that was reworked and was sprayed with 3 light coatings of primer. Tomorrow I’ll do a tape pull test to make sure the primer adhered properly.

I work in engineering so I know how important it is to have your process right, especially when it comes to applying coatings to metal. Lesson learned – do a test of your process on a scrap part first to avoid having to rework a bunch of parts like I did!

First set of parts primed and ready

I spent another two hours last night prepping the last of the horizontal stabilizer parts (minus skins) and then priming them.

Primer appears to have adhered well to the aluminum. Gonna need to refine my spraying technique though – I went through a whole 15.5 oz can spraying 3 coats on these parts, but a good amount of paint settled on to my floor and not the parts – I think I was spraying too far away. The instructions on the spray can say to hold the can 6-8″ away from the parts, so I’ll move in closer next time.

In the meantime, I’ve ordered more of the primer. I found a place online selling them for $13.95 a can, much cheaper than the $21 I paid on Amazon – and shipping is free over $99 so I bought 8 cans.

Here’s a link to that supplier:

SEM 39693 Green Self-etching primer

Work commenced on Horizontal Stabilizer

This weekend I completed inventory of both kits I received, so it was time to get started! The first assembly in the manual is the horizontal stabilizer. I’ve spent the last two days deburring and cleaning all the parts, and then will be priming them in a little “paint booth” – credit to Craig Maiman for the idea. I’m using SEM self-etching primer as I described in an earlier post, so I’ll be spraying the primer from a rattle can.

I should be ready to start clecoing these parts together this weekend.

I’m pretty pleased with how my work area has turned out – all of the parts are stored away on the wire shelves pretty neatly. I put down a roll-out textured floor material designed for garages, it greatly enhances the appearance compared to the dirty bare concrete.