Tag Archives: Empennage

Lots of Rivnuts on the Vertical Stabilizer

Hours: 1.5
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After putting the Elevator construction on pause due to the alignment issue of the center rib. I decided to get started on putting together the Vertical Stabilizer. I’ve heard back from the Factory and it turns out that they’ve changed the Rib and will be sending me the correct new versions of the ribs (EL-RIB-001-C-E-1 & EL-RIB-101-C-E-1), so I’ll have to wait until I get those.

So onto the Vertical Stabilizer – the bottom of the rear spar holds a lot of M4 Rivnuts, so it was time to updrill the holes to the correct size in order to fit the rivnuts.Getting my tools ready to install the rivnuts

Using the step-drill bit I enlarged the holes just a bit smaller than the Rivnuts and then finalized it to the exact size using a hand reamer since you don’t want the hole to be any larger than the not so it gets a tight fit.
Hand reamer marked to the correct size using masking tape Test fitting Rivnuts after reaming them to the correct size

Once I was done enlarging all the holes I took care of deburring the holes and then went to work installing all the rivnuts using the Astro ADN14 Rivnut puller attachment for my drill and adding Loctite 277 (red) Threadlocker for added strength.Before deburring the holes after I enlarged them Tools ready to install the rivnuts Rivnuts installed using my bench vise to hold the bracket in place Done installing all the rivnuts

After all that was done, I put together the spar with the brackets for a quick test fit. While doing so I also found an error in the instructions, which say to rivet the hinges on the bottom with 8 (4 a side) 4mm rivets, but actually, only the center one (where I have black clecos) should be riveted, the outer ones will be bolted to the Fuselage (which is why they have larger holes already and I temporarily used the larger golden clecos to hold it in place), so I sent the Factory a note to correct the instructions.
Vertical Stabilizer Rear spar with brackets clecoed in place

More Elevator priming & assembling center spar structure

Hours: 5
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With the weather warming up, I got to spend some time sitting in a bit of sun with the garage door open and preparing, deburring, cleaning and then priming more parts of the Elevator.

Laying out and preparing Elevator parts Primed Elevator parts

Assembling Elevator center spar

The first thing I put together was the Center Spar itself, which I had primed already together with the counterweight the other day. Setting everything up was pretty straight forward as usual and while I was working on it I had a visit from another builder of the EAA chapter I’m part of who actually happens to live very close by and is building an RV. And then another friend was visiting and I happened to have some rivets ready to be riveted, so I continue my new tradition to have guests pull a rivet on the plane and sign it.

Elevator Center Spar Elevator Center Spar riveted

Assembling the center structure to the spar

After the priming from yesterday had some time to dry and set, I went to work to put together the center rib assembly with the center spar. There are a lot of pieces that slot together in there, so it took some time to figure out what slots into which piece. for the center channel to go on:
Center Channel in place

Unfortunately I encountered a problem with the alignment of the holes on the center Rib, both left and right, with the plate as seen below:
Rib holes misaligned with the center plate Closeup of the misalignment of the elevator rib

In trying to figure out which piece is wrong, I started putting together more of the structure temporarily with clecos and the strange thing is that the other holes on the ribs are aligned fine (the black clecos below), so then I thought that it must be the top center plate.

More of the Elevator center structure in place

But then I took off the center plate to check its alignment with the outer skin and there the holes of the top center plate align correctly with the holes on the skin. So this in turn then lead me back to determining that the top (and bottom) holes on the Rib 1 must be the culprit.

It is very strange since the misalignment is pretty severe. It definitely doesn’t look like this could just be resolved by up-drilling the holes, so I sent a note to the factory to ask how to proceed. My guess is going to be that I need new center ribs.

 

Rudder Anti-collision light wiring

Hours: 2
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Now that the Rudder is almost complete, I needed to make the wiring for the Anti-collision light permanent. The existing wire of the Aveo Posistrobe Minimax I’m using has 4 wires (ground, power, strobe, sync), so I needed to splice those onto the wire so I could run it through the structure.

Since this is a permanent connection, I’m using Heat Shrink Solder Sleeves, which have solder in the center and when you heat it up, the solder melts and the sleeve shrinks down to create a good seal.

After that was done, I added some expandable braided Sleeving over the wire for extra protection.
Expandable Braided Sleeving for the wire

I up sized the hole for the wire to pass through the fiberglass tip using my step drill bits and then ran the wires through the structure and out the front hole, which I also had to drill up as per the instructions. After some more research, I replaced the rubber grommets with snap bushings. They last longer and for the front hole in particular, they hold on better since they snap in place.
Finalized hole size for the wiring to pass through the fiberglass tip Snap bushing for the wire to come out of instead of using rubber grommets

Here’s the light mounted and completed wiring done.Light mounted and wiring finished

Now the last thing to do is close up the top. Inspired by a discussion from a while ago on the Sling Builders group, I was contemplating the idea of making the fiberglass tip removable using nut plates and screws, but I think I’ll end up just riveting it closed.

 

Finishing the Rudder skin & mounting the light

Hours: 4.5
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I spent some time over the past week figuring out Electrical wiring and Antennas, talking with Adam from Midwest Panel Builders who I am working with for my panel and wiring.

Aside from that I was working on finishing the Rudder and preparing for the next parts. Jean is sending me replacements for the dented ribs of the Vertical Stabilizer, so I can put that together next and the Navigation Antenna will arrive this week as well to get that going. I will be using the Rami AV-525 VOR/LOC/GS Antenna.

Riveting the skin went all pretty smoothly. I had to take off the front top skin one last time as I had a bit of overspray on the outside from priming. A little bit of scrubbing using MEK and it was all clean.

Mounting the light to the fiberglass tip

After I finished the skin, I worked on mounting the support plate I made earlier for the anti collision light on top of the fiberglass tip.
To pull the rivnuts I’m using the Astro Pneumatic ADN14 tool and Loctite 277 Threadlocker. It just mounts to the front of my drill and then you just need to hold the shell and the drill pulls in the rivnut.

After all that was done, I temporarily mounted the light onto the Rudder and ran the wire through the structure. Then I brought over my DC Power Supply unit and made it shine brightly.

Testing the light in place using my bench power supply

Rudder Tip fitting & riveting the skin

Hours: 2.5
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After having primed the inner surface of the Rudder skin the other day, I had all the pieces together to start working on finishing the rudder.

I attached the skin onto the structure and clecoed it into place.Rudder skin clecoed in place

Fitting the fiberglass tip

Once that was done, I went to work to fit the fiberglass tip onto the skin. I had to trim a little bit away from the bottom of the fiberglass. I made a first rough measurement, trimmed it away using my Dremel and then tried to fit it in.
First trim mark on the fiberglass tip

After aligning it all, I did a second small pass to trim a tiny bit more, placed it into the skin again and then it looked all good.
Tip fit in place and held in place using some clamps

Since the instructions are very explicit to make sure that the alignment of the rudder is perfect, I checked the alignment from all sides and it all looked good.
Rudder checked for alignment using laser level Rear of the rudder checked for alignment using laser level

After all that looked good and triple and quadrupple checking that the fiberglass tip sat flush in the skin I made marks for match drilling the holes and then went to work and carefully drilled the holes into the fiberglass.
First few holed drilled into the fiberglass tip Finished drilling all the holes in the fiberglass tip

Countersinking the front of the fiberglass tip

Once that was done, it was time to countersink the holes in the front. The instructions contradict themselves – only the first 7 holes get countersunk rivets, which mathematically adds up properly to the 32 rivets (2 x 7 on the top and 2 x 9 on the bottom = 32). So after counting all the holes and re-checking the instructions and doing basic math, I decided to only countersink the first 7 holes. I sent an email to the factory yesterday and they confirmed that I was right and they’ll fix the instructions in the next iteration.
Instruction error about countersinking

Before I went to work with the countersinking, I calibrated the micro stop countersinking tool using a scap piece of Aluminum to ensure the depth was set correctly and made sure that I had the correct 120 degree pilot cutter in the tool (I made a whole post about why using the 120 degree pilot was important here).
Calibrating the Microstop Countersinking tool Making a test countersink on a scrap piece of metal

After all that was ready, I went to work, mounted the fiberglass tip gently in my bench vise and started drilling the countersink holes.
First countersunk hole drilled Checking depth using a countersunk rivetAll the countersunk holes drilled in the fiberglass tip

All the countersunk holes came out well and everything sits flush now.
Flush fit of the fiberglass tip in the Rudder

Riveting the skin

So after all that I went to work and started riveting some of the skin.Time to rivet the Rudder skin The close quarter wedge came in handy for riveting in this tight spaceRiveted part of the Rudder skin

Vertical Stabilizer Priming

Hours: 2
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In order to finish up the Rudder, I still had to prime the inner mating surfaces of the skin, so in order to get ahead I decided to also prepare the parts for the Vertical Stabilizer and prime those as well.

After removing all the protective plastic from the parts and inspecting them, I unfortunately found that there was some dents in Rib 1, 2 and 3, so I requested replacements from the factory since those are structural parts that shouldn’t be compromised.

I still went ahead and cleaned and degreased all the other parts. Luckily it’s getting a bit warmer, so I could leave the garage door open and do the cleaning outside, to make less of a mess in the garage.

Vertical Stabilizer parts laid out to inspect Cleaning Station with Simple Green cleanerParts cleaned and ready to be primed

Once I was done cleaning all the parts with Simple Green, degreasing them with MEK and rubbing them down with red scotch brite, I set up my small paint booth and primed everything.

Paint booth ready to prime Done priming the parts of the Vertical Stabilizer

Rudder skin fitting & Anti-Collision light mount

Hours: 3
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Over the past few days I spent some time organizing the next few parts of the Empennage such as organizing the Vertical Stabilizer parts and what I needed to finish for the Rudder.

Fitting the Anti-collision light

I got the Aveo Posistrobe MiniMax anti-collision light to mount onto the rudder tip and started working on fitting it on.
Aligning the strobe light seal to find out where the holes should go Marking center linePilot holes drilled Double checking the holes aligned properly and then enlarging the hole for the wires to pass through
Light temporarily on top and shining bright like a diamond.
Quick test with light on

Mounting plate

The first iteration of the Empennage assembly instructions called out for a mounting plate to go inside the fiberglass tip to add structural reinforcement for the rivnuts, but the latest version of the instructions is missing it, so I sent a question to the factory why.

In the meantime, since I assume that it’s still a good idea since both the Sling 4 instructions as well as the first version of the instruction call for it, I decided to fabricate my own.

I started tracing out the rough dimensions of the area and then measured it down to how it would fit. Then I made a first version out of cardboard to see if the dimensions I estimated would work.
Rough outside dimensions of the strobe light traced Test fit of cardboard cutout

Looked good, so then I copied my cutout onto the sheet metal and went to work cutting it out. I used a OLFA Scoring knive to score the cut, based on a tip from HomebuiltHELP. Since my metal was pretty thick I only scored it with that and then used metal snips to cut it, but for thinner metal you can actually make the whole cut using the scoring knive to make great straight cuts.Transferred cutout onto aluminum sheet Metal piece cut and ready to drill the holes

After that, I deburred all the edges and the holes and then checked the final fit in the rudder tip.Plate fits great in the tip Clecoed in place

Fitting the skin

I also test fitted the skin onto the rudder and checked how the tip will fit in. The skin came on fairly easily, but I will have to trim a little bit of the fiberglass tip so it will fit in.
Skin fitted and fiberglass tip put in place Need to trim off a bit of the rear of the fiberglass tip

I still had to prime the inside of the skin, so now that I know it all fits together fine, I will rivet the skin on and then work on the final trimming for the rudder tip so it fits in and then I will need to match drill the holes into the fiberglass tip and countersink the front holes.

Finished riveting the Horizontal Stabilizer skin

Hours: 4.5
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The pop dimpling tool that I ordered a few days ago arrived on Friday, so I spent some time trying it out to make sure it worked properly so I could finish adding the missing dimple to the skin and finish closing up the Horizontal Stabilizer.

After a bunch of research on them, I actually ordered 2 different tools, one is made by Aircraft Tool Supply and creates a 100 degree dimple, and the other one promises to create a 120 degree dimple, I’m not sure who exactly actually makes it, but it’s sold via Wicks Aircraft tools. The 120 degree tool from Wicks is DT-17014 and it’s supposed to screw into a G28 hand riveter.
120 Degree Pop dimple tool
Unfortunately the Hand Riveter I own seems to have smaller threads than the G28 hand riveter, so I decided to try it on my Milwaukee rivet gun which had the correct thread size. As I found out when I pulled with it, that ended up with too much force, so the head of the stem (which is a finishing nail) that is supposed to hold the back of the dimple in place actually deformed and got pulled into the top and got stuck.

So after that happened, I had to cut off the nail, but I couldn’t pull it out of the tool, so I got out my Dremel and cut off the top part of the bit where the deformed head got stuck in.
Nail stuck in the tool
This way I could try to use the tool like the ATS pop dimple tool (5102D-1/8) works, which just sits on top of the rivet puller.
ATS tool on the left and the other one on the right (after I cut off the top):
100 degree Dimple tools from ATS on the left and 120 degree tool on the right (after I cut off the thread head)

So now after that modification to the tool, I tried both by holding my test piece onto the existing dimples of the Horizontal Stabilizer and determined (as expected), that the 120 degree dimple has the better fit, so I used that one to make the dimple to the skin. It came out well and the countersunk rivet sits flush like the other dimples. So for one or two dimples, this works out nice and easy and I didn’t have to go and get a dimpling press.

Pop dimple tool using the hand riveter Dimple using the pop rivet tool came out well and the countersunk rivet sits nice and flush like the others

Riveting the skin

Once all that was said and done, I got to work and riveted the complete bottom of the left side skin. Then turned it around, removed all the Clecos from the top side one last time so I could apply the Sealant to the support plate like I did on the other side. And then I finished up riveting the top side.

Timelapse Video of Finishing the Horizontal Stablizer

And lastly as promised, here’s the timelapse video of the whole endeavor of the Horizontal Stablizer.

Riveting the Horizontal Stabilizer skin – part 2

Hours: 1
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Today I spent another hour on riveting the Horizontal Stabilizer to finish closing up the right side.

The top has a support plate as seen below to add some reinforcement to the skin. To prevent the large metal surfaces from rubbing, the instructions call for sealant to be added between the plate and the skin before closing it up. Luckily Matthew had already clarified with TAF what the right sealant to use is, GE5050 Metal Silicone, so I had it ready for a while.

Before closing up the skin, I needed to apply some sealant on this stabilizer plate Metal sealantSealant applied to the stabilizer plate

Once that was done, I closed it up one last time, ensuring a proper fit and the finished the riveting work.

Ready to start riveting Halfway done riveting the right side of the Horizontal Stabilizer Finished riveting the right side of the Horizontal Stabilizer

So now I’m done with the complete skin on the right side and just need to do the same thing on the left side, but I need to add one more dimple on that side that was missed, so I’m waiting for a dimpling tool to finish that, which should hopefully come in the new few days.

Riveting the Horizontal Stabilizer skin

Hours: 3
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The journey of the Horizontal Stabilizer continues with match up-drilling all the dimpled holes to fit the countersunk rivets. So basically this, multiplied by 200:

After I was done, I took off the skin one last time to clean out all the debris from the drilling and check and fix any burrs. After that it was time to put it back together again and do one last check for alignments before riveting using my self leveling laser level.Cleaning out the debris from reaming out all the holes  Alignment checked using my laser level

And then at last, time to start the riveting. I managed to finish the bottom of the right side, so 3 more sides to go next time.

One small problem I encountered while doing the riveting was, that because I was riveting straight down, it happened twice that some of the mandrels of the 3.2 mm rivets got stuck in the rivet gun, so I had to take it apart and push/pull out the mandrels.

Mandrels stuck in the rivet gun