Tag Archives: dimpling

Final Elevator fitting

Hours: 2.5
Leave a reply

After reinforcing parts of the fiberglass tips for the Elevator for the front section that is countersunk to support the flush rivets, I finished fitting of the right side of the Elevator.

When I finished the alignment of the left side of the Elevator, I ran out of clecos, so I bought a couple more when I was at Oshkosh so I could properly put the Elevator together and get everything to align correctly.

So the first order of business was to finish clecoing everything including the (correct) control tabs for the Trim Tab.
Time to cleco the right side of the Elevator Everything clecoed together including the Trim Tab

With that out of the way, I moved on to do the fitting for the right side fiberglass piece. It took a little bit of aligning and filing away a tiny bit from the back so that the fiberglass piece can slot into the metal.

Once that looked all good, I started to do the match drilling of the holed into the fiberglass.

Time to drill some holes into the fiberglass tip First hole drilled and clecoed Continuing the match drilling All holes drilled

Now the only last part to do was to countersink the front parts of the fiberglass tips in order to allow the flush rivets to sit in there. It took a bit of back and forth to calibrate my microstop countersink attachments to ensure I had a good flush fitting.

Marked out for the holes that need to be countersunk Finished countersinking the holes Flush fit of the left side Alignment checks on the right side

Elevator Fiberglass tip countersink reinforcement

Hours: 1
1 Reply

The leading edges of the Elevator Fiberglass tips have flush rivets and so they need to be countersunk. The parts that need to be countersunk are reinforced to add thickness, but the reinforcements on my fiberglass tips wasn’t long enough, so I had to add some more so I can finish them.

As you can see in the picture below, the black reinforcement doesn’t go far enough for the last two rivets on the left that are also dimpled flush.
Reinforcement not long enough for the countersinking Marked out how far I need to extend the reinforcement

I got some one inch wide fiberglass cloth tape and mixed some epoxy to extend the area that needs reinforcement. I marked out how far I needed to extend and cut strips of the fiberglass cloth to size to apply.
Epoxy mixed and ready First layer applied

A few layers applied and set out to dry for a few hours and then I can countersink the holes.Finished with the reinforcements

Vertical Stabilizer skin riveting

Hours: 3.5
Leave a reply

With the wiring finished and the Antenna fitting done, I am now finally able to close up the Vertical Stabilizer and rivet the skin.

To begin, I closed up the left side of the skin and held it in place with clecos, since this is the side where the Antenna slides through the enlarged rivet hole, while on the right side I had to create the custom notch so that I can pull the skin around the Antenna.
Left side of the Vertical Stabilizer closed up with clecos

Once that was done, I riveted on the support plate for the Antenna onto the top rib of the Vertical Stabilizer.
Riveting the Antenna support plate in place Antenna support plate riveted in place 

Now that the structure is complete, time to mount the Antenna permanently in place. Using two 20mm long M4 screws, washers and Nyloc nuts and some medium strength threadlocker I mounted the Antenna in place. Here’s the Antenna mounted in place and the wire connected to the Antenna using the BNC connector I crimped onto the wire. Antenna ready to be mounted Antenna mounted and wire connected

Riveting the skin

With all the prep work finished, I closed up the right side of the skin, made sure everything fits correctly and clecoed it in place. There are two holes on the bottom on each side that are not riveted, but instead I have to install Rivnuts in them, so I marked out those holes, so I don’t accidentally rivet them.
Vertical Stabilizer skin closed up and ready for riveting Holes where I have to install Rivnuts marked

There were two rivets that I had to shorten in order for them to fit flush near the Antenna. So I made a small template for the dept through a piece of wood and then shortened them accordingly.
Wood piece to hold the rivet in place to shorten Rivets shortened (and normal length on the left for reference)

After that, it was just a matter of pulling the many rivets on both sides of the skin to close the Vertical Stabilizer up for good.
Riveting the right side in progress Riveting the left side in progress Riveting the left side in progress Done riveting the skins of the Vertical Stabilizer

The last part was to install the two rivnuts on the bottom on each side, so after enlarging the holes using my step drill and reaming them out using my hand reamer, I got out my rivnut puller and high strength loctite and put those in place.
Holes enlarged for the rivnuts Rivnuts installed

With the Vertical Stabilizer completed, I then did a quick test fit and mounted it on top of the Fuselage and also attached the Rudder for a moment – almost looks like an airplane.Completed Vertical Stabilizer  Quick test fit of the Vertical Stabilizer and Rudder

Timelapse of building the Vertical Stabilizer

Technical Counselor visit & Vertical Stabilizer Antenna wiring

Hours: 5
1 Reply

This morning I had my first visit from my local EAA Chapter 84’s Technical Counselor to look over my build and give me some advice as part of EAA’s Technical Counselor program.

This was the first Sling kit for him and he was impressed by the quality of the kit, its completeness and the instruction plans. We looked over my completed parts of the Empennage and talked about wiring, avionics and things to look out for. He also gave me some good general advice and stressed the point of documenting, particularly around wiring, since many years down the line there’s nothing worse than finding a wire and not knowing what it is for exactly, so he was happy to see my label maker and my active use of it.

We filled out the visit report and agreed to meet again after I’m further into the build and working on the interior of the Fuselage.

Vertical Stabilizer wiring

Now, back to building. As I finished the match drilling of the dimpled holes the other day, I had to dimple the hole that was missing a dimple, so I got out my modified hand dimpling tool and quickly did that dimple.

After that I worked on finishing the wiring the run through the Vertical Stabilizer for both the Anti-collision light on the Rudder, as well as the NAV Antenna.

First I had to make another hole to run the Antenna wire through the top rib since the factory plans assume that you either install the light or the Antenna, but not both. I marked the hole location using the center punch, then drilled a pilot hole and then used my step-drill bit to up-drill the hole to the right location for the snap bushing to go in.Center punch to mark the hole location Pilot hole drilled and ready to be drilled up using a step drill bit Finished hole and snap bushing installed

After that was done, I wrapped the wire for the light in some braided sleeving for some extra protection and then ran it through the rear holes. I also installed some flexible edge protection for the hole where the wire will meet the wire from the Rudder.
Wire for the light installed in the Vertical Stabilizer Flexible edge protection

Quick test fit on the Fuselage

I then quickly measured out the length of the Antenna wire to install in the Vertical Stabilizer, cut it to size and ran it through the front holes. After I was done with that, I wanted to do a quick test fit of the Vertical Stabilizer Structure on the Fuselage to see where the holes would pass through.

Quick test fit to see where the wires come out Looks almost like an airplane

Antenna Coax wiring

Once that was figured out, I moved on and did my first crimped coax connection. After a tip I saw on the homebuiltHELP channel, I bought this rotary coax stripper, which strips both the front, as well as the braided shielding in one go.
Rotary coax stripper

Before it was ready to use I had to do some adjustments for the lengths and depths for the cut, so I took it apart, while following the instructions and then moved the blade as needed. I’m using the SteinAir BNC Connectors, so I had to move the blade that exposes the outer shielding back by one position to the point marked E and the inner blade on mark B.
Blades set on mark E & B for the SteinAir BNC Connectors Correct location for RG400 stripping
Then I adjusted the blade depth using the screws on the bottom and did a few test cuts to make sure the results are repeatable. I then put some light strength thread locker on the screws so they stay in position so I can now just use it without any further adjustments needed.

After that I did a quick test crimp of a connector to the small piece of wiring I used to calibrate the wire stripper, following the instructions from SteinAir.
Test crimp successful

Looked all good, so I repeated everything on the actual wire for the Vertical Stabilizer.Wire stripped and ready to install the center tip Connector attached and ready for the back shielding to be crimped Completed crimp of the connector Test fit of the connector on the Antenna

With all that done, I installed the wire in the Vertical Stabilizer and now I’m ready to install the Antenna and close up the skin.

Interesting side note on coax wiring and the use of a balun

One other interesting thing I learned while doing this – I tested the wire I crimped for continuity to make sure there are no problems with the wire itself by checking (lack of) continuity between the shielding and the center core. This was all good, so my crimp is good.
After attaching the wire to the Antenna however, I figured I’d also check it with the wire attached to the Antenna and had a brief moment of confusion when I did get a positive continuity readying between the core and the outside. So I did some digging and found out that the use of a balun (in my case with the Rami AV-525, it is an internal balun) can create a DC short and thus will produce a continuous reading using a Voltmeter.

Vertical Stabilizer Navigation Antenna & skin fitting

Hours: 2.5
2 Replies

Before I can close up the Vertical Stabilizer skin, I need to fit the Navigation Antenna, run the wires for the Antenna and the rudder light and fit the skin including up-drilling the countersunk holes in the skin with the rib structure.

So one thing after another, first I gave a quick test fit for the skin and then drilled up all the countersunk holes.
Test fitting the skin and aligning everything to match up-drill the countersunk holes And found one hole that should be dimpled as well

After that was done, I went to work to fit the Rami AV-525 Navigation Antenna I’m going to use. I already fit the Antenna onto the inner rib a while ago before I built the rest of the structure, so now it was a matter of fitting it all with the skin to be able to close the skin around the Antenna.

On the left side, the Antenna comes out one of the pre-drilled rivet holes, so I just had to up-drill that to the correct size.
Enlarged hole for the Antenna on the left side

For the right size, the Antenna comes out offset a bit further behind, so I marked out where I needed to make the hole in the skin, then used a center punch to get a good center to drill the hole:
Marking where the notch for the Antenna has to go Centerpunched the spot for the hole to goHole drilled on the right side for the Antenna

With the hole in place, I cut back a small notch, so that the skin can slot around the Antenna since the arms of the Antenna are fixed to the internal balun.Notch to slot the skin around the Antenna

After all that was done, I put it all together for a final test fit:Left side view of the Antenna in place on the Vertical Stabilizer Right side view of the Antenna in place on the Vertical Stabilizer

Looks all good, so now I need to finish running the wires on the inside and then I can rivet the skin closed.

 

Finished riveting the Horizontal Stabilizer skin

Hours: 4.5
1 Reply

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
3 Replies

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
Leave a reply

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

Horizontal Stabilizer skin fitting

Hours: 1.5
1 Reply

Today I was working on fitting the skin onto the Horizontal Stabilizer. It took a lot of clecos to align everything, but eventually it all came together well on both sides. The next step will be to match-drill up the dimpled holes as per the instructions.

The design for the dimples is such that the holes are drilled slightly smaller than the final size. Then they get dimpled and then you assemble everything to fit it together and finally match-drill up the dimpled holes to the final size.

Clecoing the left side of the Horizontal Stabilizer Finished clecoing the left side of the Horizontal Stabilizer Finished clecoing both sides of the Horizontal Stabilizer

I will post another timelapse video of the whole process once I’m done with the drilling and riveting.

Countersinking experiment

Why it’s important to use a 120 degree countersink pilot for pull rivets

Another thing I recently did was do a small experiment to showcase the reason to use the correct 120 degree countersinking pilot for the countersinking holes that are not dimpled due to the thickness or type of the part (such as the fiberglass tips), after we had a thread about dimpling and countersinking it on the Sling Builders discussion group.
Normal AN style solid aviation rivets are 100 degrees, so most countersinking tools sold by aviation tool supplies by default come with 100 degree countersinking pilots, but blind pull rivets like those used in the Sling are 120 degree, so hence the need to use a 120 degree pilot to get the best fit.

To showcase the why that is so important, I drilled some holes in a 0.04 inch piece of metal (which is the thickness where you start to countersink instead of dimple) and used the 100 degree pilot on one hole and the 120 degree pilot on another. The goal was to insert the same countersunk rivet (which has a 120 degree slant) used for the Sling in both and have it sit flush.
In order to get a flush fit with the metal using the rivet, the 100 degree countersunk had the be deeper. This in turn results in a larger hole and thus wouldn’t have as much material to grip onto. As can be seen below, the 120 degree countersink resulted in about 3.3 mm hole, while the 100 degree resulted in a much larger 3.65 mm hole.

Difference in hole size using 100 and 120 degree countersink Flush fit of countersunk rivet

So the moral of the story, make sure you use the correct countersinking pilot when working with pull rivets. I’ve created a separate page on drilling, rivet sizing and countersinking as a quick reference for myself and figured it might be useful for others.