Tag Archives: fabricating

Installing the Pitot Tube

Hours: 8

After a couple of weeks of taking some time off active building while life happens and figuring out and planning out some things, I’m back to actively riveting on the airplane.

Time to finish the Pitot Tube after having cut the inspection panel hole and running the wiring a few months ago and lots of learnings about new tools, from the wiring, to flaring the tubes and connecting AN fittings.

I’m using the Garmin GAP 26 heated & regulated Pitot Tube (GAP 26-20). This version automatically controls whether the Pitot Tube needs to be heated using a regulator controller that is mounted next to the Pitot Tube and will only apply heat if needed based on outside temperatures.
This basically will allow me to always turn on the Pitot Tube in my panel as part of my standard operating procedures and the regulator will control whether it actually needs to be heated to prevent icing.

The installation instructions for this can be found in the Garmin G3X installation Manual.

After studying the installation manual to make sure I install it correctly, I measured the tube and had to figure out how far I have to cut it in order to fit.

Fitting the Pitot Tube

The Pitot and Angle of Attack (AOA) mast are over 12 inches out of the box, and that won’t fit. I made an initial guess and cut a bit shorter, but I was still too long so I made a series of shortenings and test attaching the fittings until I had it dialed in.

First test fit shows that the masts are too long and need to be cut further.

In the end, I had the masts cut down to right around 8 1/2 inches. The Garmin manual says to keep a minimum of 8 inches between the probe and transition to non-metalic tubing, so I had a little bit of margin.

Time for flaring the tubes. The AN fittings use a 37 degree flare, so I got a Rigid 377 flaring tool and a metal tubing cutter to cut the tube. Before doing this on the real Pitot Tube, I made some test flares on a spare tube I bought from Aircraft Spruce.

Make sure you put the AN fittings onto the tube before you do the flaring (I may or may not have forgotten it the first time and cut and redo the flare once).
Make sure you put the AN fittings onto the tube before you do the flaring (I may or may not have forgotten it the first time and cut and redo the flare once).

After I had that dialed in, I did another test fit to get the length correct, accounting for the bend towards the tube and then mounted the fittings.

Mounting the fittings to the tube.

Final fit and connecting to the nylon tubes inside the wing after having cut the nylon tubes.

Final fit and connecting to the nylon tubes inside the wing.

Installing the regulator and wiring

With the Pitot Tube itself installed, time to finish the regulator and wiring that controls the heating of the Pitot Tube.

As I explained previously, I plan to mount the regulator unit onto the inspection panel plate, so I did some measuring and orienting to make sure the twist action of the round plate wouldn’t interfere with the wires coming out of the regulator.

Here is the final orientation that I figured out would work best (the screw will mount to the bottom, so the wires will come out the top):

Here is the final orientation that I figured out would work best (the screw will mount to the bottom, so the wires will come out the top).

I contemplated between screwing or riveting it on, but I figured that it’s unlikely that it will need to be changed out frequently, so I riveted it onto the plate.

Completed inspection panel plate with the Garmin Regulator mounted.

The last part was to create a connection from the regulator to wires I ran through the wings. I used some weatherpack connectors for this, which create a waterproof connection and a solid crimp, similar to the Delphi GT 150 that Midwest Panel uses to connect the wiring harness.

Crimped wires to connect to the regulator (blue connects to the panel to communicate with the G3X to see whether Pitot heat is active)

Final completed connection between the regular, the Pitot Tube and the wires running to the center.

Final completed connection between the regular, the Pitot Tube and the wires running to the center.

Installing the plate to the wing

The last and final part of the installation was to mount the inspection panel plate onto the wing. I did this last to prevent scraping up my arm while I had to do all the mounting inside the wing, since the backing plate that holds the plate in place has a series of pokey corners that love to eat airplane builder blood.

First I lined up the plate with the wing and then did the match drilling of the holes:

First I lined up the plate with the wing and then did the match drilling of the holes.

The I dimpled the plate and the matching holes on the wing and riveted it in place.

The I dimpled the plate and the matching holes on the wing and riveted it in place.

And here is the completed and closed up Pitot Tube and Inspection Plate that holds the regulator:

And here is the completed and closed up Pitot Tube and Inspection Plate that holds the regulator.

Timelapse of the entire installation

Pitot Electrical Wiring

Hours: 5

After cutting the hole for the inspection panel a few days ago, I continued and ran the wires for the heating.

I figured out where I want to run the wires a while back after some tinkering and I am using one of the strut channels for the length of the wing, except the very end at the wing-walk where I had to make one curve down the bottom.

After some trial and error, I found that 3/8 in size wire loom tubing fits perfectly in the channel and with the help of my Wireless Endoscope connected to my phone I was able to finagle it through the wing with some mild scrapes on my arms.

Starting to run the wire loom  Wire loom at the new Pitot Inspection hole Fishing for the loom (very bottom with the pliers)

The hardest part was figuring out a good way to come out the bottom where the wing-walk is, since the strut channel doesn’t go through there. On the last picture above, you can see when I finally managed to grip on to where I want the loom to come out of with the help of some duckbill pliers, which were a suggestion from my EAA chapters Technical Counsellor when he visited a few months ago.
Duckbill pliers to the rescue

Running the wire

With the question of where to run the wire solved, onto actually running the wires.

I am installing the Garmin GAP 26 Heated/Regulated Pitot Tube, which comes with a Regulator that needs to be installed next to the Pitot tube and controls whether the Pitot tube actually needs to be heated.

For this, there are three wires to run – two for the power and one for the discreet output, which integrated into the Garmin G3X Panel to show when the Pitot Tube is actually heated.

I ran the three wires through some braided sleeving to give them some extra protection and make running them through the wire channel easier in one go.Feeding the 3 wires into the braided sleeve

With that out of the way it “just” took a lot of back and forth, more use of the Endoscope and the thin arms of Juliana and repeated shouts of “push, push” and together we managed to run the wire all the way. She cheerfully pronounces “Congratulations, it’s a wire” as it came out the other end.
My friendly helper to run the Pitot wiring Congratulations, it's a wire

Cutting Pitot inspection panel hole

Hours: 1.5

I was planning to finish to Ailerons, but unfortunately in my final prep, I realized that I received two right side balance tubes instead of a left and a right one. The missing tube should be here sometime next week, so until then, the Ailerons are on pause.

This gave me some time to finally make the big step of cutting out the hole in the Wing for the Pitot inspection panel. I received the heated & regulated Garmin Pitot tube from the Factory and verified that it will fit nicely on the back of the round inspection cover, so I will mount that and I can keep my square inspection panel I designed for some other time.

First I did a lot of measuring and marking based on the plans. Since this is truly a moment of measure-twice, cut-once I measured and re-measured a few times.
Marking the center and hole to cut out Hole marked and alignments checked Time to prepare the cutter Marking the pilot hole for the cutter

With all the marks in place, I started with cutting the pilot holes for the center mark and the cutting head.
Using the center punch to mark the pilot holes Using the step drill to upsize the cutter pilot hole Pilot holes drilled

The final moment of truth – Time to cut the hole for the inspection panel using my nibbler cutting tool.
Time to cut a hole in the wing

I cut the first half of the circle and then reversed the tool since the Pitot tube mast was in the way of completing the cut in one direction.
First half of the circle cut - I had to reverse the tool at this point since the pitot tube mast blocked finishing the circle from this direction

The cut came out pretty well and I just had to do a little bit of sanding to smooth the edges.
Inspection hole cut Temporary placing of the backing plate Inspection Cover fits perfectly

 Timelapse video of cutting the hole

Finishing the Elevator

Hours: 2.5

With most of the preparations out of the way and half of the skins riveted, I took one more session to finishing the Elevator.

There was only one extra part I had to do for 3 of the rivets that were on the bottom edge. In order for them to fit correctly, I had to shorten the rivets so they wouldn’t protrude out.
Rivet too long to fit Fitting rivet after I shortened it I mounted the rivet in my bench vise and filed it down to size Shortened Rivets on the right and one with normal length on the left

Aside from that, I just went to town and pulled the rest of the few hundred rivets.
Time to pull some rivets Halfway done riveting the skins Final set of rivets ready to be riveted Riveting the Trim Tab

The last part on the riveting side was the front lip.
Clecoing the front lip Riveting the front lip

One of the holes on the lip has to be enlarged to fit a grommet for the wiring for the Elevator Trim Tab. I enlarged the hole using my step drill bit and then installed a snap bushing.
Marked out the hole that needs to be enlarged for the wiring Marked out the size on the step drill bit Hole enlarged and Snap Bushing installed

The last part was to install the center balance counterweight. I did some test fitting with this, but the AN3-13A bolts that one of the versions of the manual that I have mentioned are too short, so I’ll check with the factory on the proper length.
Test fitting the Balance Counterweight - the bolts are too short

With that being said, the general assembly of the Elevator is completed:

Timelapse of the complete construction of the Elevator

With the Elevator construction completed, I’ve also finished my video timelapse of the process:

Cutting a round inspection access panel hole

Hours: 2

One of the things that the factory forgot as part of the change from the Sling 4 to the Sling TSi was the required access to the internals of the wing next to the Pitot tube.

In the Sling TSi design, some inspection panels were removed including the one next to the Pitot tube. By itself, if someone was building the wings from scratch, that might be fine as long as the builder installs the Pitot tube beforehand and doesn’t anticipate to ever need to access it, such as if using an unheated Pitot tube.

However, I am going to use the Garmin heated & regulated Pitot tube, which not only requires wires to be run to the Pitot tube, but also that I need to mount the regulator unit next to it.

Since I ordered the quickbuild, I ordered it with this specification, but unfortunately the factory didn’t receive the Pitot tube from their supplier in time and shipped my kit without installing it.

So after I received my shipment and inspected everything, I realized that installing this after the fact wasn’t going to be easy, particularly with the lack of a hole in the wing. Unfortunately the factory also forgot to run the wiring to the pitot tube, which creates a whole second issue, for which I’ve been working on a solution.

I informed the factory a while ago and also gave Matthew, one of the other TSi builders a heads-up since he hadn’t started on the wings yet. The factory realized their mistake in the plans and promised to come up with a solution and send me instructions and a plan.

Drafting a plan

While I was waiting for the factory to come up with a plan, I actually started drawing up my own plans to fabricate the entire inspection panel myself and used it as an opportunity to learn and use Solidworks, which I can use for free as part of being an EAA member.
Initial draft of the panel on paper My panel design in Solidworks

Since I had the chance to chat with Mike Blyth at Oshkosh for a while and we chatted about my build, I mentioned that I was still waiting for the factory to come up with a plan for the inspection cover and he promised that he’d check on the progress when he got back to South Africa and indeed, two weeks later, I got an email with the plans.

The factory plans, in keeping with the other inspection access panels, uses the same flush round inspection cover that is used to access the Flaps and Aileron connecting rods.

Factory plans for the new inspection access panel

Since I am still busy with other things in the build and haven’t actually made my own panel yet, I am going to go with the factory plans that they have drawn up for me.

Cutting a round inspection access panel hole

There is just one difficulty to overcome – the access panel is round and large and I don’t think there are 143.4 mm drill bits I can buy in Home depot.

After a bit of research, I found a solution in using a drill attachment sheet metal nibbler that can cut around a center pivot and can attach to my Milwaukee hand drill.

Since this is quite an operation, I decided to get some practice with the tool on a piece of spare aluminum and also made a video of it, since I figured that it might be helpful for other builders in the future.

I started by marking out the circle using a drafting compass. It’s been quite a few years, but luckily I still remembered how to use it and how to find the center of the circle again by making two marks. Proof that you may indeed use what you’ve learned in geometry class sometime in life, even if it’s 15 years later. After that I clamped the piece of metal on the edge of the table.

I drilled the center pivot hole to 1/8th of an inch, which makes the pivot sit in the hole and then measured out the starting hole for the drill, make a starter hole and then used a step drill bit to upsize the hole until it aligned with my marked circle.

After that, I set up the drilling tool with the pivot and made sure that the outside of the cutting bit aligns with my circle and then attached the drill and went to work.

Here are a couple of pictures of the first circle I cut – note that briefly I had the pivot point jump out of the hole, which caused me to waver a bit which you can see towards the bottom where it’s not perfectly round, so make sure the pivot continues to stay in the hole.

Marking out the circle using a compass Clamping down the metal on the table Cut hole and the inside disk - I did waver a little bit on the bottom as I didn't hold the pivot in place perfectly for a moment. So practicing this will pay off to not repeat the mistake. Inspection cover "test fit" Tools used to cut the access panel

Annotated video of the process of cutting the hole

 

Technical Counselor visit & Vertical Stabilizer Antenna wiring

Hours: 5

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.

Rudder skin fitting & Anti-Collision light mount

Hours: 3

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.