There are several projects that may be easier to complete before the bottom wing skins are installed. The idea is to complete all of the wing internal systems like pitot plumbing, wiring, and subsystem brackets/mounts while access to the inside of the wing is wide-open; and avoid doing a lot of work through the small wing access panels later. The projects include: - Garmin GAP 26 Pitot/AoA Probe Installation - Construct the ADAHRS/Magnetometer bracket (Section 62) - Assemble, temporarily Install, and adjust the aileron control system (Section 23) - Assemble, temporarily Install, and adjust the aileron trim system (Section OP-38) - Assemble and install the autopilot roll servo bracket and wiring (Section 56) - Assemble and temporarily Install landing and taxi lights and wiring (Section OP-52A) NOTE: I highly recommend building the ADAHRS/Magnetometer bracket before installing the lower wing skins. It is much easier to test fit and adjust the bracket and mount when it is completely accessible. The fit on my bracket was incredibly tight, and required several adjustments to both the bracket and mount. GAP-26 Pitot/AoA Probe Installation – Completed 10/20/2023 I decided to install a Garmin GAP 26 heated (unregulated) pitot/AoA probe instead of the plans pitot tube. The probe is installed with a mast, which requires modifications to the bottom wing skin as described previously in 20-03. The three tasks remaining for the pitot/AoA probe installation are interfacing the probe with the mast, electrical wiring, and pneumatic plumbing in the wing. The Garmin pitot/AoA probe comes with tapped mounting holes, which have to be matched to screw holes in the pitot mast. The trick is to figure out how to very accurately and precisely transfer the location of the mounting screw holes from the pitot/AoA probe to the mast that overlays the pre-drilled holes – essentially blind match-drilling. I believe the installation of the Dynon probe is opposite of the Garmin probe since the holes in the Dynon probe are not pre-drilled, which requires the builder to match drill through the mast into the probe, and then tap the holes in the probe. Both probes have their challenges that the builder has to analyze and work through. The fore and aft edges of each mounting hole was the easiest measurement to find and mark on the pitot mast. I inserted long screws in the probe holes to account for the angle of the holes and how that angle translates to the hole locations on the mast. I marked the fore and aft edges of the holes on the main body of the probe, and then transferred those locations to the mast with the probe inserted in the mast. The top/bottom location of the hole centers was more difficult to figure out. I ultimately required 3 tries to get this measurement right. The first two attempts resulted in misaligned holes, which required me to cut off the end of the mast with the bad holes and try again. That was not a very effective approach, and I had to pay attention to how many times I could trim the mast and still maintain the minimum 4” distance between the probe and wing as specified in the Garmin G3X Touch Installation Manual. Fortunately, my second attempt was really close on at least one hole on each side of the mast, and I could make accurate measurements of those holes before trimming the mast for the final attempt. Eventually, I had good markings for the fore, aft, top, and bottom edges of each hole on the pitot mast. I started each hole in the mast with a very small #53 pilot hole. I used a center punch and drill guide to get the pilot hole as close to the center point as possible along the angle created by the curved mast. I also used the pre-drilled holes in the probe as targets to see what adjustments needed to be made as the mast holes were upsized. I made the targets by covering the pre-drilled probe holes with masking tape, and then tracing the outline of the holes with a pencil. I then inserted the probe into the mast and pushed the drill bit through the pilot hole to see where it broke through the tape below. That gave me an indication of how to adjust the location to drill the next size hole up. As the holes were upsized, the locations became more accurate; and the final holes were right where they needed to be. I completed the pitot mast by countersinking the holes by hand, and priming the drilled and cut areas. [Hole Deburring Tools, Assorted Drill Bits (#53 to #27), Dremel with Metal Cutting Disk, Hack Saw, Files, Hobby Files] The next task was the pneumatic connection to the pitot and AoA nylon tubing that was already routed through the wing ribs. The aluminum pneumatic tubing on the probe is very long, and must be sized to fit inside the wing cavity by trimming the aluminum tubing and/or bending the tubing to fit. I wanted to minimize trimming and bending as much as possible, while making it possible to insert the final result into the pitot mast. The Garmin G3X Installation Panel states, “For heated probe installations where the installer desires to shorten the provided aluminum tubing, a minimum of 8 inches of aluminum tubing should remain between the probe and any transition to non-metallic tubing to protect the non-metallic tubing from excessive heat.” The aluminum tubing for the pitot and AoA lines are just over 13” long. That length is increased with the fittings to transition from the aluminum to nylon tubing, and I trimmed off about 5 1/2” from each tube. I then used a flaring tool to flare the ends for the fittings. The tubes needed to be bent to ease the transition between the nylon tubing and the probe, so I used a 1/4" tube bender to put a 45-degree bend in the aluminum tubes approximately 6 inches from the end. Minimizing the bend, and strategically locating the bend made it possible to insert and remove the completed probe / transition fitting assembly in the pitot mast. [Tubing Cutter, Flaring Tool, Tubing Bender, Deburring Tools] The final task was setting up the wiring for the pitot heat. I ran 14 AWG twisted pair wiring from the wing root to the pitot tube for the pitot heat power and ground, which is connected with the power and ground wires on the probe. The probe has four wires (2 each power and ground), which are connected in parallel to the aircraft wiring for a 14V installation. I watched a couple of SteinAir videos, and decided to try a “window strip” and splice to set up the probe wiring. The window strip essentially creates a gap in the insulation away from the end of the wire, where another wire can be attached. I started by stripping about 3/4" of insulation from the end of one power wire and one ground wire. Next, I moved the stripping tool about 4 inches from the end and stripped about 3/8” at that location. The stripper essentially pushed the insulation toward the end of the wire, and I ended up with a 3/8” gap about 4 inches from the end and another 3/8” stripped section at the end of the wire. I cut the second power and ground wires to the length of the window strip, stripped the ends of those wires, and then made the parallel connection at that point with a solder sleeve covered with a shrink-wrap sleeve for some extra strength and protection. At this point, I essentially had one ground wire and one power wire, which could then be fitted with a connection fitting to match the ground/power wires installed in the wing. It sounds like a complicated solution, but it was not difficult to do, and I think it is a better approach than trying to crimp 2 wires together in a connector. [Flush Cut Wire Trimmer, Wire Stripper, Solder Sleeves, Heat Shrink, Heat Gun, Red Faston Male and Female Connectors, Crimping Tool]