Tonight I finished safety wiring the prop attach bolts. I had previously wired two of the 6 bolts, but had left the others so I could move on with other tasks. At the time I was working towards a deadline – moving the fuselage to the airport – and didn’t want to spend more time on the task. The first two bolts had been a real pain, and I had redone the wiring several times before I was satisfied that it didn’t suck too badly.
For the remaining four bolts, I started by practicing with the thinnest safety wire I have, which is much easier to work with. After figuring out the routing, the length required, and any other relevant details, I switched to the large diameter wire and completed the task. The bolts are wired in pairs, and each bolt has a hole through the center where the wire passes. Because of the varied orientation of the bolts, each one presents a unique challenge in getting the wire through the hole. I was lucky that only one bolt needed loosening and reorienting, and I was able to get all the others to work without adjustment.
In the end I was quite happy with how it turned out, and found that a little practice and lots of patience definitely helps.
A pair of wired bolts. The wire acts as a fail safe in case the bolts vibrate lose and start backing offAnother pair of wired bolts
Before completing the aircraft wiring, I decided to switch to a Lithium battery, and EarthX seems to be the most popular brand for RV builders. The difference in weight between the original lead acid battery and the Lithium battery is substantial. I didn’t have the original battery specs, but it must be 3-4 times heavier than the Lithium battery. There are some other benefits too, such as a longer period of output, longer store of charge, and a battery health indicator output wire.
The EarthX 1200 series is an almost exact match in size. It’s slightly deeper, slightly narrower, and the top is shaped differently. The battery came with some foam to help make up for the narrower shape. I added a washer on each side to account for the wider shape, and added some aluminum strips with foam to the hold-down bar to ensure a snug and secure fit.
The battery terminals are basically the same, so once I had modified the hold down bar and charged the battery, it was ready to go.
Original Vans supplied battery. This is a few years old now.Side by side comparison of Vans batttery (right) with EarthX battery (left)Test fitting. Not the gap under the hold down barAdded some aluminum strips and foam to the hold down barFinal installment. Note, the ground is disconnected since I’m still running on ground power at this point
I took the time to address a minor issue with the tail fairing, where it was trimmed a little too much. Right under the leading edge of the horizontal stabilizer the fairing is designed to cover the gap between two sections of aluminum. I had trimmed it slightly too much and a small 1/8 gap had been created.
I took the fairing home and added some fiberglass and micro-balloons to build up the edge about 1/4 inch. A quick sand and spray with primer and I reinstalled the fairing. I used some more micro balloons behind the fairing, using tape to prevent it sticking to the fuse, and it came out with a perfect fit on the aluminum.
The original gap. This was the same on both sides.After building up with glass and filler, this was a final step to ensure a clean fitTidied up and primed
My original plans with the control sticks was to use Infinity Aerospace stick grips. Unfortunately, no amount of trimming of the stick base was enough to create clearance from the throttle and mixture controls with these stick grips. If I had installed a throttle quadrant instead of the standard vernier controls, they would have worked out.
So I went with plan B and bought the standard Vans stick grips. These provide *just* enough clearance from the throttle and mixture controls, and they clear the bottom of the panel. There is still interference if the cabin heat vent is on and the stick is in the full forward and left/right positions, but there really isn’t anything I can do to avoid that.
The sticks just needed to have their base holes drilled, and the wire harness connectors replaced with my setup, and they were ready to install.
Holes drilled and connector replaced. I bought a spare stick base to serve as a drill guide for drilling these holes. I wasn’t going to try to drill them in place, and didn’t want to take the stick bases out of the airplane.There are fewer switches on this stick, but enough for what I need.
This morning I finished out chapter 41 (wing attach) by installing the fuel vent lines. I opted for Aircraft Specialty vent lines, just to save some time and effort, and I also installed the JD Air fuel vents.
The standard Vans fuel vent design has a fuel line passing from the tank down through the wing fairing, where it’s chamfered at 45 degrees. I’m sure this works great, but there are a couple of downsides. The line has no screen, so there’s a risk of insects or dirt making its way into the fuel line, or even the tank, and causing an obstruction. There’s also a chance I’ll snag the vent on something and damage it. JD Air makes a streamlined vent with a built in screen, so I installed these instead. Aircraft Specialty makes a fuel line that fits the JD Air vent, so that was very convenient.
The vent itself attaches to the bottom wing root fairing using a bulk-head fluid fitting, so it simply screws into position. I was then able to loosely install the fairing, position the fuel line, final torque the fairing screws, then torque the b-nuts on the fuel line to secure it in place.
Everything went well, the only bummer is the gap at the aft end of the fuel vent, caused by the curvature of the fairing. It’s no big deal, it’s just cosmetic, and no one will see it unless they look for it specifically.
I also installed fuel placards and some grip tape on the pilot side of the wing walk area.
After a weeks off for the holidays, I was able to make some more progress this week.
I finished the wing root fairings, and installed the wing root fuel lines. These are the lines that connect the fuel tanks in the wings to the fuselage.
The wing root fairings were fairly straight forward. Getting the right shape on the bottom fairing was probably the biggest challenge.
Soon after getting the shape right I realized that I needed to countersinking the holes on the tank attach bracket. And then I noticed I had more containing to do on the wing top skin, so that the top fairing could be installed.
I brought all my countersinking, drilling, dimpling and riveting equipment to the hangar today and knocked it out. The countersinks are a little tricky because the nut plates are already installed, so a #8 countersink (the correct size) doesn’t work because the pilot interferes with the nut plate threads. I used a #21 count sink bit which seemed to be just the right size to fit into the nut plates. The countersinks are fairly deep because the fairing has #8 dimples that need to nestle down into the countersinks. The aluminum stack up is several layers deep, so there is plenty of material to support the counting depth. The only tricky part was the top, inboard countersink on the tank attach bracket. This was too close to the fuselage to get the counting cage to sit vertical, let alone the drill. I rigged up a long extension, about 18 inches long, a drilled those countersinks without a cage. It was quite easy to see the depth and I just went little by little until it was done.
There are some holes that need to be match drilled, and then 3 nutplates installed on each size. I drilled, dimpled and riveted these.
I found some proseal and used it to glue down the wing spar spacers, after giving them a little shape to conform to the wing skin.
The fuel lines were next on the list. These were pre-bent by Aircraft Specialty, and they fit exactly right. The time consuming challenge was finding a way to get them into position. The line is short and quite inflexible, and the flared ends, which are easily damaged, mate to the aluminum fittings on each side.
I loosened up the fuselage side fitting so I could flex it inboard and create enough space to insert the fuel line. I had to use a wedge to push and hold the fuselage fuel line out of the way enough to insert the new line. Once the line was in position, I torqued everything up and it all looked good.
The three nutplates that I installed, this picture is of the right hand side, it’s a mirror image on the leftClose up of one of the nut platesCountersinks on the top of the tank attach bracket. The one at the top of the image is close to the side of the fuselage and hard to reach. The spacer glued into position on top of the wing spar. This hard plastic block supports the upper wing root fairingTop fairing installed on the left sideThe underside of the bottom fairing. The screw in this position grazes the end of the wing spar. Rather than installing a full length screw, I plan to order and install some shorter screws that will stop short of touching the sparThe fuel line in place. The wing tank is on the left, and the fuselage is on the right. B-Nuts are not torqued yet.Looking down at the left hand side fuel line After torquing the B-nutsEarly morning at Ramona after a rainy night
Not much progress this week. I focused on switching out the connectors for the landing lights, and then installing the landing light lenses.
The original landing light wiring setup used molex connectors for the three wires providing power and ground to the Landing and Taxi lights. I was never very happy with the crimps on the wires, the poor connection, and the awkward angle of the wiring entering the molex connector.
I decided to replace them with DTM connectors, and re-route the wiring. DTM connectors provide better wire support, are water resistant, and have a much more positive connection and locking mechanism.
I removed the landing light clusters from both wings, brought them home and switched to DTM 3-wire connectors. Once I had them re-installed in the wings, I tested the lights and then installed the landing light lenses. The wiring setup is much more robust now, and I’m sure it will work out well.
I spent some time on the wing root fairings. Each fairing consist of two parts, an upper and a lower fairing. The upper is thicker and covers the area from the flap to just forward of the main wing spar. This is designed to be walked on when entering and existing the cabin. The lower fairing is thinner and longer, and covers the bottom of the wing, and wraps around the leading edge. Forming the curve around the leading edge was a bit time consuming. The plans explain the initial bend, which is easy enough, but then some careful manipulation by hand is needed to get the final shape. It took an hour or so to get the curve right on both sides.
There are a few more steps to finish these fairings, including riveting on a series of stiffeners.
Landing light bay with the new DTM connector visible. Wing root fairings on the left wing. I was test fitting these, getting the bend right before installing stiffeners and dimpling holes etcBottom wing fairing where it bends around and forms the leading edge.
I didn’t have much time this week, but I was able to get the trim system working correctly.
Using the laptop and a long Ethernet cable I was able to use the VPX configurator tool on my laptop to send power to the trim motors. I was pleasantly surprised that both the roll and pitch servos worked correctly. I carefully verified that the orientation was correct. It would be easy to reverse either one. For example, the elevator trim tab moves up and down just like the elevator, but it has the opposite effect from the elevator itself. Pitching “up” causes the elevator trailing edge to move up. Trimming “up” causes the elevator trim tab to move down, not up. It moves opposite the elevator, providing a force that moves the elevator to change the aircraft’s pitch.
After confirming the motors were working, I was able to set the correct max, min, and midpoint settings for both servos.
I then worked on mounting the aileron trim brackets on the right wing aileron pushrod. These connect the springs from the servo control arm to the pushrod, actuating the aileron.
Aileron trim servo. The servo mounts onto the access panel at this point. Springs will attach to the holes in the end of the arm, and extend to the brackets on the pushrod. Diagram of the aileron trim system showing the springs and how they connect to the pushrod and servo armUsing the laptop to run the trim motors and to set the trim limit parametersVPX config tool. The whole electrical system can be configured and activated from the laptop. The blue Ethernet cable is a 50 foot cable that plugs into the VPX box behind the panelDue to interference between the springs and the pushrod, I bent the servo arm to gain some clearance Springs attached to the servo arm.One last picture before closing this up. Note, the d-sub connector is safety wired together
This week I’ve continued with various assembly tasks.
Lighting:
I resolved the issue with the strobe lights, finding I had mis-pinned a molex connector on the wingtip. Once I corrected the pins, everything worked just fine. It took longer than I care to admit to troubleshoot and find the problem. I learned that it’s useful to start by validating assumptions around where your wires are going by measuring impedance and verifying there is a good electrical connection. Then start measuring voltage drop, once you know your wires are going where you thought they were going.
Comparing this picture to the diagram below, you can see the difference in the pinout. This is actually how I left the connector. Previously the female molex connector actually had the correct pins, but the male was incorrect. Rather than switching the male pins, I just changed the female. How it’s supposed to be wired. I had the right hand side of this correct, and the left hand side incorrect. I changed the right hand side to match the left .Lights are all working as expected now.
Aileron Attach:
With help from a saw horse with adjustable leg height, I was able to quite easily install the ailerons. I used new hardware, except for the bushings, since I’ve had these on and off a few times. I was wondering if the install would be more difficult than when the wings were in the stand, but I found it the same, or maybe slightly easier.
I installed and final torqued the aileron pushrods, verified they were correctly rigged using the templates. The templates allow for the pushrod between the aileron and the bell crank to be correctly sized to establish the correct neutral point. Later in the week I rigged the stick-to-wing root pushrods per chapter 41, and adjusted pushrod length until I had the neutral point on both ailerons aligned with a level stick base. I was then able to test the stick clearance, and found I need to trim more off both sticks to avoid hitting the throttle (pilot side) and mixture (passenger side).
I hung the flaps and connected the pushrods, adjusting them to get both flaps all the way up, then verified they have enough clearance from the fuselage.
I also secured the wiring for the magnetometer. I had installed this a couple of years ago but hadn’t finalized the wiring. I had plenty of length so I created a large service loop and secured it out of the way of the pushrod.
Flap pushrodsCalibrating the pushrods took an iterative approach but I eventually got itWing tip template helps keep the aileron neutralFlaps on and configuredGetting the washes onto the bolt that secured the pushrod at the stick base was a challenge. Note, this picture was taken before I torqued up the nutPassenger side stick interferencePilot side stick interference
This week I made multiple trips to the hangar to work on various tasks.
Wing attach bolts
I finally torqued the wing attach bolts. The night before, I tested out my torque wrenches to ensure they were reading correctly, and they were both very close. I used a vice to hold the wrench, and then secured a weight over the arm and measured the distance from the fulcrum. For weight I used a 1 Gallon plastic jug filled with carefully measured amounts of water. The nuts were easy to torque, I only found one where it took a second to figure out how to torque it. I ended up using a socket extension that allowed some movement, so I could torque the nut without fear of bending small bits of aluminum that were close by.
Pitot tube:
I finalized the wiring and install of the pitot tube. I used butt splices to connect the pitot heat wiring, replacing the original molex connector. In the process I included a service loop to help with any future maintenance.
I also trimmed the pitot and AOA pneumatic lines at the wing root, inserting them both into the connectors under the seat. I still need to test the system for leaks, and to verify I didn’t switch Pitot and AOA at any point in the system.
Strobe lights:
I did some troubleshooting on an issue with the wing tip strobe lighting. Both sets of strobes are flashing, but weakly. There is only 6.6V at the wingtip, so I’m losing half the voltage somewhere in the system. I tried the easy tasks such as unplugging and reconnecting connectors, but no luck.
VOR Antenna
I completed the VOR antenna wiring, and was happy to tune in a nearby VOR and see a positive ID and a needle on the CDI. The reception seemed good, even though the antenna isn’t well grounded (I don’t have all the screws in the wingtip, and they provide the ground path). The job was quite simple, I just needed to cut the cable to length and install a BNC connector, then plug it into the fitting I had previously installed under the passenger seat. I added a service loop, for ease of maintenance. At the right wingtip I connected the ring terminals to the antenna and torqued them up. I also tidied up the wing tip wiring and then secured the wingtip fairing. I then fired up the instrument panel, turned in the Julian VOR and was happy to see the reception, even on the ground in a metal hangar at 20 miles, and without a properly grounded antenna.
The main spar wing attach bolts, final torquedOne of the aft wing attach bolts Signs of life from the VOR antenna. The Nav radio is tuned to 113.75, and the green line on the left hand screen (PFD) is pointing to the VOR station The VOR antenna connection under the passenger seatRight wingtip wiring. With the wingtip off, I found I could rotate it and set it on its aft edge, balanced against the wing. This made working on the wiring much easier.Service loop for the pitot heater wiring. Insulated butt splices are visible here and would be the recommended place to disconnect the pitot wiring for any maintenance Another angle of the pitot tube install. Note, the pushrod is disconnected to allow more room to access the pitot tube wiring.
