Pitot Heat Controller Mount

Posted on by Neal

I mounted the pitot heat controller onto an access panel. This will be the mid wing access panel, just inboard of the pitot tube. This was simple enough, just center in the panel, drill holes, countersink, install screws. I did run into some problems with cracks forming on the dimples on the large #8, and even #6 holes.

Drilling and upsizing holes for the controller unit
Dimpling the plate with the DRDT-2 dimpler

The first crack showed up while dimpling the mount holes using my #8 dies. A warning in the plans calls out the risk of cracks when dimpling large holes. This is compounded by the fact that the wing skin (and access panels) are about as think as you can dimple. All the stress of the dimpling process will crack any stress risers, so I found out.

This dimple cracked because I didn’t remove some scratches near the edge of the hole. When I was drilling the holes, some metal chips were trapped between layers and scratched the skin. I used scotch bright to remove them, but didn’t completely smooth out the scratches. This seems to have caused the crack on this hole. I set this panel aside and rebuilt using another (I have several in the kit). In the new panel I went ahead and drilled and dimpled all the holes, just in case I ran into another crack issue… which I did on the last hole. This hole was a #6 screw hole, and I guess I had an imperfection somewhere. The crack was not all the way through so I tried filing it out. This worked ok, so I decided to keep this panel.

Cracked dimple on a #8 screw hole.

I made some spacers to allow the skin dimples to nest without countersinking the controller box.

Countersunk spacers

I tested the install with some screws and nylock nuts on hold it in place.

Final setup of pitot heat controller unit

Then I primed the parts with some rattle can primer, put some locktight on, torqued it up and put some thread lock on.

Pitot heat controller mounted

Autopilot servo install

Posted on by Neal

I went ahead and installed the AuroPilot roll servo into the right wing. I could have waited until after the bottom skin is installed, but I felt like it would be easier to put it in now. Hopefully it won’t present too much of a challenge when setting rivets on the bottom skin.

Aileron bell crank and bushing. Nutplate gets installed for the AP pushrod
Pushrod gets attached to the servo arm, then the arm goes back into the servo

To complete the install, I also had to install the aileron bell crank. This was simple, and the the bushings just needed a slight reaming and deburring to fit perfectly. I greased the bushing to help prevent corrosion on the inside of the steel bellcrank where there is no powder coating.

Coat of grease on the bellcrank bushing

I’ll need to tidy up the wiring to really finish this off, but I’m waiting until I have all the systems installed before doing that.

Installed in the wing. Wiring still needs to be secured.

Landing lights

Posted on by Neal

This week I was working on several jobs concurrently, so I’ll post updates spanning a few days, but focused on specific areas.

I wrapped up the landing lights on the left wing, and finished wiring up the landing lights for the right wing. I still need to enlarge the right wing bracket and paint the cove black, but that should be straight forward now that I’ve done it on the left wing.

The hardest part of these landing lights is the fact that I’m not working from any complete plans. I’ve spent a lot of time figuring out how to build it, which has given me a new appreciation for the step by step instructions from Vans. The wiring harness from Vans, plus the FlyLED instructions cover the wiring, but the specifics of how to put it all together needed figuring out. I wanted to build a plug on the lights to make it easy for future maintenance, so I bought some 3 wire molex connectors.

First I drilled holes and used a Dremel tool to cut a slot to hold the molex connectors.

Part way through shaping the slot for the molex connector
Molex connector installed
Molex connectors installed

Then I started making the wiring harnesses for the lights, with the left light first. I used a solder sleeve to create an isolated join between the ground wires. In the picture below, the flue has melted, but not the solder. Turning up the heat gun and hitting this again melted the solder and created a neat connection. Super easy.

A partially completed solder sleeve. More heat needed to melt the solder and complete the join on these ground wires.

Labels helped make sure I wired the taxi and landing lights into the right ports on the molex connector.

Labels and molex pins installed

Added some service loops on the back so the taxi light can be removed more easily. This was probably overkill, but better to have too much than too little.

Left wing landing light wiring showing service loop

Before installing the left light into the light cove, I bench tested to make sure everything was wired correctly. All good!

I didn’t get any pictures, but I wired up a molex connector to the end of the wiring harness from Vans, and tidied up the wiring in the cove. Then I installed the light, using some locktight to secure the bolts. I’m happy with how it worked out.

Testing the left wing landing and taxi lights

I wired up and tested the right wing lights too, but I’ll need to modify and paint the light cove before installing into the right wing.

Wiring up the right wing landing lights

Widening Rib System Holes

Posted on by Neal

Tonight I spent time redoing some wiring on the left wing. The main task was widening the holes in the ribs, allowing more wires to pass through for the heated pitot tube, plus some spare wires.

I picked up a 5 foot drill bit extension from Amazon for a few dollars. I installed my step drill bit which has a max size of 1/2 inch, my target hole size. The first problem was the fitting on the extension, which was significantly wider than 1/2 inch. I spent time grinding this down to just a hair under 1/2 inch.

Modified drill extension. This was ground down to fit through a 1/2 inch hole

With that done, I pulled out the wiring runs from the holes in question. I decided to unpin the molex connector for the main harness, because I’m going to replace this with a 12 circuit connector. This will allow me to terminate the pitot wires along with the lights etc. I found a wiring diagram another builder used, and will borrow that same layout. Anyway, I pulled out the wiring and then popped out the snap bushings, and started stepping up the holes.

I’m only going to up-size the system holes for the wiring runs, the two “spare” sets of holes will be occupied by my two pneumatic tubes for pitot and AOA. I could probably squeeze some more wires in with the tubes, but that’s not the plan.

The extension worked quite well, and I was able to quickly drill through all the ribs. The only issue came with the very last one, the most inboard that I needed to drill, because the drill extension was 6 inches too short. I was drilling from the inboard end, and had anticipated this, so I had another 12 inch extension. All was well until the smaller extension started slipping, and quickly reamed itself out. Luckily the step drill was almost through the hole, and some quick filing enlarged the hole enough for the snap bushing.

Drill extension extending through the ribs that have been drilled. I was trying to fix my smaller extension here while drilling the final rib.

Some deburring, installing larger snap bushings, and then I re-ran the wiring.

This shouldn’t have taken long, but the tool modifications took longer than I had hoped. It was late by the time I finished, so that’s all I got done tonight.

Step drill almost through the last of the ribs. Beyond this rib, only a subset of wires need to continue out to the end of the wing, so I don’t need to increase the hole diameters from here out. The left hand bay in this pic is where the pitot heat controller will mount, terminating several larger gauge wires.

Left wing wiring

Posted on by Neal

I spent a couple of hours running wires in the left wing tonight. It wasn’t much work, but the experimenting/thinking/researching took time. I decided where to place the pitot tube, the pitot controller, and looked at a few different blogs to get some inspiration. Sadly, by the time I finished the wiring, I had already decided I’m going to rip it all out again and change a couple of things.

Running the lighting wiring harness in the left wing

I ran the left hand wiring harnesses per the plans. There are three sets of holes in the ribs, two are big enough for my pneumatic hoses for the pitot and AOA, one per hole. That leaves just one set of holes for all the wiring. This might be ok if you are just installing the regular wiring harnesses, but I’m planning to run some twisted pair wire for the pitot heater, plus several spare wires, and there’s no way that will all fit in the relatively small sized holes. I found a Vans article that describes options, and I decided to step out the wiring holes to half inch, which should solve the problem.

For reference, here’s the Van’s doc:

Wing Wiring: Routing Wires in the Wings

Fuel Tank Leak Test

Posted on by Neal

Last night and tonight I leak tested the fuel tanks using balloons, a bike pump, and lots of soapy water. I didn’t detect any leaks, but I’m going to test it again using a nanometer, and let it sit for 24 hours.

The tanks are tested before being shipped out, but I have installed a couple of additional fittings and plenty of people have found leaks in quick build tanks, so I wanted to be careful. I taped over the fuel caps, attached the hose and valve, and used a rubber band to hold the balloon in place. There’s no easy way to measure that low of an air pressure (1psi), but the balloon gives you something of a gauge. The air pressure is just to ensure that air would be pushed out any holes, causing the soapy water ssolution to form bubbles.

Balloon partially inflated as the test began

I tested it on the balloon and saw how a small leak causes an in-missable amount of bubbles.

What a leak looks like when testing with soapy water

I didn’t detect any leaks, but I also couldn’t test the back side of the tank while it’s still attached to the wing. I don’t want to drop the tanks unless I have to, so I will probably just rig up a manometer and monitor the air pressure over a day or two. If there is any indication of a leak, I’ll investigate further. If not, I’ll call it good.

Under side of the right wing tank being tested. No sign of a leak here.

Trimming Landing Light bracket

Posted on by Neal

Last night and again tonight I worked on trimming the landing light bracket W-00017, so I can install the downward facing taxi-light from the Combo light set from FlyLEDs.

I guess I didn’t take pictures of it, but last week I spray painted the landing light cove on the left wing, making it a flat black color. Two days ago I primed the landing light brackets I ordered from Vans as part of their landing light kit. I ordered everything from the landing light kit except the LEDs.

Initial cut, formed by drilling, step drilling and some hack saw work

It would have been much easier to trim W-00017 before installing it in the wing, but I wasn’t thinking that far ahead at the time. I couldn’t fit a nibbler inside the cove, so I had to drill holes and then enlarge using a step drill. Then some careful filing to get the right shape, without damaging the wing skin.

The final modification. I took out more material than I thought I would, but this will be plenty strong enough to support the light board

I wanted to get the maximum down angle on the taxi light, so I estimated the angle that the wing will sit relative to the ground (12.5 degrees), then added 10 degrees for the down angle to get 22.5 degrees. I set the taxi light at 23 degrees down and tested the fit. I needed several attempts before I was happy with the fit.

Taxi light with 23 degrees down angle, the max I expect I’ll need

Eventually I had about 1/8 clearance between the taxi light heat sink and the W-00017 bracket.

Hard to see, but the red circle highlights the clearance between heat sink and bracket