Wing Kit – Page 4 – RV-14 Build

Pitot Tube Mast Powder Coat

Posted on December 30, 2020January 1, 2021 by Neal

Last night I powder coated the pitot tube mast.

Having not done any powder coating, I had to buy the tools, and then practice by experimenting on some other parts. I bought the tools from Amazon, and the powder from Harbor Freight. Powder coating is actually quite a simple process, it involves coating a part in a powder, then heating it to 400 degrees (F) for 20 minutes to melt the powder. The trick is getting the powder to evenly coat the part, and for this a special air gun is needed. The air gun uses air from the compressor, to gently blow the fine powder onto the part. Then, an electrical field draws the powder onto the part and causes it to stick. The gun plugs into an electrical generator, and charges up the powder particles, while the part itself is grounded.

The electrical box on the left controls the current to the gun. In the background is the gun itself with a white powder canister attached.

To heat the part, I bough a cheap toaster oven ($30), which is just big enough for what I need.

The toaster oven, with pitot mast baking inside

Steeling one of the kids stainless steel mugs, I set up an initial test. I didn’t use enough powder, but it was enough to get familiar with the equipment and go through the process.

My test object, one of the kid’s stainless mugs. I’m not sure if this stuff is good-grade, so this is going into the trash.

Then I moved onto the pitot tube mast. The powder seemed to stick a little better, perhaps being steel vs stainless steel, of just getting more used to the process. Unfortunately I accidentally dumped some powder onto the mast just as I was finishing up. But it was easy to just wipe the powder off and start again. Eventually I was happy with the coating, and I carefully lifted it into the oven and left for 20 minutes. I let it cool slowly, and checked on it this morning.

Finished product; powder coated steel pitot mast

I’m happy with how it turned out. I could have cleaned it up a little better; some of the blue marker rose to the top of the paint. And I could have perhaps gone slightly thicker, but it looks good to me and I’m happy with how even the coating was and how it turned out.

Bottom skin drill/debur/dimple

Posted on December 28, 2020 by Neal

The last two nights I spent time deburring and dimpling the outboard bottom wing skins. Not much to report, just some tedious work getting this completed.

Dimpling the right outboard bottom skin.

The right wing skin done and temporarily installed with a handful of clecos. This keeps the skin out of the way while doing the left skin.

Pitot tube mount install -part 2

Posted on December 22, 2020 by Neal

Today I cut out the pitot mast hole in the left wing bottom skin, dimples the pitot tube bottom skin holes, and countersunk the rib angle holes.

The longest job was cutting out the hole for the mast in the bottom skin. I started by removing the bottom skin from the wing, then drilled the #19 holes in the skin. These are where the screws will pass through the skin and into the mast’s flange. These holes were a pain to locate because I had dimples the backing plate. That enlarges the holes, and leaves a lot of slop when match drilling. I managed to get it pretty accurate, so then I moved on to cutting out the mast slot.

I drilled and then step drilled holes at each end. Then I used a hand nibbler to cut the material away. With a rough cut in place, I switched to running a grinding bit on my drill and cut away more material. Then I finished it up with a file, and checked the mast’s clearance frequently. By being fairly careful I ended up with a good looking hole that seems square and symmetrical.

Grinding bit on my drill, getting the mast hole to the right size and shape

I deburred the holes I made in the skin, and then dimples them all. I was anxious to get that done without cracking anything, and was successful. Then I dimpled the backing plate and countersunk the holes on the angle.

Dimpling the skin

The pitot tube mast is basically ready to install now. I need to powder coat the mast, which I’m hoping to accomplish this week, then this is ready to be riveted together when the bottom skin is installed.

Pitot tube mount install

Posted on December 22, 2020 by Neal

The last month has been busy, and I wasn’t able to make much progress on the airplane. Yesterday and today I worked on the pitot tube mount install, and a couple of other odd jobs.

I enlarged a set of systems holes in the left wing ribs so I could run a pitot and static line from the wing root to the ADAHRS, that will be installed in the left wing (two of them actually).

Hole circled in red can be enlarged up to 5/8ths. Since I’m installing the ADAHARs in the wing, I need to run a static line out there.

I decided to replace the pitot mount plate that came with the Gretz mount, because it needed more joggle, but was already dimples which would interfere with the joggling process. A secondary issue was that it wasn’t really wide enough for the 14, due to the rivet spacing on the wing spar.

Bottom left is the Gretz supplied plate. Top left is the new plate I made, and on the right is the joggling device. The sheet to be joggled is inserted into the slot and laid flat. Then the sheet and joggle device are squeezed in a vice. The result was a nice crisp joggle

I ended up making two, because the first wasn’t quite wide enough, but it was easy enough to cut out on the bandsaw, mark, drill, joggle, cut out the hole for the pitot mast, and then dimple. I had to make a tool for joggling, based on an idea from EAA Hints for Homebuilders. It came out perfectly, and it’s going to be great.

I installed a piece of angle onto the appropriate rib, then fitted the bottom skin and then match-drilled holes into the skin from inside. This necessitated a new drill, so I picked up an electric angle drill from harbor freight. It worked great until the battery ran out, and I realized I didn’t have a battery charger for this brand. So annoying! I will try to get one tomorrow.

Angle drill to match drill into the skin from inside the wing

Part way through the match drilling process

Then I switched to another job, drilling, tapping and countersinking the pitot mast, prior to powder coating. The mast is steel, so countersinking takes a bit longer, but it’s also easier to control. The hard part is countersinking the curved leading edge of the mast. I ended up free-handing this, as I found I could see a little easier than if I had used the caged countersink. The end result was ok; not perfect, but good enough… I doubt I’ll spend much time looking at the pitot tube!

Drilled and tapped screw holes for fastening the pitot mast to pitot tube

Pitot Heat Controller Mount

Posted on November 21, 2020November 22, 2020 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.

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

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.

Autopilot servo install

Posted on November 21, 2020November 21, 2020 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.

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 November 21, 2020 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

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.

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 November 13, 2020 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 November 8, 2020November 11, 2020 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 November 2, 2020November 11, 2020 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.