Breathing is Good!

Installing Oxygen Cylinder Brackets

Call me old fashioned, but when it comes to operating an aircraft, I have always maintained that it is important to remain conscious. A key requirement for most carbon-based lifeforms that respire is oxygen. Most people take it for granted but if you fly in a non-pressurized airplane, it’s something that requires special thought. Furthermore, if you’re building such a plane you need to decide whether to furnish oxygen for you and your passengers or go all ‘BYOO’.

For some aircraft, especially those that fly “low and slow”, supplemental oxygen may not be a top concern. It wasn’t something I thought much about when I owned my Maule–until it was. During a long cross-country flight, returning to the Seattle area from the Midwest, I needed to climb to around 12,000 feet to clear a broken cloud layer that was “just chillin'” up against the west side of the Cascades. By regulation, I didn’t “need” supplemental oxygen (though I would have if flying under part 121 or 135), but it was high enough to feel the effects. As I was contemplating the intricacies of FAA oxygen regulations, I also found myself noticing how pretty the puffy clouds were and how everything was just so lovely and…in other words, the first signs of hypoxia.

Clouds and pointy rocks–what could be better?

When planning my RV-10 build I considered whether to install a built-in oxygen system, as some builders have, or to rely on a portable solution whenever I planned to fly at high altitude. My initial decision was to opt for the latter, partly due to being unsure how often I would really need oxygen and partly because of the cost of a permanent system. Things began to change, though, as I got further into the build. First, after pulling the trigger for pricy upgrades like after-market rudder pedals and fuel and brake systems, I became less resistant to spending large sums of money. I also thought more about the prospects of cross-country travel from our current home base in the Denver area. Facing east, the landscape appears as a flat table top for as far as the eye can see. Turn around and it’s a different story. It’s impossible to avoid the big pointy rocks if you want to head west and safe margin of error above terrain puts you squarely in the “oxygen required or highly recommended” zone. In the end, it was my wife who pushed me over the edge, reasoning (correctly) that, not only would oxygen come in handy, but a built-in system made sense for the trim level I was building towards. So, as always, when the spouse gives the go ahead to spend money, I didn’t let the moment pass.

Extensive Research?

The process of building a sophisticated airplane is a funny thing. Some decisions you obsess over, compiling graduate student levels of research materials. Others you make quickly, even if there are cost and complexity implications. When it came to the oxygen system I went with the latter and chose one from Mountain High Equipment and Supply Company. The company has been around for almost 40 years and sells all types of built-in and portable oxygen systems aimed at the Experimental/Amateur-Built market. I went with their top-of-the-line EDS-4ip system, which is a “pulse demand” system that includes all the components for a permanent install in a 4-place aircraft like the RV-10. According to the, a pulse demand system (as opposed to constant flow, like you find in hospitals) is the more efficient because it dispenses oxygen only when it detects a user’s inhalation, leading to dramatically higher durations of a given supply. Plus, as a builder who likes to build, it comes with lots of stuff to install!

I’m sure an exhaustive search would have turned up additional options, but I decided to go with this setup primarily because other builders have done the same and I knew I could learn from their experience installing and using the system. Also, Mountain High makes it easy for builders like me who are working through the build at a more relaxed pace. They sell the system in three “kits” that let you spread out the cost and work:

Plumbing Install – The cylinder mounting brackets plus the distributor outlets, electronic connectors and all the tubing
Control Head – The “brains” of the system that gets mounted in the instrument panel
“Fly Away” – Oxygen cylinder and regulator, cannulas and mask

After a quick call to Eric at Mountain High, the Plumbing Install kit was on its way to GAF (Gilbert Aircraft Factory, a.k.a., my garage).

Planning the Cylinder Bracket Install

After unpacking the kit and expressing the requisite “Ooh!”, “Ahh!”, and “Cool!”, I set about planning the cylinder bracket install. However, without a cylinder as a reference, I was unsure exactly how much space it would take up. Fortunately, Rodrigo Damazio Bovendorp clued me in to Mountain High’s loaner program. For a small deposit they will ship you a decommissioned cylinder to use during the installation. I didn’t know about this when I placed the original order, and so had to wait a few more days for it to arrive, but I’m glad I had one in hand as it made visualizing the outcome I wanted a lot easier.

It’s big, green, and MEAN! Okay, maybe not mean. In fact, it seemed quite friendly.

The first step in installing the cylinder is choosing a location. I found builders electing to go with numerous variations, ranging from inside the baggage compartment to behind the baggage bulkhead, either mounted horizontally on the floor or diagonally on the side. I’ve also seen at least one builder mount it from the underside of a shelf that spans the area behind the bulkhead. In the end, I chose to mount mine on the bottom of the empennage, port side, behind the baggage bulkhead. I determined this would make it easier to remove than if it were mounted vertically or upside down. Plus, I planned to rivet part of the bracket structure to the skin and j-stiffeners using existing rivet holes. I felt that letting it “rest” on the bottom would be a bit more secure than “hanging” it off the side stiffeners, especially in turbulence. But I’m not a structural engineer so maybe it makes no difference.

I began by placing the cylinder and bracket assembly into the tail cone and positioning it nearly up against the rear bulkhead. I wanted to leave enough room for the regulator (which I estimated to be about 4 inches deep) behind the baggage bulkhead panel. (Note that Mountain High does offer a remote regulator option, which some builders have gone with. I’ve not yet decided one way or the other.) I aligned the cylinder to be roughly parallel to the two j-stiffeners and marked the position with masking tape. (I say “roughly” because the stiffeners themselves are not parallel and so I just “eyeballed it”.)

Designing and Fabricating Brackets

I considered a few ways to fabricate the mounting brackets that the supplied brackets would bolt to. I thought about building a full shelf, but that seemed like overkill and a waste of material and weight. In the end, I decided to go with two longitudinal brackets riveted to the skin tied together using transverse crossmembers. Each bracket would include reinforcing bends for rigidity. Additionally, the supplied bracket dictated locations for nut plates that would receive AN3 bolts, so I had to decide exactly where these would land laterally. Because I also wanted to secure the fabricated brackets to the sides of the j-stiffeners (and thus needed to get a rivet gun or puller into some cramped spaces), I decided to position the port-side holes to the outboard side of the outboard stiffener and the starboard-side holes to the inboard side of the inboard stiffener. A final consideration was ensuring that I could get a bucking bar underneath the inboard bracket for the skin rivets. The additional clearance required also enabled me to level the mount laterally by varying the height of inboard and outboard brackets. With me so far?

Here’s a rendering of what I had in mind:

Note that the brackets aren’t perfectly aligned due to the angle of the j-stiffeners.

These design requirements led to me cutting out the following pieces of .040″ aluminum stock:

(2) 9″ x 2 3/4″ for the crossmembers
(2) 5 1/4″ x 3 7/8″ for the outboard brackets
(2) 5 1/4″ x 3 3/16″ for the inboard brackets

I choose 5 1/4″ for the length of the brackets because it enabled me to “capture” 5 rivets in the underlying j-stiffener.

I added 90-degree bends to the crossmembers to match the width of the supplied brackets and trimmed some of the material away in the center to provide clearance for the cylinder:

For the outboard brackets, I created bends that resulted in a 3/4″ vertical section flanked by a 5/8″ flange to match the j-stiffener on one side and a (roughly) 1 3/8″ flange for the crossmember attachment on the other. The inboard brackets have a 1 3/8″ vertical section in the middle, to account for the height difference imparted by the skin curvature, surrounded by 5/8″ and 1 7/8″ flanges for the j-stiffener and crossmember attachments, respectively:

I clamped all the pieces in place and set the cylinder in position to check he overall fit. It seemed stable and well aligned.

The next step was to attach the brackets. I started by flipping the tail cone on its side and drilling out the necessary j-stiffener rivets.

I’m the sure the original builder was very proud of these rivets. Too bad.

You can see from the photo that on the outboard one I miscounted and drilled out an extra rivet. This would come back to haunt me later when match drilling the brackets. I thought I was holding the bracket in the right spot, with my fingers out of the way, but ended up drilling through the bracket and into my index finger. Argh! Oh, well, time to update the board again:

I’m thinking about just using permanent marker.

Some antibiotic ointment and bandage later I had all four brackets match drilled.

For the rivets tying the brackets into the sides of the j-stiffeners, I used a rivet spacer to evenly locate five holes using a #40 drill bit and then went back and enlarged them to 1/8″. I then clecoed the brackets in place and match drilled the crossmembers to them using a #30 bit. At this point, because I had a bit over five inches of bracket to work with, I elected to drill an additional set of bolt holes to provide for future flexibility if I didn’t like the position of the cylinder. Extra attach points would let me customize the position of the mounting straps against the cylinder body.

Final drilling of rivet and nut plate attach holes.

Happy with the fit, I drilled 3/32″ holes for the nut plates and enlarged the bolt holes to accommodate an AN3 bolt. I countersunk the nut plate attach holes for AN426-3 rivets then primed the parts and let them cure overnight.

The following day I assembled all the parts, starting with riveting K1000-08 nut plates to the brackets. I then riveted the brackets to the j-stiffeners and tail cone skin using AN426-3 and LP4-4 rivets for the bottoms and sides, respectively. The outboard brackets went on with little difficulty due to easy access to the rivet locations. The inboard brackets took much longer. For the blind rivets, I used sections of trailing edge wedge material to create a shim that provided clearance between the head of the rivet puller and the curved edge of the stiffener. It also turned out the space I allocated under the large bracket flange was a bit tight for me to get a firm grasp of the bucking bar. I resorted to using a wooden block to position the bar in place so I could then apply pressure with my fingers. In the end I was able to get the brackets attached, though I chose to drill out and redo a few rivets that I wasn’t pleased with.

Once the brackets were in place, attaching the crossmembers and cylinder hardware was straightforward. My hole locations turned out not to be exactly perfect but the flex in the bracket flanges helped to get everything aligned and bolted down.

Next up will be locating the fill port and starting the plumbing and wiring.

Build Date(s): 28-Jan-23 to 29-Jan-23
Build Time: 11 hours

I Just Gotta Vent

One of the earliest decisions I made on mods was to replace the standard rear seat vents with a ducted system supplying air to an overhead console. While quite a bit more complicated, it seemed like a more refined and upscale solution. Many other builders have gone down this road, which includes installing NACA vents behind the baggage compartment and running SCAT (or similar ducting) to a remote-control valve to control the airflow. This then feeds air into the console cavity where passengers use additional vents to direct air onto them as desired, similar to an airliner. In theory, you could dispense with the master valve, but I’ve read that the pressurized air in the overhead console can sometimes leak out, which is less than ideal with sub-zero OATs. Since I have been working on installing items in the tail cone before it gets rivetted to the fuselage, now was the perfect time to attend to this task.

I had long ago ordered the NACA vents from Van’s and, in a fit of muddle-mindedness a couple months back, had confused them with those that come in the finish kit and get installed in the forward fuselage, behind the instrument panel. Having committed to my confusion, I believed I thus possessed two sets of vents and match drilled them for riveting to the forward fuselage and set them aside. (Note that the plans call for securing the vents with ProSeal only but I, along with a few other builders, don’t trust the smelly goop and have elected to add some additional reinforcement.) When it came time to work on the rear vents, I spent more than a reasonable amount of time looking for the “other” set of vents before believing them lost and deciding to use the “forward” set. It wasn’t until later that I realized I had dreamt up the second set all along (the forward vents are not even the same parts). The challenges with getting old, I guess. Anyway, what was I talking about?

Let’s Cut Some Holes!

Ah, yes–installing the rear vents. The big decision with installing the vents is placement. Most other examples I’ve seen feature the vents installed centered vertically in the section of fuselage skin just aft of the baggage bulkhead, below the fuselage longeron. This is roughly on the same through line as the forward fuselage vent. Variations arise based on how far aft to go. Photos taken during my “research trip” to Oshkosh in 2021 provided numerous reference examples:

Stalking and photographing RV-10’s in the KOSH infield.

I decided to follow other builder’s examples and install the vent more towards the baggage bulkhead. This also avoids a sharper bend in the ducting, assuming you want it to stay in front of the next aft bulkhead.

To locate the cutout, I first created a template using scrap aluminum (cut from the forward fuselage tunnel when installing access covers) and tracing the cutout in one of the forward fuselage skins. I then drew centerlines on both the template and the empennage section and transferred the pattern to the skin, covering the skin with masking tape to protect against boo-boos:

I can feel my pulse quicken as the moment of truth gets closer.

As you can see, I located the forward edge of the cutout six inches aft of the empennage skin edge.

Next came the delicate part–cutting the holes. One reason I’d waited to perform this mod is the intimidation factor of cutting into perfectly good aircraft skins that are already part of the finished structure. If I’d been the original builder of the empennage, I would have done this prior to riveting the skin but, since I “inherited” the component, I had to execute the cuts in situ. Fortunately, cutting the template gave me a chance to practice on a (albeit thicker) piece of aluminum without consequence.

I cut the hole by starting with a Dremel and fiberglass cutoff wheel and finishing with a fine coping saw blade, a sanding wheel on the Dremel, and some files. I was careful to trim up to the line in increments. I then test fit the vent and marked any areas with too much overlap. The final hole closely matched the contours of the composite vent. From there I match-drilled the skin using the holes I previously drilled in the vents and gave the setup a test fit.

Not shown: pool of sweat from making first cut.

Some days later, (after finally deciding to prime the inside of the tail cone), I dimpled the skins and attached the vents using ProSeal and AN426 rivets. I followed Rodrigo Damazio Bovendorp’s lead and made some aluminum backing plates to take some of the compression from the rivets (though I elected to make these in two pieces, instead of one.

More Holes! More Holes!

The next step in the process was to cut holes in the baggage are bulkhead to enable air to flow into the overhead console. This was a bit tricky because I don’t yet have a console and thus needed to estimate the hole position. (The size is set by the vent flange from Van’s). By examining numerous photos and estimating the outline of the console’s rear profile relative to the bulkhead, I was able to choose two locations I believe should work. My fixation with symmetry placed one hole close to the row of rivets at the top of the bulkhead, with the opposing hole offset to be equidistant around the centerline. Was this critical? Of course not, given no one will see these holes in the finished product, but it made my overactive synapses very, very happy.

Because the tail cone had not yet been riveted to the fuselage, I was able to remove it and use a fly cutter mounted in my drill press to perform the cuts. I have read that some builders consider fly cutters to be possibly the most dangerous shop tool out there, with a razor-sharp blade that’s nearly invisible when spinning and just waiting to slice through a wayward appendage. However, I found it quite simple to use, even in a cordless drill, and the quality and precision of the cuts to be outstanding. You just need to go slowly until the blade just barely cuts through the material. The resulting hole is perfect and smooth (though the resulting scrap does tend to have a very sharp edge).

I also performed the addition step of flanging the holes to give them a bit more strcngth, given the resulting thinness of the bulkhead in that area.

Taking (Vent) Control

The final step (for now) was to figure out a way to mount the Aerosport Products vent valve. However, let me begin by saying I didn’t really want to use the valve, or at least pay for it. No offense to the good folks at Aerosport, but $300 seemed like a lot to pay for some plastic and metal bits, an R/C servo, and some electronics. I have played around with servos and controllers and was confident I could manage to come up with some DIY electronics. The question was the housing. I went so far as to design my own version from scratch in SOLIDWORKS and 3D printed some test parts. I even came up with what I thought were enhancements, including incorporating miniature bearings for the vent flapper rods.

Many hours devoted to producing nothing useful.

I learned two things from my efforts:

It was a very effective and satisfying way to teach myself 3D modeling in SOLIDWORKS.
I have neither the time nor patience to fine tune a design for a one-off component I can just go and buy.

Well played, Aerosport, well played…

So, with the sound of a far-off cash drawer ringing in my ears, I started envisioning a mount for the (nicely done, BTW) Aerosport unit. As with other builders, I intended to mount it to the upper centerline j-stiffener, adjacent to the bulkhead flanged ducts. The challenge is that there is not much metal to grab onto. Some builders have repurposed other parts, like fuel pump brackets, but I wanted something more purpose built. I also wanted it to be easy to remove the valve assembly if needed down the road. I have also learned (the hard way) that it makes sense to plan out any complicated part(s) that I intend to fabricate.

That sent me down another SOLIDWORKS rabbit hole learning how to use its sheet metal functionality. I started by modeling the plate that would sit on top (or bottom, depending on which side you think is up) of the valve assembly and provide lateral support via two 90-degree bends. This required positioning two holes for the flapper rod caps. This would connect to two L-shaped vertical brackets that, in turn, would bolt to a third bracket riveted to the j-stiffener. I modelled each of these as a part in SOLIDWORKS and then pulled them into a final assembly (including a section of j-stiffener):

Note that I chose to model bolt and rivet holes but would locate and drill these manually during final assembly.

One handy feature of designing sheet metal components in SOLIDWORKS is that it can show a “flattened” view, making it easy to get dimensions of raw materials. This came in extremely handy on this project and I was able to get all the aluminum pieces (I used .040″ stock) roughed out, drilled, countersunk (for flush rivets), and bent in no time. (You can see in one of the images below that I used a shim to set the spacing between the two L-shaped brackets.)

Fabricating the individual parts for the Aerosport vent valve mount.

I used the existing rivet holes in the empennage j-stiffener to match drill into the upper mount and drilled holes for additional AN470AD-4 rivets as well as screw holes in the L-brackets and valve assembly (no returning it now!).

After the primed parts were dry, assembly went pretty quickly. I riveted the L-backets together (using the spacer again) and screwed them and the bottom bracket to the vent valve assembly using AN515-8R8 screws and matching washers and locknuts. I riveted the top bracket to the j-stiffener using AN470AD-4 rivets (the top rivets will get set when the top skin goes on) and attached the top and bottom bracket assemblies, also using AN515-8R8 hardware.

Pat myself on the back and then go looking for the next project.

Overall, I was pretty pleased. The mount looks well designed and has decent rigidity that should improve once the top skin is riveted in place, and the assembly is easily removable by undoing two screws.

Build Date(s): 22-Jan-23
Build Time: 7 hours

All Tied Up (or Down)

One of the mods I decided to do on the baggage area was to install a set of cargo tiedowns. I had these in the Maule M7 I owned years ago and thought they would be a handy and inexpensive addition.

Now I don’t have plans to haul an entire basecamp worth of outdoor gear, but I can foresee loading up loose or awkward cargo and wanting a way to keep it secured in the event of turbulence. Therefore, I wanted a solution that was unobtrusive yet available when needed.

I asked the Facebook RV-10 community for their thoughts and a couple replied with pointers to single L-track anchor rings like these:

One builder even nicely incorporated them into his interior carpeting:

The tiedowns are sturdy and low-profile and that allow for the removal of the tiedowns when not needed, either by removing the spring-loaded ring assembly or unscrewing the base. They are designed for automobiles and come with a backing plate, screws, and locknuts. Since these are going to be in the baggage area and I won’t be able to access under the floor, I decided to replace the locknuts with K1000-4 nut plates.

I spent a fair amount of time figuring out where in the baggage area to mount them. I wanted them laid out in a rectangular pattern as close to the far corners of the baggage area as possible. I quickly realized that the step mount access panels would be an issue, since they occupy the forward corners. I considered placing the tiedowns inboard of the access panels, to maximize the fore-to-aft spacing but this created a trapezoid pattern instead of a rectangle. In the end I decided to shift the tiedowns aft and outboard. This reduced the fore-to-aft spacing but gave me the rectangular pattern I was looking for.

I eventually decided on the arrangement on the left.

I then needed to locate and fabricate some doublers. I used some scrap .063 to create four plates slightly larger than the tiedowns themselves. The doublers are trapezoidal to account for the angle row of rivet holes in the floor. (See below for a size reference.) Fortunately, the angles are symmetrical so once I had one doubler cut to size it was simple to cut three more. (I was also able to match drill them as a set.)

I rough-fit the doublers with the floors clecoed in place to avoid interfering with the baggage floor ribs. These fit well, except for the aft port side one, which sits underneath the F-1027 close-out panel. I ended up drilling two extra holes to receive blind rivets front the close-out panel when it comes time to rivet that in place. (I had already skipped ahead in the plans and match drilled the rivet holes in the baggage floors.) I also trimmed the edges to eliminate interference with the rivet heads. See if you can pick out the extra holes in the image down below.

I also needed to sort out the orientation of the rivet holes in the nut plates. There is a lot going on in such a small area, but I was able to find an arrangement that will spread any stress forces while not interfering with existing structure. I oriented the holes in the tiedowns diagonally, so they aligned with those in the opposite corner. I reasoned this would provide for the greatest tensile strength when cargo was secured.

I marked out rivet and screw hole locations and drilled, deburred, dimpled, countersunk, and primed everything, taking extra care to keep straight the left/right and up/down orientations.

After the primer was dry, I set about riveting the cargo tiedowns in place. I started with the nut plates but quickly realized that I misaligned the screw and rivet holes, causing interference with the screws. Fortunately, I trial fit the screws on the first piece and so only had to drill out a few rivets. I enlarged the 1/4″ holes in the doubles and floors (although 2 sets of holes were just fine as-is) using a size N bit and deburred them. From there the riveting went quickly and I was able to attach the tiedown bases using the supplied stainless-steel screws.

Build Date(s): 11-Feb-23 to 12-Feb-23
Build Time: 4 hours

A Sparring Partner

With the unpackaging, inventorying and storing out of the way it was time to get down to building. I was particularly excited because, having purchased a mostly complete tail cone, I did not have much opportunity to assemble stuff. I gained a bunch of confidence by attending Troy Grover’s two-day class but it’s not the same as putting together something that will someday carry you skyward.

In fact, the first thing you start on with the wing kit (Section 13) is preparing the main wing spars. The only real “assembly” is riveting on a bajillion nut plates and a couple other things–but more about that shortly. First things first, though–it was time to “get acquainted” with the spars. The first thing Van’s instructs you to do is ascertain the correct orientation (top/bottom, left/right, fore/aft) so the instructions that follow will (a) make sense and (b) not cause you to ruin what is clearly the single most expensive component in the kits. After working with the spars for awhile the orientation became obvious but initially I made sure to triple check the plans before marking the spars with a Sharpie.

As you can see above, the spars look absolutely gorgeous in their Alodine coating. It’s a shame they get embedded inside the wing and makes you wish you had some transparent aluminum from Star Trek IV (which apparently is a thing now) so you could show them off. One other aspect that might not be so obvious from the photo is that these bad boys are heavy. After tossing around the entire tail cone like it was a shiny rag doll, hefting these thirteen foot girders on and off the workbench definitely substituted for my normal weight room routine*.

*Which is basically walking by the free weights I bought last year now collecting dust in a corner of the basement.

“Ya Know, Maybe It Should Be Longer”

Once you’ve established the correct orientation the first real assembly task is to rivet small extensions to the ends of each spar. This seems like a curious step since Van’s could easily (?) have just made the spars 8 inches longer, saving a bunch of fitting, drilling, deburring, priming, etc., and the crates the spars ship in are long enough to fit the finished product. My guess is that there is a real engineering reason for doing it this way or it helps comply with the “51% rule” since I can now say I, the manufacturer of record, “completed the spar assembly”.

Several hours just to add a few inches to the wingspan.

You can also see from the photos that I elected to prime the parts before final assembly. I had debated this for awhile since the previous builder did not prime the empennage. In the end, though, I decided to start priming parts for a few reasons. First, I noticed that, despite my best efforts to be careful, it is nearly impossible not to add the occasional scratch or scuff while working with some aluminum parts and a bit of extra protection seemed like a good tradeoff against the incremental time and weight. Second, trying to work inside the unprimed empennage was challenging due to the reflections off the bare aluminum. It was like working inside a circus funhouse.

J-Stiffener: Hip-Hop Star or Airplane Part?

With the wing spars now at their final lengths the next step was to use them as drill guides for the j-stiffeners that will eventually get laid horizontally inside the wing ribs. This is accomplished by cutting to size and clamping the two pieces (a ‘long’ one and a ‘short’ one, which overlap) against the main spar flange (with a 1/16″ protrusion) and drilling through the skin attach holes.

Couldn’t have made the spar flange slightly larger so the stiffeners would sit flush, eh?

This is repeated for the upper and lower stiffeners, making for a lot of drilling. Once I got into a groove, though, it went pretty fast, as you can see below:

Note: not real time.

The only difference between top and bottom is that there are several holes in the lower flange that do not get drilled. This is because they coincide with the access covers and, presumable, get doublers and nut plates later on. I meticulously marked these holes on the spar and, getting in “a groove” then…proceeded to mistakenly drill a couple of holes anyway. Fortunately I caught myself before drilling all the holes. I figure I can affect a repair (such as just filling the hole with a flush rivet) once I get to the wing skin attach phase. Dummy.

I marked the holes not to be drilled with arrow but forget to add, “DON’T DRILL THESE MORON!”

That (Counter)sinking Feeling

After completing the j-stiffeners and setting them aside I moved on to a really fun task–countersinking the spar flanges. (And by ‘fun’ I mean tedious and time consuming.) Again, I find it ironic that one of the first few tasks you tackle with the wing kit is to aggressively remove metal from a massively expensive piece of hardware.

The instructions are fairly straightforward and obvious since, at the end of the day, the wing skins must attach using flush rivets (or, in the case of the fuel tanks, screws) to the entire span. The important thing is to countersink to the right depth, according to the fastener being used. Again, this is fairly obvious once you wrap your head around the layout but there was one sentence in the instructions that I swear took me several hours to decipher:

Now, I consider myself fairly adept at the English language but having to parse phrases like “rib to spar flange attach rivet holes” and “inboard of the most outboard” (all with no assistance from punctuation, mind you) had me stumped. Given it was already getting late I gave up for the night and decided to take another run at it in the morning.

The new day didn’t dawn so brightly, at least as far as comprehending this instruction was concerned. Fortunately I got inspired by reading ahead in the plans and, in the end, had to draw a little diagram to convince myself I understood what to do. Here’s how it breaks down:

Each wing rib has a tab with two holes that line up with the spar flange. Those are the “rib to spar flange attach rivet holes” referred to in the plans.
Most of these holes get rivets when the skins are attached and the rivets bind together the skin, rib, and flange.
However, for the ribs that sit aft of the fuel tank, the forward-most holes (those that are “in line with the nutplate attach rivet holes”) get riveted only to the spar flange, since the fuel tank (and the wing skin which attaches to it) needs to be removable. In these locations the fuel tank skins just sit on top of the rib attach rivets.
Finally, rather than just say, “the ribs that sit aft of the fuel tank”, the plans describe the locations as those being “inboard of the most outboard fuel tank attach nutplate”.

After the rush of adrenaline from solving this mystery subsided I realized that there are only 7 holes that fit the description laid out in the plans on each side of the spar. Why couldn’t Van’s have just pointed these out in the drawings? There are plenty of other places (for example, on the previous page!) where Van’s gives instructions like, “don’t drill here”. They could have just said, “These are the 7 holes we’re talking about!!” Instead they chose a riddle the Sphinx would have been proud of.

So I (carefully, this time) marked the 28 holes that needed this special treatment and got out the countersink cage, but not before reviewing plans Section 5 for proper countersinking technique. Given the importance of the spar to things like, um, keeping the wings attached to the airplane, and that you can’t “uncountersink”, I wanted to make sure I didn’t get sloppy when drilling the several hundred holes. Van’s also recommend you make some dimpling guides out of scrap aluminum sheet so you can judge the required depth of the countersink. Troy had these available during his class and I’d already planned on making them. Now ended up being the perfect time and you can see an example below (picture taken later, after I’d installed a nut plate):

Not enough skin to get airborne but enough to check the fit.

I’ve included a few pictures below of the countersinking process but there’s nothing much to see (other than the amount of aluminum shavings) that get produced.

Note the photo showing “One of Seven” as I call her, in honor of Jeri Ryan.

Nut Plates Galore!

I’m not quite sure exactly how long it took me to finish the (initial) countersinking. I suppose I could check my build log but, in event, it seemed like weeks! Finally it was time to rivet on the (many) nut plates, both for the fuel tanks and access plates. At this point I can’t say enough how happy I am that I opted for the Cleveland Aircraft Tool pneumatic squeezer. Once I got the depth adjusted the tool made short (and perfect!) work of the hundreds of flush rivets required during this step. It was such a nice change from the “countersink, check depth, check cage, blow away shavings” of an earlier process.

That giant pile of nut plates seen during inventory dwindles pretty fast.

Once the nut plates are installed you are instructed to countersink the screw holes to fit the appropriate flat head screw. One item of note is an instruction to “spot prime” the holes created when countersinking the fuel tank attach holes. I’ve seen other builders spot prime all the countersunk holes and so I was curious why the instructions were specific to the fuel tank holes when normally priming is “if/as desired”. My guess is that these holes (a) fairly large, (b) don’t get riveted and (b) are expected to be exposed on occasion during fuel tank fitting and eventual servicing.

Given my penchant for overengineering, I decided to mask the spar flange prior to countersinking and then using this mask to avoid overspray on the spar. I think it turned nice and didn’t obscure the beautiful spar flange (that, as stated earlier, no one will ever see…).

I must’ve saved at least two ounces from not priming the whole thing.

The final bit of “nut plate madness” occurs near the spar root, which requires a handful of these clever devices be riveted onto the spar web. This is mostly straightforward except that the rivets nearest to the step bars makes countersinking and pressing a standard rivet set a bit awkward. In the end I used a manual countersink tool and a back-rivet set to pound the rivets in this tight quarter.

Designed this way to torment the builder.

Brackets and Bolts

While it seemed like I had been working on Section 13 for awhile (sometimes a full day on one step) I was still not done. The final tasks involve tapping and drilling some aluminum stock to fabricate tie down brackets and then installing them, along with aileron bell crank brackets.

Cleveland Aircraft Tool offers some excellent brackets with the holes already tapped but what’s the fun in that? I had bought a tap and die set specifically for this project and wanted to give it a go. After watching several YouTube videos on the right technique (and after acquiring some tapping lubricant) I proceeded to tap the holes to required depth.

I was pretty pleased with the results. I was careful to back the tap out after every quarter turn or so to free up the shavings and blew it clean with air. I did manage to slightly bend the flange on the first go because of how I had it clamped in the vise. (You can see that below) I clamped the other bracket horizontally and it turned out fine.

Once the hole is tapped the plans have you drill a pilot hole in one corner and use that to position/cleco the bracket to the spar so the remaning holes (for both AN470AD4/AN426AD3 rivets and AN3 bolts) can be match drilled. I used clecos to position the nut plates until I got the first holed drills. I then removed the bracket, deburred and primed it:

Feeling pretty pleased with myself I came back the next day prepared to rivet on the nut plates and then attach the bracket to the spar. It was then that I realized I had forgotten to match drill the uppermost holes that are sort of hidden underneath the spar flange. A quick detour to rectify that and the brackets went on pretty quickly.

And with that I bid farewell to Section 13, in what seemed like, in the grand scheme of things, not much time at all. I guess I better get that fuselage kit ordered soon!

Finally Winging It!

Hello my dedicated readers, er, I mean reader (thanks, honey)! This week we’ve decamped to Telluride for our annual Memorial Day getaway. While there’s no actual work happening on the plane, the break is giving me time to catch up the build log and post some (hopefully) interesting content (in between margaritas and jigsaw puzzles).

Athena tells me she much prefers the shop and “helping” with airplane building over this.

Too Big for UPS

The big news is that the wing kit finally arrived a few weeks back. I had many people ask how close the final shipment came to the estimate provided by Van’s. It was pretty close. I ordered it the first week of January and Van’s promised shipment within 16 and 20 weeks (they are now listing lead times in months–sigh). I knew shipment was getting close when I noticed the balance charge show up on my credit card. Then about a week later I got an email from the shipping company tell me I could call and arrange delivery. I thought it odd that I had not gotten confirmation from Van’s but then shortly thereafter I got a packet in the US Mail (how quaint!) giving me the details I needed, along with instructions on how to handle potential damages. I have seen some pretty bleak reports of damage during shipment and was hoping I would not have to deal with such headaches.

This photo was taken near 13th and Elmwood. Media stage in Commons Park on North side near dog park. PIO eta is 30 mins. pic.twitter.com/vfXlToB5mE
— Broomfield Police (@BroomfieldPD) February 20, 2021

Of course, this had recently happened a couple miles from our house.

Fortunately I had no such issues when the shipment arrived.

Does Van’s paint the dollar sign to signify, “If you rob this truck, steal these first”?

I’m sure the driver had some questions about the odd-shaped crates but if he did he kept them to himself.

I was tempted to explain that I was a massive pole vaulting enthusiast.

The driver was very accommodating and pushed the crates over the curb and up the driveway into my garage/aircraft factory.

After the rush of the delivery was over I realized I had made a tactical error in scheduling it for mid-week. In retrospect it would have been better to schedule it for Friday so I could have quit work and gone straight into inventory management. However, you shouldn’t attempt to build an airplane if you aren’t good at problem solving and, after thinking about my predicament for a few moments, I grabbed my laptop so I could take my remaining Teams meetings from the garage. I assure you I was definitely, sort of, paying attention.

One thing that is not on the inventory sheet is the shear volume of packing paper Van’s uses to protect the valuable cargo. I was pretty sure I could have packed a small, single family home with everything that was left over, as you can see in the time lapse video below:

Another satisfied customer of Van’s Packing Materials Company.

Inventorying the kit is a critical first step as you only have 30 days to inform Van’s of missing components and get them shipped for free. After that you pay the bill. I inventoried the large/aluminum parts as I unpacked them but there are several bags and sub-kits that require more careful study. In the end everything was accounted for with the exception of some backordered flap nose ribs, some AN4 bolts (they shipped AN3’s instead), and 3 measly K1000-06 nut plates. I felt sort of bad for making Van’s send me 3 replacement nut plates as I’m sure I have some extras but, being extremely Type-A, I could not violate the mandate to tell them what was missed. I received the bolts and nut plates within a week or so.

You Can Have a Storeroom or a Workshop But Not Both

As satisfying as the unpacking and inventorying was it left me with the dilemma of what to do with all the new pieces parts (not to mention the completed empennage) such that I would have room to work (and park my truck at night). I had already used a good chunk of the wall space for some decorative aluminum art pieces:

New York collectors will pay big bucks for this stuff.

And I’d cleaned off enough junk from some storage shelves for the smaller pieces:

It looks so cool I almost don’t want to start building. Almost…

That left the problem of what to so with larger wing skins and the massive spars. My first thought was to hang the leading edge skins from the ceiling. I bought a hardwood closet rod at Lowe’s and fashioned some plywood brackets but, after attaching the brackets to the ceiling discovered the skins were just too heavy and cumbersome to safely get them up there. Instead I opted to reposition the “elevator wall art” so I could hang the skins alongside):

Note the strings keeping the skins from expanding.

For the wing skins I decided to use the space along the wall I normally try to keep clear do I can open by truck doors. I used some structural pipe, hose and pipe clamps, and the sides of one of the crates to fashion a shelf of sorts that hold not only the wing skins but rear spars, j-stiffeners, and other long parts:

Note the all-important “anti-door whack” system.

The reason I chose to mount the shelf off the floor was that I need room to store the wing spars. While it won’t be too long before the spars are part of the larger wing structure I did want a way to tuck them away during the initial construction phases. The solution I came up with was to attach some casters I had on hand to the shipping crate. That way I can roll them against the wall when I need to:

Overengineer (ō-vər-ˌen-jə-ˈnir); verb; To make something more complicated than necessary; often implies that the complexity was added intentionally.

That left only the empennage, which had been occupying one of my rolling workbenches for the past several months. I had already decided it would live on the ceiling of the garage. The question was now to get it there. I thought about purchasing a manufactured solution like the one I use to store our Christmas sleigh (don’t ask–long story) but these are a bit overkill and expensive for what they are. Therefore I decided to try to roll my own solution.

I had previously fabricated two cradles to hold the empennage and so started by building a frame out of 1×3 boards and some plywood gussets to which these could be attached:

I used hardwood floor scraps to reinforce the pine boards against flexing. See previous definition of overengineering.

I bolted eye hooks at the corners and to the ceiling joists with the idea that I’d use rope to hoist the whole enchilada skyward and then secure it with some surplus light fixture chain I had on hand. After I trial run with ropes passed through the ceiling hooks I discovered the whole thing was too heavy to lift, even though most of the weight was surely the wood, not the aluminum. In the end I decided to add pulleys to both the frame and the ceiling to fashion a rudimentary block and tackle system. That provided the leverage I needed and, for the first time, at least part of the airplane took flight:

The empennage just rests in the cradle so to keep to sliding out and ruining both part of an airplane and two cars I threaded a bolt through a length of chain and fitted it to the tie down bracket. In the end I was pretty happy with the result as will be easily to get back down if I want to work on some of the remaining tasks.

Now, in the immortal words of Robert Irvine, “Let’s get to work!”

Let There Be Lights!

I have a problem. I’m impatient. And I have a short attention span. And, doc, when I lift my left arm really high I get this pain… Oh, right. The build.

With the wing kit ordered (Happy New Year 2021 to me!) I got obsessed with planning out the exterior lighting since a good chunk of it goes in the wings. I had researched various options from different suppliers with different strengths/weaknesses but really wanted a complete solution from a single vendor if at all possible. Then I learned of FlyLEDs.com. It’s an outfit focused in the RV market and apparently run by some Aussies (so points for that already) and unlike most (all?) other vendors doesn’t sell you something you can just bolt directly into your plane. Sounds awesome, right!

FlyLEDs really embraces the whole “amateur-built” concept by making you finish the build on the lights. (You’re building a whole airplane so how hard can this be, right?) Specifically they sell you the electronic components (circuit boards, LEDs, resistors, etc.) and you solder them all together. Now, I am old enough to remember (a) when Radio Shack was a thing and (b), in particular, Radio Shack’s “Science Fair 100 in 1” Electronic Project Kits. These were ingenious “educational toys” that allowed you to create a variety of electronic circuits by connecting components attached to a large board using wire and spring connectors.

I was particularly drawn to circuits that blinked or buzzed. I recall there was a basic VHF radio circuit included but I never remember ever getting that to work. This nascent interest in electronics caused me to own a basic soldering iron as a youth (though what I used it for is now lost to my ever aging memory) as well as a resurgent interest as an adult in the much trendier sounding hobby of “making”. This, of course, required the acquisition of a “much nicer” soldering iron (in fact a soldering station!) as well as enough microcontrollers and other components to start my own “shack”:

As you can see from the photo I had grand ambitions to build all sorts of internet-connected gizmos with sensors, displays, etc. In the end it mostly just fed my curiosity, though I did create a motor controller for a home-built TV lift and a cheesy Halloween special effect. Still, it gave me the confidence to tackle the FlyLEDs project without much hesitation.

Choosing a Lighting Option

FlyLEDs has a few different options to choose from when it comes to position indicators, strobes and landing/taxi lights. One of the primary choices to be made is whether to mount landing lights in the wingtips (integrated with the position/strobe lights) or in the wing leading edge. The integrated solution sounded clean and cool but I had heard that some traditional lighting options had issues with being obstructed by the forward edge of the wingtip. Plus, the limited space means the landing lights are not the brightest FlyLEDs offers and, if your going to do it yourself you might as well do it bright! So I opted for FlyLED’s “Original” wingtip light kit, which comes with complete with position lights, strobes and a controller board. I then added their tail position/strobe light as well. With this decided I felt “well positioned” to make the next choice.

Having decided to go with leading edge mounted landing lights there was really only one choice–for me anyway–FlyLED’s “Seven Stars” landing lights. These are their top of the line offering where the light level “goes to eleven” (or maybe seven…I’m not sure). Obnoxious? Perhaps. But they must be bright since they barely fit in your hand:

If they don’t work out at least I can use them as doorstops.

As an Australian company FlyLEDs does resell through Flyboy Accessories in the US but I decided to order directly from Oz to perhaps give the folks a bit more margin. (Plus the thought of the shipment potentially getting hung up in customs really excited me!)

Delivery and Unboxing

To my chagrin, US Customs decided to allow the heavy and obviously suspicious package through and it arrived in a week or so after ordering:

The contents were packaged well for the journey with ample bubble wrap and lots of little zip-loc bags of electronic components:

No, it didn’t come with cleco pliers–I just added that for scale.

The kit includes all the lighting components plus DB-15 connectors, back shells and pins, thermal grease (for the numerous heatsinks), and even a length of solder!

Wingtip Light Assembly

The instructions that come with the kit are quite good so there’s not much I can add in terms of tips and gotchas. I will say, though, that for best results you should be somewhat proficient in your soldering technique, in particular getting the heat transferred from the tip of the soldering iron into both components you are trying to solder. This promotes good solder flow and clean results. The fact that some of the kit components are rather large can make this tricky.

One thing the instructions recommend is to test fit the large wingtip circuit boards to the wingtips and trim as needed. Of course, I had no wings yet but wanted to get started anyway. (Did I mention I’m impatient?) If I end up having to trim the boards after assembly I’ll just be very careful. In truth I’m not that worried. There are not that many (or fragile) components that need to be soldered on.

Assembly is quite straightforward, solder the LEDs, solder the big power resistors, solder the wire terminals, connect the two halves with ribbon cable. The position LEDs come in red and green (obviously) but it’s difficult to tell them apart just by visual inspection, though they come in separate bags. Take care not to mix them up. Helpfully, the circuit boards come with colored labels that you can remove after assembly;

It’s a bit hard to tell but each “half” of the assembly is sized to fit the correct location on the wingtip fairing.

The LEDs went on easily, despite the strobe LEDs being quite beefy, and the requirement to smear some thermal grease on the back side of each:

The blue film is just a protective covering and should be removed when you’re done.

When soldering the power resistors the instructions state to leave some clearance between them and the circuit board to facilitate airflow/cooling. To get consistent spacing I used a couple metal rulers to establish an offset:

Once the LEDs and resistors are installed you can test the LEDs by connecting power directly to the contacts on the circuit boards. FlyLEDs recommends a 9-volt battery but I used my benchtop power supply. FlyLEDs warn that the units are bright and they don’t lie!

The only “gotcha” I came across was my own confusion trying to understand the instruction on connecting the two portions of each wingtip unit. The kit comes with a length of 8-conductor ribbon cable and instructs you “cut this in half” to create two pieces, one for each pair of boards. After dutifully complying I discovered that each piece was very short–too short, in fact, to reasonably allow for the two boards to sit comfortably at the roughly 90-degree angle required. I then realized I had cut the ribbon cable the wrong way–perpendicular to the wires instead of lengthwise. Argh…

I looked online for a replacement and only found options from my standard vendors (Mouser, Digi-Key, and Arrow) in the 1,000′ spool variety. Not wanting to start my own ribbon cable distributorship I opted for some 4-conductor cable used for RGB LED strips. Another reminder to measure twice, go get some coffee, measure again, and then cut once.

Controller Board Assembly

Assembling the controller board is nearly as straightforward as the wingtip boards but takes a bit longer due to the number of components. Taking my time to ensure high-quality soldering it went together in about a half hour.

One component I did not solder is the included DB-15 connector. (You can see the empty holes on the right side of the controller board.) I did this because I plan to install the controller board in a project box and want to mount the DB-15 there. This means at some point I’ll need to perform some tedious wiring, soldering and crimping.

Controller Board Testing

Once all the wingtip boards and the controller board was assembled it was time for a bench test. I used standard electronics hookup wire to connect the wire terminals on the wingtip boards to the open holes where the DB-15 connector would go. (I haven’t mentioned the tail strobe yet, because there’s nothing to assemble, but I wired it in as well.)

In truth you can perform a preliminary test of the strobe lights without connecting them because the controller board features 3 LEDs that flash in time with the main strobes in various patterns controlled by the DIP switches. Of course I wanted to experience the “full effect” (sunglasses at the ready) and even cobbled together a test rig using some 3D-printed parts:

Run for your lives! It’s Franken-lights!

As with any moderately complex electronics project everything worked flawlessly and exactly as designed on the first go! I’m kidding, of course. I discovered that the strobe lights on one wingtip were not triggering, even though the onboard LEDs worked fine. I retested the individual wiring paths and ruled out a bad connection on the wingtip board. And thanks to some explanation in the instructions as to how the strobes were controlled I was able to so some troubleshooting of circuits on the controller board using a multimeter. In the end, though, I was stumped and emailed the FlyLEDs support alias.

I got a reply from Paul at FlyLEDs (I suspect the sales, support and information emails all go to the same place) who was super-helpful in helping me troubleshoot the issue. He asked me via email to test a few things, which I did, even uploading some video of the errant behavior:

Not at all annoying to listen to on repeat.

In the end we traced it to one of he IC pins not outputting the correct voltage during strobe sequence. This was highly unusual to say the least but, with the answer in hand, Paul graciously offered to have the team at FlyBoy send me a replacement. The great news is that since the IC is simple to swap out the replacement was super simple. This enabled me to stage a full-on test in my workshop, at night, with the window blinds pulled up–no doubt to the alarm of my neighbors.

There goes Mike, hosting another weeknight rave.

Landing Light Assembly

Compared to the wingtip lights and controller, assembling the landing lights was quite simple since they don’t contain any electronics, other than those that come already soldered to the circuit boards. Construction consists mainly of assembling some 3D-printed parts and screwing them–and the main circuit board–to a giant aluminum porcupine–er, I mean, heatsink.

Each landing light (I ordered two) includes a large 3D-printed piece which holds lenses for focusing/distributing the light from the tiny (but very bright) LEDs, as well as a set of spacers that help position the lens holder. After separating the spaces from their web (very reminiscent of building plastic airplane models back in the day) the instructions state to bond them to the lens holder using acetone, which reacts with the ABS plastic. This fact came in handy when I managed to crack one of the lens holders. I simply slathered on some acetone and waited for it to cure.

The next step is to carefully snap in the small plastic lens cups and then, even more carefully still, snap the lens themselves into place. Each lens has a set of minute tabs that must align with gaps in the lens cups in order to fit securely.

The result is either part of a landing light or a flower sculpture.

You then screw the circuit boards to the heatsinks (after applying thermal grease) but I failed to get a picture of this step. All that’s left is to screw the lens assembly to the circuit board. At this point I discovered that the 3D-printed screw holes were a bit undersized (not uncommon in 3D printing) and some of the acetone-bonded spacers broke loose due to friction from the screws. However, I was not concerned since the screws are what provide the mechanical connection. I figured it would be no different then using loose aluminum spacers on other parts of the plane.

The finished result is two hefty pieces of kit. It’s hard to tell from the photo below because massive heat sinks are hidden by the circuit boards but, take my word for it, don’t drop one of these on your bare foot!

I love the “CAUTION: BRIGHT! CAUTION: HOT!” warning label.

With the assembly done it was time to grab the sunglasses and test these behemoths. You’ll notice there are three connectors on each: GND, +12V and TAXI+. TAXI+ connects only the center LED to allow for “reduced airport denizen complaint mode” while taxiing at night. Apply 12V to the main connector and get ready for “Operation Suntan”.

You can almost hear Manfred Mann’s Earth Band playing in the background.

As FlyLEDs says on their website, it’s hard to really illustrate how bring these lights are (amazing given the actual size of the LEDs). You’ll just have to take my word for it that I could have had some fun with my neighbors if I was that kind of person.

Now, when are those wings gonna get here so I can actually start building an airplane!

Wait! Did I Buy A Cozy?

With the elevator debacle under control I decided to sweep up the metal shavings and switch gears to Section 12–empennage fairings–one of the few tasks left to do. Section 12 covers the installation of composite fairings to elevator, rudder, and stabilizer tips. The molded tips come as part of the empennage kit but some must be modified by building up one side with raw fiberglass cloth. The plans are extremely basic, describing a two-step process through very clean-looking engineering drawings. Little did I know how much “character building” would be involved in saga that unfolded over the course of multiple weeks.

Some time ago I had ordered the composite practice kit from Aircraft Spruce. I ordered the version that comes with Burt Rutan’s “Moldless Composites Sandwich Homebuilt / Aircraft Construction” (a $15.50 value!), figuring it would be useful to learn from the master. For some reason this SKU was backordered (the kit with just the raw ingredients would have shipped immediately) and so it didn’t arrive until early January. When it arrived I wasn’t sure I’d made the right decision since the manual’s contents weren’t any more illustrative then what I can find online through EAA and YouTube.

Regardless, the kit came with everything I needed to get started, including West Systems resin and hardener, fiberglass cloth, flox and micro, cups, stirrers, gloves and more. The accompanying manual suggests several practice projects with which to get familiar with the materials and processes but, frankly, none seemed all that interesting. I suppose back when Rutan wrote the manual (apparently using a typewriter and ink pen) someone reading it would be mystified by this “magic” process. Today, when composite manufacturing is practically live-streamed (not only aircraft, but boats, custom cars, and more) you (or, rightly, me) feels like they understand what’s going on.

And thus I decided to jump right in.

The tasks called out in the plans are fairly straightforward and go something like this:

Trim excess material to ensure the fairing will mate with the matching aluminum part.
Remove any excess epoxy/gel coat from the joggle along the flange perimeter.
Match-drill the fairings using the pre-punched holes in the aluminum skins.
Dimple the skins and countersink the holes in the fairings.
For fairings with an open side, enclose with three layers of fiberglass cloth and resin.
Attach the fairings (except for the lower rudder fairing, which waits until lighting is sorted) using CS4-4 blind rivets

There are several considerations that affect the fit and finish of the fairings. Rather than provide a chronological narrative of the process (since that would result in a 70-page blog post) I will present some highlights of each stage along with lots of pictures as well as my observations, learnings and frustrations.

Mis en Place

As when making a great meal, each stage begins with prep work. First you must sand off any resin/gel coat in the “joggle” where the fiberglass parts get riveted to the aluminum structure:

I tried using a razor blade for the first few passes but this proved cumbersome and not all that effective. I found using a flat file much easier. Just hold the long edge of the file snug against the corner and work it back and forth until it’s square. It’s a bit hard to see in the image below but goal is to get a nice clean edge so there isn’t a gap when you rivet these onto the metal components.

Failed to get a picture of the technique but you can (kind of) see the results

The next step is to trim excess material from each part. I used a Dremel tool with a cutoff wheel as well as painter’s tape and a reference line to reduce splintering.

One thing to be careful of at this stage is the width of the flange. The plans specify a nominal width but I would recommend making it a bit oversize and then sanding to fit. Otherwise you risk not leaving enough material to support the rivets (see below).

Match-drilling and countersinking the fiberglass parts is pretty much the same as when working with aluminum, involving clecos, #30 and #40 drill bits, and countersink cage.

Match-drill #40 first, then final-drill #30

Where Are The Dressing Rooms?

One thing you might have noticed in the photos is that the fit between the rudder and rudder fairing was, er, not great. In case you missed it, here’s a close up:

Oh, by the way, see that cleco right above the counterweight attach screw? The placement of that rivet hole is ambiguous in the plans drawings (note the lack of handy-dandy dotted lines below) but the text states you need to use an odd number of CS4-4 rivets and there does appear to be a hole drawn on the forward end so I assumed a rivet was needed there. If my rudder falls off because I misinterpreted the plans then now you know why.

18 lines, 19 rivets–the story of my life…

In retrospect I would recommend prepping the fairings while assembling the tail section components so you can check the fit and attempt any adjustments. However, because the rudder was already built when I got the kit I didn’t have that opportunity. My first thought was to attempt to improve the fit with some composite treatment. (I had never used composites before and so assumed they were effectively magic materials.) After stewed on the issue, though, I decided to try to improve the fit of the aluminum skins. Keep in mind this piece has to line up with the vertical stabilizer tip fairing and I determined just slathering on fairing compound was not going to provide the finish I wanted.

My fix involved removing the rudder counterweight, filling in the top screw hole as well as the infamous 19th rivet hole with JB Weld epoxy (using duct tape over the holes), clamping the skins tight around the fairing, and re-drilling the holes.

You can see how much the top portion of the rudder skin squeeze together (about 1/4 inch) the final photo above. You can also see a layer of JB Weld I applied between the two skins after reassembling the skins. Eventually all this will be covered with a layer of composite material.

Sometimes You Can Be Too Trim

The rudder fairing was the first piece I tackled and (naturally) I took off a bit material more than needed. To avoid having the fiberglass crack at some point in the future I borrowed a tip from another builder and patched in a thin strip of 0.020 aluminum using a strip of bi-directional glass cloth and resin.

Hold me tight and I’ll hold you tight (but not too tight)

You can see that I only added the aluminum to the forward sections where the flange was too thin for my liking. Also, the tips of the cleco clamps are wrapped in packing tape to prevent them from becoming permanent fairing accessories.

I made a similar mistake when trimming one of the h-stab fairings, cutting it to close to the end, right through a rivet hole.

In this case, though, because I needed to build up the open side with fiberglass, I assumed (correctly for once!) that enough material would get laid down to provide a reasonable anchor point.

Cutting in Three Dimensions

One of the challenges of trimming these fairings in particular is getting the upper and lower curves to align with the elevator fairings. You want to follow the contour of the elevator tip and fairing, leaving just enough space to ensure the elevator can move freely but not leave so much clearance that it doesn’t look pleasing to the eye. As with my aspects of the build, the solution is to work slowly, making small adjustments as you repeatedly attach and remove the fairing using clecos.

You can see above that before you close out the aft portion of the h-stab fairing with fiberglass it protrudes a bit outside the edge of elevator fairing. My solution to this was to make the temporary foam rib (see below) a bit taller than the profile of the h-stab fairing, thus “tucking in” the outboard curve.

R V Serious?

See what I did there? Subtle Latin reference. I crack myself up sometimes!

One of the most mysterious aspects of constructing the fairings involves enclosing the open side of the elevator and vertical stabilizer fairings with fiberglass cloth. The diagram in the plans that tries to explain this is deceptively ambiguous.

The first stab is to fashion a temporary rib out of foam and shape it to the fairing profile. I ordered some PVC Divinycell foam from Aircraft Spruce for this even though the composite practice kit came with some blue foam insulation pieces. I figured I might need it for other projects at some point in the future. At this point he plans are not very explicit as to how to go about forming the rib. Here are a couple of things that I took away from the process:

You can approximate the profile of the fairing by firmly pressing it into the surface of the foam.
Given the curve of the elevator counterweight, the rib should be made somewhat concave, not straight as it is shown in the plans.
Unless you like digging out pieces of foam and epoxy from hardened fiberglass, consider wrapping the temporary rib in packing tape. Argh!
Rather than making the rib flush with the back of the fairing as shown, recess it 1/8″ or so to provide a “well” to fill with fairing compound/micro-balloons. Argh again!
Make sure to test fit the fairing and attach with clecos until you are happy with the profile. Yay!

First experience working with fiberglass and so far Virgin Galactic has not called with a job offer

As you can see from the last photo, the first layer of cloth detached from the fairings in a few places. I figured this was okay because most of the strength was going to come from the two layers applied inside the fairing. As long as I was happy with the shape (you can see this in one of the photos) I decided to move on. Also, because I did not apply packing tape there was some foam residue on the inside of the fairings but, again, since this was going to be saturated in resin in the next stage (and no one except me–and, well, you–would know about it) I felt it was okay.

The next two layers of fiberglass cloth went on pretty easily, though getting it to lay down in the tight inside curves was a but tedious. Incidentally, even though the composite kit came with calibrated pumps for the West epoxy system I found it easier to measure the resin and hardener by weight (5 to 1) since I was working with such small volumes. I used a small digital scale I had bought for the kitchen.

Super-sharp shop shears (alliteration!) and a Dremel tool with cutoff wheel made quick work of cleaning up the excess cloth and resin.

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After reinforcing the fairings the next (and last) step in the plans is to rivet them on to the appropriate tailfeathers.

Fiberglass, meet Aluminum. Aluminum, Fiberglass.

While the plans don’t dictate anything beyond this I have seen numerous builders apply composites to the joint between the two materials to make a more visually pleasing interface. In fact, the junction between the two components did look pretty amateurish. I contemplated leaving them as-is to reinforce to the FAA that this aircraft was, in fact, built by a total noob but, in the end decided to attempt to replicate my esteemed peers’ work.

In retrospect, I have to question that decision for the sake of my sanity. What became apparent quite quickly is something I’m sure builders of Long-Eze, Glasair and other composite aircraft are well acquaint with–the frustrating and fruitless hunt for smooth perfection. In a way, it is the definition on irony. I am building an aluminum aircraft, where subtle ripples in the skill and rivet lines are part and parcel, but somehow believed the tiny pieces of fiberglass at each tailfeather tip needed to exhibit the characteristics of the Hubble telescope’s main mirror. In case you are similarly afflicted I’ll briefly describe the high points here but, in truth, I am reluctant to relive this portion of the build.

I started by applying a layer of West Systems 410 filler to the individual parts in order to create a semi-smooth surface. I followed this up with a sanding and a layer of epoxy and micro-balloons. More sanding and a second layer of micro–followed by more sanding–yielded satisfactory pieces which I then riveted on to the main structures. I varied sandpaper grit from 80 to 220 and found these Durablock sanding blocks to be super useful.

I was hungry and had to keep telling myself it wasn’t peanut butter

Once riveted, I applied a layer of painter’s tape to protect the aluminum skin and repeated the 410-sand-micro-sand process to file and feature the gaps between the fiberglass and aluminum parts.

Because I love things that take multiple steps separate by hours of curing time

Once I had achieved reasonable good contours I hit the tips with a coat of SEM self-etching primer, which helped highly any ridges, valleys and pinholes. (It also offers a layer of protection to the layer of Alclad sanded off during the process.) Then it was back to spot filling with thinner and thinner coats of micro and more sanding.

You can have it in any color as long as it’s gray

In the end I was reasonably happy, if exhausted. Remember that gnarly gap between the rudder and rudder fairing? Viola!

There was also a pretty nasty gap where the v-stab met the fairing that I was able to disguise.

Now, to see how it all goes together!

Fixing the Elevators

NO, NOT THAT KIND…

So after trying unsuccessfully to connect with my EAA Technical Counselor to come look at my elevator fiasco I decided to jump in the deep end and attempt a fix myself. After much thought and a few opinions from Van’s Air Force (including one that amounted to, “just give it a big ol’ yank”) I was pretty convinced the fix I had in mind would work. Specifically, my plan was:

Remove the elevator counterweights
Drill out all the rivets in the counterweight skins
Using fluting pliers to impart a corrective bend in the end ribs
Reattach the skins and counterweights

I started with the right elevator because it had the most interference, figuring if I could get that fixed the left one would be a piece of cake. (Yeah, right.) Step one, unbolt the counterweights. Step two, turn several dozen of the previous builder’s carefully driven rivets into metal confetti:

With the skin removed I had unfettered access to the end ribs and proceeded with bending them (to my will). I created a slightly exaggerated correction figuring that when reattaching the skin (using the same holes) would have a tendency to pull in back towards the h-stab. It did as expected after I clecoed the skin but did leave enough of a gap (3/32″) to resolve the problem.

From here all there was to do was to re-rivet the skins. This went pretty quickly thanks to the pneumatic squeezer I got from Cleveland Aircraft Tool. (I also got a t-shirt but this didn’t materially affect the process.)

Happy with my work on the right elevator I took the night off and tackled the left elevator the next morning. Oddly, even though I now understood the process it still took me about the same time to finish. Here’s a gratuitous time lapse of me drilling out the rivets:

IF ONLY IT TOOK THIS LONG

In the end, I spent almost 10 hours correcting an issue that should have been done right in the first place. Happy days!

Elevator Pushrod

With the elevators themselves in limbo, I decided to move on to the elevator pushrod. In theory this is a straightforward step. You trim a piece of aluminum tube to length and then rivet in threaded inserts on each end. The aluminum tube is deceptively light and you wonder how it handles the stresses of control inputs. Of course, like an aluminum can, as long as it isn’t deformed in any way it has tremendous longitudinal strength. That means don’t dent it!

Second, you want to make sure to get the finished length correct. This is particular important with a piece like this one since, at 6+ feet in length, if you cut it short you’ll be paying as much for shipping as for a replacement piece. To complicate matters I had just broken my bandsaw blade and so needed to go “old school” with a hacksaw.

As is good practice whenever working with aluminum I measured the correct distance but then cut the tube slightly longer. I then set up some blocks on an adjacent workbench level with my sander. This would allow me to sand off the excess aluminum (being careful not to overheat it) until I had the specified length.

ROUGH CUT A BIT LONG
SET UP A LEVEL BRACE
CAREFULLY GRIND TO LENGTH

This ended up working very nicely. I measured several times as I was getting close to my mark and sanded a bit more until I had a perfect length (or at least as perfect as a my tape measure). You can see this in action here:

After sanding the pushrod to length the next step is to drill six equidistant holes for blind rivets. The plans provide an easy way to do this–cut a strip of paper that matches the circumference of the tube, mark the hole locations, then wrap it around the pushrod. It worked a treat! Now just measure the edge offset and drill #30 holes through the pushrod and insert.

DON’T FORGET TO MAKE ALIGNMENT MARKS TO EASE REASSEMBLY!

As you may have noticed, the previous builder dispensed with primer on the interior surfaces. Again, I won’t get into the endless debate here. Van’s is typically indifferent but does recommend priming the inside of the pushrod tube since, once it’s rivetted, you have no way to inspect it. I took their advice and sprayed some self-etching primer in both ends. It was a bit difficult to confirm coverage but spray was coming out the opposite end and there was enough accumulation to swirl around the inside.

Additionally I thought the outside would just look nicer with a smooth coat of primer so I scuffed it with Scotchbrite (probably not needed with self-etching primer but did anyway) and cleaned with acetone. To get a consistent coat I fashioned some simple hangers from 1×2 redwood and nails clamped to a shelf protected with plastic. I got some drips at first but quickly realized they were being caused by ill-fitting nitrile gloves hanging over the nozzle. A quick adjustment and the priming was done.

After a few days of curing there was nothing left to do but make use of my new Ace Hardware rivet pulled and attach the threaded inserts, followed by some rod end bearings.

Elevator Attach and…Whoa!

Many builders look forward to the moment when, after months of diligent and careful work assembling numerous subcomponents, you get to Section 11. The title of the this section is brief and to the point: Empennage Attach. Like all sections, it begins with an overview diagram that conveys what you will accomplish by the end. The image associated with Section 11 tells the story. You will now assemble those numerous components into something resembling a real airplane (at least if you stand at the F-1006 bulkhead looking aft and squint your eyes). I feel kind of bad that this is one of my first tasks as the new kit owner and that the previous one won’t get to witness it (but don’t worry, I’ll get over it 😁).

One of the first steps is to attach the elevators to the horizontal stabilizer. Each is first attached by two rod end bearings secured with AN6 bolts, then you drill through the (very important) control horns, at which point both elevators are tied in to a common attach point. I was sweating this step because once you drill through the steel control horns you are, as they say, committed (in terms of geometry). Anyone who has worked with door hinges know that with two attach points you can get away with a little imprecision but with three everything needs to be lined up pretty closely. Such as it is with an RV-10 elevator. You are committing almost 11 feet of painstakingly and lovingly rivetted aluminum to two 1/4″ holes drilled using nothing but the central bearing as a guide. Screw this up and you will forever feel whatever wonkiness you’ve introduced in the control stick. Eek!

Fortunately I time to contemplate this most significant hole drilling exercise as the E-drill bushing (which is used to protect the central bearing from the nastiness of the drill) could not be located in the purchased kit inventory. Another order to Van’s and waiting for USPS was in order.

After the bushing arrived I decided it was time to forge ahead, the first step being to secure the horizontal stabilizer to a workbench “just so”. You position it so that the elevators hang over the edge of the workbench–all the better to test their range of motion.

The next step involves setting the offset distance of the rod end bearings to a specific measurement (7/8″), attaching each elevator, checking the edge clearances, and adjusting the bearing distances as needed. No problem!

Before I go on I want to point out that whomever decided to put rod end bearings in such a tight location (recessed inside the elevator skins) and expected someone to be able to adequately manipulate them must have been a masochist. After several clumsy attempts to adjust them using “off the shelf” tools (and mucking up the bearings in the process) I decided to search for a better option. I did find one–a custom tool for sale on line–but not wanting to (a) lay out more cash for a finished product and (b) endure the inevitable shipping delay. I decided to fabricate my own based on what I saw. So it was back in the truck and off to Lowe’s for raw materials.

One thing that has always appealed to me about the building process is that it will inevitably involve solving problems. (Keep than in mind–it becomes relevant again later in this post.) I do truly enjoy the process of being presented with a problem and having to stare, contemplate, theorize, diagram, experiment and (eventually) solve the riddle. For this particular conundrum I decided to fall back to my woodworking and plumbing experience and fabricate a tool that would do the job. It consisted of a plug made from an oak dowel (shaped using my drill press and small milling vise) and some PVC pipe.

With a handy new tool in, um, hand, I set about to satisfy the plans instructions regarding attaching the elevators. That’s when I had my first (only?) really big “WTF” moment thus far.

I was feeling pretty clever after figuring out how to support the port elevator so I could insert the AN6 bolts into each bracket, securing the rod end bearings into place, without assistance. Then, given the precision of modern, CNC-punched parts that Van’s produces, I expected to quickly confirm that the gap between the elevator end rib and horizontal stabilizer was a consistent 1/8″ as the plans specified. Well, not only was the gap not consistent, the forward tip of the end rib was actually binding on the h-stab. (As I said, WTF?!)

I won’t relay all of the thoughts that raced through my head at that moment (as some of them are not appropriate for a family audience) but suffice it to say I did pause and stare at the situation in front of me for some time as the stages of grief started to set in. The first phase, of course, is denial, as in, “wait, that can’t possible be happening.” I checked the plans and my work and indeed confirmed that the tip was binding. This quickly gave way to anger and several more curse words were uttered. Then the bargaining began. If only I adjusted this a little here and that a little there the maybe, just maybe…no. Actually I did get the tip to stop binding by backing the outboard rod end bearing out of its mount until it was hanging by just a couple threads but that didn’t seem like a structurally sound solution. After several iterations taking the elevator off, making adjustments, and putting it back on to no avail, depression set in.

Not ready for acceptance just yet I decided to try fitting the starboard elevator. Surely this was an isolated problem–or maybe I’d just misread the plans–and the second elevator would reveal the error of my ways. You can probably guess the result. It was a mirror image of the first elevator, if not worse. What was going on here?

DISTORTIONS IN THE SKIN ARE HIDING MY TEARS

I took a carpenter’s square and lined it up with the centers of rivets on the elevator’s longitudinal axis and attempted to also align it with the rivets on the end rib/counterweight skin. If you look closely at the images above you can see that, while the longitudinal rivets are perfectly aligned, the end rib rivets are askew, progressively getting worse as you go forward.

I shot off an email to Van’s and their response was, paraphrasing, “unpossible”. Well, yes, I agreed. If you follow the plans and align the pre-punched holes this should not be possible. We discussed potential ways to affect a fix, including longer rod end bearings and grinding down the edges. Neither seemed workable for various reasons.

Going back and reviewing the plans related to fabrication of the end ribs I noticed that it is up to the builder to straighten the ribs using fluting pliers. The skin is then clecoed to the ribs and the holes are match drilled. I speculated that the ribs might not have been completely straight and, after clecoing, might have put some sort of tension on the skins such that they developed a small deformation. Match drilling and riveting the skins locked this in. If you follow the plan’s assembly sequence you build up the entire elevator before fitting it to the h-stab so it’s possible the previous builder didn’t catch the problem.

So, what to do? I think the best solution is to drill out all the rivets that attach the counterbalance skin, remove the skin, and attempt to straighten the ribs, re-attaching the skins after that. This will likely involve replacing the skins since the existing holes would not align completely. Before committing to this course of action I decided to reach out to by build instructor Troy (who is also an EAA Technical Counselor) to get his opinion. I’m still waiting for him to take a look so, until then, this part of the build is on hold. Problem solving indeed!

UPDATE: Finally decided to forge ahead and try fixing the elevators.