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!

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.

This Page Intentionally Left Blank

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.

Elevator Trim Servo Wiring and Test

HAPPY NEW YEAR, EVERYONE!!

With much of the tail cone already done by the builder I purchased it from I only a have a few options for things to work on until the next kit arrives (in a few months 😒). In preparation for attaching the tail feathers I decided to work on the elevator trim servo. In particular I wanted to (a) complete a bench test to ensure it works and (b) sort out how I was going to connect the wiring to the eventual fuselage and instrument panel.

The Ray Allen servo setup is pretty straightforward. The kit comes with the servo, a three position switch, and a position indicator display. The wiring diagram is also straightforward–connect the colors as shown.

Since I have previously dabbled in microelectronics I have no shortage of stuff for connecting components like this. One breadboard, a power supply and some hookup wire later…let there be light (emitting diodes)!

I ran the servo through its complete range and after confirming the servo electronics I moved on to the hardware. The first step was to assemble the servo linkage and it was then I ran into my first real aircraft builder decision. The plans call for the three pieces of the linkage hardware to be rivetted together using two AN470AD4-7 rivets but for whatever reason the remaining hardware that came with the kit contained but a single rivet of this specification. Now, being new to this whole every-decision-you-make-could-be-life-or-death thing I sought out some advice from the “hive mind” of RV aircraft building: Van’s Air Force. One respondent suggested I just take a longer rivet and cut it down using a rivet cutter. While I admit it’s a great suggestion I don’t (yet) own a rivet cutter. Not wanted to delay the process by ordering a single rivet to be delivered via USPS during the Christmas crush I decided to use a AN470AD4-8 (just a mere 1/16″ longer than specified). I figured as long I managed to create a good shop head I would be fine. The Cleveland Aircraft Tools “Main Squeeze” rivet squeezer made easy work of that.

PRISTINE PLASTIC COATED
DEBURRED WONDERFULNESS
TWO RIVETS LATER
FIRST THING I EVER RIVETED FOR MY AIRPLANE

The next step was to deburr the trim bellcrank and assemble everything. That’s when I ran into conundrum #2. The bellcrank mounts were too close together and I could not fit all the called-for hardware in the gap between the two angle pieces. With the holes in the F-1095A servo bracket already drilled I decided to drill out the rivets in one of the brackets and fabricate a new one. Fortunately the kit came with some leftover 3/4×3/4 aluminum angle stock and this went pretty quick thanks to band saw, sander and grinder with Scotch-Brite wheel.

MEASURE SIX TIMES…
…CUT ONCE
SHAPE, DEBURR, ADMIRE
EVEN A BUCKING BAR NEEDS SOME SUPPORT
FIRST BUCKED RIVETS!

Because I had all the hardware already out I sorted out the positioning by first drilling the 1/4″ hole for the bellcrank hardware, connected the bellcrank, and then match-drilled the three mounting holes using the holes in the servo mount as a guide. In the end it probably shifted the remade mount outboard about 1/8″ but that was enough for the bellcrank to move freely. Four rivets later (I screwed up one and had to drill it out) and the bellcrank was in business.

At this point I couldn’t help but wire up the whole assembly and watch the bell, er, crank!

I am curious to see how this all goes together since the forward bellcrank attach point dips quite a bit below the bracket and seems like it would interfere but, hey, after all these years I assume someone would have fixed it if it were a problem.

The next step was to create an attach point for the wiring harness I planned to build. I wanted to be able to (somewhat) easily remove the servo assembly as needed and so there needed to be a way to disconnect the wiring running up front. The servo lead wires are pretty short and so you need to route them to a point quite close to the servo. Based on prior art from Mouser I decided to fashion a bracket that would hold a CPC (see below) from .020 aluminum sheet.

I started by fabricating a cardboard template that would provide enough space for the connector and a tab that will be used to rivet the harness mount to the servo mount. I also added flanges to provide stiffness to the part.

I transferred the cardboard dimensions to aluminum and drilled out holes for the connector using a step drill and the mounting holes (not quite getting them aligned straight but, heck, it’s buried in the back of the empennage after all). Then I cut, sanded and deburred the final piece (being careful to drill stress-relief holes at the bend points) and bent the flanges in a vise.

FABRICATING THE WIRING CONNECTOR BRACKET

I then had to decide where on the servo bracket to mount it. It needed to be close to the servo but could not interfere with the mounting screws. I offset it enough to provide clearance and then test fit the entire assembly in the empennage.

With the hardware sorted and connected I moved to how I was going to mount and route the wiring. As I mentioned earlier, I got the ideal to use CPC (Circular Plastic Connectors) from Mouser, and so did some research on them. I liked the fact that they are pretty foolproof and easy to manipulate in tight spaces and so, after shopping around, I ordered a bunch of components from Arrow.com:

Now, all of those components are relatively inexpensive. What’s not inexpensive is the tool needed to crimp these particular connectors. At $200+ it seems like an extravagance at this stage but I see myself using these connectors a lot so I’m sure I’ll recoup my investment over time. (And, by the way, I also got the pin removal tool because I know I will screw something up at some point.) In addition to the specialty bits I also got some wire loom and silicone tape from Amazon and was ready to fabricate a wire hardness.

The first step was to cut the wire loom to length and thread the bare wires through. Of course I failed to recognize this as the first step and went ahead and attached the female sockets. This required carefully unrolling/re-rolling the loom around the wires. Argh…

Before I crimped the wires on the servo I tried practicing with some scrap wire, sacrificing a few connectors in the process. I found it a bit cumbersome to position the wire in the connector in the right way and also hold the two at the right spot in the tool. Also, the tool uses a ratcheting mechanism that doesn’t release until the connector is fully crimped so it’s nigh impossible to correct the alignment if you misalign something. Eventually I discovered that if I closed the tool until the first ratchet position I could maneuver a pin into the correct position and it would stay there. Then I could feed the wire into the open end and finish the crimp. In the end I got all five servo wires crimped without any screw-ups. Time to declare victory and go home!

CLOSE UP THEY LOOK LIKE TINY LIGHTSABER GRIPS

Actually I forged ahead and finished the servo-side wiring by attaching the wire loom and silicone tape, inserting the pins, and attaching the shell clamp.

To finish out the wiring tasks I created a temporary wire harness to use during the install/adjustment process and tested everything on the bench. I only had one brief moment of panic when the servo didn’t work before realizing I’d inserted one of wires into the wrong row on the breadboard!

The final elevator trim task was to finish the E-616-PP trim cable cover plates, to which are rivetted a set of cable brackets. The previous builder had purchased a set of milled cable brackets from iflyrv10.com, but only after match drilling the holes using the stock Van’s brackets so these ended up as scrap. (Actually I ended up using them as #30 countersink guides.) Van’s brackets are nothing more than a nut welded to a piece of steel and if I had built the tail from scratch I would have upgraded as well.

For a reason never fully explained, he had ordered one replacement plate so one of my first orders placed to Van’s was for a second. Since, at that point, I had not transferred the project over to my name I’m sure the folks processing the order were perplexed why a “non-builder” was ordering this very specific part. A few days later I had my part and was ready to complete the step…until I realized I had somehow neglected to include a rivet puller with my tool order. Fortunately this is a non-aircraft specific tool so a trip to the local Ace Hardware store rectified the problem.

The assembly process went pretty quickly. It would have gone faster but it was the first time I got to use my dimpling table so I spent considerable time making sure I had the right dies, adjusting the table height and ensuring I was dimpling on the correct side of the skin.

Now, on to bigger things!