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?

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.