Empennage

Not exactly the most productive day.  I was out pretty late at a concert, the band of a former coworker of mine. (shameless plug for Atlantans…Seven Handle Circus, AWESOME)  So after getting home about 2 AM, I slept in pretty good.  Finally got out in the garage around midday.

The instructions for riveting the trim tab are kind of vague, and there’s sort of a lot going on here as well for such a small piece.  I did a fair amount of research on handling all the riveting tasks here, and thought I had a pretty good handle on things.  Even though the instructions call for riveting the lower flange of the spar on first, I knew that doing so would really limit access inside the tab, which I needed to rivet the control horns on.  Actually, I don’t think the instructions ever literally tell you when to rivet the horns on.  So I decided to rivet the horns first, before the spar. (of course, I omitted the forwardmost rivet on each half, since it goes through the spar as well)  This wasn’t much of a problem with the no-hole yoke, but since I have the 3″ and not the 4″, I didn’t have any way to reach the aftmost rivet on the longer horn half.  I tried to come up with some creative ideas, but eventually I just relented and used a blind rivet there.

OK, now for the spar itself…this spar is a bit odd, since the upper flange points forward, while the lower points aft.  Kind of limits access to the rivets there, but I thought I had a good handle on this.  Research indicated that these could be back riveted, and I just figured I’d do that…until I actually was looking at my piece.  I felt like i had to pull way too hard on the skin to get it out of the way for back riveting.  I don’t want to bugger up my trailing edge bend.

That left me with limited options.  The spar is too large to get in there with any of my squeezers.  I suppose I could have bucked the rivets, but there’s no good way I’ve found to clamp the unfinished tab down steady enough for that.  Finally, I hit on a possible solution.  Back when I did the Sportair workshop, we actually did some rivet setting using the C-frame, albeit only with 470 rivets.  Pretty simple, just put the work under the C-frame and bang on it to set the shop head.  And getting the C-frame shaft in there required less skin pulling than the back rivet set, since it was thinner.

Seeing as how I hadn’t done this in a long time, and never with flush head rivets, the prudent thing to do was to practice first, so I grabbed a piece of scrap and drilled and dimpled a few holes.  I taped the rivets in place like I was back riveting, got Josie to hold the assembly in place under the C-frame, and started banging with the dead blow hammer.  A little at first…then harder…harder…this rivet really doesn’t want to set, odd.  I stopped to examine the work and found a problem: the manufactured head of the rivet was not sitting flush in the dimple.  I guess this is why the back rivet set has that spring-loaded collar, to hold the work against the plate and keep the flush head from ending up proud.

So I decided this technique was not a good idea.  Better to get a longeron yoke for my Main Squeeze and do it right…I probably could have borrowed one, maybe from Daniel, but I’ll undoubtedly need one again, so I went ahead and ordered one for myself.  Besides, I feel like there should be some kind of minimum waiting period before I bother Daniel again.  Oh well…I’m on hold until that comes in later this week.

I didn’t even take any photos today.

It finally happened: I had to borrow a tool.  Last time out, I found that I was going to nee a longeron yoke to get the lower trim tab spar rivets squeezed.  I went ahead and ordered one last Sunday night, but I unwisely decided to go with an unfamiliar supplier, because they were a good bit cheaper than my usual destinations. (Avery and Cleaveland)  Well, that turned out to be an unwise decision…when I’d gotten no ship notification or anything after a few days, I called the place and found that the yoke was on backorder…until APRIL.  So I cancelled that order, and learned my lesson about not going with trusted suppliers.

Unfortunately, that left me unable to work on the tab for yet another weekend…until my good friend, flight instructor, and RV-7A builder Scott Will offered to loan me his longeron yoke.  Didn’t have to ask me twice.

Josie and I had a brunch thing today, and then I found myself attacked by a very persistent nap urge afterwards, so I didn’t get out in the garage until late afternoon.  While we were out, we stopped by Harbor Freight; I wanted to get some storage bins for rivets, because I’m not really liking the little drawer unit I’m using now.  While I was there, I also picked up some little tackle-box-type bins, which I intended to use to arrange my drill bit drawer in the tool chest.  That drawer was in horrible need of attention; I’d just sort of tossed everything vaguely drill-related in there since I got the chest, and the disorder was annoying even me. (and I’m one of those cluttered-desk-is-a-sign-of-genuis types)

The old clutter:

Newly organized:

I decided not to move my rivets and such to the new bins, since I’ll very shortly be getting a large quantity of hardware, which might affect how I want to organize it.  So I moved on to the trim tab.  As expected, the longeron yoke was perfect for the lower spar web.  The only real difficulty was figuring out how to clamp the tab down and keep the skin spread so I could get in there with the squeezer.  Once I figured that out, though, things went quickly.  I also found a good use for a little inspection mirror I had lying around…can’t really see those rivets on the bottom otherwise, much less take photos of them:

Next up, the other half of the hinge has to be drilled to the elevator.  So the trim tab has to be aligned properly with the hinge in place, then the elevator half gets drilled.  I used a piece of angle aluminum I picked up at Home Depot to serve as a nice straightedge along the trailing edge of the elevator and trim tab. (I was having so much fun I forgot to take a picture of this setup)  Then I had a bit of a problem…with the trim tab in place, it’s only possible to clamp the hinge half to the elevator on one end.  I didn’t want to mark the hinge half, pull everything apart, and then drill, because I could see that ending up with the tab being aligned badly.  So I decided to do the drilling with the tab still in place.  I clamped the hinge half at the accessible root end, then went down the line, drilling a hole, then clecoing that hole before moving along.  In this way I got the trailing edge alignment to look very nice.  Finally, I drilled the holes to hold the bent ears on the root end together.

Everything clecoed together:

FInally, it was time to start riveting.  But there’s a bit of a gotcha in the instructions here: They have you carefully align the trim tab and the elevator with everything clecoed in place, then the very next step is to set the rivets in the top web of the trim tab spar.  Problem is, the holed in the tab ends take countersunk blind rivets…so those holes need to be dimpled.  Good luck figuring out a way to do that after you’ve riveted the spar!  So I removed the clecos in the top web, dimpled the blind rivet holes, and then once again temporarily mounted the trim tab to the elevator.  Once I’d gotten the twist right, I went ahead and set the blind rivets in the root end first.  Then I removed the tab and set the solid rivets in the spar.  Very nice.  That just left setting the last rivets in the elevator, for the hinge half I’d drilled earlier.  No problem there.

That would have been a good stopping point for the evening, but I had to do one of those “pointless-yet-enjoyable” things first.  I wanted to get the whole trim system in place and do a test run of the trim motor, so I could watch the trim tab move.  Not strictly necessary right now, but ultimately lots of fun.

Josie got a picture of me running the trim motor:

And I took a short video of the tab moving, and added some music for humorous effect.  I get the idea from watching this video that the reflective aluminum really confuses the autofocus on my camera:

I’m coming down to the end of useful work on the tail.  With the completion of riveting the left elevator on Sunday, the next big task is to roll the leading edge of both elevators.  Since the left one was already down on the table (as opposed to the right one, which is hanging from the rafters), it was a logical candidate to get the rolling treatment first.

I’ve done this task before, on the rudder, so I wasn’t really expecting a lot of drama.  A lot of people stress over the leading edge roll, but I don’t recall the rudder being a huge problem, and my blog entry seems to confirm that.  I did actually have some issues tonight though.  I had a lot of trouble getting things rolled properly at the tip end; it seemed like I really needed a smaller-diameter pipe to get a tight enough bend there.  I ended up getting things as tight as I could manage with the pipe, and then doing a large amount of “massaging” by hand.  This “massaging,” for the record, is an operation fraught with peril.  Trying to bend the skins by hand introduces a lot of inconsistencies in the bend, and then it takes a lot more massaging to undo the problems caused by the previous bouts of massaging.

Here I am doing some “massaging”:

The section between the two rod end cutouts was, by far, the most problematic.  I must have clecoed and unclecoed that assembly six or seven times before I was satisfied enough to rivet the thing.  It’s still not perfect, and the skin bulges up a touch between the rivets, but not enough to be a problem.  Luckily, this seam will be completely hidden from view once the plane is together, so it’s not really  big cosmetic concern.

Finished leading edge:

I had kind of hoped I might get both leading edges rolled tonight, but all that trial-and-error work ate the night up fast.  That’s OK, I’ve got plenty of time this weekend; once I get the other leading edge rolled, I can hang the elevators on the h-stab, get everything aligned properly, and drill the control horns for the center pivot mount.  I’m also considering some different storage ideas for the completed empennage; I’d have to take the elevators back off to hang it overhead again, which seems like a waste of work.  Who knows…there might end up being some new and interesting decorations in the house soon.

Whew.  This post actually covers work done on two days.  I got quite a bit done Sunday, but wasn’t able to get anything written up that night.  I managed to get a little time in this evening as well, and get the elevators hung. (Well, mostly.  Still have to do the center bearing.)

Sunday started off with rolling the leading edge of the right elevator.  Mindful of the problems I’d had with the left one, I picked up a smaller diameter section of pipe to use for doing the (smaller) outboard part of the roll.  I used nothing but a 3/4″ pipe on the rudder, but I found it impossible to get the elevator skins bent sufficiently with it, hence the large amount of massaging involved.  This time, I used the new 1/2″ pipe to roll the outboard two sections, and it came out far, far better.  Actually, I rolled the furthest outboard section a little too much, and had to pull it back out a bit to get everything lined up.  In the end, it all worked out, and without so much of the trial-and-error I had to do with the left elevator.

The next thing to do was to start working on getting the elevators hung, but first I needed a couple of tools.  First was an improvised rod-end bearing tool made using PVC pipe sections.  This makes it easy to install the rod ends that the elevators hinge on without marring them.  Second was a set of temporary pins to use when hanging the elevators.  These hinge pins eventually go together with bolts and nuts, but getting those in is a pain – the temporary pins are much easier to use until everything is finalized.

Tools:

With those done, I got up on the ladder and pulled down the H-stab, which had been hanging in the rafters since…looks like August. (Really? Six months?!?! Wow.) With it on the bench, I was all set to hang an elevator!  Or so I thought…first thing I noticed was that my nifty hinge pins didn’t even fit in the holes!  I’d turned the tips of them down enough that they’d go into a rod-end, but not the hinges…but seeing as how the hinge brackets are powdercoated, it’s not surprising the holes are undersize.  Turns out the bolts that will eventually hold things together wouldn’t fit either.  So I got out the drill and reamed them out to the proper size such that the bolts would fit securely.  Still, my pins wouldn’t fit, so I ended up having to redo them to get the tips small enough to slide in easily.

Josie got a photo of me test-fitting a pin after turning the tip down for about the third time:

Finally, they fit!  And soon enough, I had the left elevator sitting in place, held by those lovely homemade pins.  Thing was, it couldn’t move…I neglected to get a picture of this, but the H-stab skins actually overlapped the elevator counterweight skins by a bit; these would need to be trimmed eventually.  The next step, according to the instructions, is to drill the hole in the control horn to match the center bearing.  But here I had a dilemma…the elevator is supposed to be clamped in place in trail before drilling this.  The overlapping H-stab skins do a good job of this, and I’d seen folks on VAF recommend letting them hold the elevators in place for the control horn drilling operation.

I, however, have an issue with this approach.  Until those H-stab skins are trimmed, you have no way of moving the elevators and ensuring that they have the correct amount of travel and don’t bind or rub or anything.  I wasn’t comfortable just hoping that they’d be OK…so even though it sort of meant more work, I trimmed the H-stab skins first.  To do this, I marked a point where the counterweight skin ended.  Then, after removing the elevator, I figured out the proper place to drill a #12 hole where the corner of the trim needed to be.  Corners like this need to be radiused, so drilling a hole to start with is a good way to take care of that problem.  Then I used a cutoff wheel in the Dremel to make the rough cuts, cleaned the cuts up with a cutting bit in the Dremel, followed with a file to smooth everything out, and finally deburred all the edges.  I was a little nervous about cutting the skin, but everything went great.

Here’s my first trim, completed:

Of course, I had to repeat that task on the top of that end of the stab. (It’s upside-down in the photo, so the first trim I did was on the bottom)  Then I had to hang ghe right elevator, mark that skin, and trim those two corners as well.

The bottom of the H-stab spar also needs to be trimmed to allow clearance for the elevator control horns.  I marked the edges of the horns while each elevator was mounted, and after finishing the skin trims, this was the next task.  Cutting this made me very nervous.  There is a very serious-sounding warning about not taking any material off the spar reinforcement bars.  Oh, and the center bearing brackets are in there as well.  So there’s plenty of stuff available to foul up if something goes wrong.

I used the same basic technique as with the skin trims: drill #12 holes for the corner radii, then use the Dremel to make the initial cuts and clean them up.  I decided to be pretty conservative about the spar flange trim, to make absolutely sure I didn’t hit the reinforcement with the drill bit.  Then I was very careful with the cutoff wheel, especially while I was working near the bearing bracket.  I still managed to take a bit of powdercoat off the brackets though…must have just barely rubbed them.  There doesn’t seem to be any actual metal removed, so I’ll just need to touch these areas up with a bit of primer.

Whew!  Now I could hang each elevator and check it for proper travel.  Lefty got first dibs here, and I was pleased that it exceeded the specs with no problem.  I was ready to drill the control horn for the center bearing!  But wait…I put the drill bushing and bit in place, and it was obvious something was wrong.  If I’d drilled the way things were, the hole would be so far back on the horn that it would actually interfere with the tube portion by the time I had it the full size of 1/4″.  I was quite puzzled, especially since I’d triple-checked that the rod ends were set to spec.

After going in for some research, I went back out to look at how the counterweight skins lined up with the ends of the stab.  Presto!  They weren’t parallel.  Seems the root end of the elevator needed to come back a bit to get them aligned.  This would also move the horn aft and hopefully take care of the problem with the center bearing hole.  I dredged up some high-school trig skills and worked out how much I needed to move the rod end to get things lined up.  I was hoping to avoid doing a bunch of trial-and-error for the alignment…and it worked!  First try repositioning the rod end, I hung the elevator again and the alignment was perfect.  Score!

Of course, this meant that I needed to check the elevator travel again.  I didn’t expect my adjustments to cause any problems here, but I wanted to make absolutely sure.  That turned out OK, so I inserted the drill bushing and the bit and now the hole location looked great, so I drilled the pilot hole. (My drill bushing fits a #21 bit; this pilot hole is later enlarged to the final size of 1/4″)  I repeated this whole process on the right elevator; it also needed a bit of adjustment on the rod ends for alignment, and then I got that pilot hole drilled as well.  Finally, with both elevators off, I drilled the control horn holes to 1/4″.

There were a couple of housekeeping tasks to take care of next – torquing the lock nuts for the rod ends, adding torque seal to those as well as the bolts holding the elevator center bearing.  Finally, it was time to hang the elevators for real.  Let’s just say that installing those bolts and nuts is no fun at all.  There’s very limited access to the rod ends, and there may have been a few naughty words thrown about as I repeatedly dropped washers and nuts while trying to get everything started.  Then there was a lot of tedious wrenching – you can only turn the wrench about 1/12th of a turn at a time, so it takes a bit of work to get everything tightened down, but eventually got them done.

All that’s left is to get the center bearing done.  The instruction say to use stacked washers here,which looks like a pain to get right.  Getting the thickness of these spacers right is essential to having good elevator movement with no binding.  One of the well-known DARs on VAF recommends fabricating your own spacers here instead of stacking washers, and I think that’s what I’m going to do.  I picked up some spacers to cut down a few days ago, but had decided the washers would be better until I saw how tight it was between the horns and the bearing.  Better to maneuver one spacer in there than a series of washers.

That will be a task for another night though.  Maybe tomorrow night, we’ll see…I’m feeling on a roll right now and I really want the satisfaction of having all the hinge points torqued down so I can see if my elevators swing freely.  I’ve seen where some guys have spent a lot of time on these, so I predict a strong sense of satisfaction if I get it right off the bat.

I managed to make it out into the shop for short while Tuesday night.  I had a couple of things on my to-do list for the night: Fabricate spacers for the center bearing, and clean some of the well-embedded sweaty hand stains from the skins, especially on the h-stab from before I made a habit of wiping the skins down with acetone after every work period.

The spacers turned out to be a bust.  I’d previously picked up a couple pieces of 1/4″ ID steel spacer stock.  The first problem was figuring out what thickness they needed to be for each side of the horns.  There’s too much stuff in the way to just get the calipers in there, so that’s out.  I ended up sort of eyeballing the calipers against the gap and using that as a starting point.  I made the initial rough cut by chucking the spacer in a drill and spinning it against a hacksaw blade clamped in the vise.  This gave me a nice straight cut, though it was messy and needed a good amount of cleanup.  I chucked the cut piece in the drill and spun it while going to work with a file.

A quick check showed that it was a good bit to thick, and this is where the spacer fabrication procedure got ugly.  I couldn’t figure out a good way to carefully trim down the spacer.  I tried spinning it in the drill while hitting it with a file, but that was going extremely slow, and it would have taken forever to get the size right.  So I unwisely went to work on the spacer with the bench grinder.  That got the amount of material I needed off quickly, but now the ground end was no longer square.  I tried to fix that by spinning it in the drill again and working with a file, but that didn’t go well either.  Finally I decided to put the spacers aside and move on to cleaning the skins.

The basic problem here involved skin oils, and sweat in particular, getting on the skins.  Some time back, I set aside a skin for a few weeks, and when I picked it up again I could see where the alclad was marred in some suspiciously hand-shaped patterns.  Some work with a rag and acetone cleaned things up a bit, but it was obvious that the sweat had done damage.  From that point on I made a point of always wiping down any skins after I’d been working on them.  Even that isn’t a perfect solution; it tends to leave ugly streaks on the skins that are better than sweat corrosion, but still ugly.  In any case, I hadn’t learned this lesson when I was building the h-stab, and it had some pretty ugly spots.  Besides the cosmetic issue – which is easily discounted by the old “the paint will cover that up” line – I was worried that corrosion might continue as the stab sat in storage.

So after going to the VAF brain trust, I found a simple answer: aluminum polish.  On the way home from work, I stopped by the auto parts store and secured a can of Mothers aluminum polish and some bonnets for my orbital buffer.  A good attack of the skins finished with a vast improvement.  There are still some light scratches and marred spots, but the bad sweat corrosion spots are gone, and things look great again!

This procedure probably wasn’t really necessary, but it made me feel better and only cost about an hour and a half of my life.  I can deal with that.

As for the spacers, I’ve decided to get some aluminum pieces to use instead of steel; those will be a lot easier to massage to the proper size.  I also figured out a good way to measure the gap for the spacers: I have a set of feeler gauges out in the garage somewhere.  They should be long enough to get into the gap, and I can stack them until they fill the gap, and then use the calipers to get a proper measurement of the gap. (or just transfer the measurement directly to my spacer stock, we’ll see)

Today I stopped at no less than three Ace Hardware stores, trying to find aluminum spacers for my elevator center bearing.  I knew they had them at the Ace I went to over the weekend, where I got the pieces to make my drill bushing.  I just figured – quite incorrectly, as it turns out – that it was just something I could find at any old Ace.  Wrong.  I found one near my office and went there over lunch.  No aluminum spacers.  I considered calling around to find a convenient store that might have them, but in the end I decided to just go where I knew they were.  Unfortunately this meant sitting in lots of annoying traffic…and I was in said traffic when I spotted an Ace (not the one I was going to) in a strip mall.  I pulled in there, hoping for success…nope.  And now I had to get back out into traffic, ARGH.  Finally I got to the third Ace, got what I needed, and headed on home.

My idea of using feeler gauges worked great.  I stacked them until I’d filled the gap, then used the calipers to get the dimensions and set a “reference,” and went to town on spacer #1.  This time I used the bandsaw to make the first rough cut, then used the file followed by emery cloth to get the piece to where it would just fit into the gap.  Perfect!  I repeated the process for the second spacer, and I was feeling good about the night’s work!

Now I just needed to install the bolt through the horns, spacers, and center bearing, tighten it in place, and check again for free movement of the elevators.  And that was pretty much how I thought of the task, in a trivial way.  “Oh, let me just install this bolt real quick, no worries.”  What a chore that turned out to be.  See, the holes in the control horns are pretty close to the tube sections that ties into the elevators themselves.  As such, the bolt head and nut were both very close to this, to the point that neither a socket or box-end wrench would fit on it.  And then there’s the h-stab spar in the way as well.  Basically, I couldn’t get any kind of normal wrench on this thing.  I tried a few weird ideas, but none of them worked very well.

Frustration:

Finally, I gave up and decided to make a new tool by destroying an existing tool.  I had an extra 7/16 wrench lying around, quite eligible for sacrificing to the kit plane cause.  I held it in place near the nut, marked a cut line that would make it short enough to work around the spar, and went to town with the hacksaw.  A follow-up on the bench grinder to smooth the edges, and I had myself a nice homebrew stubby wrench.  It worked great, and I had the nut torqued in no time. (Luckily these smaller bolts don’t require a lot of torque, which would have been difficult to deliver with the stubby wrench)

New tool:

Now that all the attach points were tight, it was time to unclamp the elevators and check for binding.  Those spacers are essential here; if they’re too small, torquing the center bearing will put a side load on the rod ends and prevent free movement.  My elevator, however, swung freely.  I couldn’t even tell a difference from before I had the center bearing in place.  It was also cool to see both elevators move in unison.

This pretty much makes the horizontal ready to be stored somewhere until such time as it’s mated to the fuselage.  I installed the the trim tab and motor just for the sake of keeping everything together, and then decided to move on to the vertical.  First, I pulled the rudder down.  I’d sort of hung it briefly before just for fun, and tried to set the rod end depths correctly, but I only had an analog caliper then, which made me suspicious of my measurements.  So I started by check the rod ends with my new digital caliper – they were pretty close, but I did end up adjusting two of them, just by one turn each.

After pulling the v-stab down and looking at both parts, I decided they should get the same cleaning treatment I gave the horizontal last night, so I went to work with the aluminum polish again and got them all shiny.  Then it was time to try and hang the rudder.  This is a good bit tougher than the elevators; with those, there are only two hinge points to line up, but the rudder has three.  I’d say that the difficulty increases by more than 50%.  I was, however, able to get them in and the pins in place, but it was difficult.  I started to put the bolts in, but had ever more difficulty with that; eventually I decided that maybe I needed to tweak the rod ends a bit.  With three of them, alignment becomes more of a problem than with the elevators.

Once I took the rudder off, it occurred to me that an easy check would be to try and sight down through the rod ends for alignment.  Sure enough, I couldn’t get a good line of sight down all three.  I ended up threading the bottom one out a turn, and the middle one in a turn, and then I could see very well down all three.  I wanted to try hanging it again to check, but it was after 11 by this time and definitely going on bedtime, so I called it a night and went in.

I figure tomorrow I can hang the rudder, set the vertical assembly on top of the horizontal for a photo op, and then figure out where I’m going to store these things.  I have a bare wall in the dining room that’s just the right size for the horizontal.  I’m not sure about the vertical though, both in terms of where and how to hang it.  Guess I’ll have to figure it out soon…

I guess this pretty much brings work on the tail to a close for now.  I could start work on the fiberglass tips, but I don’t have any of the materials or anything.  I’m just going to save that for when I’m in fiberglass mode way down the road.  I really only had one simple goal tonight: to get the rudder hung.  That turned out to be kind of an exercise in frustration, just because it took a lot of trial-and-error to get things lined up properly.

Last night, I thought I’d found a useful solution by sighting through the rod end holes to verify their alignment.  But the first time I slipped the rudder into place today, it was clear the alignment was still not correct.  Turns out the hinge points on the v-stab aren’t exactly in line, so the rod ends on the rudder had to be moved to account for this.  To make a long story short, it took probably eight or nine trial runs before I finally got things to line up.  And of course, even when I did get the alignment right, I still had to pull the rudder one more time to torque the jam nuts in place and apply torque seal.  Only then did I get to install it for the last time. (for now, at least)  I made sure to stand the assembly up and check the rudder for free movement and no binding before adding and tightening the nuts.  A good wipedown to get rid of fingerprints, and…that’s it!

Of course, there had to be some photo ops with this thing.

I feel kind of lost now with nothing to work on.  Although I do still have to figure out storage for this stuff.  I’ve got a place for the horizontal assembly, but I have no idea yet how to stash the vertical.  In the meantime, I’ve got to find myself a new car, since mine got wrecked this past week.  And there’s some other stuff around the house I can be catching up on.  I figure my wings should be here in about three weeks.  I also am planning on doing a semi-scientific rattle-can primer shootout when I finally get a weekend with nice weather.

OK, again not a lot got done tonight. What was supposed to be a quick adjustment to the riding mower ended in a stripped bolt and general annoyance, but even though I wanted to go inside and mope, I decided to still do something on the plane. (also, this would not be the end of frustration tonight…more on that later)

While I didn’t log anything as useful work last night, I did spend some time tidying up a workbench, dismounting the vise, and moving away the tool cabinets I usually have beside it – this was all in preparation for bringing the horizontal stab down off the wall. The time to fit it to the fuselage is upon me, but before I do that, there’s a service bulletin to be dealt with. This involves adding some reinforcement to the forward spar of the stab, where cracking has been observed in some aircraft. It’s not required that the repair be done unless cracks are observed, but it seems prudent to me to do it now as preventative maintenance.

Anyway, last night wrapped with me bringing the stab down to the bench, ready for work to start. Tonight I began by removing the elevators – which I’d just been storing installed on the stab. First, I removed the AN4 bolt through the center bearing. This bolt runs through that bearing and each elevate control horn. It’s important to be careful removing this bolt; in the space between each control horn and the center bearing is a handmade spacer, sized carefully to exactly fill the gap and prevent binding of the surfaces. So I carefully removed the bolt, placed the spacers back on it in the correct portion and orientation, and made sure to mark which side of the airplane the bolt head should go to.

Next up are the two outboard pivot bolts for each elevator. Nothing too horrible here, though access to these things is a bit obnoxious. But I got all four off, removed the elevators, and set them aside. OK, now to just put these four AN3 pivot bolt/nut/washer combos with that AN4 assembly I removed earlier…hmmm…uhh, where did that go?

And this is the other frustration of the night. I looked for that stupid bolt/but/washer/spacer assemblly for half an hour, to no avail. I don’t even understand how I could have possibly lost it. At no point between the time I marked it and the time I finished removing the elevators was I outside of about a ten-for circle. There just aren’t that many places I could have physically put it.

But…I never found it. Even after going inside, sitting for a bit, and then going back with a hopefully-clearer mind.

So I guess either it’ll magically turn up, or I’ll get to repeat the exercise of fabricating those spacers. Probably have to order another AN4 bolt, pretty sure it was a unique length that I only had one of. Which is also annoying since I just placed an order with Spruce for some assorted stuff.

Oh well. I guess tomorrow I’ll see if I can get going on actual SB work.

Back at it again! Before I got to actual plane work tonight, I had a goodie box from Aircraft Spruce waiting for me at home. There was only one thing (well, four things) in there I really needed – four longer AN3 bolts to properly assemble the throttle. I also bought a bunch of AN3 nylock nuts and washers, just cause it seemed my supply was a little lower than it ought to be. I’ve been trying to keep separate the nuts I use for temporary assemblies, and only use new ones for final assembly, but I think I’ve been going through more than I need to. Technically nylock nuts shouldn’t really be reused at all, since the nylon locking stuff degrades after a while. And lest anyone think this isn’t serious business – the deadly crash at the Reno Air Races a few years back was traced to a nut that had been reused too many times and lost its ability to stay tight.

Anyway, I’ll put that soapbox away…the last thing in the box was the expensive item I added so I could get free shipping. It’s my heated AoA pitot tube from Dynon, and hoo boy is it shiny and fun to look at:

Not going to need that any time soon really, so it’s now sitting on a shelf. Before getting going on the real work for the night, I took those bolts and reassembled the throttle quadrant to its now-painted mount, then added the cover plate just to see what it looked like. I think this turned out pretty well:

I even laid it in the fuselage to see what it would look like in place. Seems decent to me:

That went on a shelf too – I decided not to actually install it in the fuselage, as specified in the manual. I figure I might as well leave it out until I really need it there.

And then it was on to the real work of the night, getting going on the h-stab service bulletin work. At a high level, the work involves removing the inboard ribs, partially disassembling the forward spar, doing the work to add the reinforcements, and then putting everything back together. Tonight I just worked on drilling out all the rivets between the skin and those four ribs.

There’s been no shortage of rivets I’ve drilled out over the course of this project, but they were always in small numbers, just a few at a time. Here, I was removing them en masse, which opened the door to getting careless. Drilling out rivets is precise work, and it’s a lot harder to keep the precision up when you’re doing it 40 or so times. Nevertheless, I got all the rivets out, and there’s only one hole where I think I may have enlarged it slightly.

The ribs are still in place for now – I also have to drill out the rivets attaching them to the spars. That part is going to be tougher; I won’t have great access to the manufactured heads, so I’ll probably have to use an angle drill for them. And there will still be even harder ones once I get to removing the reinforcement angles from the spar – those project into the stab a bit. That’ll be where I’ll have to be really careful not to damage anything.

But anyway, that was all I got done tonight. Hopefully I can get all this SB work knocked out this weekend, and move on to mounting this thing to the fuselage…

Whew. While I’m making decent progress on getting this SB done, it’s proving to be a real drag, and I can say with conviction that I’ll be happy when it’s done.

First up today was drilling out the rivets common between the inboard stab ribs and the spars. These took…some time. Universal head rivets are already a little tricker to drill out than flush ones, since it’s harder to keep the bit centered on the round head, but adding in the limited access made these a lot more fun. Long story short, pretty much each rivet presented its own unique challenge. But I did get them done, and without any apparent damage.

Next up were the rivets between the spar webs and the reinforcement angles. For these, I had better access…sort of. It was easy to get to the forward side of the spar, but that side had the shop heads, not the manufactured heads which is where you normally do the drilling out.

In the end, I decided to drill these rivets out from the shop head side. My reasoning here is that that’s the side where the angles are, and if I’m going to damage a part and need to replace it, I want it to be the reinforcement angles – which I’m removing anyway – and not the actual spars – which would be a royal pain to replace.

I’m not sure if that was a good idea or not, but so far, I’ve managed to not do any real damage. I did slightly enlarge one hole, and I put some semi-deep scratches on one of the angles, but those should be easily removable. But boy, did it ever take a long time to get all these out. Drilling the shop head means there’s no real way to be sure the drill is centered not he rivet shank, so some serious care is in order.

So, at the end of the day, I had all the rivets in the center of the spar removed, which is good news:

The bad news is that, as much trouble as I had getting these rivets out, they’re still comparatively a cakewalk compared to what’s coming. Now I have the sixteen inboard rivets to deal with, which are inside the stab structure:

I’m really torn about whether to drill these out from the angle side (with the shop heads) or the spar side. Access is far tighter on the angle side, which would kind of multiply the difficulty of drilling out from the shop head side. It’d also make it a lot harder to drive out the rivet shanks after drilling them out. But there’s still that whole point of preferring to damage the angles. I’m seriously considering pausing work on this SB and ordering a rivet removal tool from Cleveland. Using that tool makes it easier to be certain of being centered on the shop head, and also prevents drilling too deep. I’ve looked at this tool in the past, but never felt it was necessary…but adding in the limited access and high stakes here is making me think it might be worth it.

Actually, I might ask around a the neighborhood coffee thing tomorrow morning, maybe someone has one of those already and I can borrow it. I know there are a few people out here with some serious tool collections.