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’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.

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:

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.

First things, first, I have to send out thanks to Daniel Schoning, who came to my rescue and helped me fix my fouled-up hole in the elevator spar from Thursday night.  I’ve sort of talked with Daniel a few times via the VAF forums, and was vaguely aware that he was nearby and working on a -7, but I’d never met him to my knowledge.  Well, when I posted inquiring about options for fixing my mistake, he volunteered his large collection of tools and rivets to help me out.  I started off the morning at the EAA 690 pancake breakfast, where I met Daniel and we chatted a bit before heading over to his house.  True to his word, we had the hole drilled out to #21 and filled with a 5-5 solid rivet in no time.  I also got to get a glimpse into my future; he’s working on his fuel tanks for his wing kit right now, so I spent a bit of time ogling his partially-assembled wings before heading home to get back to work.

Once back in the garage, I set about riveting the skeleton and skin together.  Things were going along quite smoothly when I had one of those thoughts that generally portends bad things.  “I’m sure making good time out here…it would really be annoying if I forgot to do something inside the elevator…”  Of course, mere moments later, it occurred to me that I had, in fact, forgotten something.  The plans call for a dab of RTV to be placed at the trailing edge of each stiffener pair; this is to help tie the stiffeners together and prevent cracking of the trailing edge.  Yep, I forgot all about that.  And at this point, I’d squeezed about 75% of the rivets between the skeleton and skin…that’s a [b]lot[/b] of drilling out.

Before doing anything, I ran back inside and searched the good ship VAF, where I found that (not surprisingly) this is a very common problem.  Several guys had contacted Vans over this mistake and gotten the OK to continue and not stress over it.  The consensus seems to be that the RTV helps make up for a bad trailing edge bend; with a good bend, there should absolutely be no problem.  One builder who is also a DAR has been flying his RV-6 for about 15 years with no RTV…whew, this was good news.  I was not excited at the prospect of drilling out probably 40-50 rivets.

With that issue behind me, the rest of the rivets were squeezed with [b]almost[/b] no problems.  I did use the wrong length rivets for a few holes, and had to drill out those six and replace them, but that was no sweat.  Drilling out rivets doesn’t make me as frightened as it used to.  

The (mostly) finished product:

With that, it was back to the trim tab again.  Not really a lot to do here; all the drilling to the spar is done, so everything came apart to be deburred and dimpled.  The top flange of the spar gets countersunk instead of dimpled since the hinge goes under it.  When I did this countersinking in E-606PP, I had some issues; some research in the meantime helped me to much better this time.  I backed the spar up with a piece of 2×4 scrap in the vise, used plenty of pressure on the drill, and everything came out beautifully.  Then I cleaned the spar and the horn halves, dried them, and went to priming.

Hooray, wet primer:

There really wasn’t a lot else I could do until the priming was done, but I did try to do some research and experimentation on final assembly of the trim tab.  Access to the inside of the thing, particularly riveting the horn halves, is going to be interesting.  The other concern is the blind rivets that hold the bent ears on the ends in.  The plans call for CS4-4 rivets, which are #30 diameter and have a flush head.  So somehow I’m going to have to dimple those ears…but they don’t get drilled until [b]after[/b] the spar is riveted to the lower side of the tab skin, so access will be a problem.  A little testing on scrap indicates to me that the skin is too thin for countersinking…that would have been an easy approach, but noooo.  Maybe the pop rivet dimple dies will work.  I’ll just have to do some research and some more tinkering with scrap tomorrow before I figure out what to do on the real thing.

Ugh.  Well, I guess I was overdue for a not-so-great night of work.  Still, in keeping with my “don’t dwell on the mistake, just move on” attitude, I got plenty of other stuff done even after my foul-up of the night.  More on that later.

After dinner (which gave some time for the space heater to warm things up a touch), I went out and decided to work on the trim servo mount first.  That makes it sound more complicated than it is;  there are just three flush rivets for each mount bracket, for a grand total of six.  I probably could have gotten them with the squeezer, but I decided to back rivet them instead.  That went off without a hitch, and then I got out the screws and bolts and mounted the servo.  Easy enough…I did a quick test fit of the entire assembly into the bottom of the elevator skin, and all looks good.

The finished trim servo assembly:

OK, now on to the skeleton!  I really felt like I was going to have a productive night…in no time at all, I’d riveted the E-705 root rib and the control horn in place, and then I moved to the tip rib.  There are four 470 rivets that attach this rib assembly to the spar.  Two of them are simple to squeeze; they go between the rib web and a flange on the end of the spar, and there’s good access on both sides.  The other two are a bit more of a challenge, as they go from the rib flange to the spar web.  On both sides of the spar web, the rib face is very close, and the flange of the counterweight rib gets in the way on the forward side as well.  No good way to get a squeezer on those.

Obviously, I’d already done this once, on the right elevator.  That time, I used the rivet gun with the double offset set to hit from the aft side, with the bucking bar in the more confined space forward.  I was nervous when I did those, but I took my time and they came out great.  I took the same approach here as well; the first rivet I set was beautiful.  The second, not so much; it folded over a bit, so I carefully drilled it out, with no ill effects to the hole.  On the second try, despite being even more careful to hold the bucking bar square, I folded the shop head even worse.  This time, when I drilled it out, the hole looked slightly elongated; a check with my #30 punch confirmed it.  Argh!

I seriously considered stopping for the night right then and there.  And there was a time that I would have done just that; gone inside and wallowed in my failure, grumbled about ruining parts, blah blah blah.  But it was still pretty early, and I was determined not to end the night on a bad note.  So I sat and considered my options for repair before moving on to drilling the trim tab.

My first inclination is to drill the hole out again and drop a -5 rivet in there.  I need to verify that I can get OK edge distance for that for one thing; moreso, it could possibly just exacerbate the problem.  If I’m having trouble bucking a -4 rivet, a -5 rivet could be even worse and increase my chances for mistakes.  I think an alligator-type pneumatic squeezer might be just the thing for this spot, but I don’t have one and can’t afford to buy one right now.  Maybe I can find someone locally who can lend theirs out for a day.  I’ve also wondered if maybe there’s a good CherryMax type blind rivet I could use here in the larger hole.  End result, I’ve got some research to do, and I’ll of course hit up the VAF brain trust as usual.

So anyway…with that failure behind me, I moved on the the trim tab.  I came up with a good plan for handling the alignment issues while drilling the hinge to the top spar web and skin; basically, after figuring out the proper positioning for the hinge on the tab, I’d mark and drill the first hole in the hinge alone, and also final-drill the corresponding hole in the spar and skin together.  Then, I could put all three together, drop a cleco in that hole, and work gradually from there to keep everything lined up.

I was expecting to have the finished elevator to use while working out the lineup, but I just clecoed the whole thing together for the purposes of working on the tab.  With some creative use of wood blocks, I was able to line everything up and get an idea of the gap between the trim tab and the elevator skin.  I’d read the other night of builders having edge distance issues with the hinge and the elevator, so I wanted to figure out the big picture before drilling everything.  Once I knew the gap between the tab and elevator, I could then figure out how to best position the hinge to avoid edge distance issues.  It’s maybe a bit more work than the instructions call for, but it should prevent future problems when it comes time to put everything together.

So with all that done, I implemented my Grand Hinge Drilling Plan, which worked great.  Then I flipped the tab over and match-drilled the lower spar web to the skin.

That’s pretty much all I could do tonight, plus it was getting close to 11 anyway.  The parts will need to be deburred and I’ll want to prime the spar, but I can do that this weekend.  I don’t want to start final assembly of the tab until the elevator is really done, so that’ll have to wait until I figure out how to handle my buggered-up hole.

The temperature today got up almost to 70, so I just had to take advantage of the weather to get in a bit of work in the garage.  Basically, I had two things on my short list: start riveting the elevator, and prep/prime the trim motor mount angles that I drilled last time out.

First things first: the riblet I fabricated, as well as the inboard portion of the trim cutout spar, have limited access and thus will need to be attached with MK-319BS blind rivets.  These require a slightly larger hole than #40, so I decided to start by drilling those out to size.  This way I could get any nasty metal shavings out of my elevator before closing it up.  I went and grabbed my drawer of MK-319BS rivets, and noticed…well, there aren’t very many in there at all.  Ten, to be exact, and I need…let’s see…eighteen.  Hrm.  Looks like it’s time for another Aircraft Spruce order…I’ll have to wait on those before I can put the elevator together. (I could probably work around some of the holes while I wait, but it seems better to just hold off on the whole thing)

OK, next order of business, the trim motor mounts.  Gave them a good deburring, dimpled for the flush rivets, gave them a good scrubbing, blew the air off, hung them on the front of the heater to fast-dry. (sort of ironic that even on a warm day like this, I found a reason to run the heater)  I went inside to scarf down some dinner and sit with Josie for a bit, and once I went back out, the pieces were nice and dry.  Normally I prime in the driveway, but in this case, since I had just a couple little pieces, I opened the garage door and set up just inside the overhang.  Shooting primer on those pieces was quite easy.

In between primer coats, I riveted the hinge reinforcements and nutplates to the spar.  While doing this, I noticed a spot that I didn’t quite cover perfectly with primer, so since I had the primer out anyway, I gave it a little touch-up after finishing the riveting.  Then I moved on to riveting the E-703 and -704 tip ribs together.  The next steps called for riveting the E-705 root rib and other items to the spar…but since I’d shot some extra primer on that, those steps would have to wait.

Well then, I’ll start looking at the trim tab itself.  It starts out easy enough; there are two pieces that make up the control horn for the tab.  The tab spar is clecoed in place, the two horn pieces are clamped together, and then they get drilled to the tab itself.  Only some of the holes for the horn assembly are drilled, so the rest have to be drilled from scratch using the horn pieces as a drill guide.  No sweat there, though the instructions were kind of badly written here.  For whatever reason, they only tell you to drill one of the horn pieces, even though both need to be drilled.  I read all the way through the tab instructions and saw nowhere that it specified drilling the other (ie if there was a particular reason to wait), so I assumed it was an oversight and went ahead and drilled both pieces.

Next step is to take care of the top half of the spar-tab interface.  Now things get interesting; in addition to the spar and skin, the hinge on which the tab pivots has to be attached.  The spar and skin are both prepunched, but the hinge is not.  So the spar and skin need to be aligned very precisely so the holes will match up; normally this is what clecos are great for, but they can’t be used here because the (hole-free) hinge has to be clamped and drilled in assembly as well.  So basically I have to figure out how to align three pieces at once and clamp them in place.  This seemed like the kind of operation I might want to do some research on before proceeding, so I decided to call it a night.  At least it leaves me with something else to play with while I wait on my shipment of rivets.

The lovely trim tab assembly:

Main goal for today was to get everything primed; as I’ve mentioned before, my “paint booth” is my driveway, and thus I depends on both good weather and daylight to be able to shoot primer.  Since the days are still short, right now that means that priming is a weekend-only activity, and not getting primer shot today would have basically meant no work until next weekend.

First, though, I had a bit more prep work to do.  Last time I final-drilled my new E-606PP, but it still needed to be deburred, dimpled, and countersunk.  The riblet I made needed the same treatment.  Most of this is pretty basic stuff, but since last time I finished off an already questionable E-606PP with a horrible countersink job, I was veeery careful with those.  I didn’t ruin any holes today, but a few were a little funky.  Countersinking in general seems to be giving me trouble; that in turn concerns me because, to my knowledge, one of the first tasks on the wing kit involved making a lot of countersinks on the spar.  I most definitely don’t want to mess that up…I guess I’ll be spending some time practicing countersinking on scrap between now and when the wings show up.

That done, it was out to the driveway to scrub everything down.  After blasting the newly-cleaned parts with air to get most of the water off, I went back in the garage and got to work on the elevator skin, which needed to be deburred and dimpled.  Next I started looking at assembling the trim motor; the instructions indicate that this is best done before the elevator is closed up.  This also seems to be one of those situations where the training wheels come off instruction-wise.  The only thing the instructions say about the trim system is basically “Refer to the drawing to see how your trim system goes together.  You should probably do this now.”  Granted, it’s not a complex piece by any means, just a couple of angle pieces that need to be drilled to the trim plate; but still, I guess the level of handholding up to this point kind of spoils you.  Ever mindful of getting ahead of myself and fouling something up again, I decided to go inside, take a break, and do some research on putting this piece together.  This had the added benefit of allowing some more time for my cleaned parts to dry before I shot primer.  I was surprised to find basically no information about putting the trim system together.  I guess that indicated that it was probably extremely simple and I was just getting really worked up.

Back outside, I started shooting primer and tinkering with the trim some more in between coats.  Finally, I saw the information I’d been missing in the plans: some dimensions indicating the placement of the trim motor mounting angles.  With that, it all became quite clear.  I spent the rest of the priming time getting those parts lined up, making sure the trim motor shaft wouldn’t interfere with the slot in the plate, and finally clamping the pieces in place and drilling the rivet holes.

The “finished” trim motor/plate assembly (not really finished, just clecoed together):

With that, the priming was done and it was time to head inside.  Josie and I have dinner plans tonight, so I need to get myself showered so we can head out.  I should be able to get the trim assembly finished and the elevator riveted together this week, then it’s on the the trim tab.  The bit of reading I’ve done on that piece indicates that it’s a good bit more complex than it looks.  We shall see…

So I’ve kind of been talking myself out of working in the garage the past few nights.  It’s been cold, and the little space heater I bought doesn’t seem to be able to keep up.  Tonight, however, I vowed to get some work done in spite of the cold…and truth be told, it really wasn’t bad at all once I got out there and moving around. (though I did kick the heater on about an hour before I actually went out to work)

Anyway, first order of business was pretty mundane – final-drilling the holes in my shiny new replacement E-606PP trim spar.  Nothing too exciting there, and the same for deburring those holes.  At this point I suppose I could have gone ahead and dimpled/countersunk the spar, but I decided to move on to fixing the trim tab cutout on the elevator.  I started by making a cardboard template to match the outside of my trim tab.  By using this as a starting point for marking my cut lines on the elevator, I could help ensure that I ended up with a nice even gap to the tab when I was done.  

Once I’d marked the cut lines, it was time to cut the ears off.  Well, that makes it sound a lot more casual than it actually was.  I was pretty mindful that I was about to take a Dremel to my (mostly) pristine elevator skins, and there was definitely opportunity for parts ruining.  So I double- and triple-checked the cut lines, then checked them again for good measure…and finally there was nothing left to do but actually cut.  So I fired up the Dremel and went to work.  It was actually kind of funny…I kept moving the cutting wheel close to the skin, and then sort of backing off the reconsider.  Finally, I really did actually make a cut.  It was really pretty uneventful when you get right down to it, but there was a lot of anticipation for me.

First cut:

Both ears gone:

Whew.  Now I had the ears gone, but the resulting edges were extremely rough and not quite straight either.  So out came the vixen file and I spent a fair amount of time easing those edges down, getting them straight, and getting them aligned.  Then there was some further cleanup with a regular file and the edge deburring tool.

OK, now to fabricate the riblet itself.  I generally followed this procedure from VAF, cutting down an E-703 rib to make my riblet.  Some other guys make the riblet from scratch, cutting sheet stock and bending it that way, but I decided to take the “easy route.”  I started by measuring the skin to get a good first-pass idea of how long to cut the rib, then I went to the band saw and made the first cut.  The resulting piece was slightly too long (by design, really), so I ended up trimming a bit more off with the band saw.  As recommended in the VAF thread, I drilled a #30 hole in the rib face so I could use a cleco as a handle.

The rib after the first cut:

Next I clecoed the trim spar in place on the elevator and worked out the positioning of the rib; sliding it forward or aft changed the way the skin sat, so I had to find a “sweet spot” of sorts to get everything to line up.  That done, I drew my layout marks on the skin, laid out the rivet line, marked the holes, and drilled them in the skin alone.  That done, I put the riblet back in place, clamped it in, and carefully used the skin holes to drill into the riblet, clecoing it in place as I went.

The resulting piece fits quite nicely:

And now the trim tab lies in place quite nicely as well:

It was nearly 11:00 by this time, definitely quitting time.  So I cleaned up and went inside to the warm zone.  I still have to deburr and edge finish the riblet, as well as dimple and countersink the trim spar; once that’s done, I’m hoping I can shoot primer on everything this weekend and be assembling the elevator next week.  Then it’s on to the really fun stuff: putting the trim tab together, installing the actuator system, and checking function.  In the near future, I get to test the trim motor and watch an actual control surface move…fun times!