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!

Wow, talk about a roller coaster day.  When we left off last time, I’d dimpled E-606PP where I was supposed to countersink, and I stopped the work day right there while I decided how to handle that little mistake.  After some hearty discussion with the hive mind at VAF, it seemed that the best course of action was to flatten the dimples I’d created, countersink the piece like it was supposed to be, and move on.  Just to make sure, I performed a test on a piece of scrap of the same thickness as E-606PP; I drilled a #40 hole, dimples that holes, flattened that dimple, and then checked the flatness of the material and the hole size.  Hole size looked good, and while the material wasn’t perfectly flat, it was certainly acceptable.

Hooray, I don’t have to throw yet another piece in my scrap pile!  Or so I thought…I immediately got to work with the squeezer and flat sets, going down the line and flattening those pesky dimples.  Nothing to it…hmm, wait…now the spar piece looked like it had developed a bit of a bow, and was no longer straight.  I attempted to cleco it in place on the elevator skin…yup, it is definitely no longer straight.  Hmm…well, luckily, I do have tool specifically designed for straightening pieces like this; in fact, it gets used on pretty much every rib with a curve on the plane.  So I broke out the fluting pliers and went to work on the spar flange.  Five minutes later, and it was straight again.

Oh, wait a second…the whole reason I had to flatten those dimples was because the hinge attaching the trim tab needed to sit flush against the inside of the spar flange, which I had just proceeded to put little flutes in.  Well, maybe it’ll be OK once I get everything together…I went ahead and broke out the countersink.  After setting the depth properly (a trial-and-error affair I don’t particularly enjoy), I went to work on the spar.  The very first hole I countersunk…something didn’t quite feel right as I was doing it.  I pulled the countersink bit out, and somehow I’d managed to wallow the hole out to an oblong shape.  Clearly this spar just wasn’t meant to go on my aircraft.  Into the junk bin you go!

In retrospect, it was probably trash as soon as I decided to flute it.  I don’t think that assembly would have gone together right with those flutes in place.  It just so happened that I buggered up the countersinking, which in turn made me make the decision to replace.

This, in turn, changed my plans for the day significantly.  Originally, I’d wanted to fix E-606PP, go clean all my skeleton parts, and then shoot primer on them once they’d dried.  Then I’d have everything ready when it came time to rivet the elevator.  Well, there’s no point hurrying to prime everything when I’m going to have to wait for a replacement part.  Instead, I decided to attack the “ears” for the trim tab and the elevator trim tab cutout.  These things have a pretty solid reputation among RV builders as Things That Are Frequently Buggered Up.  I figured I’d go ahead and go after them, and if I messed something up, I could at least order all the replacement parts at once and save on shipping.

A little more on these bends: The trim tab, as well as the edge of the trim tab cutout in the left elevator, don’t have ribs like the ends of most other surfaces.  Instead, there’s extra material on each side of the skin; these little tabs are bent down and riveted together to close off the ends of these pieces.  Many builders, frustrated with the difficulty of getting these bends right, have taken to simply cutting the tabs off and fabricating custom “riblets” instead. (example)  Over the past couple of days, knowing that this task was ahead of me, I did quite a bit of reading on the subject, seeing how other builders had done the bends.  Opinions on the task ranged from “not really that bad” to “nigh impossible.” (I’m paraphrasing here; I don’t think I’ve actually run across a build log yet that used the word “nigh” in a sentence)  Anyways, I decided to go ahead and try the bends.

If one is following the instructions, one will end up bending the tabs on the elevator first.  Which I did, which was, in retrospect, a mistake.  There’s a lot more stuff in the way of the job in the elevator than the trim tab, plus there’s just a lot more material around that you have to work around while bending.  I know that now, but I didn’t know that when I started this task.  So first up, I endeavored to fabricate a bending block.  The instructions say to use wood or particle board; I happened to have some scrap MDF left over from my workbench build, so I decided that would work well.  A little work with the band saw and belt sander, and I had this little guy:

He seemed to be up for the task.  OK, next step, mark the bend line on the elevator.  Here again, access is kind of difficult; after a few attempts to wrangle a square and Sharpie in there to make the line, I adopted a plan B.  I went ahead and stuffed the inside portion of the bending block in place, then used the square to move it around until it was square to the cutout area and in the proper position.  Then I used the Sharpie to mark where the block would sit.  Now I needed to secure the block in place.  The instructions say to use double-sided tape, but I didn’t have any around.  No problem, surely the old trick of making a tiny roll of single-sided tape would work, right? (Spoiler alert: the answer is NO)  With my blue masking tape in place, I got the block in position, added the outside piece on top, and clamped the thing down.  Then I got another block of wood and started tapping on the tab.  Oh cool, it’s starting to bend…oh crap, the inside bending block is moving out of place.  ABORT!!!  Great, now I have a slight bend that’s too far in and not straight at all.  I tried resetting the whole jug and bending again, but the block moved again and I just made the nasty bend worse.  OK, it’s time to stop and rethink this thing. 

This was the first time in a while that I really let a mistake get to me.  I’ve been pretty good about taking things in stride, fixing them or replacing stuff as needed, and moving on if possible.  This time, though, I was facing replacement of the whole elevator skin, probably $100 in parts at a time when I’m already worried about getting the funds set aside to pay the balance of my wing kit.  Rationally, I knew I could probably save the elevator skin, but it was one of those time when emotion completely overrules rationality.

I went inside to do some more reading on the subject.  After about 30 minutes of actually reading, instead of just skimming for the stuff I wanted to hear, I learned that there were a few key points to getting these bends right:  Using hard material for the bending block, using good double-sided tape to ensure the block didn’t move, and making sure the assembly was clamped very, very tight.  I’d been using a couple of these clamps; they’re great for general use, but there’s a limit to how much clamping pressure they can exert.

So off I went to visit Lowe’s Aviation Supply; half an hour later, I was back home with a chunk of red oak, two 6″ C-clamps, and a $10 roll of carpet tape, which I was about to use maybe 2% of before putting the rest of the roll on a shelf for eternity.  Oh well, such is homebuilding.  

I set about making a new bending block set.  The first time, I’d tried to measure the angle of the elevator trailing edge and recreate that; this time, going off another idea I’d read, I used the elevator root rib to get the angle right and draw my cut line.  The result was much better-looking than my first attempt.  I also decided to bend the trim tab and then move on to the elevator if I could get the technique right.  A bunch of careful minutes later, I had the block in place inside the root end of the trim tab:

…and clamped down with the other half of the block setup:

Once again, I went to work with a hammer and a block of wood.  This time, things went great, actually beyond my wildest expectations.  After getting the bend mostly done, I finished it with the rivet gun and flush set, then repeated the process on the top side.  It came out looking absolutely beautiful:

Repeating the process on the other end of the tab was a piece of cake.  It went so well, in fact, that I decided to capitalize on my rejuvenated work day and try to save the elevator.  The one good thing was that the bend I fouled up was on the bottom of the elevator; if I could flatten it enough to be safe, but not necessarily perfect-looking, at least the only people that would notice would be small children…

So I got the elevator skin back out, cleaned the tape off the bending block, stuck it in the trailing edge, and used it as a backer while I worked over the bad bend with the rivet gun and the flush set.  I wasn’t able to straighten it out completely, but it was definitely OK to try bending again.  So I did the whole deal again.  It was a little tougher this time; the inboard trim tab cutout part of the skin gets in the way of bending the forward part of the tab.  I ended up doing the rivet gun portion in two stages; I’d hit the trailing edge area as much as possible, then move one C-clamp so I could get at the rest.  The result wasn’t as perfect as the trim tab, but still acceptable to me:

The only concern I have came when I got out that trim tab skin and held it in place on the elevator.  Right now, the outboard edge is barely making contact with elevator tabs that I bent.  At first I thought maybe I should have bent the elevator tabs further in, but I couldn’t do much more without them interfering with each other. However, upon closer inspection, the tabs on both the trim tab and elevator aren’t bent quite to ninety degrees; I think once both spots are riveted in place, it will pull the tabs in enough to eliminate the contact.  If not, I may have to order another trim tab and bend it a little differently to shorten the whole unit a touch.  Hopefully that won’t be necessary…I’ll probably seek the feedback of the VAF folks on this one too.

So all in all, quite a day.  I went from small failure to larger failure to great success, and ended up at “I think this is going to be OK.”  Roller coaster indeed.

EDIT:  OK, after further consideration and inspection, I’ve decided to cut out the bent areas in the elevator and fabricate a riblet to go in there.  I got to thinking about the clearance issues, looked at my preview planes for clearance specs between the trim tab and elevator, and got concerned about being able to meet the minimum clearance.  I decided to run out to the garage and clamp the ears together to sort of “preview” what the ears would look like once they were riveted.  When I did that, I suddenly noticed that the elevator bend isn’t even straight; towards the trailing edge, it curves outward, and that’s where my clearance problems would be.  Not good enough for my plane, so it’s coming out.

Decided to spend a little time out in the garage tonight; I’d like to be able to get these skeleton parts primed this weekend if possible, which means I need to get deburring, dimpling, and other prep done before then.  And about half of tomorrow is out because I have to attend a CAF meeting down in Peachtree City.

Anyway, things were pretty straightforward.  I got comfortable in my Official Deburring Chair and started going to town on the skeleton parts.  Once all the holes were taken care of, along with the nooks and crannies where the bench grinder can’t get to, I moved on to the aforementioned grinder to take care of the edges of everything.  Once I’d finished that, I was about an hour in.  Next up: Dimpling.  Again, no worries here; I went to town on the spar, ribs, and the short rear spar for the left elevator, E-606PP.  This piece closes off the trailing edge of the elevator where the trim tab mounts.

Of course, just as I was thinking how productive I was being, I found out I’d done something dumb.  I’d actually decided to stop for the night and go spend some time with Josie, but before I went in, I wanted to read ahead in the directions a bit.  Just a couple steps ahead, there was instruction to the effect of “Machine countersink the top flange of E-606PP and dimple the bottom flange.”  Hmmm, I just got done dimpling both flanges.  Why would it need to be countersunk anyway?

Oh, wait.  The hinge piece for the trim tab sits on that top flange.  Hence the countersink instead of dimpling, to give the hinge a flat surface to rest against.  ARGH!

At first, I tarted to go ahead and try to fix my mistake.  I figured I could use the rivet gun with flush set and the back rivet plate to flatten those dimples back out.  But then I got to thinking some more…first, if the dimples didn’t get flattened thoroughly, how would the countersinks turn out?  For that matter, how might that combination of flattening and countersinking possible affect those holes?  Hmm, alternative idea: Maybe I could leave the dimples there, an countersink the hinge itself so the dimples would sit inside.  Drilling the hinge piece in place might be a little more challenging, but I wouldn’t risk ruining E-606PP.

Bottom line, though, I got to this point by getting ahead of myself and working without thinking.  Trying to figure out in a flash how to fix my mistake was liable to end up with me compounding that mistake, so I decided to leave things as they were, quit for the night, and seek the advice of the hive mind at VAF.  So we’ll see if there’s an issue with my idea of countersinking the hinge that I didn’t think of.

Oh, I also did another time lapse tonight.  I figured it might be amusing to have footage of me going through the drudgery of deburring.  I even added some amusingly boring music this time.