Empennage

Started off the day with some flight time.  I’d originally reserved the plane intending to run over to the Spitfire Restaurant for lunch with Josie.  Then I got an email which reminded me that this was the first Saturday, which meant it was EAA 690 pancake breakfast day!  Even better, the breakfast program sounded interesting; a talk from the LZU tower manager.  Luckily, no one had reserved the plane for the morning, so I just edited the reservation to start earlier.  So we flew from PDK to LZU, ate pancakes, heard lots of interesting stuff about ATC, then flew over to WDR for lunch before heading back home.

After a brief rest back home, I strolled out to the garage to start priming.  This didn’t exactly get off to a great start…when I picked up the ribs, I immediately could see a discolored spot where the part sticker had been on one of the tip ribs.  Checked with my finger…it’s sticky.  Still got sticker residue on there.  I found the same thing on the other tip rib.  Apparently I was slacking when I was cleaning these parts…so I went to work on them again with Simple Green and a green pad and got the rest of the residue off.  But now I had to get them dry, and I didn’t want to wait another day to prime.  So I got creative.  First I used the blow gun on the compressor to blast as much loose water off as possible.  Then, I went inside and…um…used Josie’s hair dryer to finish drying the ribs.  Yes, really.

So then it was back to priming.  I was sort of pleased that I’d gotten past this little hiccup and moved on with the day…until I started shooting primer on the spar.  Immediately it was obvious that there were some oil spots or something on it, because the primer simply would not stick.  I actually watch primer migrate off these spots just after spraying.  Again…apparently my cleaning technique is getting really sloppy.  So I repeated my past performance, scrubbing the spar again thoroughly before blasting it with the air gun and the hair dryer.

Then, yet another problem cropped up.  I could tell that the can of primer I was using was getting low…and oh look, it seems to be the last can.  So I got to make a quick run out for a primer restock.

While I’m talking about primers…I think I’m going to try something new on some scrap pieces while I’m waiting for the wings to come in.  I haven’t been all that pleased with the Duplicolor stuff, despite some endorsements on VAF.  At first I thought maybe it was my technique, but I feel like I’m doing OK now, but quality is still so-so.  NAPA 7220 is another commonly recommended primer, so I think I’ll pick up a can and shoot some on some of my scrap pieces.  If I like the results, I’ll probably switch to that once I get going on the wings.

Anyway, despite some setbacks, I still got the skeleton parts primed today.  I still need to deburr and dimple the rest of the skin, but that should go fast, so I think tomorrow I can get going riveting the elevator.  Then I get to have more fun in the wonderful world of leading edge rolling…

Sorry, no pictures today.

This thing’s almost done!  Kind of oddly bittersweet though…at the same time I’m pleased with the progress I’m making, and all the good feelings of seeing a part come together, I’m acutely aware that I’m getting closer to a period of no building while I wait for the wings.  Oh well…worst case, I can always work on the fiberglass stuff while I want, I suppose.

First things first, I still needed to deburr and dimple the elevator skin.  Nothing fancy here, just time-consuming.  I find the edges of skins to be some of the more tedious work; I’m just using an edge deburring tool on those, maybe a file for some of the tight spaces.  I’m thinking I should get a die grinder with a small scotchbrite wheel for some of these edge finishing tasks that don’t really work for the bench grinder.  I also went ahead and drilled the leading edge holes to #30; even though the instructions call for doing this after rolling the edges, I don’t like the idea of trying to hold that stuff in alignment, or the inability to effectively deburr the holes, or the drill shavings maybe getting inside the elevator.

Also, while doing the deburring and dimpling, I took a look at the pieces I primed yesterday and found a couple spots I wanted to touch up.  So in between working on the skins, I shot some primer in the driveway.  In order to speed drying, I resorted to hanging the pieces in front of my radiant heater once the primer had flashed dry.  This seemed to work well; when I worked with the pieces later, I noticed no problems with primer coming off in the areas I’d touched up, so I guess it hardened sufficiently.

Next up, riveting the E-704 and -704 tip ribs together.  These just sit together back-to-back and go together with some 470 rivets.  I decided to use the rivet gun on these, but for some reason the rivet set was really banging on the rib itself; I had a little ring of missing primer around each of the manufactured heads.  I found this odd, but for some reason my brain didn’t make the connection that maybe I was doing something wrong.  So I just took the new assembly out in the driveway and shot some more primer to fix those rings.

I moved on to riveting the reinforcements and nutplates to the spar.  I shot the first rivet, got the same ring around the manufactured head…and suddenly, I had an idea what the problem was.  Yep, I grabbed the wrong rivet set, I was using the set for -5 470 rivets.  That’ll do it…derp.  Swapped it for the right set, and magically all my subsequent rivets looked great!  Of course, I had one more spot to touch up with primer…and the next step was to start riveting ribs to the spar, which had wet primer.  So once again, I set my parts in front of the heater, and went inside to warm myself up a bit and have some food.

An hour later, things started really coming together.  I riveted the tip rib assembly to the spar, then flush-riveted the root rib to the spar.  It felt kind of odd to use 426-3 rivets on understructure, even though I understand the purpose…the control horn goes on top of this area.  Those control horns were the next item; 12 rivets squeezed and they were done.  Next the instructions say to rivet the E-713 counterbalance skin to the elevator skin.  That sounded a little odd to me, but a look at the plans made it all clear.  Most of the rivet holes where the elevator skin overlaps the counterweight skin also go through the tip rib or spar, and can thus be squeezed with everything together, but two rivets on each side only go through the two skins.  These two rivets would be inaccessible once everything was together, so riveting them first allows the use of solid rivets instead of blind rivets. (though I did notice that the plans specify optional blind rivets for those holes)

One thing the instructions didn’t specify prior to putting the skeleton in place was putting the dabs of RTV in the trailing edge where the stiffeners overlap.  I didn’t forget the need for this though; I put my dabs in before getting started with the counterweight skin. (which would have made it a lot harder to get back to the trailing edge)  I also gave the insides of the elevator skin a good wipe down with acetone before buttoning up.

Now the skeleton went into place, and it was a simple matter of just squeezing a bunch of rivets around the perimeter.  The main (minor) issues I had here were getting  the assembly on the workbench in a stable position so I could squeeze.  Since the counterweight was already in place, the thing really wanted to try and flop off the table.  Some creative use of wood blocks and boxes of clecos (to weight down the trailing edge) got me through this.  As with the rudder, I didn’t have any good way to use solid rivets in the tight spots at the trailing edge, so for the last rivet on both the root and tip ribs, I drilled out to 7/64 and used MK-419BS blind rivets.

This seemed like a good time to stop for the day; I’ll get Josie out maybe one night this week so we can get the leading edge rolled.  Or I could just wait and roll the leading edges of both elevators at the same time; this is the way the instructions seem to indicate.  I’ll have to have both elevators out once I’m done anyway so I can fit them to the horizontal stab; I suppose I could just do the leading edge rolling and other fitting tasks on a weekend day.  I’m not quite sure what I want to do, actually.  Maybe I’ll wake up tomorrow morning and come to a conclusion.

This is the tip rib assembly that I fouled up using the wrong rivet set, just after I shot some more primer to fix the lovely rings I made.

Here’s a blurry photo of the skeleton. (the photographer in me is annoyed with this picture.  Oh well.) (Also, that back corner is horribly cluttered. Definitely going to be another garage cleanup day in my future, before the wings arrive.)

And the (almost) finished elevator!

When we left off last time, I was trying to decide whether to roll the leading edge of the right elevator now, or go ahead and start on the left elevator and roll both leading edges at the same time, once I finish the left and the time comes to hang both elevators from the horizontal stab.  I ended up making the decision based on a pretty boring rationale.  Specifically, I wanted to work in the garage tonight, but Josie had to work late, since it’s her busy season at work.  With no one to help roll the leading edge, and me itching to work, I went ahead and hung the right elevator from the rafters in the garage (it’s getting crowded up there!) and got going on the left.

All of the work tonight went pretty fast, probably because I’ve already done all this (with slight modification) on the right elevator.  I drilled the hinge reinforcements to the spar, drilled the two tip ribs together, then clecoed the counterweight and its skin in place on the tip ribs before drilling the two mounting holes for the counter weight.  Then I removed the counterweight, clecoed the tip rib assembly to the spar, and match drilled those pieces.  Next the root rib went on and was match drilled, and then it was time to cleco the skin in place.  With the skin in place, the clecos between the root rib and spar can be removed to make room for the control horn, which was the next item to match drill.

At this point we hit the slight difference between the left and right elevator, due to the presence of the trim tab.  The root rib is of course truncated, and there’s a second spar that goes in the trailing edge of the elevator where the trim tab will mount.  The next step for me was to cleco this spar in place and match drill it to the root rib.  After that, it was just a matter of going all around the skin perimeter and match drilling all the holes between the skin and skeleton.

It was creeping up on 11 PM by this time, so after pulling the elevator apart again, I decided to stop there instead of getting started with deburring all those parts.  I did go ahead and countersink the counterweight for the mounting screws, even though that’s a few steps ahead.  This was mostly because I’d gotten my countersink out earlier to swap out bits, and I already had it mounted in my cordless drill.  I countersunk the right elevator counterweight using an air drill, and while the results were acceptable, there was clearly some wobbling of the countersink.  I decided that maybe it would work better to use a slower speed drill, which the cordless is good for.  It was a good strategy; the countersinks in this counterweight are flawless..

Also, what with the kind of benign nature of tonight’s work, I decided to forgo the usual few photos for something a little different.  When I was about halfway through clecoing the skin to the skeleton, I decided that a time lapse of the evening’s work would be a nice addition to the build log. (it also helps satisfy the “proof you built the thing” requirement when this project is done)  On the one hand, I wish I’d started the time lapse earlier; it would have been cool to see the elevator come together from individual pieces and then come apart again.  On the other hand, I neglected to change the camera settings before I started shooting, and thus I filled my memory card up in the space of about 50 minutes; given that oversight, I wouldn’t have been able to shoot the whole procedure anyway.  I also shot in 4:3 aspect instead of 16:9.  Oh well.

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.

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.

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!

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…

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:

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.

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.