Empennage

Ordered the blind rivets I need to continue with the rudder from Spruce today, so they’ll be here tomorrow.  Tonight I wanted to put together my rig to use when I get around to bending the leading edge of the rudder. (and subsequent control surfaces)

The basic idea here is that you use a length of pipe to roll the edges.  This pipe gets taped to the edge of the material, and then as the pipe is twisted, you end up with a nice round bend in the aluminum.  The potential difficulty-based on reading other builders’ experience, of course, not my own-is keeping the pipe down on the table and pulled tight against the edge being bent.  While reading about this, I ran across a nice setup that seemed very useful.  Dan Horton from VAF simply used a few u-bolts to hold the pipe down against the table in place, and as the pipe was turned, the rudder would naturally slide towards the pipe.  Proper tension pretty much takes care of itself.

I liked this idea, but I didn’t like the idea of drilling holes in my nice workbench to mount the u-bolts, especially when you consider that every time I needed to space the bolts differently, I’d have to probably drill even more holes.  I wasn’t sure how else I would do it, but I went to Lowes after work anyway, figuring I’d just walk the hardware aisles and try to brainstorm a solution.  Eventually, I hit on a simple, flexible, nondestructive idea.  The only material I needed in addition to the length of pipe was some steel bar stock.  When I got home, I cut the bar stock into four 9″ lengths, then put two right-angle bends in one end of each piece.  The resulting “hook” can be clamped to the side rail of the table, and the bent portion hooks over the table and holds the pipe itself.

Of course, it remains to be seen whether this works as well in practice as it does in my head…

A couple pictures of the rig: (I still need to fine-tune a few things, but I’ll wait until I’m ready to roll the dges to do that)

Shorter night in the garage than I figured for tonight.  Had some things to do around the house and didn’t get out there until about 8:00.  Then it didn’t take long before my sore back made me decide to go in and rest. (Side note: I apparently got this sore back from mowing the grass, of all things.  I’m not that old, am I? *sigh*)

Anyways, my MSP-43 blind rivets from Spruce arrived as expected, but before I riveted the control horn brace into place, I wanted to verify what I needed to to the four skin rivets on each side in order to use the CS4-4 blind rivets there.  I knew I’d need to drill out to #30, but what about the dimple?  Luckily, I have a number of scrap pieces sitting around.  I used one of an old ruined rib as my experiment piece; this was a particularly good test, since it was already drilled and dimpled for -3 flush rivets.  So I drilled to #30, dropped a CS4-4 in…yup, sits proud.  Out came the 1/8 dimple die set, I redimpled the hole…rivet sits nice and flush.  Good to go.

So I clecoed the skin back to the skeleton one last time, and drilled the eight holes in question out to #30, pulled everything apart, deburred, and dimpled to the larger size.  Easy enough; now I clecoed the horn brace back into place and proceeded to set the MSP-43 rivets between the horn and the brace.  Next were the three solid rivets between the brace and the root rib, also easy.

Before clecoing the skin back into place for the last time, I needed to put a dab of RTV at the trailing edge where each pair of stiffeners meet.  According to the instructions, this ties the stiffeners together and prevents cracking of the skin from vibration.  All I know is that it feels a little odd to take my shiny clean skin and shoot a mess of RTV in there, but oh well.

Finally, I got the skin clecoed on, and this was the point where I decided to call it a night.  All the remaining skin rivets can be hit with the squeezer, so they should go quickly tomorrow.  The only place I see the potential for delays are at the trailing edges, where clearance is tight.  Hopefully I can get in there with the thin-nose squeezer yoke, but if not, the plans provide for alternate blind rivets in there.  We’ll see how that goes.  And, of course, how my edge-rolling setup works out.

Whew!  Another piece of the puzzle together…when I got out to the garage tonight, the first order of business was squeezing all the skin rivets.  This went pretty fast, even though I had to drill out one rivet when I stupidly used the wrong length.  Whoops.  I ended up using a blind rivet in the last trailing edge hole on the root end on each side…there was no way I was getting in there to squeeze, even with the thin-nose yoke.  Per the instructions, I simply drilled to 7/64 and used a MK-419BS blind rivet.  No problem.  That took all of about an hour.  Now all I had left to do was roll the leading edges and rivet them together.  I figured this wouldn’t take too horribly long.  It didn’t take horribly long, but it did take longer than I expected.

My rolling rig worked pretty well overall.  The only real problem I had was that the very end of each hook was touching the table; this in turn would eventually contact the spar once I’d rolled to a certain degree, thus stopping progress, in some cases before I’d even gotten as much of a roll as I needed.  In a couple cases, I removed the hooks and rolled the pipe sort of freehand to tighten up the roll a bit.  It sounds fairly straightforward when I explain it here, and really, the procedure isn’t that complicated.  However, there’s a lot of somewhat tedious work here- putting the pipe in place, tearing off innumerable strips of duct tape, taping the pipe in place, being careful to get each strip of tape at about the same tension/lineup.

The top two sections ended up coming together nicely, although when I pulled them together the exposed edge wanted to pop up a bit.  So I got out my hand seamers and added a little extra bend at the very edge, which helped that seam tuck in a bit better.  The lower section was a different story.  The rolls there were actually further towards the edge than they really should have been; the result was that when I pulled them together, the edges were rolled in a bit too far.  So I did the opposite down here with my seamers; I used them to straighten the edge a bit.  This got the edges to lie more-or-less flat, close enough that the blind rivets would hold without too much trouble.

Then it was just a matter of going down the line, pulling clecos and setting blind rivets.  And then it was done.  I really wanted to pull down the vertical stab and put the rudder in place just for fun, but it was getting late.  So I placated myself by just screwing in the rod ends that serve as hinges for the rudder.  Here I had a mild moment of potential panic…all three rod ends I screwed in acted the same.  They went in fine for a few turns, then got very tough to turn. (I didn’t force anything)  Suddenly I had a horrible thought: what if the tail kit included two different, but very similar, sizes of nutplates?  If I’d used the wrong ones, there’d be almost no getting to them now.  I’d pretty much just have to start the rudder over again.  A quick look through the parts list shut down this crazy failure fantasy.  I’m still note sure why the rod ends are tough to screw in, but I’ll worry about that later.

The rudder all riveted together:

Here I am painstakingly tearing strips of duct tape and laying them between the pipe and the skin:

And the finished product:

So I took a few days off the project after finishing the rudder, but jumped right back into things today.  Time for the elevators!  This starts pretty much like the rudder did: first step is to cut and prepare a bunch of stiffeners.  I had expected to do these for one elevator at a time, but the instructions actually have you cut them all and do the back riveting for both elevators before getting into the nuances of the individual units.  I considered not doing them all at once, but decided it probably would be simpler to knock them all out at once.  Plus I could just check stuff off in the instructions instead of having to note steps that I’d only done for one elevator, and so on.

So I sat down in my garage chair with a pair of snips and went to work rough cutting the stiffeners.  32 of them, to be precise.  An hour or so later, I had a bunch of rough cut stiffeners and a tired right hand. (Side note: I think my forearm muscles are growing, presumably due to the exercise regimen of snips, cleco pliers, and rivet squeezers.  Maybe I should market this program as RV90X or something.)

There was a bit of confusion at this point for me.  The plans call for modifying some of the stiffeners for the left elevator, specifically the D/E/F units, by trimming some material off the trailing end.  At first, I misread the plans, which seemed to indicate that I should cut about two inches off each stiffener.  This made no sense whatsoever to me; the left elevator is substantially different from the right due to the trim tab, but these stiffeners were outboard of the trim tab.  As far as I could tell, the skins were identical in this region.  So I got out the laptop and did some Googling.  I found where another builder had had the same confusion, and eventually realized he was reading the plans wrong.  The measurements called out in the plans are not amounts to trim off the end of the stiffeners, they’re distances from a particular rivet hole to where the trim should be made.  Measuring that (correct) way, the trims were far less drastic.  Basically I ended up cutting, at most, an eight of an inch off each stiffener.  I’m still not sure what the purpose of this is…I can only assume that the Van’s folks know what they’re doing. (I’d better hope so!)

With that out of the way, I broke out the bench grinder and went to work cleaning up the cut edges, rounding the corners, and smoothing everything out.  This was pretty tedious.  I’m not sure how long I spent standing in front of that grinder, but by the time I was done, there was gray aluminum dust everywhere.  It was so impressive that I felt compelled to take a picture of my filthy right hand:

Next up was clecoing all the stiffeners into place on the skins and then match drilling.  At this point, it becomes important to keep track of which stiffener goes where; this was simple with the rudder, since there were simply two of each length stiffener, and I only needed to keep track of whether a particular unit was for the port or starboard side.  Not so simple with the elevators.  Well, the right is easy; like the rudder, there are only two of each length.  On the left, however, there are a number of equal-length short stiffeners that go ahead of the trim tab.  So I had to work out a system for both telling top/bottom stiffeners apart and numbering the equal-length units.  For the record, my plan basically says that odd number of punch marks go on the upper stiffeners, and even numbers on the bottom.  The number of punch marks increments from inboard to outboard.  So the innermost stiffener on the top gets one marks, the next three marks, and so on. (I wrote all this down on the instructions in case my memory fails me)

The instructions also call for clecoing the trim cover doubler in place and match-drilling it at this point.  Presumably this is because it gets back riveted just like the stiffeners.  I must confess that I had to cleco that thing in place three times before I finally got all the holes drilled.  There’s no nice linear pattern here like with the stiffeners.  The instructions don’t call for any more prep on this piece before back riveting it into place, but I think I’m going to go ahead and attach the nutplates for the trim cover before I back rivet it to the elevator skin.  I’m sure this will be easier with the doubler not attached to the skin.  But I have to order some more dimple dies before I can do that…I need #6 screw dimple dies for these things.  One lesson I’m gradually learning is that the list of tools Van’s has on their website is by no means complete.

Anyways, next I went back to the garage chair and deburred all the holes in those stiffeners and the trim cover doubler.  Then I dimpled all those holes I’d deburred. I could have comfortably called it a night there, but I decided that I wanted to get the stiffener holes in the skins deburred as well.  I figure I can get the stiffeners prepped and primed next time out, then recruit Josie to help with dimpling and back riveting all at once.

At that time, I really did call it a night.  I got a lot done today, which I have kind of mixed feelings about.  It certainly feels good to be productive and such, but I’m acutely aware that I’m running out of work to do on the empennage, and I still don’t have the wing kit ordered.  I guess there’s just going to have to be some downtime between finishing the empennage and starting the wings.  I guess maybe I could do the fiberglass work for all the tips, though most folks seem to save that for later when there’s lot of other fiberglass work to be done…we’ll just have to see, I suppose.

Lots of stiffeners:

Lots of stiffeners, dimpled.  And the trim cover doubler:

So yeah, i got all the stiffeners and the trim reinforcement plate primed today.  After I’d shot primer, I embarked upon the deceptively simple-seeming task of changing the spark plugs in Josie’s car.  Five of them were really easy.  The sixth was anything but easy; I’m pretty sure we spent two hours on that one plug alone.  By the time that was done, it was dark and I needed to sit back, relax, and allow my rage at the engineers at Nissan die down.

At least it’ll be a little while before I need to prime again, so everything else upcoming can be done in the garage, without needing good weather or natural light.  Also, I scheduled myself for a BFR next weekend.  I haven’t flown since this past March, and I’ve been putting off the BFR forever and a day.

I’m going to have to get a heater for the garage really soon.  Luckily it was quite warm here today, and so it remained nice outside well into the evening, but that won’t last.  That, in turn, is going to be a concern if I intend to keep trying to put in shop time in the evenings after work.

Anyway, my first order of business tonight as to rivet the nutplates onto the trim reinforcement plate.  The instructions don’t specify to do this now, but it seemed to me that it’d be easier to rivet the nutplates on now as opposed to after the reinforcement plate was attached to the skin.  However, ever mindful that there might be a good reason to wait, I read all the way through the elevator instructions.  At no point did I see them specifically say to rivet the nutplates on, so I presume this is one of those little details that they leave to the builder.

Then it was on to dimpling the skins.  Nothing to really write home about here; it’s just dimpling.  I finished by wiping the skins down with acetone before putting them away for the night.  I learned back when it was hot that leaving sweat on the skins can make the alclad coating look nasty.  I’m not sure if it’s actually damaging to the skins or not, but it seems to smart to play it safe; so I’ve made a habit of always wiping the skins down after a shop session.

I probably won’t be able to get to back riveting the stiffeners until this weekend.  Tis the season for holiday gatherings; I’ve got mine tomorrow night and Josie wants me to come to hers Wednesday.  Thursday night we’re going to Cirque do Soleil, and who knows what might be going on Friday.

A beautiful baby trim reinforcement is born:

Jeez, another layoff.  I actually started on the back riveting last weekend.  I did get a bit done, but I needed a second set of hands and Josie was unavailable for reasons which I don’t remember.  So I just knocked off and intended to pick back up another evening in the week.  Unfortunately, I got extremely ill Sunday night and remained that way until Wednesday, at which time Josie came down with the same symptoms.  So it wasn’t until today that I was able to get back to work.  I did, however, get my long-overdue BFR out of the way Friday night, so at least I’m legal to fly again. (which is goos, since I’m planning on flying home to NC for Christmas next weekend…)

Anyway, nothing really complex happened today.  I’d already back riveted the trim doubler in place, and gotten all the stiffeners on one side of the left skin, save for the two aftmost rivets on each, which required a helper to hold the skin out of the way.  Really, I should have waited for help for all this; the rivets I shot solo last weekend were frequently not my best work.  I guess aligning the rivet gun, holding the set in place, and trying to hold the skin out of the way while squeezing the trigger was a little too much task overload.  Today we got right back to work shooting those aftmost rivets I’d skipped before, then went straight to work on the other side.  This is also a nice time to have a helper, when you’re dropping all those rivets into the skin holes, taping them in place, and so on.  We got through the remainder of the stiffener riveting in just over an hour.

Next was bending the trailing edges.  I took some time to review the procedure here before starting.  This is one of those times when the construction manual isn’t much help.  It basically says “Construct a bending brake to bend the trailing edges.  After bending, check for straightness with a good straightedge.”  So I went back to my post on bending the rudder trailing edge.  That gave me some good insight on how I did it before, but I wish I’d taken pictures of the rig.  I’m fairly certain I didn’t do it the exact same way this time.

But whatever, I got them bent, things are nice and straight, and it’s time to move on to working on the skeletons.  I’m going to try to get back out in the garage in the evenings after work this week; I haven’t done any weekday work in ages, and building weekends only will take me an eternity. (especially with the short weekend work day I’ve been doing)

The bending brake setup.  Two clamps hold the brake to the bench, while two more clamps hold the skin in place on the brake.

Checking for straightness

The finished skins

Well, it’s been some time since I got in some weekday evening work, but I think I made up for some lost time tonight for sure.  A tick over four hours in the garage, and I’m down to just dimpling and priming before I start riveting the right elevator together!

The evening started with clecoing and match drilling the reinforcement plates to the spar.  Then I edge finished and fluted the E-703 and-704 ribs. (the instructions seem to call for doing this for the ribs to both elevators, so I did, then promptly tossed the left-side ribs back under the workbench)  The two ribs for the right rib got match-drilled, the I clecoed on the counterbalance skin, fitted the counterweight, and prepared to drill the counterweight attach holes.

I spent some time agonizing over this – here I had to drill a hole into the counterweight skin, through a couple inches of counterweight, and out through the end and counterweight rib flanges.  I was acutely aware that if I drilled at a bad angle, I could come out on the far side and be in a bad position on those flanges, and then they’d be ruined, I’d have to order more replacement parts, etc…

A drill press might have come in handy here, assuming I could have somehow mounted the rib/skin/weight assembly in such a way that I could drill it.  But since I don’t have a drill press, I set aside my fun air drills in favor of the cordless.  The sole reason for this is the cordless has a little bubble level on it, which I could use to ensure I drilled straight.  This technique worked like a charm…I was still all kinds of nervous, but the holes in the rib flanges ended up located quite nicely.

Next the counterweight came out and the end rib assembly got clecoed to the spar along with the root rib.  The root rib was match drilled to the spar, then out came the skin and the skeleton was clecoed into place.

The next step was to cleco the control horn into place.  I had a tough time getting that thing lined up…seemed like it wanted to really fit snug against the spar and rib, and I had to use a little grunt to get the holes to line up so I could cleco it in place.  This was made even more difficult due to the powder coating on the control horn – the holes are already undersized and tough to get the clecos through, and with the powder coat on top of all that, it’s even tougher.  But I finally got the thing clecoed in place and match drilled the rivet holes. 

Next I match drilled all the skin-skeleton holes, and took one last longing look at my temporarily-assembled elevator before tearing the whole thing apart again.  The counterweight skin was dimpled for the attach bolts, the counterweight itself was countersunk to fit against the skin, and then I got to spend some time in my Deburring Chair hitting up all the rivet holes and lightening holes before firing up the bench grinder one last time to finish the edges of the rest of the skeleton pieces.

I still have a couple unanswered questions I’m going to research before proceeding further.  The attach between the E-702 spar and E-709 root rib uses flush rivet, since the control horn has to sit on top of that particular joint.  The instructions call for countersinking the spar, but this material is thin enough to dimple…I mean, after all, I’m going to be dimpling the flanges where it mates with the skin.  I’m not sure why countersinking is specifically called for here, but I want to find out before proceeding.  I’d rather dimple personally, I find it easier to do consistently than countersinking.

The instructions also call for beveling the edges of E-713 where it tucks under the skin to provide a “smooth transition.”  This seems fairly straightforward, but I’m curious if there’s any particular technique here.  I feel slightly weird just going to town on the edges of the counterweight skin…

Anyway, I’m not sure if I’ll get in any more work until after Christmas.  Josie and I are planning to rent an Archer and fly to North Carolina to spend the holiday with my family, then head back home Christmas afternoon to catch dinner with here family, but the weather is looking iffy.  In any case, we’ll be gone all weekend and well into next week.  Hopefully I can get my dimpling done and prep and prime next weekend, maybe finish assembling the elevator during my New Year’s days off work.

Preparing to drill the counterweight

Completed counterweight attach holes.  You can see in this photo how much distance is between the skin and flange, and how there’s ample opportunity to drill crooked and cause a problem.

And the temporarily assembled elevator just before I tore the whole thing apart.

Ugh.  I kind of feel like I squandered a lot of good work opportunity yesterday. (I did this work on Monday, and I’m just getting around to writing this up now)  First off, I slept in later than I probably should have, though on the other hand it is vacation…but anyway, my goals for the day were to get everything dimpled and cleaned for priming, and hopefully get around to priming while I had good weather and daylight.

Actually, it turned out I had a couple other steps to do.  In addition to the normal dimpling, I needed to dimple the rivet holes between the spar and root rib; these rivets are flush because the control horn must rest on top of them.  The instruction call for countersinking the spar, but I elected to dimple instead.  These same part will be dimpled where they join the skin, so I saw no reason not to dimple them here as well.  Well, until I got to dimpling the flange of the root rib…it was kind of tough to get those due to the acute angle between the flange and rib.  I had to break out the pop rivet dimple dies for this one.

Next, some of the edge of the counterweight skin needed to be tapered where they sat under the skin.  I decided to simply hit these up with the bench grinder to achieve the taper, but first I needed to mark the areas that needed to be tapered.  So I temporarily reassembled the tip rib components to the spar; with everything in place, it was easy to see where the edges of the skin would sit and to mark the counterweight skin overlap areas.  The taper itself was easy to do with the bench grinder and the scotchbrite wheel.

The rest of the dimpling went fast…well, 95% of it, that is.  The last few holes at the narrow end of both the root and tip ribs were pretty tough to do.  I probably spent twice as much time on those eight holes than I did dimpling all the other elevator components.  After doing some research, I think I’m going to invest in a set of Avery Tool’s vice-grip dimplers. (ARGH!  They’re out of stock!)  They should do a better job in the tight spaces than the sort of haphazard rigs I’ve been coming up with.

Then it was out to the driveway to scuff and scrub all the parts prior to priming.  Last time, I found out how much longer it took for this stuff to dry now that it’s cooled off outside…and it was even colder yesterday than last time.  I tried to jump-start the process by blowing the newly-cleaned parts with the air gun to get rid of some of the water, then I left them out to dry while I retired inside where it was warm for a late lunch.  After lunch, I was feeling a little tired, so I laid down for a nap…I wanted to give the parts more time to dry anyway.  I’ve tried to prime parts that weren’t completely dry before, and let’s just say that it doesn’t work well.

Unfortunately, when I woke up again, it was already starting to get dark.  Too late to get any priming in, and the forecast for New Years was rain, rain, and more rain.  This morning, I thought about trying to prime just inside the garage with the door open, but the primer specifically says not to use it when the humidity is high.  So I’ll just be waiting until this weekend to get back to work.

I think I’m going to go ahead and order my wing kit this week.  I’ve got the funds for the deposit, and getting the balance set aside during the eight week lead time won’t be a problem.  Most importantly, I’m going to be done with the empennage in the near future, and I’d like to minimize downtime.  I will need some time to clean and reorganize the garage for all the wing parts, but not eight weeks…

The tapered edges of the counterweight skin:

Look how much fun I’m having scrubbing the elevator parts!