Empennage

*sigh*

Obviously, work output on this project has gone down quite a bit.  I’ve been out of town two of the past three weekends, with all the associated planning.  Outside of that, now that it’s starting to heat up outside, it’s been a little difficult to motivate myself to go work in a marginally-air-conditioned garage.  But those are still excuses; I could work past this stuff, I just…haven’t.  Today, however, I resolved that I was finally going to get back in the swing of things.  On the docket was back riveting the rudder stiffeners.  If there was one thing I was sure I could do well, it was back riveting.  Back when I did the EAA workshop, I pretty much set every rivet perfectly using this method.

Of course, I should have learned by now that the worst thing I can do is go into a task thinking it’s going to be a breeze.  It’s as if the cosmos detects my overconfidence and delivers the smack-down of failure.  Honestly, it’s kind of getting a bit old.

But anyway…things started out fine, not that there’s much challenge in dropping a metric buttload of AND426-3-3.5 rivets into skin holes and covering them with rivet tape.  I then flipped the skin over, carefully placed the first row of rivets on the back rivet plate, laid the stiffener in place, put the rivet gun with back rivet set in place, gave it a short flurry of taps, and removed the gun to find…a beautifully clinched shop head.  ARGH!

Huh, I sure thought I was holding the gun straight.  Might as well move on down the line and come back to that botched rivet later.  The next rivet, I very deliberately put the gun in place, gave it a few taps, stopped to take a look, then gave it a longer blast…then gazed in black wonder at yet another clinched shop head.  I then repeated the feat a third time in a row.

Rivets too long maybe?  I had previously double-checked the callout on the plans, but something must be amiss.  Surely this couldn’t just be a case of operator error…out came the calipers.  Nope, rivet shank length was pretty much dead on the required 1.5D.

At this point, it was creeping up on 10 PM. (I got a late start)  Not wanting to disturb the neighbors with more riveting, I decided to drill out the botched rivets and call it a night.  Which I did, enlarging all three skin holes in the process.

*sigh*

Some research mentioned the possibility of the back rivet set being worn, and upon inspection, it does seem like the set is able to wobble around quite a bit in the nylon collar.  Might be normal, might not be, but hey, a new set is under $30 from Avery.  Might as well add that on so long as I’m ordering some “oops” rivets for my newly-enlarged holes.

I’m not at the point of surrender by any means, or anything like that, but the constant stream of mistakes is getting a little old.  Then again, this is why you start with the relatively inexpensive empennage kit, I guess.

In our last installment, I’d freshly mangled some additional sheetmetal while attempting to back rivet stiffeners to the rudder skin.  Lest we forget, the whole reason I skipped ahead to the v-stab and then rudder was because I fouled up some parts fot eh h-stab and had to order replacements.  Since I’m now waiting on some more stuff from Avery to continue with the rudder, I decided to go back to what I’m supposed to be working on first anyway…yeah, the h-stab.

I screwed up the tapers on the forward spar reinforcements by trying to rough cut them with a hacksaw, and then fine-tune with a belt sander and the scotchbrite wheel.  This time, I decided to go ahead and acquire the tool I should have used in the first place: a bandsaw.  A trip to Lowe’s this morning took care of that, and after some time getting the thing set up, I did some test cuts using the ruined spar angles and…man, this thing cuts through aluminum like butter.  Very nice.

So I got out my replacement reinforcements, laid out the cut lines, and had them trimmed down in no time with the bandsaw.  Some cleanup and corner rounding on the scotchbrite wheel, and I had them done in no time.  Yep, having the right tools really does make all the difference.  Next up was bending the “ears” of the reinforcements.  Seems like I’ve read where some other builders approached this with great trepidation, but I honestly thought it was pretty easy.  Clamp them in the vice, tap with the dead blow hammer, check angle, repeat until done.  Easy as pie.  Bending the flanges on the HS-702 forward spar channels was even easier.

The next step was the cut the HS-805 main nose ribs.  These attach to the forward spar where the reinforcement angles lie, so some relief cuts need to be made for them to fit around the reinforcement pieces.  Here again, the band saw was wonderful; after using a drill to create the corner radius of the cut, the bandsaw took care of the rest in no time.  Again, a little scotchbrite wheel action finished things up.

Now it’s time to really get serious.  Out came the rest of ribs for the h-stab; they all had to be edge finished and the fluted.  Lots of little nooks and crannies to be taken care of, but I’m starting to get a system in place for handling ribs.  Next, I decided which ribs would be for the left/right side of the plane (or port and starboard, as I prefer…no ambiguity there like L/R), and then it was time to do some clecoing.  The portside stab skeleton went together easily, then I match-drilled the holes.  The inner main ribs, HS-804/805, aren’t predrilled, though.  The skin has to be clecoed on, and then the ribs are drilled using the skin as a guide.  That, too, was straightforward and went well.

The next step was to cleco on the forward spar reinforcements, and then holes have to be drilled through a bunch of pieces at once; namely, the HS-804 main rib, HS-702 spar channel, and the spar reinforcement.  The main problem here is that there isn’t a lot of space at all to work with.  The instructions recommend an angle drill, but mention that a long drill bit can be used as well.  I do have a long drill bit, but after considering the situation it still seemed like a setup for disaster.  I’m thinking it’s better to play it safe and go ahead and snag an angle drill.  In the meantime, I’ve still got a lot of steps to repeat on the other h-stab half, so there’s no shortage of work while I order the angle drill and wait on delivery.  In a way, this builds on the lesson with the band saw: sure, you can get stuff done with subpar tools, but it’s more work and there’s a lot more chance for stuff to go awry.  Right now, I’d like to have stuff go well, hence the decision to order the right tool instead of trying to MacGyver it.

Anyways, by the time I hit this point, it was after 7 PM and I was getting hungry.  I did some internet research, which confirmed that I wasn’t going to buy a worthwhile angle drill locally. (unless I went to Spruce, an hour away and undoubtedly closed)  Josie wanted to watch a movie, so I called it a night.  Tomorrow evening, I hope to work on the starboard h-stab half and get it to the point where I need the angle drill as well.  That should be here Friday, so I can pick right back up after work then.  At this rate, I should be able to have the skeleton riveted together this weekend, and before long it’ll be skin riveting time…

Properly tapered spar reinforcements:

And now they’re bent:

Hey, that looks like an airplane part:

Short work night.  Not because I’m busy, but because it didn’t take nearly as long as I thought to get to the point where I had to stop and wait for a new tool to arrive.

Last night, I assembled all the parts of the port h-stab skeleton and skin, and did all the match-drilling up to the point the instructions called for an angle drill, which I didn’t have.  The drill was ordered from Spruce today, but work didn’t have to stop…I still had to repeat all these steps on the starboard stab.  So that’s what I worked on tonight.  It actually went really fast, and before long I was stuck yet again.

Luckily, I got the ship notification from Spruce just a bit ago, so I should have the drill tomorrow and be able to jump right back into things after work.

In the meantime…well, the instructions certainly don’t call for temporarily assembling the entire h-stab right now, but how I could I resist the opportunity to spend ten minutes adding a few clecos and ending up with something I could stare at while cackling madly?  I figure there’s some value in detours like this that help remind you that yes, you are going to end up with airplane-type stuff eventually.  Motivation, I tell you…

Got a late start tonight after going out for dinner with Josie.  I did, however, get my angle drill in, so I was able to continue working right where I left off.  First up were the tasks requiring the angle drill: drilling the rivet holes between HS-404, HS-702, HS 810/814, and HS-405.  These were a piece of cake with the new angle drill.  From there, I finished drilling/match-drilling all the skin-skeleton holes.  Then everything came apart, I drilled the last eight holes in the outboard ends of the spar reinforcements, and that was that!

By this time, it was going on 10:00, and I’d been at it for 90 minutes.  I figured that completing the other stab would keep me out there until 11:30, at which point the neighbors might not appreciate the constant sound of spinning air drills and a running compressor.  Plus I have to get up early in the morning for the EAA 690 breakfast.

I did notice an issue as I was taking the port stab apart, and a look at the starboard stab showed the same issue.  The forward most holes between HS-405 and the skins are all a little tight on minimum edge distance.  I don’t see how I could have done this any differently, though… those holes are drilled using prepunched holes in the skin as drill guides, and the rib is further positioned quite positively off the rear spar channel.  There doesn’t seem to be any way that rib could have been shifed forward to allow for proper edge distance.  A touch of research seems to indicate that this is a common problem, and that the universal advice from Van’s amounts to “build on!”  But I’m sort of a nervous Nellie, so I think I’ll ask the folks over at VAF just to be sure.  Worst case, I think I could shore things up by adding an additional rivet without a lot of fanfare.

Bad edge distance!  BAD!!!

Well, overall this was a surprisingly unproductive weekend, at least as far as the plane was concerned.  I pretty much procrastinated myself out of my available work time on Saturday.  Today Josie was doing a NASCAR driving thing at Atlanta Motor Speedway, so I tagged along to watch the fun and get pictures.  This was after we got up at 7 AM to watch the MotoGP race, and then met her family for breakfast.  By the time we got back, a nap was definitely in order, but then we got out in the garage and got to work.

Nothing stunning really; I finished all the drilling on the starboard h-stab while Josie got to work deburring all the numerous holes in the port h-stab skeleton.  By the time the night was over, everything was drilled and deburred, ready for cleaning and priming.  Side note: there are, um,  a lot of holes to be deburred in that skeleton.  I’m writing this mostly so that I can look back and laugh at myself when I’m working on the wings, at which point I’ll presumably learn a new definition for “a lot of holes.”

Yup, with the sole exception of dimpling the skins and finishing the edges, there’s nothing left but riveting.

I was able to get an early start today; I had some medical stuff to take care of in the afternoon, and wasn’t sure how long it would take, so I took half a day off work.  Once I got home, it was straight into the garage and down to business.  First order was to dimple all the skeleton parts, which didn’t take long.  Then it was out to the driveway for some quality time spent cleaning and scuffing all those parts.  Of course, about this time I could hear a good old Georgia summer thunderstorm moving in, so I ended up moving the parts into the garage so they could dry.  

Luckily, the storm barely skirted us.  Clearing skies and a look at the radar confirmed that it looked like I’d have a good window for priming, and it indeed worked out well.  A couple hours later, I had a bunch of nice primed parts.  In the meantime, between primer coats and with some help from Josie, the vinyl came off the skins and all those rivet holes were deburred. (she also relieved me while I was dimpling earlier; with just a hand squeezer, the old forearms get a bit weary after a while)

I guess tomorrow the real fun starts!

Prepped parts drying in the driveway.  Gotta love my “custom” hitch-haul drying rack…

“Please rivet me!  Please!!!”

Late start in the shop tonight- Josie and I went out to dinner and didn’t get home until 7:30 or so.  Once we got home, I turned on the A/C in the garage, let things cool off for a bit, and then got right to work on the rear spar.  Nothing too fancy here-the two reinforcement pieces are clamped into the spar channels, and you rivet away.  The only caveats are to make sure you skip the holes for the ribs and elevator hinges.  As recommended in the instructions, I put some blue painter’s tape over those holes to keep myself honest.

Once the reinforcements and channels were attached, the next step was to rivet on the outer elevator hinge brackets.  Finally, it was time to bolt on the center hinge bearing, which was where the only oddness of the night came.  I dutifully dug out the proper bolts, nuts, and washers. (noting to myself along the way that it was time to buy another storage bin for these things)  I went to push the first bolt through the hinge bracket-and it wouldn’t fit in the hole.  Huh?

Well, there were basically two possibilities here: either the instructions called for the wrong hole size, or I misread them and drilled the wrong hole size.  I checked back and found that the holes should have been drilled to #12.  I then compared the bolts to my trusty drill bit gauge…yep, #12 is the perfect hole size.  I don’t know what I drilled those holes with, but it wasn’t a #12 bit.  Going through my bit collection, I found that I did indeed have a #12 bit…weird.

The only remaining issue was that these holes had been match-drilled with the bracket clecoed in place.  Well, with the large holes I had drilled now, there was no way to really clamp the thing in place and match-drill again.  So I just separately drilled the holes to #12, hoping that everything would line up…and it did.  On went the bolts, nuts, and washers, and the rear spar was officially done!

I really wanted to move on to the front spar, but it was getting late as usual, and I try to knock off the air tool usage after 10 or so, especially the rivet gun.  No worries though, the front spar is a lot simpler, far fewer rivets to take care of there.

The finished product from tonight:

Unfortunately, my cobuilder was a bit under the weather today, which put a bit of a damper on stuff I wanted to get done.  Still, I got all the remaining skeleton assembly and skin prep work done, so now it’s on to putting the skins on.

Skeleton work was pretty easy; the HS-810 and -814 reinforcements get riveted onto the HS-702 front spar channels, and then the HS-405 and -405 inner ribs are riveted onto the front spar.  This work went pretty quick.  I did foul up one rivet that I tried to squeeze, only to have it start to fold over, but I got it drilled out with no drama and just used the rivet gun on the rest.

After that, the skins still needed to be edge finished and dimpled.  Normally, I’d have a second pair of hands for this, but with them unavailable, I went at it alone.  That required a bit of creativity, but nothing too horrible.  I did, however, secure my place in the figure-eight club towards the end of the dimpling session.  I was nearly done when I whacked the C-frame and heard what I would describe as a nonstandard noise.  Yup, I made a new hole.

I went ahead and finished the other dimpling, then went back to deal with the figure-eight.  After a bit of research, I used the flush set in the rivet gun and the back rivet plate to flatten the partial dimple.  I then drilled it out, deburred the new hole, and then redimpled the original hole.  The results look satisfactory; I should be able to fill the accidental hole with some epoxy and then rivet the rest of the skin as normal.  Since the mistake is on the bottom of the skin, nobody should ever see it, especially once paint goes on.

Completed spars, temporarily stored on motorcycle “sawhorses”:

ARGH:

So here I am, freshly back from my first-ever (and certainly not last) trip up to Oshkosh, and it’s definitely time to get back to work.  A short confession before we get started here: some of the work described herein was done almost two weeks ago, but I didn’t do a post then mostly because I spent about 15 minutes in the garage and when I stopped, I was quite furious.

Anyways…when we left off before, all the h-stab skeleton prep was done and it was time to start skinning.  The first step in the instructions is to rivet the HS-707 nose rib to the top side of the skin.  That seemed straightforward at first: cleco in place, looks good, start riveting.  I started from the trailing edge end and moved forward, which in retrospect may have been a bad decision.  I had no problem keeping the skin pulled against the rib until I got to that last rivet on the leading edge.  Here, the skin is pulled into a more noticeable bend to sit against the rib, and without the cleco in place, the skin sat a good 1/2″ or so from the rib.  After some thinking, I clecoed the HS-708 rib to the HS-707 rib and clecoed both to the bottom side of the skin.  This pulled the skin tight against the rib, but also made for some tight quarters.  A little experimentation, and I had the bucking bar in place…I fired the rivet gun…crap, the shop head is clinching.  Drill-out time!

Ever mindful of the opportunity to damage my nice skin, I drilled carefully, popped the manufactured head off, and started trying to drive the shop head off.  Boy was it stubborn…and when I finally got it off, I realized my error of judgment.  With nothing to brace the rib flange, it had bent itself pretty severely.  Oh, and despite being careful, I’d enlarged the skin hole.  I expressed my frustration in some terms which shall not be repeated here, stomped out of the garage, and found something else to occupy me for the rest of the night.  That ended up being the last time I was in the garage pre-OSH as well, what with trip prep.

So tonight, I resolved to get past that pesky thing and move forward.  One important step here was to swallow my pride and get help.  I drove all the previous rivets solo, awkwardly holding the bucking bar and gun at arm’s length.  Which is kind of dumb when you have a lady around who’s expressed plenty of interest in helping.  So yeah, I took advantage of her services tonight.

After careful consideration, I decided that there still wasn’t any better way to pull the skin flush than to cleco the bottom side to the nose and main ribs, so I did that.  I then recruited my help to hold the bucking bar while I drove my first-ever “oops” rivet.  All in all, it was less stressful than I’d built it up to be.  Next, I clecoed the tip rib in place, and set about riveting the bottom side of the skin to HS-707.  Again, here having a helper was, well, helpful.  We got those rivet shot in no time.

Next step is to cleco the front spar in place and blind rivet HS-707 and -708 to the spar.  Seems easy, but oh wait…the only rivet puller I have is a cheapo unit from Lowes or something, and the head is huge.  No way to use it in the tight confines of the stab that I can see.  So I stopped for the night, and tomorrow I’ll see about finding a rivet puller that fits in tight spaces better.

(no pictures tonight, I’m afraid…)

Went right back to work on the port stab today.  Over my lunch break, I made a run over to Harbor Freight Aviation Supply to see if they had a blind riveter with a smaller head.  Turns out they did.  Plus, the head also swivels, which might come in handy for some odd places in the future.  For $9, I think I can get my money’s worth out of the thing. 

Once I got home, a bit of experimenting confirmed that my new riveter would work just fine for the current task.  I recruited Josie to come hold the stab in a better working position, and the three blind rivets were set in no time.  Next step was to start riveting the HS-702 spar and HS-708 main rib.  This was by far the most flush rivets I’d set.  At first I had Josie helping me by bucking while I ran the gun, and we had a decent rhythm going.  But she wasn’t feeling totally great, and had even stayed home from work, so after about 30 minutes she (rather apologetically) went inside.  I found that the spar rivets weren’t too difficult to shoot solo, so I shot the rest of those myself.  I was able to get Josie back out to help with the rib rivets, which were a bit too awkward to comfortably shoot solo.

Out of all that, I only had one rivet that had to be drilled out; I apparently let the bucking bar slip and the shop head started to fold.  But I caught it early enough that it was easy to extract, and I didn’t damage my skin at all!

It was getting pretty late by this point, so as much as I would have loved to move right on to the starboard skin, it was quitting time.  I also would have merrily squeezed the rivets on the ends of the stab, but instructions have you leave these for last, once the rear spar is clecoed in place.  Not sure what the reason for this is, but I don’t have a good reason to depart from the instructions, so I won’t.

Tomorrow evening is free as well, and it’s a work-from-home day for me.  I’m hoping to get out in the garage early and get all these steps repeated on the starboard skin.  Once that’s done, I’ll pretty much be home-free on my first assembly!

Mostly-riveted port skin:

A nice little row of shop heads: