Empennage Fitting

I received the aluminum bar I needed to make the shims that go underneath the attach angles of the front spar on the horizontal stab.  The plans give measurements to get all of the layout angles for the shims right, but I just put a square piece in place under the attach angle, drilled the bolt holes through to match the existing ones, then traced around the attach angles to get the layout.  A few simple cuts and some sanding and the shims were done and in place (temporarily).

The rear of the horizontal stab has to be elevated a bit to get the incidence set to zero.  An 11/32 bit placed under the rear spar should get everything where it needs to be.  With that in place, I put a 12" long drill bit into the aft tooling holes of the ribs to get a measurement.  Then I put the same long drill bit in the forward tooling holes of the nose ribs and measured there. It was within 1/64", so I'm calling that good!  I drilled the bolt holes in the two vertical attach bars that come out of the fuselage and connect to the rear spar.  I temporarily bolted things together with the top two bolts.

The elevators have to go back on for the 100th time so the pushrod can be put in place, as well as a check for general fitment.  The right elevator looks great in terms of how it lines up with the horizontal stab.

For whatever reason, the left elevator looks less great.  I'm not sure what is causing the difference in gap between the two sides.  There's not really much wiggle room when building them, so it's hard to imagine what I could have done to create such a difference from side to side.

I slid the pushrod into position and bolted it to the bellcrank and the elevator control horns.  This is just temporary for now (I still have to prime the pushrod), but helps to get everything set to the correct length.

When I bolted the pushrod bearing to the control horns, that's when I realized I had a potential problem.  The instructions prior to this point had said to drill the control horns together by clamping the elevator counterbalance arms to the horizontal stab.  In theory, that should put the trailing edges in a neutral position, and drilling the control horns based on that should mean perfect alignment.

Once I got everything hooked up, I saw that with the counterbalance arms level to the horizontal stab, the left elevator trailing edge was 1/2" below the trailing edge of the right side.  I've emailed Van's to find out what the best way forward is.  I've looked online, and there are a suspicious number of people who have had the exact same issue, down to the same 1/2" measurement.  So there is a possibility that I either just built a twisted elevator, or something about the manufacturing of that side continues to spit out some parts that end up being a little off.  Some builders said they noticed it early and instead of lining up the counterbalance arms to drill the control horns together, they lined the trailing edges up instead.  Of course, that means that in neutral they have one counterbalance arm that is up and one that is down.  Ugly.  Others have said they left it all alone and have noticed zero negative flight characteristics (one DAR said that an RV6 he looked at had this issue.  It was already flying, and the builder decided to rebuild the elevator, only to discover it didn't change anything about how the plane flew).  I'll see what Van's has to say.  It's possible I could drill key pieces of the elevator apart and correct it, but I'm not sure.  Worse case scenario, for a few hundred bucks and a weekend of time I could have another elevator built.  Based on what I've seen online though, I wouldn't be surprised if they said that it's unlikely to have any perceivable impact.  The joy of building is that I can always fly it, and if I don't like it, I can always build a new part and replace it.

Moving on from the horizontal stab, it's time to mount the vertical stab.  I drilled and temporarily bolted a mounting plate to the front horizontal stab spar.

The front spar of the vertical stab has to be cut down a bit to fit in place.  I have no idea why they don't just ship the spar the right length or have you cut it before you build the thing.  They do weird things like that all of the time.  I set the vertical stab in place and clamped the rear spar to the aft most bulkhead in the fuselage.  There are a few measurements called out in terms of where the whole thing sets vertically.  After a lot of tapping and back and forth, I finally got it in place.  Next up, ensuring it's actually at a right angle to the horizontal stab.  100 measurements and tapping later, I think I got it.  Every time I'd tap the top portion one way or the other, that meant it slide a little vertically as well, so each tap meant remeasuring both planes.  I haven't drilled or bolted it in place yet.  I wanted to take a step back and come back to it another day to double check things.

Elevator Fitting

Switching gears from fuselage plumbing - time to start fitting the tail feathers to the fuselage.  I pulled the horizontal stabilizer and elevators out of storage.  The garage is getting awfully full!

The elevators are connected to the horizontal stabilizer with two rod end bearings that screw into nutplates attached to the elevator spar.  Van's says the max measurement from the spar to the center of the bearing is 7/8", so I took it a little past that to start.

Getting the bolts into the rod end bearings while holding the elevator with the other hand was easier said than done.  I screwed some boards to the bench to act as a clamp for the horizontal stab to keep it from moving around.  I put both elevators on just to see how things line up before doing any drilling. The control horns don't line up well at all, but after some searching online I found that this is par for the course.  Once everything is mounted to the fuselage the control pushrod will be drilled to the control horns, so having them match up doesn't really matter as long as they are drilled together in the end.

I took one elevator off so I could get at the control horn to drill it to the center bearing (on the rear spar of the horizontal stab).  The elevator has to be in trail before any drilling is done, which is accomplished by clamping the counterbalance arm to the horizontal stab.

In order to drill the bolt hole in the control arm that connects through the center bearing, I needed a 1/4" metal bushing of some sort to help get a center hole started.  I looked through every bin at Home Depot and couldn't find anything that would work, so I ended up going the 3D printer route.  It seemed to work okay, although not as accurate as if it were metal I'm sure.

Once the pilot hole was drilled into each control horn, I final sized it to 1/4".  The next step is to put both elevators back on the stabilizer to match drill the hole that the control pushrod will connect to.  I was done for the day though, so just for fun I put the horizontal stab on the fuselage just to see if it was going to fit in the space I had.  It's going to be tight!

Elevator Trim Tab & Wing Access Plates

The proseal that joins the foam ribs to the skin in the trim tab has been curing for a little over a week, so I decided to finish up the trim tab today.  It's a little fiddly because there isn't a great way to clamp the remaining portion of the hinge to the elevator while the trim tab is actually attached.  I had to do a lot of back and forth until I got the hinge in a place that allowed the trailing edges to line up, as well as left the required space between the elevator and trim tab in the middle where they meet.

I match drilled all of the holes, double checked the alignment of everything, then pulled it all apart and cut the hinge to length.

Everything went together pretty well and the trim tab moves freely.  I still need to bend the hinge pin and safety wire it in place, but I need to order safety wire.  I have a running checklist of items that still need to be done so I don't forget.  Likewise, the counterweights still need to be added to the elevators.  Considering that the elevators can't truly be balanced until they are on the fuselage (and again after paint), I just decided to leave the counterweights off for now and will bolt them in when I join everything together.

With the elevator done and a little more energy from dinner, I decided to keep chipping away at the spar nuplates.  I had all of the tank attach points done on both spars already, but there are also a number of nutplates needed for 3 access plates on the underside of each wing.  These nutplates are slightly smaller for a #6 screw vs the #8 of the tanks.  Each access plate has 4 screws that go trough the spar.  The method for countersinking the screw hole was the same as before, except this time a #40 countersink pilot is what fits in the threaded nutplate hole to keep things centered.

I upsized the prepunched holes in an access plate and dimpled them as a check to make sure my spar countersinking was okay.  The reference I found on VAF said that a #6 countersink should be less than .3125" wide, and mine were just under .3100". The fit with the access plate was great.  Tomorrow I'll drill, deburr and countersink all of the access plates. We'll see if I remember that the 4 holes I did tonight are for #6 screws, but all of the other holes on the perimeter of the access plate get #8 screws.  No idea why the difference.

Trim Tab & Wing Crate

Today was trim tab day.  Funny how a part so small can take so long to do.  I'd already drilled, primed and dimpled the skin and spar, so the next step was to bend both ends of the skin to make 90 degree tabs for the ends.  I sure wish Van's had made these bends!  There were 4 bends to make.  By the time I got to the 4th one I had it 50% figured out, meaning the first three were kind of a mess.  On the first one the form slipped little by little as I hammered the bend in place. That made the bend about 1/8" beyond where I really wanted it to be.  Part of me wanted to order a time skin and try again, but it's just a trim tab, and I know it's really not a huge deal.  By the end, I'd learned to clamp things down as tight as possible (which unfortunately led to a few creases in the skin that I'll have to put some lipstick on down the road) and also back the bottom form up with a 2x4 that was screwed to the bench so it wouldn't migrate as I hammered on it.

I feel like this blog is kind of like confession - look closely and see if you can spot my mistake in the picture below.

Somehow, when prepping the skins to receive the control horns, I missed dimpling a hole.  The vast majority of the time that's not a big deal at all since you can just dimple when you find the mistake.  In this case, I had already riveted on the control horns by the time I saw it.  My only options were to drill out all of the rivets in the control horns or simply try to dimple both layers of aluminum at the same time and accept the less than perfect outcome.  I opted for the latter.  The result was actually fairly good, so moving on.

The hinge that links the trim tab to the elevator was next.  This is a great example of how the instructions have changed over the course of the build.  Whereas initially they walked step by step through things, that's no longer the case.  Now, it says things like "cleco, drill, deburr, and dimple the skin and spar and hinge."  That leaves a lot to figure out just by staring at the plans and trying to figure out where to make cuts, what order to stack parts in, which side is "up" on the hinge, etc.  I think mostly it's a lesson in the fact that the minutia really doesn't matter in most cases.

I didn't get any pictures of the next part because of the mess - time to Proseal the foam ribs into the skins.  People aren't lying.  Proseal is incredibly sticky and messy!  The only gotcha with this was the fact that my digital scale doesn't measure in small enough increments to do the 10:1 ratio.  I only needed a very small amount to cover the foam ribs, so I had to eyeball the ratio to a certain extent. Time will tell if I got it close enough.  A lot of head scratching and double checking later, I had the hinge cut, drilled, and riveted onto the trim tab spar.  I put my wood forms over the foam/Prosealed ribs to squeeze it all together and will leave that in place for the next week while it cures.  Following that, I'll need to match drill the other half of the hinge to the spar on the elevator, then this will all be done and it'll be time to mate the elevators to the horizontal stabilizer, and do the same with the vertical stabilizer and rudder (an initial fit anyway - the final fit isn't done until it's all attached to the fuselage).

It's hard to believe, but that means it's time to start the wings!  I was ready to pack it in for the day but just couldn't help from at least taking a look at what I am up against.  I pulled down the bag of wing hardware and organized it.  A lot of the rivets could be consolidated with the leftover tail rivets of the same size, but there was a shockingly wide variety of new rivet sizes for the wings.  I had no idea so many slight variations of blind rivets existed.

I unpacked the spar crate (1 of 2 wing crates) and pulled the spars out.  I'm not sure what will be the most convenient orientation to work on these, but for now spun my workbench 90 degrees.  Ultimately the spars will get mounted on a stand, but I'll probably leave them on the bench for the first few build steps.  They are in good condition with the exception of one scratch in the right web that will need to be sanded/smoothed out.  Since these are already alodined, I'll either just hit the scratch with primer or buy an alodine pen for the area I fix.

I stared at the plans for a solid 30 minutes to decipher the first sentence of the instructions. I think I've got it sorted out now - basically my first step is to install a ton of nutplates (looks like Van's uses the term nuplates vs platenuts) in the inboard spar flange.  These will partially be how the fuel tank attaches to the spar.  So that one sentence of instructions will take me a number of days - set up a way to hold the spars, countersink, prime the countersink, and rivet on the nutplates.

The next question I need to answer is whether I'm going to build one wing at a time or both simultaneously.  I'd prefer to do both at the same time, but it depends on space.  We'll see if I can figure out a way to get the wing jig in place for both wings and not run out of room.

Left Elevator Trim Tab

I started on the trim tab today.  I didn't end up doing much though, because it became apparent pretty quickly that my head just wasn't in the game.  I didn't screw anything up, but I wasn't thinking far enough ahead to keep from having to stop and redo something that wasn't mentioned in the plans but that I should have done.  The instructions are getting more and more sparse at this point, so you really have to think through how everything goes together before you start on a step.

I clecoed the trim tab to the Z spar and then squeezed the trailing edge per the plans.  Basically, they have you squeeze the edge little by little to flatten it out so that it's a straight line from the edge to the spar with no dip or puckering.

The trim tab horns get riveted to the bottom of the trim tab and attach to the control arm from the servo.  I had to modify the supplied parts just a bit since I'm using electric trim instead of manual.

I primed the parts using the Duplicolor rattle can primer.  I can't say that I'm a huge fan of the stuff.  It has an incredibly strong smell that just never seems to go away, and it doesn't seem very tough.  I'll try another brand once this can is gone.

Left Elevator & Trim Tab

There was no waffling on whether or not to use pop rivets or solid rivets on the bottom spar this time around.  The time savings of the pop rivets is just too much.  I don't know why people spend hours and hours figuring out how to put solid rivets here!  I'd rather finish and fly the plane.

The second trim tab spar was riveted in.  As expected, the pre-punched holes lined up perfectly, so there was no issue with not having match drilled it in assembly.  For now, only the bottom side is riveted.  The top isn't riveted until the trim tab hinge is done and in place, which I will do along with the trim tab itself.

The counterbalance ribs were next.  The result of this has me scratching my head a bit.  While it's fine, the trailing half of the ribs where the elevator skin attaches doesn't sit super level with the rest of the elevator.  It's that way on both top and bottom, so it's almost like the rib is just slightly undersized, making the skins dip inward at the edge of the elevator.  I did a lot of bending with seaming pliers to get it as level as I could.  I checked and rechecked, and there's nothing that I can see that I did wrong, so I think it's just how the parts are made.  Like most things so far, this will only be noticeable to me, and I'm sure I'll forget about it when the plane is in the air.

The trailing edge was next.  Because the trim tab takes up half of the elevator length, the trailing edge is pretty short compared to the right elevator.  Using the aluminum angle as a straight edge is kind of a pain because it takes a while to drill through, so I thought I'd try using a piece of plywood instead.  This was every bit as straight (maybe straighter actually) as the aluminum angle and much easier to drill through.  I match drilled through the top skin, wedge, bottom skin, and into the wood and clecoed in place while the 3M tape set up.

I used the same drill press setup for countersinking the wedge as I did for the rudder and right elevator wedges.  It works really well and with such a short piece of wedge was done quickly.  Then I back riveted the trailing edge and filed down the portion of wedge that was sticking out.  Here's where I noticed that I probably goofed in my initial match drilling setup.  I don't think my skins were completely flat when I was drilling the wedge and bottom skin, because the amount of wedge sticking out from the top and bottom skin is not the same (meaning the angle on top and bottom wasn't perfect so the skins don't meet at the same point on the wedge).  The edge is the straightest I've made so far though.  The skin difference of where it meets on the wedge is probably on the order of 1/32-1/16", so not exactly something that will likely matter in the performance of the plane.

The last step for the elevator was finishing up the 3 aft rivets in the counterbalance rib (left open to make dealing with the trailing edge easier).  The last aft rivet was a nightmare.  The space is too small to get any kind of a squeezer yoke in, and after 3 attempts at bucking it (and drilling out the rivets 3x), I gave up and decided to just use a pop rivet on the bottom side.  I should have just gone with a pop rivet to start with.

I didn't get much done on the trim tab itself, but started by making a couple of blocks and foam ribs for it.  The foam ribs will be Prosealed in place, basically as stiffeners, and the wood blocks are used to pinch the skin down until the Proseal cures.

Left Elevator - Try Again

I got a surprise today!  I ordered the replacement trim tab spar on Monday, and I half expected to get a note from Van's saying that parts are delayed and it would be weeks or months before I would receive it.  They must still have enough raw material in stock to keep a supply of individual parts though because they shipped right away and I received the part today.  I also ordered some fuel tank sealant ("Proseal" but a different brand) since I need that to finish the trim tab itself, and I'll also need it sooner rather than later when I start the fuel tanks.

Since I already had the elevator set up to start back riveting the top stiffeners in place, I went ahead and finished up with that before redoing the trim tab spar.  I was originally assuming I would squeeze the rivets for the trim servo doubler, but figured I might as well back rivet that too.

From the outside you can now see how that doubler works - it's mounted inside the elevator so that the servo mount plate itself will nest on top of it and screw into the nuplates, leaving everything flush on the outside.

Now it was time for take two on the trim tab spar.  I couldn't really match drill the spar in place since the mating skins are already dimpled, so I just reamed the holes to the proper size.  These parts have been so accurate that I highly doubt it'll cause any trouble during assembly.  Learning from my previous mistake, I clamped a piece of wood to the back side of the flange that gets countersunk.  Then I drilled matching holes into the wood.  The idea is that on material this thin, the wood will give the pilot of the countersink bit a guide once it's through the material.  It worked much, much better and the holes turned out great.

I wasn't about to set up the spray gun to shoot primer on one part, so I just pulled out the spray can primer instead.  I'm sure my twitching from having two different colors of primer will go away in a  few days.  This will eventually get painted anyway, so it doesn't really matter.  It'll just be a reminder of the first (probably not last) part I screwed up.

Left Elevator Continues

When it comes to these elevators, I think I spend more of my time flipping parts around in awkward holding contraptions than actually building.  Following what I learned in doing the right elevator, I went ahead and riveted the counterbalance ribs to the spar before starting to rivet the spar to the skin.  I don't know why the plans don't have things in this order.  It's a whole lot easier to set 5 specific rivets in those ribs and spar before the skin is in place.  After completing that, the skin got put into the torture device so I could open it up beyond 90 degrees and put the spar in place.

Just like the right elevator, getting the bucking bar in place to rivet the spar to skin rivets was pretty awkward.  The only way I found to manage it was to have the bucking bar held up against the top of the spar web by two fingers, then pushed against the flange and rivet with my thumb.  By the time I was done bucking, I had a serious cramp in my fingers, but it's done!  It's hard to see those rivets at all, let alone get a good picture, but for the most part they all turned out pretty decent.

It's always fun to do something a little different, so I ended the night by dimpling the nutplates so they would mate with the dimpled trim tab mounting plate, then riveting them in place.  This piece gets permanently mounted to the bottom of the elevator inside the skin, then the plate that the actual trim servo mounts to is held in place by screws that use the nutplates.

Left Elevator Riveting

I know it's only been a few days, but I feel like it's been eons since I've been able to make much progress on the build.  I was able to get out in the garage for a few hours tonight and clear my head with some riveting.  Funny how therapeutic that is.

Similar to the right elevator, I started by clamping the top side of the skin down and rolling the lower skin back so I could get at the stiffeners for back riveting.

Next I moved on to the counterbalance ribs.  The primer from this batch of parts is much smoother than previous batches.  I didn't thin it with 10% water this time, and that seems to have made a difference.  From what I gather though, the variables of temperature, humidity, and dilution all play off of each other, so it's anybody's guess what the right mix will be next time.

After the counterbalance rib webs are riveted together, the counterbalance skin goes on.  I'm slowly learning the proper order to do things in, like which edge to start clecoing or riveting first to make skins fit easier.  Things like this aren't always pointed out in the manual, but after spending hours cussing at a single rivet hole you start to figure out the tricks.

The elevator spar reinforcement plates and plate nuts (or nut plates....I see it both ways and people always argue that their way is the correct terminology) are riveted on next.  I don't know that there's a better feeling than using the pneumatic squeezer on rivets.  It's still incredibly satisfying for some reason.

I had forgotten to prep the spar and end rib before I primered.  Unlike most assemblies in this area, these need to be flush head rivets, not universal heads, because the control horn has to be attached here.  So I dimpled the rib flange and spar holes.  The primer held up just fine.  I squeezed the flush head rivets and then bent the rib flange back to the proper angle (it had to be straightened a bit to get the holes dimpled and riveted).

Lastly, I riveted the control horn to the spar and rib.  Just like on the right elevator, this was a pain.  I don't know if it's because the holes just don't line up perfectly or because of the primer that has to be dabbed into the control horn holes.  The control horn is steel, so once you match drill the holes, there's no protection for the freshly reamed holes.  I always dab some primer in them, but once it dries, I think it makes for just a small enough hole that getting the rivet through is a total pain.  I ended up reaming out a few of the holes and just installing rivets wet with primer.