Autopilot Brackets

I'm trying to find random things I can accomplish while I'm waiting for my back ordered primer.  I installed the Dynon pitch servo bracket on the elevator bellcrank rib.  Ignore the lovely primer scribbles on the vertical rib - I had to cover up a bunch of scratches to the Rustoleum primer where I looked at it funny.  Hence the reason I'm not a huge fan of the spray can primer.

The roll servo gets installed in the right wing.  Most of the original brackets say in place, but Dynon adds in a few pieces to accommodate the servo.  Here's the original setup:

I replaced the bottom bracket, as well as added a diagonal rear bracket arm (hard to see in the picture, but it's by the arrow) that will support the servo itself.  To allow the servo to connect to the bellcrank, a spacer and plate is added to the bellcrank.  This will eventually get a pushrod that connects the two.  For now, this is all that I'll put together though.  I'll buy the servos when I'm ready to start doing a lot of the wiring in the plane.

Firewall Assembly

I've read that it's best to back rivet the firewall since the stainless is pretty easy to ding and bend up.  My big back rivet plate is a bit too big to be able to do all of the rivets, but it'll work for the vast majority.  It sets in between the firewall flanges okay, but because of the curve at the top of the firewall, the plate can't quite extend out to the vertical row of rivets on each side.

Thinking I was being efficient, I put all of the rivets in and taped them with rivet tape so I could flip the firewall over onto the back rivet plate just once.  This turned out to be rather inefficient, since I found a lot of the rivet lengths the plans called out were too short for my liking.  Some were fine, but most of them going through more than two layers ended up being one size too short.  I ended up replacing a bunch of them with longer sizes.

Flipped over onto the back rivet plate and ready for all of the bits.

The nice thing about back riveting is how fast it goes!  It probably only took 10 minutes to finish everything except for the corner brackets.  There were a number of rivets in those that I had to finish with the gun and bucking bar.  The firewall recess will be riveted on as late in the build as possible, since it provides a convenient space to reach through when mounting all sorts of things inside the cockpit.

While doing some research, I just happened to stumble on the fact that the fuel pump doubler (at the bottom of the firewall in the middle) is not actually necessary in my case.  The plans and instructions say to put it in and don't give any indication that it might not be needed.  It turns out, that doubler is only used for fuel pumps in a carbureted setup.  For an injected engine, the electric boost pump is bigger and is mounted on the floor of the cockpit in front of the seats instead.  When I discovered this, I asked around, and it turns out it's a common oversight.  Since the holes were already drilled and dimpled, I went ahead and attached the doubler.  It's possible I'll use it for mounting something else down the road.  If not, I'll just put bolts through the open nutplate holes and seal it up.

Firewall Primer

I figured I may as well see just how far the drops of primer I had left in the can would  go.  I didn't really expect to be able to even finish the firewall stiffeners, but gave it a shot just in case.  Turns out I had just enough to finish up. I moved the heat lamp over by the open garage door and set the priming table up under it.  It was about 50 degrees out, but the lamp bumped up the temp just enough for things to dry relatively quickly.  The only problem I ran into was the fact that it was a gloomy day and the lighting made it tough to see how much primer I was laying down.

Shop Reorganization

Still no sign of when the primer I ordered will be back in stock, so not much building will happen for a while. The fuselage was already starting to fill up the bay it was in, so today I decided to do some shuffling.  I pulled everything outside (we actually had a nice break in the rain!) and made a total mess of the garage.

I ultimately need more width and length for the fuselage, so I slid the table saw over and moved the drill press and band saw into that spot.  That freed up a few more feet of length.  I also slid my workbench with the sander and grinder around to the other side of the post, then shoved the wood workbenches over a few feet as well.  That middle bay is now completely crammed with stuff, but at least it gives me space to work on the fuselage.  I have the tailcone on the workbenches for now until I finish riveting the bottom skin.  This should all work fine until I get to the point where I need the room to test mount the wings and mount the tail.  Then I'll have to reorganize again.

Firewall (4)

I only had a little bit of time to work on the plane today.  I finished up all of the countersinking of the firewall stiffeners.  Now I think I'm officially done with everything I can be until I get more primer.

I took the tailcone off of the saw horses and laid it on the table.  I think it's going to be easier to back rivet the bottom skin with it laying on its side like this vs having to have someone lay underneath it to hold the back rivet bar.

Firewall (3) & Pitch Autopilot Bracket

I'm getting really close to being at a stopping point until I get more primer.  The pile of parts to be primed is getting pretty deep!  I took a quick break from the firewall to figure out the pitch autopilot servo bracket that got delivered recently.  The only measurement they provide is the distance of the front flange of the bracket to the center of the bellcrank pivot point.  How the bracket is attached to the bellcrank rib is left up to the imagination of the builder.  They simply say it can be bolted or riveted to the rib.  Since I had left three holes open in the rib, I decided to just go the rivet route.  The bracket comes with a bottom flange that can be riveted to the skin.  They say it can be cut off though, so instead of drilling more holes in the skin, I decided to remove the flange and just rivet the bracket to the rib.  I match drilled to the top three rivet holes in the rib/angle, then drilled another two rows of three rivets.  This bracket is all I need to install for now (after I prime it...it's in the pile).  The servo and connection to the elevator bellcrank can be done later.

Back to the firewall.  I needed to deburr the holes, but the stainless steel was far more difficult to deburr than aluminum. I tried a cone shaped grinding stone in the die grinder, but the holes just ate it up.  Then I tried a drill bit, but it wouldn't cleanly trim the burrs.  I asked online and the suggestion was to use a cutoff wheel at really low speed.  That did the trick.

Next up, dimpling.  All of the rivets used on the firewall are flat head rivets with the manufactured head on the front side.  This makes the firewall smooth on the engine side so mounting brackets is easier.  The stainless is very easy to dimple since it's super thin, but it dings and deforms much more easily than aluminum sheet.

Since the firewall gets dimpled, that means all of the brackets, spacers and stiffeners have to be countersunk.  I got about halfway through with them before stopping for the day.

Firewall (2)

I made the stiffener for the bottom of the firewall recess and match drilled it to the firewall.

Next up was the brake bracket.

The firewall recess is also made of stainless steel.  Everything fit fine except for the top two holes.  The 1/8" hole was off by a half of a hole on both sides, and the 3/32" hole below it was almost as bad.  Every other hole was spot on.  Because of the bends, there was absolutely no shifting of the holes (well maybe if I had taken a hammer to the metal, but I didn't want to do that).  I looked it up online and it turns out that this is a very well known issue.  The holes are either drilled slightly off, or the bend is wrong.  I found comments about this going back decades, so evidently Van's doesn't think it's worth fixing.  I tried to line things up as best as I could, but in the end I elongated those couple of holes pretty bad.  I'll have to see if it's a problem down the road when I rivet the recess in.  That'll be a long time though - you leave it out to allow for a nice big hole in the firewall to ease installing things.

The last piece for the firewall is a fuel pump doubler (for the auxiliary pump).  I triple checked the spiderweb of measurements on the plans, cut it out and drilled the holes. 

I didn't realize how easy it is to drill through aluminum until it was time to drill through the stainless!  I clamped the doubler in place and used the holes to drill the firewall.  It's a bit slow with a lot of messy lubricant.

Center Section Skin, Firewall & New Parts

The last thing I had to finish up for the center section was dimpling the bottom skin.  I did most of that with the C-frame dimpler.  About half way through, the ram in the dimpler just froze and wouldn't slide up and down for some reason.  I took it out and cleaned it off, but that didn't change anything.  Then it dawned on me - with the radiant heater cranking, the ram itself was heating up, but the metal of the barrel that it slides in (much thicker) was still pretty cold overall.  I measured the barrel and ram and found that they are the exact same size, down to .001", so I suppose it doesn't take much heat differential to make the ram expand enough to matter.  I turned off the heater and within 5 minutes, everything was working normally again.  

Getting done with the skin meant I could turn the heater back on and add the ambience of the orange glow to the rest of my pictures.

I had to place an order for more primer from Aircraft Spruce, but with shipping being what it is, I always try to order at least a few things to take the sting out of it (order enough and the shipping is free).  I won't order most avionics until I'm almost ready to install them since those get outdated as fast as personal computers, but for pretty much everything without a computer screen, it doesn't really matter when I get it.  Since I've decided to go with a Dynon panel, I ordered the Dynon heated/regulated pitot/AOA (very nice because it measures the temp and only draws enough power to keep the pitot from freezing vs having only an on/off, with the "on" being blistering hot).

I also went ahead and purchased the attach brackets for the pitch and roll servos.  If I install the brackets now, the servos can be purchased and installed right at the end of the build.  I don't know that much will change with servos between now and then, but as long as I have the brackets in, there's no reason to rush and get the servos just to have them sit.

Now it was time to backtrack!  The center section needs to be primed before it can be assembled, but as luck would have it, my big order from Aircraft Spruce got me all of the things I don't need right away, but back ordered the primer.  Figures.  So the center section is done and ready to assemble once I have the primer.  Truth be told, I've seriously messed with the idea of just spraying a little primer on the flanges and mating surfaces of the ribs and calling it a day.  I know that's more than adequate to have the plane outlast my lifetime since everything left to build is an internal cockpit part and not exposed to the elements.  If the rest of the primer is backordered too long, I may end up just going that route.  We'll see.  I'm type A enough that I will have a hard time with a 95% primed plane and 5% not, regardless of logic.

Anyway, now that I have most of the backordered parts from Van's, I need to backtrack and work on the firewall.  I forgot to get a picture of just the parts, but here's the general idea after some of it has been clecoed together.  Van's pre-drills a lot of the stiffeners, which is really nice.  I know they could pre-drill everything, but I'm guessing the 51% rule is what keeps them from doing that.  They have to leave enough tasks for me to do.  The firewall is a very thin (shockingly thin) sheet of stainless steel that has a flange around the entire perimeter for stiffness.  It's still a super flimsy thing.  It gets covered in stiffeners and brackets.  The picture below is far from everything, but it is the starting point for stiffeners.  The 4 white powder coated brackets in the corners are steel brackets that the longerons and other things will attach to.  The side with all of the stiffeners is the cockpit side.

It's a little deceptive to see everything laid out, because just about every intersection of stiffeners or brackets has pieces underneath or around them.  For example, the center vertical stiffener that joins the diagonal one and the bottom horizontal one has one triangular spacer, plus another full spacer on top of it, followed by one of the large aluminum angles I fabricated a while ago.

Center Section - Deconstruction

Now for the depressing part - taking all of my hard work apart.

It took most of the day to take everything apart and get the holes deburred.  I still have to deburr the skin itself, but that's for another day.

Center Section - Bulkheads

I don't have many pictures that justify the amount of time I spent working on the plane today.  The next step I had to accomplish was adding the front 904 bulkhead onto the aft 904 bulkhead so the front row of holes of the bottom skin could be final drilled to the bottom bulkhead flange.  This was a simple task, but I spent gobs of time getting the spacer blocks as close to the right size as possible.  The blocks are just temporary, but they hold the fore and aft bulkheads the right distance apart so the wing spars can slide in tightly down the road.  Too tight and getting the wings on will be a bear.  Too loose and....well we don't want the wing spars to fit too loosely!  I had already made a couple of blocks a while back that were really close to the right width, but slightly big.  I started to lightly sand the surface to close in on the right width.  Easier said than done when you're talking thousandths of an inch.  Van's says make it 1.438" wide to match the thickness of the spar.  What I found to be the problem was that if I got the blocks really close to that number, as soon as I put them into the spar and clamped them down, they compressed a little bit.  I think after a lot of trial and error (and pieces of paper) I got it all close enough.  The spar has 10 bolts that will snug everything together, so I'm actually more worried about it all being too tight than too loose.

One of the last steps before the tedious deburring, dimpling and countersinking begins is to drill the 904H side doublers in place.  These help tie the fore and aft bulkhead portions together.  The doublers have pre-punched holes, but there are no holes in the bulkhead (aside from 4 reference holes to line the doubler up).  I very nearly screwed up, because I didn't initially see that the doubler isn't quite symmetrical.  It's close enough not to notice until you put it on the bulkhead wrong and it looks slightly off center.  Thankfully I realized this before I drilled any holes.  All I had to do was flip it around, but I'm wondering how many people have gotten caught by this.

I got the left doubler finished and made it 90% through the right one before it was time to take the dogs for a walk.  That means tomorrow I'll probably start taking it all apart and figuring out what gets dimpled and countersunk.  I can go ahead and dimple and/or countersink everything but the ribs, since the skin is already primed and the 904 bulkhead doesn't get primed.  Unfortunately I'm almost out of primer and they are out of stock at the moment, so it could be a little while before I can prime and assemble.  I have plenty to do though - the tailcone bottom skin still needs to be riveted and I can start building the firewall since I finally have the backordered parts.

Center Section - Outboard Ribs

Back at the outboard seat ribs.  It feels strange to flute ribs to make them curved instead of straighten them.  Now that I had the approach figured out after thinking through it last night it actually went fairly quick though.  I got both the right and left ribs clamped in place and match drilled them through the skins.

After the outboard seat ribs were done, I moved on to the outboard baggage ribs.  These are a little different because they lay with the web flat against the skin as opposed to the flange. The first one gave me way more trouble than I care to admit.  The instructions for these are non-existent, and unfortunately, the plans are also very little help.  All the plans say to to do is line the edge of the rib up with the edge of the skin.  The main issue was the fact that the angle of the rib didn't actually match the angle of the skin.  As soon as I'd line up the front, the back edge was 1/8" away from the edge of the skin.  It took me an hour of looking at various plan views and pictures online and inching things back and forth before I figured out that the aft portion of the rib doesn't actually have to line up with the skin.  The front portion does because the side skin in this area is actually riveted to the flange itself.  The aft portion of the side skin just curves around the flange and is riveted underneath as opposed to the flange, so it doesn't matter if the flange matches up exactly.  Why they couldn't just say that in the instructions and save people hours of head scratching is beyond me.

With that figured out, I clamped the left rib in place and match drilled the web to the skin.

Each end of the rib needs an attach strap to bridge the gap between the end of the rib and the last skin hole (I still don't see why Van's doesn't just modify the shape of the rib).  I found a scrap piece of .032" sheet and cut out the straps.

The aft attach strap is supposed to be like the top one in the picture.  But since the aft portion of the rib doesn't line up with the skin, I had to remake them to create more meat at the end. Otherwise the holes in the skin were way too close to the edges of the strap.  I made a jog in the strap so the end could stick out beyond the edge of the rib flange and capture more of the skin.  Hard to explain, but it worked.

The next big question mark had to do with the portion of the rib flanges that have to be cut out for the step pipe to clear.  Again, the instructions provide no guidance, and the plans don't show any actual measurements.  I took that to mean that the actual size of the cutout doesn't make any structural difference (that was the consensus on most of the other build blogs I looked at as well).  I eyeballed the arc that needed to be cut out and used a cutoff wheel to do it.

I thought holding the step in place would help me figure out if the cutout was good enough, but it looks like the portion of the tube that goes inside will have to be cut to length at some point, so even that wasn't a perfect measure.  Oh well, I think it's good enough.  Worse case scenario, I can modify it down the road when the step is actually attached.

After the left side was finished, the right side took a fraction of the time.  Like 15 minutes for the right side vs hours for the left.  I guess that means I can be taught, right?

Center Section Skin

I inventoried the backordered items that arrived last night.  Besides the one bag of goodies that is still on backorder, there were 3 pieces missing that should have been sent.  I contacted Van's and they are sending them right away.  The parts that were starting to hold me back (besides the firewall parts which made me skip starting the firewall completely) were the baggage ribs, so with those in hand now I could keep moving on the center section.

The outboard baggage ribs needed a large hole cut in each of them since I'm installing steps on the plane.  The steps (which also came in the backordered bundle) attach to the side of the fuselage, but there is a 1 1/2" steel tube that extends inside under the baggage floor, through the outboard ribs and gets anchored by a plastic block.  I couldn't find a hole saw the right size, so I pulled out the fly cutter of death and used that.  It's actually not that terrifying as long as I drop the drill press speed to its slowest setting.

In order to final drill all of the ribs to the skin, I flipped the entire center section over and put the skin on top.  I started out on a step stool, but by the time I got to drilling I gave up and just climbed up on the table so I could stand over it all easier.  It's funny, apparently 45 is the age where you start looking for steps to get up and down from heights because the short hop down onto the floor feels like a fall from 10 stories up. 

With all of the ribs and the bulkheads final drilled to the skin, I moved on to a couple of parts that seem like afterthoughts in terms of manufacturing and instructions.  The outboard seat ribs don't have any holes pre-punched in them because the row of rivets on the skin is not a straight line.  I assume they don't punch the holes in order to give some wiggle room in bending the rib to the right curve, but it would be great if they would at least mention it in the instructions.  There's not a single word about this rib aside from an earlier reference to clamping it in place so it can be drilled "later."  After a bit of head scratching I started fluting the rib to give it a curve (about 1/4" or so in the middle).  With every change I had to set it back in place and use a marker to mark where the holes in the skin were so I could then remove the rib, see the progress and modify the curve.  It got late, so I didn't finish these yet.  At least I have a game plan now, so I think it'll get it done pretty quickly tomorrow.

The other piece that I need to think about is this corner rib in the baggage area (F-623 for the nuts following along in the plans).  Again, the instructions don't say much at all.  From what I can gather from the drawings, it lays flat against the skin and lined up with the outer skin edge.  The front and back ends of the rib have to be cut off so they don't hit the spar or outboard baggage rib, then little sheet metal pieces get riveted on in place of the cut off portions.  It's goofy.  These areas don't see to have any variability in them, so I have no idea why Van's doesn't just make them the correct shape to begin with.  The plans also show that a portion of the flanges needs to be cut out to make room for the step, but there are no details of where or how much.  So I guess I just take a chunk out that's hopefully big enough to clear the steel pipe.

As I put more and more on this center section, I'm realizing just how small my garage is going to get once I attach it to the tailcone, then especially once I put the forward skin and firewall on.  I'm planning on reorganizing the garage as soon as I get the truck tires mounted that are taking up so much floor space right now.  With those gone, I'll break down the big crate (I'll have to figure out where to store those parts, but it's mostly the skins and firewall, so I'll be using them soon) and shove all of my workbenches over into that center bay next to the wings.  That'll give me more width for the fuselage.  For the length issue, I'll deal with that by relocating my big floor standing tools.  Those all take up a good 6 feet or so of room.  I'll slide the table saw over to the next bay, then slide the bandsaw and drill press all of the way back up against the garage door.  I think that'll give me all of the room I need until I'm ready to hang the engine, at which point I'm sure I'll have to reorganize again.

Speaking of the engine, I am going to pull the trigger and place an order and deposit on one to lock in my price and production slot.  Last year engine prices had huge bumps two times during the year, leading to something like a 25% increase.  So it's already going to be ridiculously expensive, but I figured I may as well lock in at that price vs suffer another one or two potential price increases while I wait.  I won't need the engine for at least a year and a half, if not longer, but they are currently 14 months behind anyway.  I spoke to the sales rep and he said they can work with me once we get closer to the production slot, so if I'm not quite ready for it they may be able to bump me down the list a little.  He said they do pickle the engine to last at least a year before running as well.

The standard Van's offering for the RV9A is a Lycoming -320 (160 hp).  They have two basic levels - the "normal" engine and the Thunderbolt engine.  The Thunderbolt is simply Lycoming's performance build, so closer tolerances for balancing moving parts and a few other odds and ends that supposedly make for a nicer running engine.  They charge an arm and a leg for it of course.  I've ultimately decided to go with the Continental Titan engine instead.  It's actually considered a Lycoming clone that has been modified with some improvements.  Kind of funny, given that Continental is Lycoming's main competitor.  Continental bought ECI Titan, an engine parts manufacturer who also built these clone engines, a number of years ago and brought the production in house.  Because it's essentially a Lycoming clone, it can be used with the exact same engine mount and cowl from Van's.  The reason I went with Titan was the fact that you get far more bang for the buck compared to Lycoming.  Titan has many of the same performance features that the Lycoming Thunderbolt package does, but at a significantly lower price.  All of the pilots I know who have a Titan really like them.

Titan doesn't make a straight -320 (or even -360), which are the standard Lycoming sizes.  Instead, Titan strokes the -320 and -360 engines.  Depending on the build options, the stroked -320 makes between 174-180 hp, as opposed to the 160 hp of the typical -320.  I don't actually care all that much about the extra horsepower since the RV9A performs great on 160 hp, but since I want the Titan engine anyway, the extra power is just a bonus, mostly for climb performance (it won't change the top speed much at all).  Since it's hard to say what the long term story will be with 100LL avgas, I want the option to run auto fuel if I need to.  Because of that, I'm going with the 174 hp engine, which uses low enough compression that it can run auto gas.  I'm ordering a hollow crank so the engine can support a constant speed prop if I ever choose to go down that route, although in all likelihood I'll start out with a fixed pitch prop.  They just plug the crank for the fixed pitch scenario.  In terms of ignition, things may change in the next year or two, but for now I've ordered it with dual P-Mags (by eMag).  These are sort of like old school magnetos but with a modern twist.  They are an electronic ignition, so much more powerful than magnetos, but instead of typical electronic ignition systems that are dependent on the electrical system, the PMags are a self contained system that will keep running after an electrical failure.  Lastly, I'll go with fuel injection over a carb.  I know the carb is simpler, but fuel injection is more efficient and without the danger of carb ice. 

Center Section Ribs

An early Christmas present from Dad - an infrared heater!  I had to do some rewiring in the garage to get another 240v plug for it, but it was definitely worth it.  For a brief moment I thought about mounting it on the ceiling or wall, but I really wanted it to be portable enough to move across the garage when I need to prime parts.  I ended up just repurposing one of my old wing jig stands and mounting it to that.  It's amazing the difference it makes on a cold day!  The best part is no more cold tools!  That alone makes a huge difference.

The seat ribs all had a pretty good bend to them so needed a bit of fluting to flatten them out.

Clecoed the seat ribs to the aft center bulkhead, match drilled, and cut the holes for wiring conduit.

The seat ribs all get riveted as well as bolted to the center bulkhead.  The instructions make it sound like the ribs should already be drilled for the bolts, but they aren't.  I looked it up, and they get AN3-10 bolts, so I grabbed a 3/16" drill and match drilled the ribs to the bulkhead.

The next step was to start adding the baggage ribs to the 705 bulkhead.  Just like two of the seat ribs, the inside two ribs have to have half holes carved out of the flange to match the wiring holes in the bulkhead.

Next up, connecting the baggage area to the seating area.  I could only get so far though, because some of the back ordered items that I've been waiting on are the outboard baggage ribs.  I called Van's a couple of days ago and asked if they could ship all of the back ordered items they have instead of waiting for everything to be ready.  They agreed, and everything except for one bag that is still not in stock actually arrived today!  It didn't get here until late tonight, but at least I have the parts I need to keep rolling now.