Drilling Fuselage Longeron - Right

I got the side skin curves to a satisfactory match (at least I think so - we'll see if I still feel that way when it comes time to rivet).  The next step is to drill the longerons to match the side skins.  I started on the right side and clamped everything together to ensure the top of the longeron stayed even with the edge of the skin while drilling.  I started drilling from the tail, moving forward and inserting a cleco in every other hole so I could remove the clamps as I went.  That's a lot of holes to drill!  Can't wait to countersink all of them.

Side Skin Bends

Take two for bending the side skins.  It seems like a simple task, but getting these curves to match is easier said than done.  (The pictures make it look like the primer got really beat up in the process, but actually it held up really well. For whatever reason, the EkoPoxy in this color gets scuffs from any aluminum that touches it, but it's not scratched at all.)

This was about as close as I could get the curve.  It's not as tight as I would like it to be, but I think it'll suck together once it gets dimpled and riveted.  A curve alone would be pretty easy, but since the front end has to be a 90 degree angle, it complicates matters.

I fell prey to what a lot of other builders have - the relief hole at the front 90 degree bend ended up cracking.  I had read about this, so was careful to make sure the hole was well deburred, but no luck.  I think it's due to the amount of back and forth bending that happens as the aluminum is worked to the right angle.

I haven't figured out if I'll just stop drill it and leave the crack or file away the entire thing.  I'll see what I can find out from other people.  I thought I learned my lesson and moved to the other side. I made the bend, and as I was fitting it to the tailcone, another crack.  The left side crack was only about 1/8", whereas the right side was 1/4".  It's irritating, but at least I know I'm in good company.

The last thing I did today was drill the hole that the step goes through.

Arm Rests & Side Skins

 I was gearing up for a real fight with the side skins today, but somehow everything miraculously fell into position overnight.  I'm still scratching my head on that one.  It only took a few minutes to get the side skins mated to the tailcone.  I have no idea what changed, other than a night's sleep.

With the side skins clecoed on, I moved to the armrests.  I had to flute these a bit to straighten them out, then match drilled them to the side skin.  When I'm ready to attach these permanently, I'll make a few modifications to beef them up.  They are well known for giving way if a big dude puts their weight onto them.  I'll put some extra J channel under the inside lip and probably some small aluminum angle brackets where they attach to the bulkheads.  That should make them much stiffer.

And just like that, the side skins have to come off again for the next step.  The aft portion has to be bent to match the conical shape of the tailcone 706 bulkhead.  The front end of the bend is a 90 degree angle that then opens up to a curve at the aft portion.  I clamped the skin to the table with some angle, then drilled more angle to the edge to help with the bend.

My first attempt came out just okay.  I put it back on the fuselage to check it and am not in love with the fit.  I wasn't paying close enough attention and let the angle put a little crease in the front 90 degree portion.  The aft curve isn't quite right either, so I need to pull the skin back off and try again.  I'll get another night of sleep and see if the magic fairies fix this too.

Center Fuselage Side Skins

The fuselage grew today!  The center section slides over the tailcone bottom skin and the baggage ribs rest up against the 706 bulkhead.  It looks a little precarious setting on saw horses, but this is the tried and true method.  It was fairly easy to cleco the bottom skins together once I got the front portion of the center section at the right height.

That is where the "easy" part stopped.  Next up were the side skins.  I wasn't looking forward to this part just based on all of the horror stories I've read about how difficult it is to get the rear portion lined up.  Turns out it's all true.  I was able to get the skin to front and seat bulkheads clecoed in relatively easily, but that's where it stopped.  The rear row of holes that connects to the tailcone side skins was so far off that it made me wonder if there would ever be hope of matching things up.  I went ahead and put both skins on just to have them off the workbench, but after a couple of hours of shimming and moving things all over the place I finally gave up for the day.  That rear row of holes is still 3/4" off.  That seems like an impossible amount to overcome, but people say it's indeed possible once you get everything moved to just the right position.  That's for another day.

Finishing Center Section

I finished up the passenger side crotch strap mount.  My threaded drill bits for the right angle drill came in, so I got to play with my new toy to see how it works.  Aside from having a constant small air leak somewhere (it's old), it makes drilling holes in tight quarters 100x easier.  The process went much faster and the result was much tidier than the other side.

I match drilled the mount to the rib webs as well as the seat pan, then put the nutplates in place and pop riveted everything together. 

With that done, the center section was ready to be attached to the tailcone.  The first step in doing so was to insert the longerons in the tailcone so that they are even with the top edge of the side skin.  The instructions say to flip the tailcone over to do this, but I found that to be too awkward.  I turned the tailcone upright instead and just slide the longerons in place and clamped them to the skin.  I was a bit nervous putting the longerons in place, because a long time ago I had to cut a big notch (like more than 3/4 of the longeron angle width) in the top portion of the longeron to accept the vertical bars that will eventually mount the vertical stabilizer.  I was sure that I had measured wrong, or the plans dimensions would end up being wrong and the longerons would be useless.  Thankfully, the notches and the measurements needed to nest everything together at the rear were spot on - I'm talking width of paper spot on! Phew!

I rolled the tailcone back over and set up another sawhorse for the front center section bulkhead verticals to rest on.  All that remains now is to move the center section over and get it clecoed to the tailcone bulkhead.  I'm waiting on my muscle to get home for help with that though.  The center section isn't actually all that heavy, but it would be too awkward to do alone.

Center Section - Outboard Ribs

Nowhere in the plans does it show that the outboard seat ribs get drilled for nutplates, but they obviously need them so the front seat pan can be screwed into them like every other rib.  I grabbed my nutplate jig and drilled the rivet holes, then dimpled and riveted on the nutplates.  The plans mention that nutplates right next to the side skin are hard to get a screwdriver on, so it suggests running a tap through each nutplate to make the screws go in easier.  This isn't normally kosher to do because it removes the self locking shape of the nutplate, but for a small percentage of screws in a seat pan, apparently it's no big deal.  After these ribs were finished, I went ahead and set up the passenger side seat belt mount, so I'm ready to finish that as soon as the right angle drill bits arrive.

Center Section - Seat Belts (2)

I spent most of the day crawling under vehicles, so not much action on the plane.  I have about 10 rivets that I need help setting before I move on to the next big step (center section to tailcone), so I'll enlist Rose when she's back in a few days.  I could throw up the bat signal for help, but it's about 10 minutes worth of work and not worth the drive for anyone else.  In the meantime, I'm just slowly working through the seatbelt crotch strap mounts.  I finally broke down and bought a used pneumatic right angle drill on Ebay.  I'm still waiting on the drill bits to arrive (it takes threaded bits), but I can already tell this is going to be a huge help.  The head is much, much smaller than my other cheap right angle attachment, so it'll be able to get into tighter spots without forcing the drill bit to be at an angle.  That was a big struggle with this seatbelt mount, so I'm going to wait to finish the passenger side mount when I have the drill bits.  These drills are insanely expensive for some reason, but I got a good deal on this one vs buying new.  I have a feeling I'll be kicking myself for not buying it sooner.  I could have used it in a lot of locations in the wings.

I used a nutplate as a template and drilled the additional holes in the tops of the mounts.  I dimpled the holes, as well as the nutplates, then riveted the nutplates on.  The mounts are riveted in place with pop rivets.  The primer on the rib webs looks all scratched up because it is.  I couldn't get the holes deburred very well with the deburring bit (the rib aluminum is much harder than other sheet aluminum), so I just took sand paper to them.  The sand paper scuffs up the primer, but still doesn't burn through it.

I don't need the hardware for ages of course, but figured it would be easier to just drop the bolt and nut in place now vs having to search through the plans later on to figure out what size I use.

Center Section Floor & Seat Belts

All I had to do today to get the center section ready to mate with the aft fuselage was match drill the seat and baggage floors to the ribs then put the optional 5th point mounts in for the seat belts.  Normally all of that would be pretty quick, but Van's didn't prep a lot of things they normally do, so it made for a bit more work than I was expecting.

I started out by match drilling the seat and baggage ribs to the floors.  My first gotcha was in the tunnel section of the seating area.  The seat pans here get attached with nutplates, but unlike most areas Van's didn't pre-punch the holes in the ribs for some reason.  The screw holes in the seat pans were also not the right size, so they had to be upsized as well.  The tunnel uses two different nuplates - you can see that half are the typical type with the screw hole in the middle of two rivets, but a few are nutplates where the screw is on the end of the nutplate and the two rivets holding things on are on only one side.

I still haven't quite figured out what the story is with two of the holes at the front edge of the seat pans.  Most of the holes alongside the front edge are for screws that go into nuplates attached to the bulkhead flange, but the two middle holes have no nutplates to mount to.  I triple checked the plans and they are indeed supposed to be left like this.  I'm sure buried in the drawings somewhere is something that will clue me in as to what goes here, but for now it's a mystery.

One of the biggest time sucks today was in how often I clecoed all of the seat pans down, only to find a reason I needed to pull the clecos out.  I bet I had it all together and pulled apart at least a half dozen times.  One of the things that caused some trouble was the pre-cut notches for the main seatbelt anchors.  All four of them are cut so that they rub against the anchors and make it difficult to slide the seat pans into position.  I finally took a file to all of the notches and opened them up another 1/8".

The outer two seat ribs have blank flanges and have to be drilled to match the seat pan pieces.  Since the ribs are curved, this was easier said than done.  I had to pull the seat pans out many, many times to get things lined up.

I had already fluted the bottom side of the ribs in order to get the curve it needed to match the bottom skin, but I hadn't fluted this top side yet because I wasn't sure where the holes would be.  I put the seat pan on top of the rib and marked where the holes were so I could make sure not to flute in those areas.  It took a few iterations to get the curve right.  The web of the rib also needs to stick out beyond the seat pan.  Van's recommends using a piece of .032 sheet as a spacer.  I think the point of this is simply to ensure that the rib web is what the fuselage skin will press against vs letting the edge of the seat pan hit the side skin and chew into it.  After I got the ribs curved and rivet holes drilled, I did the same for the front portion of the rib flange.  It's the same process, but this portion of the rib isn't riveted to the seat pan.  The front pieces that make up the seat pans are held on with screws and nutplates so they can be removed for access to the controls.  I'll still need to drill the rib flanges for the nutplate rivets and attach the nutplates down the road.

I've had the pieces for the removable section of the center seat ribs sitting on my bench for a long time.  They won't be put in place until the controls are in, but I decided to go ahead and rivet them together.

The section of flange that I cut out from the ribs is simply riveted to an attach bracket.  The bracket gets bolted to the rib web, allowing the seat pan to still screw into the nutplate in the flange.

Now for the maddening part!  On the advice of just about everyone, I decided to purchase the optional 5th point "crotch strap" mounts for the seat belts.  Even though the 9A is not aerobatic, the crotch strap is hugely beneficial and I think should be standard equipment.  Having the 5th harness point keeps the lap belt from riding up during an accident, which can make a significant difference in overall trauma and safety.  I've also heard many people mention that it makes a big difference in turbulence as well (the RVs are pretty light planes, so they can get bounced around pretty good).

This was one of those tasks where reading the page of directions made it sound super easy!  All I had to do was locate the anchors between a couple of ribs, drill them, and rivet them in place.  Easy!  Maybe a picture will show how "easy" this really was.  Somewhere in that mess of scrap angle and half a dozen clamps is the actual mount.  The top of the mount needs to be level with the top of the ribs (the seat pan will get screwed to it), plus it needs to be vertical.  None of that sounds difficult to accomplish, but the tight quarters really made it tough.  The biggest issue I had was that even my angle drill was too big to get a drill bit parallel to the web of the mount (the angle drill isn't too long - the problem is that the head of it is still fairly thick, so if the hole is close to the web of a piece, the drill bit can't go in without being pushed out at an angle).

With all of the clamps removed, you can see what this is supposed to end up like - simple!  The mount is made up of two pieces (the piece of aluminum in between them is just a temporary spacer).  The holes on either side where the clecos are are the ones that gave me fits.  There was just no easy way to get a drill in there.  I finally just had to let the drill bit go in at an angle.  I think given that the material is so thin, it should be fine.  An angled hole in thick material is a major problem, but I think I'll be okay here.  This took so long, this is where I stopped.  I still need to match drill the mounts to the seat pans, drill a hole for the bolt of the actual seat belt hardware, then pull it all out and prep it for riveting.  Of course then there is the passenger side to do, but I imagine that will go much quicker now that I've struggled with one side.

Center Section Bottom Skin (2)

It took a lot of stretching and contorting, especially for the lines of rivets towards the center, but I was able to get the bottom skin riveted by myself.

The next step is to match drill the baggage and seat floors.  It's actually starting to look like a cockpit!

When putting in the baggage floors I found an error that I had to correct.  I put the nutplates onto the baggage ribs a few days ago.  Once I put the floor in place though, I realized that the nutplate is actually supposed to be attached to both the rib and the floor sheet together.  I drilled out the rivets and pulled the nutplates off of the ribs.

My back is incredibly tired from all of the stretching and bending with the riveting, so even though I have time left in the day, I'm done!  Tomorrow I'll finish clecoing on the flooring and get it match drilled.  I'm getting close to the point where the center section will be flipped over and attached to the tailcone.