Another productive day in the shop yesterday.  Continuing my work on the fuselage, soon to be taken apart again for debur, prime, reassembly then final rivets.  I have some plumbing of wire to do from the front cabin are to the tail section and I've got fit up the rear cabin windows before I close everything up.

Like the bottom fuselage skin, the top skin tapers towards the rear.  The large hole in this picture still needs to be flanged, but it is the passthrough for the upper elevator control cable.  The hole is covered by the horizontal tail assembly and fairings once the are mounted.

Finished trimming the front upper edge of the top skin at the longeron corners and trimmed the skin across the blue line.  With this properly fit, the forward end of the longeron can now be drilled and clecoed.   Eventually the rear edge of the cabin skylight window will attach to this front skin edge.

Reaching the top of the cabin was tricky, but there is actually just enough room to stand on the workbench to drill, trim and debur holes and edges.

I've bought a 90 degree aircraft air drill which I will use to back drill the wing mounting plates at the top corners of the rear cabin, just waiting for it to arrive this week.  I'll post pictures when I get it, but think of the shape of a large dentist drill and you'll be close.  For now I'm holding the wing plates in place with C clamps to check fit as I square up the cabin.

The fuselage currently sits on the bench in a tipped back position, so I needed a way to extend the centreline of the top of the fuselage in order to plumb bob that centre relative to the bottom of the fuselage.  I cleco clamped a strip of 093 aluminum extended forwards along the top centreline and strung a plumb bob weight downwards:

I know the fuselage cabin is slightly out of square (leaning very slightly to the pilot side without the other cabin structure in place yet).  To adjust the square of the cabin, I borrowed one of Ron's turnbuckles and strung it passenger bottom corner to pilot top corner of the cabin.  Tightening the turnbuckle pulls the cabin square.  It didn't take much to bring it into line, maybe two or three turns.

For the plumb bob, I used the pipe reaming tool head.  It is heavy enough to quickly dampen any swaying of the plumb bob line, but not so heavy as to pull down on the fuselage cabin roof.  As added bonuses the reamer can be tied and centred on the plumb line easily AND it has a pointy end for really accurate line up with the centre line of the lower cabin skin.

Here is the original square of the cabin - surprisingly close considering nothing else of the cabin structure is connected yet:

After a couple of turns of the turnbuckle:

Obviously string and turnbuckles won't be what holds it all officially square, I'll bolster it more externally when the time comes to tighten things up.  But this gets it in position to measure the cockpit side walls and floor and where it attaches.

Also with the cabin squared up, I finished drilling the top skin to the upper longerons from cabin back to tail.  I found it helpful to use a ratchet strap lightly around the fuselage to pull the longerons inwards to line up with the skin edges as I work towards the tail.  It's this tension that gives the fuselage it's rigidity once riveted.

Every 3rd rivet hole on the top longerons drilled to A3.  Next will all the holes aft of the baggage area up to A4.  The picture below really captures how tapered the fuselage actually is.  The tail is clamped for now to ensure the longerons maintain their taper curve until I figure out order of operations for the balance of the rivet holes and the bolts that hold the fuselage side rudder attachment plates. The longerons need to be trimmed to match the side skins.  The small hole just in front of the clamp is the front edge of a passage slot for the lower elevator cable that runs between the hole and the tail end of the top skin hold for the lower elevator cable.  It will be slotted soon:

Super stoked to see the fuselage coming together and that it is almost perfectly square as it sits!

Rough placement of the upper rudder hinge plate - this was one of my earliest pieces I cut from 0.125 aluminum plate using the early cardstock templates.  I know I'm on the right track as it fits exactly where it should on the tail:

​All four of these longeron ends get trimmed to match the side skins:

A look inside the tail looking forward through the tail bulkheads.  This large area gets covered by an aluminum fairing that is attached to the rudder and pivots inside this spot:

I marked where the top, side and bottom skins ends meet the longerons, marked them for trimming then peeled back the skins a bit to facilitate trimming with the Dremel (just like the front ones):

Looks like the top skin is a bit short?  It matches at the front edge correctly, so I know that is right, so what's going on here.

I remeasured the entire length of side and bottom skins and they are in correct relative position too.  But once I remeasured the top skin, I seems I cut the tail end 10mm too short!  Everything else on the top skin including the cross members, the upper doublers, the passage holes - all correct.  Thankfully this 10mm shortage has no impact on the function of the tail or the rudder attachment structure.  It would have much worse at the front end where the main spar channels are or if I'd cut the longerons too short.  Still not sure where I made the mistake, but glad it didn't require replacing the entire top skin, that would have been a major set-back (and expensive!)

As more of this enormous project comes together, more intersections of items to complete start to cross on my list of things to do.

Back in September 2018, I travelled to Mexico Missouri for the Zenith factory Open House Weekend (full 6 part blog story about my trip)

One of the prime reasons to travel all that way was to meet with other builders, get some airframe parts that I couldn't fabricate/bend myself direct from the factory and most importantly have some of my Corvair motor parts assessed by the Corvair aircraft engine authority William Wynne who was also in attendance that weekend (he hasn't missed one since they've been doing them)

William had a look at my cores and offered to take them to his shop in Florida for re-work and at the time my plan was to start that process in parallel with my build.  Of course that didn't happen for a number of reasons, cost being one of the them.

Fast forward to last week when I contacted them to inquire of my cores were still available in their warehouse as now I was ready to proceed with the work - four + years of them holding them for me was a lot to ask.  Thankfully despite my tardiness in getting them moving through their processes, my cores were in fact still available and sitting in storage awaiting my decision.

I received a quote last week for the required work and in discussion via phone with William I now have a solid plan to get the engine work rolling.  It's expensive work, but the value in having the recognized expert and his associates do the required work is great value in having a solid engine to fly behind.

Work includes deep cleaning the cylinder heads and piston chambers, new valves, new valve seats, exhaust value rotators and welding on intake pipes.  The engine case I sent unfortunately doesn't make the cut and requires too much work to make it viable, so I'll need to replace that with another core (they are easy to obtain).  The core crankshaft I had was too rusty to be ground, so they will supply the core which will heat treated (nitride process), stress relieved, the journals be ground/radiused, bearing surfaces polished, new crank gear welded on and the crank will threaded for the propeller hub safety shaft.  When that is done, a 5th bearing is added to the crank, ground concentric and shipped back to me with a 5th bearing housing.

All this work is being done by experts and gets me past the half way point of having a ready to bolt on engine.  Again well worth it.

William is a great writer.  He often reminds people that none of this is possible if you aren't in the arena.  I am in the arena and I continue to participate.  It can be an expensive undertaking, but ask yourself honestly if you can put a price on your dreams what would it be?

Holiday season and IT change freeze is generally over and I'm back into the swing of ongoing projects at the paying job and was gone on the road all week.  It was great to be back in the shop this weekend working my other (non paying?) job.

The more this aircraft comes together, the more complex the order of operations seems to become.  I probably spend way more time figuring out not what to do next, but what should come next.  Every drilled hole connects something to something else, and I have to always be cognizant that I don't drill something before all parts of that particular joint/juncture/assembly are ready to be positioned.  So far so good, but I've got many, many things in the future to consider as I work.

As the greater fuselage assembly comes together I need to decide how to fit and add the tinted Lexan rear cabin windows.  These windows are is one thing that doesn't actually join with something else.  Just a row of rivets around the perimeter of the window opening holding the Lexan in place (remember, these windows are not pressurized or designed to open and close, essentially just portholes to let the light into the rear cabin area).  As the appearance of the rivet lines on the outside edges of the windows is what shows, I think it best to layout and drill the holes in the fuselage cabin skin, then drill through the Lexan window.  The windows will be added after painting of the plane is complete, but I want to fit them soon before the cabin is closed up and access will be more difficult.

The rivet line needs to be 10mm outside the window opening, the window Lexan is 20mm wider:

I want the rivet line to exactly match the window curvature, 10 mm outside.  I could cut yet another cardstock template and trace it, but I thought why not make a simple tool that can mark the edge with a fine tip Sharpie, so this is what I came up with.

I cut a simple triangle from a scrap piece of 025 aluminum.  Two A4 solid rivets are the edge guides and the hole for the Sharpie exactly 10mm offset below that.  I used longer rivets and the rivet squeezer to just pinch them enough that they hold in their holes tightly:

Here is the backside.  I rounded the tips of the triangle and bent them forward slightly so the tool rides smoothly across the skin. 

Here's a short video of how it works.  Careful with the volume on the video - Ron is working with the grinder in the background and I didn't get a chance to edit out the audio before posting!

https://youtube.com/shorts/OqJJnmhwhU0

I might remake the tool and use a smaller Sharpie hole as I don't like the thickness of the rivet layout line this one leaves:

Finished adding the rear horizontal bulkheads.  The required "L" angles are added to the top of them where the top fuselage skin will connect.  This is also where the fore and aft horizontal tail supports get mounted once the tail is ready for fitting, so it's a "no rivet zone" until later:

This middle cross "L" doesn't have a bulkhead to connect to, but is an important support for the entire tail structure.  It's going to be fun to add later once the top skin is on! - more on this later in the build

Rear cabin uprights now in place between the rear cabin windows with a couple of clecos to hold them.  This helps square up the sides more and eventually will make up the rear half of the vertical flapperon push rod tube covers.  Also in the picture is the centre bearing support channel.  I have it propped up close to where it belongs, but will wait for the control rod placement before drilling the rivet lines on it.

Speaking of control rods, I got more hardware and 4130 tubing of various sized from Aircraft Spruce this week, all part of the control system.  I'm planning on dual control sticks so I had to add some more to my original order plans:

Also picked up the 3mm tinted Lexan sheet for the rear cabin windows.  I realized when I got it home that it is not only tinted, but it also has UV coatings.  Not required, but nice to know it will be better able to withstand sitting in the bright sun when I fly to Tahiti (just kidding) :)

Another weird camera angle?  The top right longeron looks like it is huge and touching the ceiling - it is not.  I clamped the main wing spar channel in place to get a feel of where it will sit once the top skin is in place and how the cabin side channels meet up to it.  Not pretty, but this fit up confirms the side skins are equally matched on their respective lower longerons.  This is only a temporary fit to check things out and won't allow the top skin to be rolled out, so I took it down immediately after the picture was taken - couldn't take a chance of it falling and punching a hole through the bottom skin either!

As I rolled the top skin on top of the upright fuselage sides I realized that there isn't much room to brace  the top skin on and any slight outward swing of the upper longerons would allow the top skin to fall inside.  To prevent the longerons splaying outwards, I tied them together (see the orange twine below) in a narrower width than the upper skin.  I also added the the upper skin stiffeners to help as I rolled it out:

It's starting to look like a fuselage!

I'll need to fire out the best way to add the upper fuselage skin diagonals.  Like the sides, they overlap the longerons on the inside of their curvature, but at least with the bottom and side skins, I had access by reaching over or around to fit them:

With a little of wiggling and sliding back and forth, I got the top skin aligned in the proper position relative to the front edges of the side skins.  The forward edge still needs to be trimmed - I left it long when I was laying it out to ensure fit before trimming if needed (see order of operations comment above).  I temporarily clecoed the forward upper fuselage doublers in place to check fit:

Blue line on the left is approximately where the front edge will eventually be trimmed back to - 30mm forward of the rivet line for the skin/main spar joining point.  Blue line on the right is a marked to show the trimming of the skin where it meets to the upper longeron edge.  This will be trimmed later as well:

​With the forward upper fuselage doublers in place, I now know where I can trim the outside edge of the skin - it has a notch that matches the doubler, but I can't make that cut until I trim back the longeron and the skin will lay completely flat on the longeron - yet another C before B but only after A order of things:

Picture of the right cabin side which shows the eventual notch to be cut out - this too will be more clear later:

Now with a confirmed location of everything, I can safely cut the longeron to match the cabin sides.  Trace a line with a fine Sharpie:

To avoid damaging either of the fuselage skins, I tied back the the side skin with orange twine and propped up the upper skin on top of cleco I inserted in the hole - perfect!

Used the Dremel tool with a cutoff wheel to trim the longeron back close to the line:

Untied the side skin, laid it flat against the longeron and clecoed it in place - still some minor trimming to do:

Slow work with a sanding drum on the Dremmel and some careful filing by hand and he longeron is now matched to the side skin:

Now I can fit the rear wing attachment plates to the front side of the cabin upright channel at the front edge of the side skin:

With the wing attach plate in place and confirmed flush with the cabin side skin I finished pilot drilling several of the cabin upright channel holes to finalize its position on the skin.  The attach plate will be drilled to the channel later, after back drilling the existing holes through the main spar channel when it is in place - then, with it secure in place, I can square up the cabin before finish the drilling on the uprights - man, that's a lot of steps in order to get this in place, but probably one of the most important connections in the airplane, so it's worth the extra effort to think it all out.  The cabin upright channels  still need the inside corners bent, but that will happen when I fit the rear upright covers, another thing to keep my mind occupied I suppose.

Lots more to come soon, including more bending, drilling, deburring, priming, head scratching, followed by more bending, drilling deburring, priming and riveting.  Always learning, but also always getting closer!! :)

Thanks for following along!

Happy New Year everyone!

Back in the shop over the holiday weekend and moving forwards with the build-up of the rear fuselage.

With the passenger side fuselage skin now in place (see above picture), I can duplicate drill the forward side gussets.  A LOT of the parts on the fuselage are left/right clones of each other, so once I have the right side skin in place, I can match drill the right gusset, then backdrill through it so the left gusset is a perfect match.  Both of these will be added later, once the cabin floor and sides are fitted.

Disassembled the passenger side skin, and prepped it for priming paint at the join locations:

​Prime completed on all sections aft of the baggage support channels.

While the passenger side priming paint dried, I rolled out the pilot (left) side skin, clecoed the diagonals into place and mounted it in place on the left lower longeron, same method as the right side.  The only difference on this side was matching the exact fore/aft position of the right side.  A bit of measuring from several locations confirms all is square:

With the primer now dry, I added the diagonal supports back to the right side skin and prepared to lift it back into place on the lower right longeron:

Both fuselage sides in place, clecoed to the bottom skin.  Here I've temporarily added the torque tube bearing support angle in-front of the hell-hole, and started fit-up of the pilot side baggage support channel:

​Wood supports screwed to the table helps support the skins and keeps the fuselage somewhat close to square:

Top longerons in place (these were fitted to the side skins previously when I was completing the diagonals):

More looks rearwards inside the rear fuselage.  Even without the top skin or forward uprights installed yet, the fuselage is fairly straight and stout.  The passenger side baggage angle is now fitted:

Camera doesn't capture the full length of the boxed up fuselage, but it takes up most of the entire workbench:

Next up, finish upsizing the pilot side rivet holes at the lower longeron, and complete the horizontal tail support structures/bulkheads.  Also need to run the wiring conduit along the inside edge of the fuselage  that will carry the wiring for the tail navigation lights and the control wires for the elevator trim system.

With those done, I can start adding the top skin.  That will require standing up on the table I think!

Thanks for following along, lots more to come.