It's that time of year. Shorts and Tees one week, then freezing cold the next. October into November has weather been beautiful and I have no right to complain , but November into December has been less than stable. At least I can light a fire in the shop woodstove and keep working on the plane.
Flipped the right side fuselage skin over and finished right sizing the holes I could in preparation for debur and riveting.
Top longeron on the right in progress, going just as well as the left side:
Moved the right side fuselage skin aside on the bench and started fitting the rear fuselage side skins. Left side skin is the "master" so I used it to back drill the seam holes (camera distortion makes this look shorter in length than it actually is):
Stacked the other side rear fuselage side skin to match drill it from the "master":
Rolled out the right side skin and stacked the left side on top to match drill them:
I realized very quickly that by adding additional diagonals on the other skins, I needed to make more "L" angles for this second side skin and for the top skin to come. The method I like best for making "L" in the least amount of time is first scoring the 025 sheet in 38mm wide strips, but then waiting to separate them until I have several in line:
Once I have the number of strips or blanks scored, I debur the edge that still sticks out proud of the bender (left side in picture below):
Then, I pull the scored sheet outwards and snap-bend the first blank - this leaves the first blank in the bender for deburr and sanding:
One by one, the blanks are snap-bent off the sheet, deburred and cleaned, ready for bending to 90 degrees:
From blanks to "L", ready for placement and fit up:
Laying out the diagonals and fuselage skin stiffeners:
Flip the skin over and fitting up the upper longeron:
I sometimes think there must be literally pounds of drill shavings to clean up and dispose of as I work through this project!
Still amazed how distorted the camera image is. Here is the rear most side skin. It almost looks wider here than the front of the fuselage!
Layout the skin flat again for window cut-out, using the same method as the right side skin:
Slow and steady, lots of cutting oil:
Deburr and cleaning up the edges with sandpaper and ScotchBrite pad:
Now that both fuselage side skins are matched to the same stage, I trimmed the forward edge of the left fuselage skin where the cabin and door will meet the fuselage:
Stack the trimmed left fuselage skin on top of the right:
Use the match drilled rivet holes to line both skins up perfectly (windows are perfectly matched too!):
Trace the edge onto the other skin:
Trim away at the blue line using shears:
Both fuselage side skins now match each other.
Rolled the fuselage sides up and put the fuselage top skin back on the bench to add the stiffeners:
Match drilled the upper wing spar carry-through channels and angle together. These were the pieces I decided I couldn't bend accurately enough so I bought what I needed from Zenith. The purchased pieces matched up perfectly with each other and with my scratch-made rear doubler angle:
All the effort and thinking about the drill/assembly order to match drill the spar carry-though to the upper fuselage skin and corner doublers paid off. It fits perfectly (although I still need to do some trimming of the forward edge once the fuselage is assembled):
What appears to be waviness in the assembly is just a rough edge on the top skin. This will be trimmed back later as the fuselage gets assembled. The picture shows where the wing pick-up plates will attach as well (holes on left side):
Took a break from the fuselage for a bit to contemplate some the control assemblies I'll be making in the coming month or so as the fuselage comes together First up are the mounting plates for the flapperon mixer control tube. These are made from 080 thick 4130 chromoly steel, common to aircraft structures:
The flapperon control tube is 1-1/4inch diameter seamless chromoly tubing:
Eventually these plates will be welded to a stub end of a piece off the end of this tube and a AN6 bolt will protrude through the hole. The bolt will be the mounting point for the flapperon bellcrank, sandwiched between two nylon bushings. More on these later.
The push rod tubes for the flapperon controls (and others) are smaller diameter tubes. In one end, a nut is inserted that will allow threaded rod to be inserted which connects to a rod end. This allows almost infinite adjustment of the push rod length when it comes time to adjust the rigging of the control surfaces.
The plans state to weld the nut inside the tube, but the required nut doesn't fit inside the tube?
Rounding off the point corners of the nut on the bench grinder, rounds it out enough to fit the inside diameter of the push rod tube:
I used a long bolt here to test fit the rounded nut in the tube. These push rod tubes will be welded up later along with the threaded rod inserted.
Before assembling the fuselage and taking up the entire workbench, I decided to start assembling the cabin sides. These normally come pre-assembled in the factory kit, but as I am scratch-building, it's another assembly I need to make myself from the beginning.
Laid out some 032 sheet and started laying out the cabin side skins as per the plans:
Took a fair amount of time to lay everything out correctly - lots of tapering angles and considerations for cutting door sill radii, etc.
Much like the fuselage side skins, these cabin skins are mirror images of each other. So I used the same method as the fuselage. Make one as a master, use pilot holes in the master to create the twin. Here the side skins are stacked, with pilot holes in the perimeter for holding them square and pilot holes for the radii where the cabin door sills will be:
Each cabin side also has an 032 doubler sheet that is fastened between the outward facing cabin side skin and the internal extrusions that make up the cabin skeleton. Using the two inner door sill radii, I made up rough cabin side doublers which will be matched drilled later with the extrusions - so many things to think about and decide on order of fit-up/assembly as I go!
Next up was cutting the radii that make up the lower rear cabin skin. The step drill is good for this 16mm diameter hole:
The cabin door opening is defined by three 47mm diameter radii connected together from the rear of the cabin skin forward, eventually curving upwards at a 19mm radii to meet the upper cabin frame. It's hard to describe verbally, but the following pictures may show it fairly clearly.
Used the fly cutter to cut the 4 radii in each of the skins and the matching doublers:
Here is the rear most radius, before trimming the door sill. The angled reactangle represents the eventual rear edge of the cabin skin where it matches the rear cabin of the fuselage. The small hole in the top left circled in red is one of the perimeter pilot holes that I use to keep the skins aligned for match drilling later. Eventually once everything is complete and ready for solid riveting, these pilot holes will be trimmed away as scrap metal, leaving just the completed cabin skin:
A quick stack of the rough cabin side skins confirms the second skin pilot holes match where the new radius holes were cut (measure thrice, cut once!)
Second cabin side skin radii cuts in progress:
Cabin skin doublers also have the door sill radii cut to match the parent cabin side skin, using the previously drilled pilot holes:
More aluminum debris from the fly-cutter to clean up!
So far, so good on the cabin sides. Have some challenges coming up, including how to bend the rear cabin side longeron extrusions. 0125 angle extrusions by default do not like to be bent , but the plans call for just that. Time for an email to Zenith to find out how they do it for the factory assembled units.
Thanks for reading along. Still more to come soon.
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Husband, father and 911 dispatcher. Long time pilot with a licence that burns a hole in my pocket where my student loan money used to be. First time aircraft builder. Looking to fly my own airplane.