Fuselage side skin drilling

To get the longeron lines to align with the holes, I had to deburr/trim the top edge a bit, since it fits underneath the mid-cabin deck:

Mid-fuselage skin top edge, flush against the mid-cabin deck

With this, I match-drilled the skins to the longerons:

Match-drilled right forward fuselage longeron
Match-drilled left forward fuselage longeron
I then clecoed the forward side parts in place, including the forward side skins, and final-drilled/match-drilled all the holes:

Forward fuselage side parts in place (except for the skin)
Forward side skin, match-drilled to the understructure
All forward fuselage side parts in place
Upper channel match-drilled into steel firewall support bracket

While drilling the firewall bulkhead, I had a small alignment problem - the longeron was slightly too long and pushing the flange forward, making the holes not align - so I had to do those later, after trimming the longeron:

Misaligned holes on the firewall bulkhead flange
Longeron pushing the firewall bulkhead forward
Trimming the longeron forward tip

We also drilled the longerons to the gussets, which was slightly challenging since the pilot holes are in a tiny corner and "upside-down" - at least 3 hands required:

Match-drilling the longeron gusset holes
Longeron gusset match-drilled into longeron
Longeron gusset holes (very tough location to match-drill from below)
Another challenging (actually impossible without modifications) hole is the forward-most hole in the forward fuselage channels:

The right-most hole is impossible to drill or later rivet (upper fuselage channel)

Same impossible hole on the lower fuselage channel
For this one, apparently I will need to trim some of the firewall side angles for access - I wish I had realized this while still building the firewall.

I drilled all the other holes, which includes all the channel to firewall bracket holes:

Firewall bracket match-drilled from upper fuselage channel
as well as the floor to lower fuselage channel:

Floor panel match-drilled to lower fuselage channel

With almost all the drilling done, it's now time for a lot of deburring and countersinking, then primer and dimpling.

Time lapse:


Total fuselage side skin rivets: 0
Total fuselage side skin time: 60.4h

Fuselage side skins: woodwork, twisting, countersinking, bending, and some drilling

I twisted the ends of the longerons by the required 2 degrees:

Longeron end twist at exactly 2 degrees
I installed them back and started countersinking the mid-cabin decks - first the screw holes:

Countersunk mid-cabin deck screw holes
then the rivet holes on top:

Countersunk mid-cabin deck rivet holes

For the skin clamping blocks, I couldn't find hardwood 2x4s anywhere local, so I ordered them online (here) and got some very precisely-cut pieces by mail. I got one hard maple and one red oak since I wasn't familiar with working with either and wanted a second one in case I screwed up:

Maple and oak 2x4s I ordered

Just to be sure we had some idea what we were doing, we started by making the same cut on a 2x4 (which we can still use for the other skin, where a radius is required in the clamping block), before cutting the maple:

Cutting the hard maple at just the right angle

Clamping block (one from a regular 2x4, one from hard maple)
The cut was far from perfect, but likely good enough for the intended purpose of bending the skins.

Since the second clamping block needed a radius and could be done with a 2x4, we made the additional cut on that as well:

Modified clamping block made with regular 2x4


We then started the repetitive work of bending the bottom parts of the skins with those blocks, to make them fit the curve at the aft end of the fuselage:

Bent and clecoed mid-fuselage skin
Rinse, repeat for the forward skins, except that for these, the roll construction angles aren't attached with clecos, and we didn't have any single clamp strong enough to hold them in place while twisting, so we had to use several clamps and mount it backwards:

Clamps for bending the forward fuselage skins
Bending the forward fuselage skins
The result was also quite good:

Bent and clecoed forward fuselage skin

Fuselage skins clecoed in place
Fuselage skins clecoed in place

I then started final-drilling the holes, including those of the baggage floor angles:

Right-side baggage floor angle attached to skin

Left-side baggage floor angle attach to skin with shims

The forward sides of the mid-fuselage longerons are attached to the gussets, which I also match-drilled:

Gusset match-drilled into mid-fuselage longeron

Since we were doing wood work, I also used the excess tip from the 4' maple beam to make a couple of blocks for twisting the fuselage channels:

Fuselage channel with spacer blocks for twisting

Fuselage channel spacer block height
Twisted fuselage channel

On a completely unrelated part (done while I waited for the wood), I separated, partially deburred, clecoed and final-drilled the side vent parts:

Separated vent parts

Deburred and final-drilled vent parts

Still a ton to do for the fuselage sides, but I'm glad that the most-hated parts of bending, twisting, etc. are over. I'll likely only do anything else significant after I'm back from Airventure.

Time lapse:



Total fuselage side skin rivets: 0
Total fuselage side skin time: 44.2h

Fuselage longeron work

We continued with the dreaded section 29, and while it takes some effort to "refine" the parts into the proper shape (i.e. beat them into submission), it has worked out well, and all the longerons are formed and drilled:

Formed and drilled mid-fuselage longeron
Formed and drilled forward fuselage longeron
We failed to find appropriate wood (hardwood 2x4) locally to bend the skins, so we skipped to later steps for now while that comes in the mail. We aligned and match-drilled the baggage door seal angles to the mid-fuselage longeron:

Mid-fuselage longeron attached to baggage door seal

Mid-fuselage longeron attached to both baggage door seals
We then clecoed those longerons into position, and trimmed the lower flanges of the baggage door seal angles:

Mid-fuselage longerons and seat back brace clecoed into position

Trimmed flanges of the baggage door seal angles
We started putting the whole thing together for more match-drilling and to assert alignment:


As another random item from later on, I also bent the clips that attach the lower fuselage channels:


Still a lot to do, especially after that wood comes and we can actually bend and use the skins.

Time lapse:


Total fuselage side skin time: 22.2h

Forward fuselage ribs and bottom skins complete

We riveted the center section side plate to the surrounding parts:

Center section side plate riveted to the bulkhead side channel

Center section side plate riveted to the forward bottom skin and bulkhead side channel

To install the floor panel again, of course I had to remove one of the bolts I previously installed, since it's in the way:

Bolt that prevented me from installing the floor panel

Then we tried to install the landing gear mounts, to drill some holes against the forward floor panels. First, it wouldn't go in, so I had to bevel a corner of the center section bulkhead (per the recommendation on the manual):

Trimmed corner of the center section bulkhead, to fit the landing gear mount

With that, the mount went in (kinda, sorta):

Fitting the landing gear mount

Such a simple task, it should have been - pop the mounts in, make two holes, take it out, done. Except nothing lined up:

Misaligned landing gear mount holes

Turns out the part was catching on the seat rail supports:

Seat rail supports where they were preventing the landing gear mount from sitting in the right position



After trimming that, the front part was catching and also needed some significant trimming:

Aft flange of the seat rail supports that were also interfering with the landing gear mount

Trimmed seat rail support to allow landing gear mount installation

Since that removed a lot of the primer, we touched it up with the rattle-can type:

Primer touch-up on trimmed center section bulkhead corner

Primer touch-up on seat rail support

With that one also out of the way, now the mount flange was not parallel (grrrr), so (per Van's recommendation) we beat it with a hammer back to where it should be:

Landing gear mount flange, not parallel to the side plate

Landing gear mount flange, now parallel to the side plate

Landing gear mount flange with shim in place

With that, over 10 hours of careful work later, we could tighten the bolts and mark the intersection of the rivet hole line and edge distances on the mount:

Installed landing gear mount

Landing gear mount forward brace mount plate in place

Landing gear mount forward brace mount plate with hole locations marked

Landing gear mount forward brace mount plate, drilled for AN3 bolts

The other holes to drill were through the shim and landing gear mount flange:

Landing gear mount flange and shim with holes drilled

Side skin through which the landing gear mount flange holes go

Finally, I removed the side skins, drilled nutplate attachment holes where the landing gear mount "leg" bolt holes are, and riveted the nutplates:

Landing gear mount forward brace mount plate holes with nutplate attachment side holes

Installed nutplates for the landing gear mount forward brace mount plate bolts

With all this, the section is finally complete (except for the few items that this section would have me build but not use, like the seat floors). Now comes the dreaded section 29 (side skins).

Time lapse:


Total forward fuselage ribs and bottom skins rivets: 786
Total forward fuselage ribs and bottom skins time: 131.8h

Popular posts