Forward fuselage riveting

I finally started riveting the forward fuselage parts, starting with the smaller ones:

Riveted smaller parts for the forward fuselage
I riveted the attach angles to the forward fuselage ribs:

Attach angle riveted to forward fuselage ribs
which, for some rivets, was kinda tricky with the squeezer, given the nutplates were already on:

Riveting through an opening to clear the nutplate
I riveted together the bottom forward fuselage bulkheads and seat rail supports (note - those nutplates could also have come later, would've made it easier to rivet them to the skin):

Bottom forward fuselage bulkheads riveted to forward seat rail supports
then started riveting the floor ribs:

Forward bottom skin riveted to floor ribs
Before riveting the next parts - the bottom forward fuselage bulkheads - to the skin, I decided to check how they'd fit against the vertical angles, and am glad I did - they did NOT fit, due to interference with that innocent-looking nutplate, on both sides:

Bulkhead hits the nutplate edge before the holes align :/

Other bulkhead also hits the nutplate before the holes align
That side of the bulkhead had plenty of edge distance, so I trimmed off another 1/8" from them with the bandsaw+grinder:

Bottom forward fuselage bulkheads marked for trimming

Trimmed bottom forward fuselage bulkhead
I then wrapped it in tape before the final edge deburring, such that the file would remove the tape only where I actually had to re-apply primer, and protect any existing primer:

Deburred trimmed bulkhead edge with tape for selecting priming

I then used the rattle-can primer for this small touch-up:

Primed trimmed bulkhead edge
and finally riveted those onto the skin as well:

Bottom forward skin riveted to floor ribs and bulkheads / seat rail supports
While waiting for my riveting partner (a.k.a. the wife), I also fabricated the landing gear mount shims, which are used slightly later in this section:

Landing gear mount shims cut to size
Next step is partially riveting the systems brackets, then it gets interesting, by joining the skin and parts above with the parts from the firewall section.

Time lapse:



Total forward fuselage ribs and bottom skin rivets: 438
Total forward fuselage ribs and bottom skin time: 92.4h

Fuselage side skin side plate countersinking

While building the forward fuselage ribs/bottom skins, I realized the center section side plates would be quite hard to machine-countersink at the expected time (middle of section 29) with how close they are to the center section bulkhead assemblies, so I clecoed them to the skins, match-drilled and machine-countersunk them at that time:


Just a small step to save time later.

Time lapse:


Total fuselage side skin rivets: 0
Total fuselage side skin time: 10.7h

Forward fuselage countersinking, fuel pump shelf and primer

I continued by machine-countersinking the center section bulkhead to accept the skin dimples:

Machine-countersunk forward center section bulkhead holes
I also took advantage of not yet having the bottom skin on, in order to more easily attach and match-drill angles that make a shelf for the EFII install. I'm roughly following the instructions from the Aircraft Specialty hose kit, and may get the kit from them.

Aluminum angles to make a shelf for the EFII pumps

Leveling the two sides of the EFII shelf angles

We had done primer on the skins earlier in the month:

Forward fuselage bottom skin, scuffed but not yet primed

Forward fuselage bottom skin, primed

This weekend we then did another large batch of primer, to get all the parts that need to go on the skin, before the skin is attached to the forward ribs and firewall bulkhead:

Forward fuselage parts before primer

Primed forward fuselage parts

More primed forward fuselage parts

Next will be a lot of dimpling and riveting of those parts.

Time lapse:


Total forward fuselage bulkheads, ribs and bottom skin rivets: 0
Total forward fuselage bulkheads, ribs and bottom skin time: 70.2h

Mid-fuselage bottom skins ready to rivet

Finally coming back to this section and making progress!

I took a step from section 44, and drilled the mid fuselage skin nutplate holes to size - the goal is to attach the two forward-most nutplates before riveting the skin on, since they're in somewhat tight spots after the skin is installed. The others should be easy to squeeze rivets for later:


We finally primed the bottom skins:




then proceeded to remove the vynil from both for riveting:


We then dimpled the skins, and next will start riveting them on.

Unfortunately in that batch of primer I forgot to include the TAS antenna doubler, which is way easier to rivet on before the skin is in place (because the heat tee goes over it), so I'll do that batch before continuing with this section.

Also related to the TAS antenna, I was thinking of cable paths for it, and wondering if I could put the TAS in the tailcone and run the 4 cables straight back (so exiting the tunnel to the right, then going through the rear spar bulkhead. The main question I had was about drilling a big (1/2" or so) hole through the rear spar bulkhead, so I contacted Van's support and send them this annotated picture, and they confirmed it's OK to do so:

Rear spar bulkhead hole location for running cables to the back

Time lapse:



Total mid-fuselage ribs and bottom skins rivets: 412
Total mid-fuselage ribs and bottom skins time: 84.2h

Forward fuselage skins and ribs deburring, fuel return path and bottom TAS antenna location

I finished deburring the remaining parts for the forward fuselage, and dimpled the ones that were already primed (the forward fuselage ribs):

Most forward fuselage ribs deburred parts

Deburring and trimming mid seat rail supports

Dimpled forward fuselage ribs
I also did some work in planning for the fuel system. Since I plan to use the EFII System32, I followed the steps from others who have run hoses for it, and may end up getting the hose kit from Aircraft Specialty, so I followed their instructions, starting with enlarging the systems brackets holes - the original one is the right size for a 1/2" snap bushing (plus another which is meant for brake lines and thus much smaller), but I'm planning to use 3/8" fuel hoses with grommets, so I enlarged it to 5/8" for the grommet). I did this by transferring the holes to a backing piece, enlarging them to the right direction on the backing piece (away from the screw hole and away from the top bracket edge), then transferring back with a unibit:

Transferred existing holes to a backing piece

Enlarged holes in backing piece, to transfer back to brackets

Enlarged systems bracket holes

Systems bracket with grommets
Of course I did screw up and had to re-make two of those top brackets :)

I also enlarged the forward fuselage rib holes to 9/16" for the fuel return lines:

Enlarged center hole for fuel return line (before deburring)
I added a hole for those lines through the side skins and center section side plates:

Hole position on the side skin for fuel return line 
Enlarged fuel return side skin/side plate hole
Per the post on antenna positions, I made an antenna doubler for each tunnel section:

Antenna on aft tunnel doubler

Forward tunnel doubler for TAS antenna
I'm not going to install the forward doubler just yet - the aft tunnel is harder to rivet in (with the heat tee over the spot), so I'll just add that one for now).

Next up, a bit more deburring and then primer and riveting to complete this section!

Time lapse:


Total forward fuselage ribs and bottom skins rivets: 0
Total forward fuselage ribs and bottom skins time: 61.3h

More on antenna positions

For antenna positioning, I tried to put the forward tunnel parts around the place they'd go, and reailze it gets really crammed in there (plus, forward of the fuel valve goes the EFII pumps, filter, etc.):

The forward tunnel gets pretty crowded
Photos of the fully-assembled tunnel from others also seem to confirm that.

so I'm now reconsidering the TAS antenna position - putting it in the aft tunnel may be well worth the trouble of running the cables to it, and on the upside that'd bring it close to being aligned with the top antenna - so I checked whether there's clearance for the cables below the pushrod, and there seems to be enough:

Potential position for the TAS antenna in the aft tunnel

Just to give me some margin for decision, I'm going to add doublers to both places, and decide later.

Furthermore, I looked at the G5 installation manual and realized that it has an internal antenna - unclear if that'll be enough, but I'll be holding off on adding a third GPS antenna for the time being, and if I do I may add it to the top of the dashboard, just for some installation diversity.

Updated antenna positions

I had previously planned the antenna positions both disconsidering convenience of mounting the antennas, and assuming I'd have the MotoPOD on the bottom. Given this, I took some time to re-plan their placement taking both into consideration (click on any of these for a larger version - original file here). In these drawings, the solid circles are the ideal ground planes, and other circles are additional restrictions.

Top view - ELT, Stormscope, COM, GPS and TAS antennas
I no longer need separate UAT and transponder antennas. Given that Garmin requires a minimum of 3' of cable from the transponder to the antenna, I moved that antenna to the rear part of the tailcone:

Side view with all antennas

Bottom view - transponder, COM, NAV and TAS antennas

I added a third GPS antenna - one for the GTN, one GPS+XM for the G3X (PFD only), and one for the G5.

TAS antenna details - ideal and minimum ground plane plus distance to other antennas
I moved the bottom TAS antenna to inside the forward tunnel, since the aft part of the tunnel has no easy way to run cables to it, and very little clearance near the skin, with the elevator pushrod going through it. The distance between the top and bottom antennas is about 21", which should add a bearing error of about 0.2˚ for a target at 1 mile (perfectly acceptable, I doubt the TAS has that level of precision anyway):

Distance between the two TAS antennas - this introduces ~0.2˚ bearing error for a 9 or 3 o'clock target at 1sm

With the transponder antenna moved aft, I'll try using the original XPDR antenna hole for my bottom COM antenna. It's unclear what kind of performance I can get from the ground plane at that location, but since the ground plane area is only about 20% smaller than the top antenna's, I'll just plot the VSWR after the tailcone is attached and see (and if that doesn't work, I'll add another hole in the baggage area and plug this one).

COM ground plane area is ~1371sqin (ideal is ~1662sqin, ~20% more)
I was also briefly worried that the tailcone antennas might be too close to the ground in a maximum takeoff rotation position, but a quick measurement showed that's not the case (i.e. the tail would hit the ground first):

Tailcone antenna ground clearance at maximum rotation attitude

Given that none of these require any structural changes for now (only the top TAS antenna will give me trouble), I'm deferring any installation steps to later when I actually have the avionics - who knows what else may change until then.

Mid-fuselage ribs and bottom skin deburring and dimpling

The outboard rear seat ribs weren't aligning with the skin holes, so I had to flute them, which was quite annoying when already attached (I even got a smaller fluting plier just for this):

Fluted outboard rear seat rib
I match-drilled them properly and removed the skin, then started deburring and dimpling all the ribs and bulkheads for

Deburred and dimpled ribs
All center section bulkhead holes and the holes with tabs on other bulkheads were machine-countersunk:

Machine-countersunk holes on aft center section bulkhead

Dimpled and machine-countersunk holes on rear spar bulkhead

Dimpled and machine-countersunk holes on fuselage bulkhead
Next I need to deburr and prime the skins so I can start riveting them on.

Time lapse:


Total mid-fuselage ribs and bottom skins rivets: 412
Total mid-fuselage ribs and bottom skins time: 75.0h

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