Tailcone avionics and battery mounting

Before joining the tailcone to the fuselage, I cut and drilled a tray for avionics (to be refined later when I actually have the avionics to mount):

Match-drilling the tailcone rails to the avionics rack

Avionics rack screwed in place

With my intention of using 2 EarthX batteries, I had to figure out how to attach them (the standard bracket doesn't do a good job since the batteries are smaller).

Physical parts for the battery installation

 I took that as an excuse to learn Fusion 360, model the parts, and sketch some ideas there:

I started with some custom brackets to attach it to the existing structure, unmodified:

Higher "shelf" for the second battery

Battery hold-down bracket that only attaches the EarthX vertically

Battery hold-down bracket that fits the EarthX shape all around it

Those would work, but they add some weight and are not really "elegant" solutions, so I tried a few options with EarthX's official box (which I also had to model):

Attaching the batteries with the EarthX official box

Attaching the batteries with the EarthX official box, laterally

(if these models are useful to anyone, you can find them here)

I showed this to Van's support and they didn't like the idea of the underlying ribs being loaded asymmetrically, so I ended up cutting both sides and using their battery boxes:

EarthX battery boxes

The goal is to double-flush rivet them (with a spacer inbetween), so I had to do some testing on thicknesses and rivet lengths before cutting the spacers (ended up with 0.063" for the spacers):

Double-flush rivet thickness testing

Battery boxes clecoed together with spacers

Machine-countersunk battery box holes

I cut of the sides of the original battery mount and attached the new joined boxes to it:

Modified battery mount

Battery boxes on the new battery mount

After primer, I'll rivet this all together and effectively complete section 10.

Time lapse:

Total tailcone rivets: 1866
Total tailcone time: 231.8h

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