This advice on routing and installing aircraft electrical wiring is specific to construction of a Vans RV-8, but builders of other kitplanes will also find it useful.

For the most part, my wire routing is from the front right firewall where my battery is located, to the circuit breakers on the F-8101 right console.  Then forward into the right gear box, across the F-802T L.G. box upper brace, into the left gear box and to the switches on the throttle quadrant.  From there they run through the left gear box, under the F-881PP-L mid cabin cover, through the main wing spar, and back the left side of the aircraft.

I ran my aircraft electrical wiring for the wing tank senders down the respective right gear boxes, then under the mid cabin panels, and out the side of the fuselage to the tanks.  I used a small rubber grommet for the hole through the fuselage.

I’m happy with the way the wiring turned out, except for right behind the panel.  If I were doing it again, I would change my aircraft electrical wiring slightly to make removing the main panel easier. (See what I would do different)

My Wire Routing

Wire bundle just aft of gear box

Aft cabin floor wires

Flap wire and GPS antenna

Forward right wires

Two images of the wiring bundle just aft of the main spar

Aft fuselage wires

Forward left wires

There were two spots that were a little difficult to work with while running the wires.  Here are some thoughts on them.

Bottom of the gear boxes

Because I needed the return fuel line, I enlarged the hole at the bottom of the F-802B-L bulkhead.  When I ran the aircraft electrical wiring, I thought the extra hole I made would be enough.  That wasn’t the case.  I later realized the electric and pitot/static lines wouldn’t all fit, and I would have to cut more holes.  Had I known from the beginning how much stuff was going to run through here, I would have made the hole bigger to start with, and could have achieved a much cleaner look.

I have two ideas how this could be done better.  The first is to make one hole large enough for everything.  The fuel lines would run through on their own.  I would then use an adel clamp to hold the electric wires, and one each for the pitot and static lines.

The other idea is to make several holes.  But if this is planned out from the beginning, they can be made the right size and location before the gearbox is riveted together, or if it’s too late for that, drilled before anything is installed.  Two small holes with a rubber grommet would each hold the pitot and static lines.  A third hole, slightly larger, again with the rubber grommet, would hold the aircraft electric wiring.  The fourth hole would allow the fuel lines to run forward.  

Of course, a combination could also be used.  You can combine items into one hole and use clamps to hold things off the edges.  Be careful not to squish the pitot/static lines.

Aft end of the main spar

I followed Vans instructions and drilled the electric and pitot/static holes as described on plans OP-11 DETAIL G and DETAIL H.  I then strung the corrugated conduit through the spar and aft under the floor.  There was no problem until I installed the W-816 aileron pushrods.  The conduit interfered and rubbed against the pushrods as they moved.  I had to cut the conduit away so I could bend the wire bundle tight enough to keep it from rubbing.  I turned it 90° and clamped it to the spar, then ran it under the pushrods.

Aft end of the main spar after corrections

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