Empennage fairing layup and filling

Some of the fairing holes had become too large with countersunking, and we were afraid they wouldn't hold the rivets, so we followed Van's suggestion and made some metal backing strips from 0.016" aluminum (for the record, the strips were 2x 17.25", 2x 24.5", 4x 5.5", 2x 16.5" and 2x 6"):

Backing metal strips for various fairings

We then match-drilled them and used resin to "glue" them on the parts, then applied spray-can primer to give some protection:

Fairings with backing metal strips clecoed on

Fairings with glued and primed backing metal strips

To rebuild the bottom rudder fairing gap without the bulbous light portion, we filled it with expanding foam (Great Stuff Large Gap) - or tried, but made a big mess and then had to trim and sand it down quite a bit. Luckily we had protected everything inside and around the rudder with tape:

Massive blob of expanding foam around bottom rudder fairing trailing edge

Initial cut of bottom rudder fairing foam

Trimmed foam on bottom rudder fairing trailing edge

and then covered that with a couple layers of fiber, sanded, realized we sanded too much, then added another layer:

Laying up fiberglass on rudder bottom fairing trailing edge

Fiber layup on bottom rudder fairing trailing edge

Bottom rudder fairing after first round of sanding

Bottom rudder fairing with second fiber layup over trailing edge

The final result was pretty good for a first attempt at layup, and it matches the rudder nicely:

Bottom rudder fairing with modified trailing edge, after sanding

Bottom rudder fairing sitting in place

To fill the "gap" (different protrusion) of the elevator forward faces between the fairing and the metal, we added a few layers of fiber, then sanded it smooth:

Sanded elevator fairing forward face

Elevator fairing forward face with laid-up fiber layers (and peel ply)

Elevator fairing forward face after sanding

We also used resin with flox and some cab-o-sil to fill the gaps between the empennage fairing and the stabilizers (and later the tailcone), then sanded a smooth ramp around the edges which gave a good fit/look:

Applying filler to the empennage fairing

Empennage fairing after filler cured

HS leading edge on empennage fairing, after filler cured

Empennage fairing with filled/smoothed stabilizer edges (forward edge not yet done)

With the gaps done, I could finally machine-countersink the fairing (using a #40 bit), then enlarge the holes to #27. The last two pages of the plans are kind of confusing and some guess work was involved (like that I had to countersink the two holes that overlap with the empennage gap cover).

Empennage fairing with finished edges and countersunk holes

Finally, we started trying to fill the gaps between the metal and fairings, but there's still a lot of sanding and filling to be done:

Gap between elevator and elevator fairing filled with resin (not yet sanded)

Next in this section, we'll work on the horizontal stabilizer fairings, before we start disassembling the rudder and vertical stabilizer to work on the rudder top and the rudder stop SB.

Time lapse: 

Total empennage fairings time: 40.9h