Tail Fairings

 
 
NOTE:  photos link to full size image

Rather than fabricate rudder cable exit fairings as the plans show, I purchased a set of pre-made fairings from Aircraft Spruce (PN 12-00635). The quality was much better than my attempts at the plans-built fairings.
The fairings are shipped oversized, and are trimmed to suit.
The fairings are riveted in place. I aligned the back of the fairing with the end of the skin cutout. This way, should I need to remove the rudder cable, there is plently of clearance.
Before I started building my Sonex, I found this picture of a custom fiberglass tail fairing. I really liked it, and combined with the small gap in the elevator skin, a fiberglass fairing seemed the best way to go.
RV's use this same type of fairing. It looks nice and functions well.
The first step is to protect the aluminum from epoxy. Overlapping strips of clear packing tape serve this function.
Next, modeling clay is applied to shape the contour of the fairing. I used a multi colored pack (Walmart didn't have plain old gray), and it looks kinda funky here.
The clay is shaped and carved until the shape is right.
The fairings will be made using 2 layers of BID fiberglass cloth. I ordered 2 yards of it from Aircraft Spruce. As it turned out, this was way too much. One would have been plenty. I made a simple pattern, cut out some cloth, and draped it over the clay.
The epoxy I chose is West System Epoxy. It has good consistency and is easy to work with. West also sells epoxy and hardener pumps. This makes mixing in the proper ratio simple and very convenient.
The mixed epoxy was then pored over the cloth to wet it out. West epoxy responds very well to heat. As it warms, it gets very thin and penetrates the weave of the cloth easily. A heat gun close by made the wetting out very easy. After the first layer of cloth was finished, the excess epoxy was squeegeed off and the second applied over the first. The second layer took less epoxy to wet, and again excess epoxy squeegeed off. The fairings were then left to cure for a couple of days.
When the glass had cured well, the whole fairing was pried off the tape and clay mold. It released pretty well, with no damage to either the fairing or the tail.
It did happen to remove most of the clay along with the fairing!
The tape was then pealed off and discarded. Any residue will be removed with lacquer thinner.
The chunks of clay were scraped off the inside of the fairing. There is still a bit of residue that will have to be scrubbed down with lacquer thinner after the initial trimming of the fairing is completed.
I trimmed the fairings with a dremel cutoff disc. The initial trim was oversized and then refined to the final shape.
With the fairing back on the plane, I could refine the exact shape I was looking for. I made up some paper templates so that each side was shaped the same.
After they were trimmed and sanded, I mixed up some epoxy and micro spheres to make "wet micro". This was then smeared on all over the fairing to fill in any low spots.
When mixed right, the micro is easy to sand, and produces a smooth, even surface. Start sanding with 80 grit to cut the micro to shape, then finish up with 150 and 220 prior to painting.
The sanded (but unpainted) fairing looks pretty nice on the plane!
Primed and ready to paint and install for good. The completed weight of the fairing is under 1 pound.

 

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Updated: 4 June 06