(page 40-08) Fiberglass fairings for wingtip position/strobe lights

The fairings as they arrive with the lighting kit from Van's must first be trimmed to some nearly invisible lines scribed into the fiberglass.  The approximate nature of these lines was immediately obvious to me when I compared the left and right fairings, the most obvious difference being the aft

ends which match up with the hand-holds in the closeout.  I didn't notice this difference until I had already finished the trimming, but I suppose it won't matter considering that once installed it's impossible to see both fairings at once.  I puzzled over the proper fore-and-aft positioning, finally settling on sliding it aft until the aft end of the fairing butts up against the existing rivet in that area.  This required re-trimming the curve where it matched the hand hold.

Speaking of existing rivets, three LP4-3 rivets per wing must be drilled out when installing the fairings.  It would have been nice if the build manual had pointed out that if the lighting kit was going to be installed, these rivets should be omitted during construction of the wing closeouts.  Not a big deal, I suppose, since the offending shop heads and other debris that comes with drilling out rivets can be removed through the large holes in the closeouts specified for the wires.  While making these large holes, I opined in an earlier post that it seemed that a 3/4-inch hole with suitable grommet should have sufficed, although it did occur to me that having a hole big enough to reach into the wingtip may prove beneficial.  Little did I realize just how beneficial.  After completely riveting the right closeout, I discovered to my horror that a pair of fluting pliers had been left in the wing.  With

visions of drilling out 20 or 30 rivets dancing in my head, I instead enlisted the aid of the Spousal Unit (my favorite IronMan triathlete and wife, Karen) who was able to reach through both the wiring hole and a rather small lightening hole in a rib to retrieve the pliers.

The trial fit looked pretty good, with the flat, vertical face of the fairing upon which the light mounts seeming to be oriented properly relative to the wing, so I drilled the holes corresponding to horizontal clecos in the picture.  The fairing has dimples showing the remaining hole locations, except for three holes which must be match drilled into existing holes in the wing closeout (the three whose rivets had to be drilled out previously -- the two nearest the hand hold and the forward-most one in the closeout).

A band of flox-epoxy mixture is added to the upper flange of the fairing (the wing is upside-down in the picture) and is clecoed in place before the epoxy cures.  A release agent such as car wax is liberally smeared on the surface where the epoxy-flox will touch, allowing removal of the fairing.

This theoretically ensures a tight fit of the upper flange of the fairing against the wing tip.  For my first attempt at this I used too little flox-epoxy to fill the voids and had to repeat the process.  A glob of children's modeling clay is used to keep the flox-epoxy out of the area where one of the three nuts securing the mount for the light goes, visible in the picture at left.  I could have used a smaller glob.

Holes for the light mounting bracket are drilled at three dimpled locations.  At first, I doubted the dimple locations because it caused the centerline of the bracket to not be aligned with the centerline of the teardrop-shaped flat surface.  After holding the light up to the fairing, I decided that they are correctly located.

The holes in the fairing along the flange where the flox-epoxy is added get machine counter sunk for flush-mount rivets.  The flox-epoxy gives enough meat to do this.  If the fairing shown doesn't seem to match the picture from the build manual, it's because the manual shows the left wing and I built the right wing first.

The wiring requires crimping Molex connectors on all the appropriate wires and inserting them into the connector housings.  At this point in the build, I'm pretty confident with the crimp tool (of course you absolutely must use a crimper made for Molex).  I learned from watching how-to videos on EweTube (they're still a bunch of sheep) that for the #18 wire we're using, a superior crimp can be had if the tabs on the Molex connector which grab  the wire insulation are shortened about 1/32nd inch.  The tabs which get bent over and plunged into the conductor are OK as is.

 The final step involved sealing the whole thing with Flame Master (aka Pro-Seal) and riveting it to the wing tip.  Update: When I ordered the goop formerly known as Pro-Seal from the Mothership, the package which showed up says 3M Aerospace Adhesive AC 240-B 1/2.  Same stuff, I suppose.

I tried to fill the gaps between the fairing and the
aluminum by smearing the Pro-Seal, but the appearance is not satisfactory.  I'll use some sort of filler before paint.