For mounting the wingtip lights, my original concept for a upswept winglet wasn’t going to work – there is no place to run the wires out at the end of the factory wingtip. Therefore, I went back to the drawing board, and came up with a fairing that goes under the wingtip. The new design looks a lot like the Cirrus SR2x-style up to about their 3rd generation; newer Cirruses have sleek conformal lights in the wingtips. My design is two pieces: (1) a base that attaches to the factory wingtip in three locations, and (2) an aerodynamic cap, designed to fit tightly over the Whelen Microburst lights I bought. The fairing uses thermoset brass threaded inserts for the screws to thread into. The fairing itself was 3D-printed using a carbon-fiber infused polycarbonate, which is both light and strong, and able to withstand high temperature without deforming (in my tests, I didn’t see any deformation until about 200°F; my goal was for it withstand 150°F).
I glued down some rivet backing washers inside the fairing before riveting the fairing to the wing. The washers help spread the load across a larger area of the fiberglass, so hopefully this will help prevent cracking in the future. After riveting, I applied QuikFair to the joint between the wing and wingtip, to smooth out the appearance. After some trial and error, I found that an old credit card works best as a spreader for the QuikFair paste. I’m pretty impressed with the product — once I figured out how to apply to properly, it goes on pretty smooth, dries quick, and is quite firm once cured. After the wing is painted, the joint should be all but invisible.
I also had to build up the flap and aileron, which I waited to do until this point since the aileron needs to be assembled carefully to line up the ends with the flap and with the end of the wing.
At this point I’m ready to put the wing away onto the storage rack and start focusing on the firewall, engine and propeller.