Monday, March 11, 2013

Fitting Of Left Wing Landing Light Lens

Don’t you love those seemingly simple tasks that are really not? Case in point, fitting the landing light lens. Van’s has apparently “upgraded” the landing light lens to one at least twice as thick as the lens that shipped with earlier lighting kits. I know this first hand because the landing light lens that came with my original lighting kit shipment is much thinner than the lens ordered for the second landing light received at the beginning of the year. The edges of that thin lens are warped somewhat at the outer edge … not realizing at the time most of the lens material is ultimately trimmed away, I called Van’s and was sent a new replacement which was also the thicker version. So I have both thin and thick lenses to play with.

An issue with the new thicker lens became apparent early on … the initial trial fit revealed a huge gap either at the top or bottom of the landing light cutout depending on how the lens was positioned. Because of the thicker Plexiglass material, the curve of lens really won’t flex much as all.  Decided to place the thin lens inside the wing for comparison and the thin lens resulted in a near perfect fit by pressing it towards the leading edge a little bit. To visualize the difference between the two lenses, they were placed side by side for comparison, it was determined the thicker lens is bent too much resulting in the poor fit.
                                          The thicker landing light lens is in the foreground and the thinner lens
                                           is in the background. Notice the difference between the two curves.

I do like the idea of using the thicker lens because it should be less prone to cracking, so an attempt was made to “make” it fit by carefully heating it with a heat gun and gingerly relaxing the curve. After a couple of cycles of heat and tweak, the lens fit is much better, but still not as perfect fiting as the thinner lens is. There is still a small gap between the wing skin and the lens which is more pronounced on the inboard side of the cutout and in particular, the bottom inboard side … I don’t think I can make it any better because it is on the leading edge curve and the transition to the curve on the bottom. Not sure what could be done to reshape the curve accurately without risking possibly damaging the lens. Anyway, the decision was made to suck it up, move on and drill holes. Note: To avoid possibly scratching the lens material during trial fitting, trimming and drilling, the lens was covered with blue painters tape for protection.
                             While pressing as hard as possible on the lens from behind to keep it as flush as possible
                              to the leading edge, Jan drilled out the Plexiglass using a Plexiglass drill bit.
             Photo of the lens drilled and clecoed in place. Lens is covered with blue painter tape to prevent scratching.
            The fit is the worst on the bottom inboard portion of the lens which can be seen in this photo if enlarged.

In a future work session the lens will need to be trimmed back much more to fit the backing strips and the overall width adjusted. Now that the lens is rough cut and drilled, along with the landing light wiring finished and the flaperon brackets installed, it is time to schedule having the EAA technical counselor(s) visit again. During the last visit, they mentioned wanting to do a final inspection of the wing before closeout.