Construction Details - Nav Lights Part 2




The mounting plate ('B') has been drilled to receive the lamp housing and electrical leads. This photo also shows a layer of 1/2" foam (green in color) glued to the top of the 2" layer (under the letter 'A') This additional thickness is necessary for a complete match of the shape of the fairing to the profile of the wing at the boxed tip. This will be clearer in the shaping and sanding steps below.







The upper edge of the outboard mounting plate has been shaped to the profile of the light fixture. Both mounting plates are glued to the foam fairing with thickened epoxy. The outboard plate is rivited to the underside of the tip bow. This plate is also glued and rivited to the inboard plate where they overlap on the underside of the fairing.







The foam drilled out and shaped to receive the lamp housing and power leads.








The foam fairing will be shaped so that the fabric covering will smoothly span from the boxed tip to the tip bow around the light fixture. The profile of the navlight has been traced on the flat portion of the fairing and a smooth airfoil has been traced from the front to back of the foam. A piece of coarse sandpaper taped to the edge of a narrow straightedge makes a cutting batten long enough to span from the fairing over the boxed tip. Keeping this cutting batten perpendicular to the boxed tip, notches are sawn down just short of the profile line traced on the fairing. These notches are spaced as closely as possible without risking tearing out the foam between the notches. They will cut deeply at the ends and much less so in the middle. You can see here why the small piece of 1/2" foam needed to be glued to the middle of the fairing.







Next, the material between the notches is removed with a saw blade. Care needs to be taken not to cut below the profile line on either the outboard or inboard side. The airfoil-like shape of the fairing will begin to emerge but the surface will be very rough.







Another sanding batten long enough to span to the box is made up but this one is wider (that's a piece of 1x2) and fitted with a medium grit paper. It's held roughly perpendicular to the box, like the cutting batten, and used to smooth the top surface of the foam as well as to bring it down to the profile line traced on the outside. Circular as well as reciprocating movements work well. Light pressure will keep from tearing the foam especially near the ends where it's narrow. If you do get a tear, not to worry. It can be repaired with epoxy and microballoons (WEST 410 filler). You don't need to obsess about perfect surfaces here; the fairing will be covered with both fiberglass and the covering fabric. These will cover a multitude of defects. What you are looking for here is a fair overall shape.







Navlights Part 3

Navlights Part 1


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