Step 5: Landing Light
I will not be using the landing light system as described in the plans. I'm mounting a high-beam halogen lamp into the nose cone. This particular light is a low-profile, sealed beam halogen headlight from the Camaro, Firebird, and other Chevrolets. The headlight fits perfectly into the lower hemisphere without substantial modifications. I'll need to make a mounting frame to hold the light in the nose. It will be adjustable so I can adjust where the beam is pointed. Since the NG-32 center rib has to be removed to make room for the light, I'll add two ribs on the sides of the light to provide structural support for the nose cone as well as to form the enclosure for the light. I will also try my hand at drape molding a plexiglass lens for the nose cone. I may or may not need the reflector since the headlamp has its own reflector.
Here's the concept:
I toyed for YEARS with putting small but powerful lights in the wingtips or in the lower winglets. While very attractive, these ideas just got too complex for me to implement. I was able to find several small lights that would fit into such tiny spaces, but I was unwilling to pay the big bucks needed to buy them. Apparently, the smaller and more powerful the light, the higher the price! Plus, "small but powerful" equates to a tremendous amount of heat. I didn't want to risk melting the fiberglass or foam in such critical structural areas. I dismissed putting lights into the ends of the strake leading edges because of (a) the fire hazards, (b) the canard blocks most of the light anyway, and (c) I may convert that part of the strake into more fuel capacity.
In the end, push came to shove. I needed to close out the nose so I could contour the fuselage. So I dismissed elegance for simplicity.
Making the Light Frames
Try as I might, I could not find an auto parts store that stocked a trim ring for a Camaro. The trim ring is the frame that fits over the outside edges of the light to hold it into the headlight receptacle. So I made two rectangular frames from some 1/16th-inch aluminum sheet I had on hand. The headlight is held in place between the two frames with four screws. I riveted a section of hinge across the top of the front frame. The hinge is bolted to two EZ-points installed into the NG-31 horizontal bulkhead in the nose. The hinge, which is slotted, allows me to make adjustments on the ground to move the light up, down, left, or right to set where the beam is pointed. These adjustments are made through the ballast door on the top of the nose cone. I have no plans to make the light adjustable from the cockpit while flying.
Installing the Light
The NG-32 plywood rib was removed to make room for the headlight. To get the light positioned properly, I added a strip of foam and glassed it to the NG-31 horizontal bulkhead. You'll also note that I had to notch out the NG-31 horizontal bulkhead and remove some of the foam from the F-0 bulkhead to make room for the headlight's connector. I installed two more EZ points into the strip of foam. The frame hinge is bolted to the EZ points. This light assembly is just the right size to be installed, removed, and serviced through the ballast door on the top of the nose cone. So far, I'm very happy with how this is going.
Building the Enclosure
Since the center rib was removed to make room for the light, I floxed in two foam ribs on the sides of the light to provide structural support for the nose cone as well as to form the enclosure for the light. The next steps are to glass the ribs and drape mold a plexiglass lens to for the nose cone.
Drape Molding the Acrylic Lens
I finally got to see what all the fuss was about. It's pretty cool. Just take a piece of acrylic, heat it to 275-degree F oven until it softens, then let it "drape" to shape on the part where it's going to go. In this case, it was easier just to stick the whole nose cap in the oven and let the acrylic sag into shape. The lens looks milky when it's at 275 degrees, but will return to clear when it cools down. You can see the black lines outlining the size of the lens and where it will go.
Sounds easy enough. But there was an initial learning curve to get over. But all in all, it's pretty EZ.
1. When starting with a flat sheet of acrylic, place a layer of felt onto a baking sheet. A soft T-shirt will suffice if you don't have any felt. Place the acrylic over the felt. It helps to start with an acrylic piece that is near the size of the area to be draped. The acrylic sheet above is too large for the job.
2. I warmed up the acrylic to 275 degrees. Any more than that and bubbles will start forming in the acrylic.
3. Prepare the piece to be molded by covering it with felt (or more T-shirt material). The felt keeps the acrylic from being imprinted with the surface of what it's being molded to. In the pictures above, you can see I didn't use any felt on this first test piece. Sure enough the acrylic picked up the hash markings from the fiberglass weave.
4. When the acrylic is at temperature, put on oven mitts, lift the acrylic off the felt by the corners, and drape it into position over the part. The acrylic should sag nicely into place.
In the case of the nose cap, the acrylic sagged into shape just fine while warm, but the "ears" in the extreme concave parts of the nose cap wouldn't stay conformed once the acrylic cooled. The "ears" would curl up and wouldn't stay flush to the surface. What I needed was to vacuum bag the acrylic. Not having a vacuum pump, I tried some "persuasion" of using a weighted object to hold the acrylic into conformation while it cooled. So I used a zip-loc bag filled with rice. It wasn't heavy enough and I eventually placed two bricks over the rice bag. (BTW, the acrylic is sandwiched between two pieces cut from my least favorite LSU T-shirt.) But the ears still curled just a tiny bit.
So I thought to myself, what can I use to hold those ears down? What can I use? Let me think.... Come on, Wayne, think..... Dry Wall Screws!!! Yeah, I'll try my trusted friends!!! The screws don't go through the acrylic. They're screwed in adjacent to the acrylic and are used to clamp down on the "dog ears" made from bits of mixing sticks. I put the screws and dog ears into place and stuck everything in the oven. As the acrylic relaxed and conformed, I tightened the screw which tightened the dog ears. I switched the oven off and left for church while the acrylic cooled gradually in the oven. This worked perfectly!
I cut the lens to size, floxed it in place, then glassed the inside overlap with 1-BID. I painted the light enclosure white, then floxed and glassed on the nose cap.
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