I'm using the "Duckworks" kits which Van's sells. It's a very well organized kit with solid instructions. However...don't believe the hype when the instructions say you can complete an installation in a few hours. That's a gross understatement for your first time. Anyway, here's what you start out with...a halogen automotive light, a plexiglas lens, paper templates, and all the mounting hardware (frame, rivets, nutplates, screws, etc.).
The first thing you do is take the bulb and reflector out of the light, and discard the body, retainers, and glass.
They give you a paper template for the cutout size and position. You align the template with the next inboard rib (this whole contraption goes in the outer bay), and you align it forward/aft by measuring from the spar edge of the skin (18.75" in this case). Tape it on, trace the pattern, remove the template, cut to your heart's content.
It's always unnerving to cut into a finished component...I made the gross cuts with my die grinder and a cutoff wheel.
That cleared the way and I got out my left- and right-handed tin snips and went to work. Then I used a sanding wheel in my Dremel tool. Then I filed. Then I used emery cloth. Then I used ScotchBrite. That took at least an hour to get this sucker perfect. I wanted symmetry and perfect edges, and it was worth the effort (not really, just in my mind). Here's a shot of the finished hole from the inside...
...and from the outside.
Next you slap the template back over the hole and mark locations for the six screw holes. Drill those holes through the retainer strips.
The light bulb and reflector screw into a frame, and the frame gets screwed to the adjacent ribs. So you have to rivet nutplates to the ribs. You really only need two nutplates, but there's an optional 3rd hole for an additional position option. It's gonna be a waste for my tailwheel configuration. For a nosewheel aircraft, I think it makes more sense to be able to tilt the light back, but not for a tailwheel. Anyway, I drilled the extra holes and put nutplates in just in case. You never know. These nutplates get pop-riveted in. I could have squeezed them if I was outgoing, but this stuff is hidden anyway.
The frame comes in two pieces to accommodate different rib spacing (RV-6 and RV-7/8 wings vary), so you measure the width and drill/debur/dimple/rivet the two pieces of the frame together, as shown here.
Next you're ready to mount the light assembly in the frame (after installing nutplates in the frame for the reflector retainer screws, of course)...
And screw the sucker into place.
Done? Not by a long shot. This is about the halfway point.
At this point I'm going to digress and talk about Boelube. This is the coolest stuff I've ever seen. As you may have surmised, the use of nutplates runs rampant in these Van's aircraft. Everywhere you turn, there are 50 nutplates for this and that. The nutplates actually come with the hole slightly out of round...this is intentional, I'm told. It provides more grip for the screw so it doesn't vibrate out. All well and good, except it's an absolute bitch to get the screw in the first time! Lots of people have complained about this and some people tap their nutplates before inserting a screw. That smoothens it out nicely, but you lose most of that as-designed gripping tendency. So I read some advice from some builder out there who recommended "Boelube." I had never heard of it, so I went and did some research.
Boelube costs about $3 for a "push-up stick" of white waxy crap. But it's the most valuable white crap you've ever seen. This stuff is awesome. Just sort of drag your screw through it before inserting it in a nutplate, and you'll never strip a screw head again! I'm a diehard proponent of Boelube now, and I'll never go without. It works as advertised, if not better. Cleaveland Aircraft Tool sells it. Get some.
Anyway, Boelube made screwing this all together incredibly painless, especially considering the funky angle of trying to screw into the rib nutplates through the lens hole, while trying not to touch the halogen bulb or reflector (skin equals oil equals hot spot equals dead bulb sooner than you want). Anyway, here you can see the mounting/adjusting screws on the inner rib. There are large washers on there to cover the large holes in the frame. There's a lot of adjustability, it seems. We'll see how it works out.
Here's the lens as shipped. You have to trim the hell out of it...about an inch off all around plus you have to follow the curves. Why? Because you can't mount this lens from behind! You have to squeeze the sucker through the hole, then phenagle it around and screw it in place without having your hand back there. How? I don't know...keep reading.
Here's the lens after being trimmed and shaped (no cracks...cool!). The process of shaping was surprisingly easy, because I used...and get this...the stone wheel on my bench grinder. I know, I'm freakin' crazy! But it worked like a charm. I'm as surprised as you are disgusted. Don't worry, I tried it on a piece of scrap first. The wheel just ate right through the plastic (I wore a respirator the whole time, though, paranoid of breathing plastic). The instructions recommended a belt sander, and hell yeah, I would have used one if I had one. But the grinder did great and left the edge so much smoother than I would have thought. But I still took a fine file to it to get it perfectly straight, and then I used 240-grit sandpaper to get the edges perfectly smooth and rule out the possibility of stress cracks forming later.
I wish I had a picture of the next step, but fortunately for you (I assume you're a builder) the instructions are good for this phase...you make a "tape handle" so you can pull the sucker against the inside of the skin while you drill. Drill slowly, enlarge slowly. Don't rush plastic. It will crack. Fortunately mine did not. Anyway, here's the lens after being shaped, sanded, drilled, deburred, and countersunk. Ready to roll...almost.
The screws need something to grip and support the plastic, so you've got these retainer strips. Six more nutplates...18 more holes to drill, debur, countersink, etc.
The kit comes with double-sided foam tape which works great to hold the retainer strips in place.
A little wipedown with Plexis (my plastic cleaner of choice...I'm loyal to it after using it for a while on my Mooney), a bit of coaxing to get the lens into the "cavity" scratch-free, screw it in (don't forget Boelube), and it's done. Well, almost...it's not wired up yet. (The following view is upside down, by the way.)
Here's the top view. The gap between the plastic and the skin is much less than I thought it would be. I had heard from other builders that the fit sucks, but mine is pretty dern good for a first timer, I must say. (This view is from the bottom of the wing.)
Hooked it up to my wife's Ford Escrap's battery, and it worked great! It's definitely going to need an adjustment to get it pointed inboard a bit, but I guess I can wait until the airframe is assembled.
This process did not take "a few hours" like the instructions say...it was more like six or eight. I imagine I can do the one in the left wing in much less time, though. Most of the time was spent getting the hole and the lens shape perfect.