Matt's RV-7 Project

Some time ago I bought an expensive SIRS whiskey compass, and preparing for its installation has been on my to-do list for quite some time. Since I'm still on flu recovery detail, I figured this would be an easy enough project. First I had to go find the rollbar, brace, and forward top skin:

I marked a location on the rollbar brace that puts the bottom of the compass about a half-inch above the glareshield, to allow room to install a nice-looking trim piece later on.

I marked a centerline on the rollbar brace using a handy piece of angle, and drilled two rivet holes using a V-block. I won't actually rivet the compass mount to the brace until I first send it off to be powder coated.

I tested the internal lighting with a bench power supply… yep, it works.

Then I ran wires from the panel light dimmer to a spot just below where the compass will mount, and put a plug on it. Didn't remember to take a picture of this, but you can imagine what it looks like. The compass is now back in its box, and will likely be one of the last pieces of instrumentation to be permanently installed.

I have this idea that I'll install a small map light on either side of the cockpit… I haven't figured out exactly where I'll put the dimmer knobs, or even the lights themselves, but that hasn't stopped me from buying a pair of LED lights and dimmer modules. One of the latter is shown here:

I mounted a dimmer to the F-721A canopy deck on either side of the cockpit, which seemed like an okay location.

I removed the included attachment feet and made some mounting brackets out of scrap alclad. The odd shape is required to clear the traces on the board, and the nutplates are there to allow me to remove the thing later on if it goes blooey.

Just to see if it would all work, I hooked up one of the dimmers to one of the map lights and a bench power supply…

Well, it all works. Eventually I'll find a place to put these.

You might recall I was displeased with the way the audio panel wiring was impinged upon by the crosswise brace at the top of the radio stack. This weekend, I fixed that particular glitch by drilling out the rivets in the piece of angle across the top of the cutout in the subpanel, and very carefully enlarging the cutout by another half-inch. At various times I was going after the subpanel with a unibit, a cutoff wheel in a dremel, various files, and a scotchbrite wheel in a die grinder… luckily I managed to avoid nicking any of the hundred or so wires back there.

New reinforcement pieces were cobbled together out of various pieces of scrap I had laying around. Since I was working around a bunch of existing structure that couldn't be moved, it was kind of a puzzle figuring out the best way to get everything attached securely together.

Here's what the finished product looks like from the aft side. Compared to the previous version, the new brace is substantially higher. There is a 0.032" spacer between the angle and the subpanel, which is bent around underneath to form a kind of cable guide.

A little piece of scrap angle ties the new horizontal brace to the existing vertical piece. It's kind of cheesy, but it's plenty strong. There's plenty of room now for cables and connectors to pass through. You can also see that I had to use another screw and nut in the inboard hole, since there was no way to get a squeezer in there and I didn't want to risk smashing something delicate with the rivet gun.

I also changed the desiccant material in the engine dehydrator plugs again… the dark blue one is filled with fresh silica, and the other one is old. Later on I baked the old silica until it was the same color and the new stuff, and dumped it back into the container.

I ran wires and installed connectors for the rudder trim switch (lower center) and its associated speed control (upper center).

I used some miniature connectors for the 26-gauge wire on the Ray Allen trim components. I used the size of pins and sockets that are rated for 22-26 gauge wires, and doubled the wire strands back on themselves before crimping… worked great. I also bundled all the small wires together with a piece of double-wall heatshrink to provide sort of a strain relief.

Same thing on the rudder trim switch side. Also: Dear Ray Allen company, what's up with you guys and 26-gauge wire? Would it kill you to use something slightly heavier than can be used with normal tools and connectors?

Since I have a habit of only posting extreme closeups, here's a few overview pictures to show how the wiring is progressing. First, a wide shot of the whole panel. The glare is due to the garage door being open to let the extremely nice weather in.

Big fat bundles of wires surround the main bus fuse blocks, but it's all relatively tidy.

Wire bundles running back through the spar and out to the wings. I'm starting to run out of room in the snap bushings that go through the F-704 center section. You only get a total of four half-inch diameter holes to pass all your wiring through, which may be enough for a simple VFR airplane but is totally inadequate for an intergalactic spaceship like I'm building. I know some people have drilled extra wiring holes here, but since the spar is so critical I think I will wait to get blessing from the factory before I go poking any more holes in it.

Looking aft towards the tail… I do have two extra snap bushings in the lower F-705 bulkhead web, which were approved by the factory. I had originally intended those to be used for running wires to the ELT and strobe power supply, but now I'm thinking of moving the ELT somewhere else (yes, again) and switching to LED strobes, which don't need a power supply. However, I have enough other wires and antenna cables that need to get back to the tailcone that I'll probably end up using these for other purposes. You can see in this photo I've already started running trim wires for the passenger stick through one of them.

Big coils of wire are starting to pile up aft of the baggage bulkhead, in preparation for some future date when I get around to crawling back into the aft fuselage to run wires to the empennage and aft-mounted antennas. Not to mention retrieving whatever else has fallen in there.