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Fuse blocks mounted, panel laid out— for now.

January 10, 2011 / posted in Electrical / 1 Comment

5.5 hours.

4AWG and 6AWG wire suck to work with. Period. They don’t bend easily, and when they bend, they don’t stay bent until they’ve been bent that way for a while. But I got the main and e-bus fuse blocks mounted on the subpanel, facing forward, and I can actually get to the fuses in flight.


The main bus. The actual mounting is a bit higher, with the feed post at the bottom. It’s all about where the wires get run.


The e-bus fuse block. This feeds the avionics and EFIS. In case the alternator tanks, there’s an alternate feed to this that comes directly off the battery.

After this was the fun of getting the fat 6AWG wire to the main bus in such a way that it doesn’t chafe on anything. The last thing I want is a wire rubbed raw and arcing against the airframe. Along with this wire, I ran the starter contactor load wire and e-bus feed, as well as the master battery contactor load wire. At this point, I’m stuck. I can finish prettying up the wires in back and start sussing out where and how I’m going to run flap and trim wires from the sticks, but at this point, I’ve done all I can do before the next shipment of electrical bits shows up. I didn’t even know what bits I needed until today. I didn’t know it was OK to put more than one wire into the shank of a PIDG ring terminal. But today, I also finished my panel layout, for the most part. That means I know where the major components and switches are going to go. I really have no idea where to put music input and aux power, but I’ll get to that momentarily.


Panel_v1
Click to open full size.

Stainless Steel Providers.

January 4, 2011 / posted in Electrical, Firewall Forward / No Comments

5 hours.

Oh yeah, it was a good day. Not only did it not require the use of an AK-47, I got a lot of momentum going on firewall-forward wiring. The overall schematic is still rather nebulous, but it’s based more or less on Bob Nuckolls’s Aeroelectric Connection, drawing Z11. In this scenario, there’s a main bus, an endurance bus, and a small always-hot bus. I’m toying with the idea of deleting the always-hot bus and just putting in a switch for the alternate e-bus feed because quite honestly, an always-hot bus is an excellent opportunity to drain every last molecular twitch out of an otherwise healthy battery.

Also, with the acquisition of a Garmin GNS430W, my avionics stack is now complete. EFIS, audio panel, transponder, nav/comm/gps, done. Good god, I’d love a cigarette right about now… But the upshot of this is that the the electrical picture is now complete. I have to provide power for these devices, plus the various other implements of flight, namely trim, strobes, lights, and autopilot servos. How does that work? Common wisdom is to start at the battery and work your way back. Instead, I ran loads for lighting and strobes, and today I ran starter and e-bus feed, and they’ll collide behind the panel in a Gotterdammerung of switchgear and fast-on tabs.

So the next step is, how to get the electrons from where they are to where they need to be? I had a few simple rules, gleaned from the Aeroelectric Connection and the mighty oracle of Van’s Air Force, to wit:

1. Thou shalt not run thy strobe cables alongside thy data cables.
2. Thou shalt not run thy data cables alongside thy power wires
3. Thou shalt provide ample room to service thy components after the holy top deck skin is on.
4. Thou shalt not run thy wires below tubes which carry fuel, for the drips from leaks onto that which arcs may beget the inferno.
5. Thou shalt not allow breath or light to pass between cabin and engine compartment.
6. Thou shalt not expose thy wires to sharp metal edges.

The first step was to figure out where to make holes in the firewall for pass-through of electrical cable and sensor data.


A little off from my original guesstimate, but this’ll do.  A 1-inch hole accommodates the SafeAir1 firewall Passthrough, a stainless steel gizmowith a rounded outlet to let wires exit in any direction without chafing on one side, and get sealed with fireproof tape and goop on the other.


After a little cleanup, it looks OK.


My original estimate for the size of the MGL RDAC engine monitor module was way off, and MGL doesn’t actually publish the dimensions of the unit in the installation guide, which is problematic. So I scoured the newly-minted mglavionicsusers.org forum and found the answer I needed, then made this ghetto-ass mockup from the battery box packaging and a roll of blue masking tape.  This made me reconsider the location for the data wire hole.   In theory, there should only be one data wire going aft, that of the RDAC itself.   All the engine probes and sensors should go from the engine to the RDAC.


How do you make a meal out of stainless steel?   Chew slowly.   Everybody gets all weird about stainless steel, and true, it’s a whore to work with, but remember, if you can scratch it, you can cut it.   This is a 1″ hole saw, about three bucks from B&B hardware.  The trick is to dunk the end of it in Boelube and go SLOWLY.   Make your pilot hole with a #40, then move up to 1/4″, which is the size of the hole saw’s pilot bit.   This one’s so dull it won’t go through warm cheese, but it serves as a good guide for the hole saw.   Then, if the teeth of the hole saw are sharp at all, you should be able to grind your way through the firewall fairly easily.   Keep it from heating up.  If it starts to smoke, put more Boelube on it.    The amazing torque of this Makita cordless drill is also helpful.  It’s relentless.   If you’re working above the battery, cover the battery with a sheet of plastic or something.    You don’t want stainless steel chips grinding away between your battery and the firewall.


For added fireproofing, I used a bead of my leftover Fire Barrier 2000 around the FPT (firewall pass through) flange, just to seal the deal.  Not that it’s very necessary; you get pretty much an airtight lock when the two halves are screwed together with the firewall between them.

And there you have it.   Starter load wire, main bus feed, and e-bus feed, all going through the firewall just like they’re supposed to.  What this photo doesn’t show is the firesleeve I forgot to put on the outside of the FPT before I ran the wires through it. It also doesn’t show the master contactor load wire I put in shortly after.  I put the fire sleeve on and clamped it down with one of the hose clamps provided in the kit.

Since I was feeling inordinately proud of myself, I figured I throw the engine mount isolators on there.   Still not sure how they go, I’ll have to check, but the red bolt protection nipples are a nice touch.

Up in the corner next to the VA-168 manifold, you can see the second FPT.   This will carry a data cable from the RDAC back to the EFIS, with room for future additions should I wish to take my life in my hands with some sort of electronic ignition.

And here I am, sitting in the focus of the Dynafocal brainprobe.   Maybe I can infuse it with some of my own sentience, such as it is.

I just got off the phone with my cousin, Navy SEAL and former SDV electronics tech, who assures me, despite my misgivings, that the switchgear on the panel and the power routing is not a problem.   Nor is anything else.  Where it gets tricky is the audio wiring, where impedances must be matched and other arcane spells must be cast.   I’m going to bring him out here from Yuma for the hard stuff, I think.

On. The. Gear!

December 27, 2010 / posted in Electrical, Firewall Forward / No Comments

10 hours.

Over a couple of days that is. This week I tucked into wiring. I had to drill some new grommet holes in the baggage bulkhead on each side so I could slip some fat strobe wires up one side, and some fat RG400 coaxial cable down the other. Performing this task is difficult. I don’t have a large drill bit that screws into my 90 degree drill, so I had to make do with a countersink. A countersink can, in a pinch, be used as a drill bit. Drill your 1/8″ pilot hole, then push the countersink all the way through. Hole gonna need some cleanup, but that’s OK. I finished up running the strobe and coax for the ELT and tail strobe, along with power wires, then ran two lengths of RG400 cable aft for the GPS antennae up the left side after making a couple of new holes in the baggage bulkhead for some grommets.. This should take care of the eventual two GPS’s, the one in the MGL Odyssey and the one in the GNS430W. Yes, I’m going to get a GNS430W, because it contains 3 pieces of very necessary equipment in one box. On the other side, I ran two high voltage strobe cables and the strobe powerpack and tail light power wires.

I had some leftover coaxial so I ran it through the spar to a spot picked out for the COMM antenna on the left side under the seat panel. When the new load of coax comes in I’ll run the wire for the transponder antenna and reserve a healthy length of wire for the run down the left wing to the Archer antenna.

Not much to look at right now, but this will eventually get cleaned up, fully routed, and fully dressed.

But the fanfrakkingtastic thing is this:
I got the plane on the landing gear today!

To do this, I rolled out my trusty engine hoist.

It’s hard to take a self-portrait with an iPhone 3G, but this is me, positioning the hoist in order to lift the ship high enough to get the gear leg into the tube on the engine mount.


Lifted off the ground with one gear leg on. Judge me by my size, do you?


The plane supported only by its own landing gear.


From the side…

So now I have to cut a couple more holes in the firewall for electrical goodies, but the good part is, I’ve got a rolling airframe on which to hang the engine, which should be done soon. On the down side, it’ll be harder to get in and out, so I’ll have to come up with some kind of platform to make that easier. I have to go back down the Jeffries Tube a couple of times to clean up some wiring, but not too much work back there. Next is running battery and alternator cables, figuring out the wiring busses, actually choosing switchgear, and finalizing the panel design.

The Jeffries Tube.

December 13, 2010 / posted in Electrical, Fuselage / No Comments

3 hours.

In Star Trek, the Jeffries Tube (named after a member of the original series’ production crew) is a long, narrow tunnel from the engine room to the warp drive nacelles of the USS Enterprise. On the RV-7, it’s the space behind the baggage compartment going all the way down the tailcone to the 3rd-to-last bulkhead. Working down there really does make wish such things as aircraft elves existed. Unfortunately, they don’t, so I had to crawl down the Jeffries Tube to drill holes in bulkheads for wiring grommets, carrying a big cordless drill, a bit for the pilot hole, a bit for the grommets, a deburring tool, and the grommets themselves. I was able to get the grommets in and start the wiring run for the strobe cable and tail light power wire. It’s a slow process, and being mildly claustrophobic and crammed into a metal tube reminded me of my recent unsettling, yet action-packed U-boat dreams. I’m going to be spending a lot of time down there. I also have to drill grommet holes for the ELT coaxial cable and set up the wire stays for everything. I’m trying to avoid drilling more holes in the longerons and j-stringers, but I do have some adhesive-backed cable tie holders that will need to be placed.

As an aside, I finished the lower empennage fairing. These two stupid pieces of metal are supposed to have a rubber seal on them, but there’s no way that’s going to fit. Also, there’s no point in making these things removable, so I riveted them on. So now I have a 1/16 to 1/32 gap along the horizontal stabilizer at the root. So I lose a knot. Big deal. If it concerns me later, I’ll create a proper fiberglass lower fairing. Speaking of fiberglass, I got the empennage tips riveted on. they’ll need a coat of primer/paint, but they’re done.

Also, yesterday I got a call from Tim at Tim’s aircraft. My spam filter de-rezzed his pdf of the engine repair estimate, but I got a new one from him. Nearly eleven grand. Ouch. But now I have nitrided steel cylinders instead of that godawful cermichrome and it’s going back together as soon as the magnetos come back from the specialty shop. I just hope he doesn’t flinch at installing the AFP fuel injection system. But what that means, brothers and sisters, is that I’ll probably be hanging the engine in the not too distant future. At this point it’s now time to get down and dirty with the remaining amounts of money and see if there’s enough for avionics, remaining FWF, interior package, taxes, training, and hangar rental at my phase 1 airport.

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