Bearhawk Construction Log Section of

Flap Trailing Edge

admin — Fri, 15 Apr 2011 19:00:28 +0000

This morning I used the irons to smooth the rudder and prepare it for spraying. I’ll wait until the flaps and ailerons are done before I start spraying, since that process is better suited for larger lots. Speaking of the flaps, I started on those today too. I put the left flap and aileron on the wing, drilled out the temporary pop rivets, and checked for alignment per the Avipro manual instructions.

Left Flap Trailing Edge Adjustment

I made a slight adjustment and riveted the flap trailing edge in place. I wiped off the accumulation of dust from the flap and brushed a coat of polybrush onto the leading edge. I’m not sure if this is required or not- the manual says to precoat wing leading edges, and this seems like a miniature wing.

Left Flap Ready to Cover

Leading Edge Pre-Coat

I also added a bit of anti-chafe tape to the trailing edge rivets, and I had to stop there for today.

Wiring the GNS430

admin — Thu, 14 Apr 2011 22:30:28 +0000

Here’s the rudder. All of the taping is done and it’s ready to smooth.

Rudder ready to smooth

I connected several more wires to the 430 today. It has a bunch of them, and it would have been many more if I were using a remote annunciator and indicator. The connectors on the back are divided into the three main functions of the unit- VHF Communication, VHF Navigation, and GPS. The VHF Comm connector uses standard size d-sub sockets, except for the power in. Garmin calls for slightly larger wires on the power inputs for the Comm, so they use these fancy connectors that are a bit longer and allow for the bigger wires. Each of the three connectors includes two power inputs, though I think the duplicates are more for power delivery than redundancy. It was tempting to connect one to the ebus and one to the main bus, but Garmin says that each pair should be connected to the same bus. Some folks connect the two power inputs to a single splice just forward of the connector and then run a single cable to the fuse block. I ran two separate cables all the way to the fuse block and gave each one a fuse.

GNS430 Power Wires

I connected all of the wires for the GPS function of the 430, which are routed through the high-density D-sub connector with lots of holes. Most of those holes are for functions that I’m not going to need, so that job went pretty quickly. The transponder is all done except for the power feed, since I ran out of that size of wire. I’m trying to minimize my orders to Stein and B&C, but that’s easier written than done. So as of today the 430 GPS wiring is done, the VHF Comm has power only, and the VHF Nav is still empty.

Rudder Lacing and Taping

admin — Wed, 13 Apr 2011 23:10:58 +0000

These nice weather days have provided an excellent opportunity to spend some time in the hangar. Here’s the rudder after the first coat of polybrush:

Bearhawk Rudder

Rudder Rib Reinforcement Tape, 3/8 inch

I finished the rudder rib stitching in about an hour and a half. This is one of those skills that gets faster with experience.
I marked the areas for taping and brushed on the pre-coats of polybrush for the tapes. While that was drying I made a few more wires. Next up are the RS232 wires that connect the transponder to the 430. These cables allow the GPS to tell the transponder when we are moving so that it can automatically transfer between Standby and Mode C.
It was time to get back to the taping:

Rudder Taping in Progress

Rudder Rib Stitching Done

The picture above shows the pre-coat areas for the tape, the reinforcing patches around the hinges, and the chordwise tapes.
The next few pictures are documentation for the seat upholsterer. I’ll include them in case you might need them for the same purpose.

Front Seat Area

Seat Position Adjustment

Outboard Seat Track

Inboard Seat Track

The Dynon sensor for manifold pressure has 1/4″ mounting holes. I didn’t want to use heavy 1/4″ bolts to mount it, since the smaller 3/16 bolts would still be very much structural overkill. Also, as I found with the shunts, 1/4″ nutplates are much more difficult to find and work with. I cut some aluminum tube bushings to reduce the hole size and adhered them to the sensor with a little bit of JB Weld

Dynon Manifold Pressure Sensor

Dynon Manifold Pressure Sensor Back

Once the epoxy cures I’ll trim it flush.

Covering and Wiring

admin — Tue, 12 Apr 2011 22:24:09 +0000

Today I shrank the fabric on the rudder and applied the first coat of polybrush. While I was waiting for one side to dry I returned to the wiring. My 430 rack was a second-hand find, and the previous owner chopped off the wires right behind the connectors. I took all of those little stubs out today, which would be the first step in putting in the new wires.

While I was studying the diagram for the architecture wiring I found that I had incorrectly wired the alternate ebus feed to the main bus instead of the battery bus, so I fixed that. I also returned to the wing wires. Richard had populated each conduit with two black wires and three white wires. There are essentially two circuits in the aeroflash unit- position lights and strobes.

I’m not interested in being able to turn on the aft-facing white position light without also turning on the corresponding red or green position light, so I only need two leads. Both units are safe to ground locally, so there’s no need for a ground wire to come all the way through the wing. This was a handy change, since I was running a bit short on 18-gauge wire and was able to use much of it in the wiring from the panel to the wing roots.

I also added the wires for the Dynon OAT sensor, which I’ve decided to locate just aft of the left wing strut where it meets the wing. This is a high-drag area already, and the sensor will be in the shade for an accurate reading. It will also be out of the way so I won’t bump my head on it!

Rudder Covering

admin — Fri, 08 Apr 2011 17:30:27 +0000

I took advantage of another great weather day to work on the rudder. I applied the fabric and it’s ready to shrink. This is a short entry, but it was a short day in the hangar too.

Wing Wiring

admin — Thu, 07 Apr 2011 22:30:46 +0000

Today I finished wiring the D100. The last step was to splice together the DSAB wires, which are the wires that allow the three Dynon units to communicate with one another. I also started working on the wires that run through the wing conduit. I realized that I need to order more cable for the Dynon magnetometer. This is a 4-conductor shielded cable and with the sensor mounted in the wing tip it looks like I’ll need more than 20 feet. Richard had already run the wires for the aeroflash lights, but I wanted to be sure about which one was which. To make this job easier, I used a battery and my voltmeter.

Wire Identification

I labeled two wires, then taped each one to a battery terminal. On the other end I measured for voltage until I found the corresponding wires. This system works very well as long as there isn’t any risk of a short on the measuring end. While I was working on all of that I heard an airplane flying by. Our little airport doesn’t get a lot of traffic, so it’s always worth stepping outside when someone stops by. It turned out to be a very fancy Maule!

Visiting Maule

I took several pictures of a few details, including uphostery and that sort of thing. The weather was perfect, so I started preparing the rudder for covering. This was a simple matter of drilling some drain holes on the aft edge of the horizontal ribs and wiping the structure down with the polyfiber C2210 prep solvent.
I also started wiring for the transponder. It’s a very simple process compared to the Dynon units, and especially compared to the 430, which I’ll start shortly.

Dynon Wiring

admin — Wed, 06 Apr 2011 22:07:27 +0000

I started out today by drilling a hole in the firewall for the EMS wires. The thermocouple wires for the EGT and CHT sensors

are fairly large, so the hole is about 1/2″ in diameter.

EMS Wire Hole

I added a serial plug for the HS34, since I learned that it also needs to be able to receive firmware updates.

Dynon Serial Ports

Those brown wires are the thermocouple leads

The thermocouple wires were already in the connector, so the process was very simple.

I also installed the aileron balance tubes for what will hopefully be the last time. The weather is warming and it’s going to be time for covering pretty soon.

Aileron Balance and Wiring

admin — Wed, 06 Apr 2011 01:45:52 +0000

Today I had a visit from fellow Bearhawk Builder John Rheney. It was great to have him stop by, since most of my visitors are not Bearhawk builders. We were able to talk about several of the special challenges and hard decisions in the building process. My Aircraft Spruce order from Sun-n-Fun arrived, and I got several new goodies. One is a new fuel valve to replace the Andair. The Andair is a great design for most applications, but for ours it doesn’t work very well. Since the outlet is on the bottom, the height ends up being a limiting factor. Here’s the alternative- the SPRL valve, which is available from Aircraft Spruce.

SPRL Fuel Valve Top

See how much shorter this one is, since the outlets and inlets are on the sides?

This little cap covers the tachometer drive. Since our electric EMS doesn't use a tach cable, we need to cover that hole with something.

Tach drive

While I was doing all of that Tabitha was working on her window design.
Next I installed the panel annunciator for the low volt circuit. This is especially rewarding work, since now when I turn on the master a light on the panel blinks. If you don’t know what I mean, then I’d have to ask if you’ve ever made an electrical system or circuit. Hearing the battery contactor click is exciting, but blinky lights are much more visual. I found these fancy LED mounts at SNF for cheap, but I wanted to replace their unknown wires with aircraft grade tefzel wires. This has been a strict policy of mine for all wires aft of the firewall.

LED mount disassembled

All that I’m using from this particular mount are the three silver pieces in the middle of the picture. I have a high-intensity LED that will replace this conventional one.

Low Voltage Annunciator Installed in the Panel

I’ve made provisions to duplicate all of my annunciators. This provides extra redundancy in case one fails, and also adds to the ambidexturous nature of the panel layout.

Low Voltage Annunciator Wiring

Just to recap, the function of this indicator is quite simple. When the master is on but the alternator is off, the light blinks. This is a great way to detect an alternator failure in flight, and also a great reminder to turn the master off after flight.
I pulled the lead balance tubes back out of the ailerons and checked the weight. I had originally filled them to 6 pounds each, but after further discussion with other builders I decided to remove a little bit of that lead. I drilled out enough to make the new weight 5 pounds and 3 ounces.
I ran a few more wires, including the Dynon ammeter, ground, oil temperature, all grounds, and power feeds.

The wires are slowly multiplying, one wire at a time.

D180 Wiring

D100 Wiring

Wiring Alternator and EMS

admin — Sat, 02 Apr 2011 00:15:01 +0000

I was getting ready to install the ailerons and I realized that a few of the hinge mounts are missing nut plates. I riveted those on and added the ailerons and right flap onto the wings. I ran the control wire from the alternator back to the switch and crowbar overvoltage circuit breaker. I’m using separate toggle switches for the master and alternator, which is different from the split style switch that is more common in production airplanes. I connected a few more wires, including the serial update wires for the D100 and D180. These serial ports are for updates to firmware and such.

Alternator Circuit Breakers

Left side switches

Here you can see my wooden mock EFIS. The Garmin products make electrical connections on the back of the mounting racks, while the Dynon producs make their connections on the back of the actual unit. In the Dynon case the leads have to be a bit longer, and this arrangement helps me keep them uniform. These three wires that you see here are for the serial port.

This little box houses the low voltage and audio amp circuits that I made. It also supports the serial connections for the Dynon boxes, as you can see on the lower left.

Here's a nice reference picture of the accessory case, with the SD-8 in perspective.

The little red plug in the middle of this picture is where the oil pressure sensor connects. The nipple can't go in with the engine on the mount. I remember reading that once, but I didn't think to put the nipple in before I hung the engine. It's not a big problem, since I'll certainly have the engine off again later.

I’ve been spending more time with the wiring instructions for the Dynon units, and at this point I have most of it figured out. One big question mark is how to attach the single compass sensor in my dual installation.

Installing the Alternator

admin — Wed, 23 Mar 2011 01:00:28 +0000

In the last installment you might remember that I damaged the ebus alternator by shorting it to the airframe ground. The good news is that I was able to find a replacement for just the diode, and thus reuse the circuit board and mounting hardware that I got from Bob at aeroelectric.com. I clipped the leads off of the old diode:

Damaged Ebus Diode

Then used the soldering iron and hemostats to remove the stubs. This seems to be the most effective way to protect the integrity of the holes, and since the old chip is trash it’s no loss. I soldered the new chip in place and devised a slightly more robust mounting method:

The improved Ebus Diode mount

The silver screw will hold the white plastic piece in place, and the brass screws will handle the electrical connections.

Here it is in place:

Ebus Diode Insulator

Just to check for shorts, I turned on the master switch with the battery disconnected and applied my ammeter in series with the battery and battery lead. I got a steady .686 amps, which is about right for what the battery contactor needs to keep itself open. That’s also a good number to know- I had counted on 1 amp for my load analysis. The Z13/8 system allows me to open that contactor in the event of a primary alternator failure- in that case, the ebus can be powered by the standby alternator and the main bus is shed entirely. This low-consumption configuration keeps the current demands in line with what the SD-8 can put out.
The fuse block that I’m using for the battery bus is hollow on the back. The metal parts are recessed so that they don’t short out on the firewall, but I’d rather have something other than air between the two since the feeds are protected only by the size of the wire going to the bus.

Back of the battery bus

I used a little bit of high temp RTV to “pot” the back, filling in the air space and providing an extra layer of insulation. This will also keep gunk from collecting in there.
I installed a powerlet style lead on the battery so that I can hook up a battery maintaning charger more easily. I used the connector that came with the charger, but I shortened the leads considerably and crimped on new rings.
I took a few minutes to clean the dust off of the trailing edge of the wing. One of the drawbacks to our hangar arrangement is that dust flies around and settles on everything. An occasional cleaning is a small price to pay for our low overhead!
I also added the rest of the alternator brackets:

Plane Power Case Mount Alternator Bracket

And the alternator itself:

Plane Power Alternator

Everything lined up perfectly. Next I installed the aileron balance tubes in the ailerons and trimmed them just a hair so that they’ll fit.