Bending at the Brake

This afternoon I stopped by Brad’s place and used his brake to bend the steel pieces for the aft window. Wasn’t it nice of him to let me do that? While I was there I also bent the aluminum pieces that will go on the windshield posts to help support the aft edge of the windshield and seal out the rain and drafts.

Testing the D100

In another stressful moment of truth, today I powered up the D100 for the first time. I started by verifying each pin in the wiring again. Here’s the unit that I found on eBay. It’s slightly used but in great shape:

Dynon D100

Dynon D100

Here’s where the backup battery hatch is. I was surprised to see a battery in there, since the seller didn’t advertise it as being included. This little hatch is on the right side near the bottom.
Dynon Backup Battery

Bonus backup battery

Here’s what the pack looks like:
2200 mAh 18650 Lithium Cells with Charging Circuit

Bonus backup battery

With no other excuses, I put in a fuse and turned it on.
D100 Powered Up

Powered up

It works just like it is supposed to, except that the backup battery doesn’t take a charge. That’s probably why it wasn’t advertised as included! I’ll try taking the pack apart to see if I can replace the cells. In this case at least I have the connector and onboard charging circuit to harvest from the old pack. While I was waiting to see if the pack was going to charge, I installed the nose bowl to be sure that the landing aluminum wasn’t going to interfere with the starter. Here’s how it looks:
I'll need to trim a little off of the top.

I’ll need to trim a little off of the top.

I shortened the back bracket by 3/4 inch or so just to provide a bit more clearance.
Here's where it will go

Here’s where it will go

I attached it at the bottom first:
Nose Bowl Light

Nose Bowl Light

I’ll make a provision for adjustment in the top bracket, which will allow me to aim the light once we try flying with it.
Nose Bowl Light Side

Nose Bowl Light Side

It was so nice to see the D100 in the panel that I also got out the HS34 to see how they would fit together. I found that they won’t fit together very well at all, at least not without more cutting.
Dynon Clearance Shortage

Dynon Clearance Shortage

The problem is that I cut the hole based on the published dimensions for each box. Since those dimensions don’t include the outer flange, and since the two share a hole, I needed to add another 1/8″ or so to the width.
648- New Cut Line
The picture above illustrates the problem. It’s not a big problem, and a few minutes with the dremel and file will have it all worked out. If only I could say the same thing for the HS34 mounting bracket! I would rather not drill new holes in the panel, so instead I’ll drill new holes in the bracket. These holes will not have adequate edge distance, so I’ll have to come up with a doubler to put in front of (aircraft forward) the bracket flange. This will make a sandwich, with the instrument panel and doubler being the bread, and the HS34 bracket being the balogna, or cheese for vegetarians.

Cargo Door Gas Strut

I cleaned up and primed the fuel line support that I welded on last time:

Bottom Fuel Line Support

Bottom Fuel Line Support

Then I made one just like it and installed it on the right. While I had the primer out I sprayed a coat on the intake scoop to see how my fiberglass work was coming along. Sometimes it’s hard to tell without a coat of paint.
Fiberglass needs more filler

Fiberglass needs more filler

As you can see, it needs more work.
Intake Scoop

Intake Scoop

This is one of those areas where the part is certainly airworthy, but if I spend more time sanding and filling, it will look much better. Next I started working on the gas strut that will hold the forward cargo door open. The aft cargo door is held open by gravity, so it doesn’t need a strut. I found some threaded balls to use on the ends of the strut, and though the front ball will bolt onto the door sill, the rear ball will have to attach to the door frame somehow. I didn’t want to weld the ball on, since there’s no telling what kind of metal it’s made of. This seemed like a good job for brazing. Being that I haven’t ever brazed before, I tried a practice joint with some exhaust scraps.
Practice brazing

Practice brazing

I heated both parts until they were just starting to glow, then applied the fluxed brazing rod as I would solder. It seemed pretty straight forward, so I moved right on to the real parts.
Brazed on ball

Brazed on ball

Here’s the end result:
Cargo Door Strut Installed

Cargo Door Strut Installed

Cargo Door Open

Cargo Door Open

I used a 10-pound strut, which was the smallest that I could find. So far it holds the door open, but that’s without the skin or window. If it doesn’t stay open with the extra weight of those items, I’ll get a 20-pound strut instead. Both have the same external dimensions.
Here's how it falls with the door closed

Here’s how it falls with the door closed

I’m planning to use a small section of aluminum between the skylight and the windshield. I cut the piece out of .020 sheet, and installed the GPS antenna.
Roof Aluminum

Roof Aluminum

I’m planning to bend the sheet at the red line, then insert that tab into the windshield channel. The back of the aluminum piece will go over the skylight front and will be secured by the same screws that hold down the skylight.

Fuel Line Tabs

I came out for little while today to sand the last layer of filler and add another.

Scoop Filler

I worked some into a little gap at the back of the scoop

AC 43.13 says that fuel lines should be supported every 16 inches. I can’t see how it’s possible to span the distance from the aft side of the front door to the clamp on the diagonal tube under the door bottom, so I made up a little tab:
Fuel line support tab

Fuel line support tab

I welded the tab to the outside of the flange, since it was much easier to get to.
Fuel line support tab welded

Fuel line support tab welded

Since the metal part slopes inward, the weld bead should clear the fabric. While I was welding in that area, I had to figure out how to remove the headset jacks so that I could get the wires out of the way. This was the solution that I came up with:
Big hole/little hole

Big hole/little hole

The headset cables run through the little hole on the left, so i drilled the big hole on the right and connected the two with a very small version of the Erie Canal. That reminds me of a mule named Sal, and makes me think of Albany and Buffalo, which I usually don’t do on my days off.

Adding Filler

In replacing the engine mount bolts, I found that I needed a second washer to get the castle nut in the right place. I installed those washers on each one, but I didn’t put any cotter pins in yet. Odds are good that I’ll have to take the engine off again before we fly. I sanded the prior coats of filler on the nose bowl joint and scoop, and added another layer to the scoop.

Oil Cooler Continued

I added the first layer of superfil on the windshield fairing, and another layer on the intake scoop. It will take several layers and lots of sanding to make them look reasonable.

Filler on Windshield Fairing

Here’s the first layer of filler on the windshield fairing

The oil cooler support will attach at the crankcase bolt just above the number 2 cylinder. I removed the original case bolt and added a longer version, and used the torque wrench to tighten the nut.
96 inch-pounds for the 1/4" case bolt

96 inch-pounds for the 1/4″ case bolt

I welded one of the ends of the oil cooler brace, and also welded a bit more on the number 2 exhaust pipe. I added the fittings to the oil cooler too:
Oil Cooler Fittings

Oil Cooler Fittings

While I was there I did a little deburring on the number 2 cylinder baffle.

Still More Fiberglass

This evening I worked on trimming the windshield fairing. I wanted to have an equal distance above and below the fold point, so I started by drawing a line along the the fold point. I used a square and a sharpie to mark a line along the fiberglass and used the belt sander to trim the fairing to those lines. I also started making the steel tube brace that will support the oil cooler. I’m using a 4130 steel tube with flattened ends.

More Fiberglass

Today was a quick session. I added two more layers of fiberglass on the windshield and one more layer on the intake scoop.

Fiberglass Windshield Fairing

This morning I started on the fiberglass windshield fairing. First I applied contact paper to the windshield and boot cowl so that the epoxy wouldn’t stick to the expensive bits. Then I put a nice coat of automotive wax on the contact paper to make sure the epoxy didn’t stick to the inexpensive bits either.

Contact Paper Mask

Contact Paper Mask

I built up the first part of the fairing with two layers using the technique that Eric and Bob have published in the past. I taped a big trash bag to the table and wet the strips with epoxy. Then I squeegied most of that out with a hotel room key card. Then I put those strips in place and smoothed them out.
First 2 Layers

First 2 Layers

Trash Bag Layout Area

Trash Bag Layout Area

After lunch I came back and welded a few more exhaust pipes and sanded another gasket surface.
Exhaust Pipe Detail

Exhaust Pipe Detail

In the picture above you can see the weld fillets that run parallel to the exhast flow. Bob says that these help support the circumferential weld between the pipe and the flange.

Oil Cooler Support

This morning I started by finishing the rest of the lightening holes for the headrest parts.

Head Rest Parts

Here’s a stack of parts for the headrests

Next I made a few doublers for the oil cooler area on the back left baffle. I’m really guessing here with how much support I’ll need. I’ve studied a few other airplanes and copied what I have seen.
One doubler plate ready to cut

One doubler plate ready to cut

Match Drilling

Match Drilling

Sandwich Parts

Sandwich Parts

I’ll have to add one little filler strip to take up the gap where the top doubler doesn’t continue down to the bottom.
Filler Strip

Filler Strip



You can see that I’ve left several holes open. These get rivets from other sources, including the pop rivets that hold the rubber to the top of the baffles, and the rivets that hold the side baffle to the aft baffle.
The other side

The other side

Here's the whole sandwich from the side view.

Here’s the whole sandwich from the side view.

Side riveted to back

Side riveted to back

Same again

Same again

I added lightening holes to each of the headrest lower brackets
Headrest parts

Headrest parts

Then I deburred all of those holes and started to prepare the boot cowl and windshield for the fiberglass fairing that will go there.

Smurf Extract

The fiberglass from yesterday was cured well, so I used the belt sander to trim the outer edge further.

Polyfiber Superfil

Doesn’t it look nice now? Don’t look too close- it’s full of pinholes and other imperfections.

Ok, so here's a closer look.

Ok, so here’s a closer look.

To fix those problems I mixed up a batch of superfil, aka smurf extract. To spread the filler evenly in the corner, I used another hotel key. These have turned out to be quite handy and useful for this kind of work.
Rounded Corner on the Key Card

Rounded Corner on the Key Card

That rounded corner gave me a nice filet of filler.
Smurf Extract

Smurf Extract

While that cured I spent more time on the headrest structure. I found a good deal on a set of electrical knock-out punches on ebay, and it turns out that they make great lightening holes in aluminum. I sharpened the old tools on the belt sander and made a few test holes. These are some of my favorite new tools, because they are so simple to use and maintain, and because they make such nice holes.
Electrical Conduit Punch

You can see how the punch works in this view

Knockout Punch Aluminum

Here’s the end result in some scrap aluminum.

Lightening Hole

This lightening hole took only a few minutes to make and debur.

While I was working on that Tabitha did more planning for the new window frames.

Engine Intake Scoop

Since the first headrest turned out well enough, I bent the parts for the other 3. I made some measurements for what type of support I’ll need to make for the oil cooler also. Since the intake scoop is going to need a fiberglass flange to attach to the cowl, I’m going to construct it right on the cowl. I used tape to apply a big trash bag to the aluminum:

Fiberglass intake scoop

Fiberglass intake scoop

I put 3 layers of 1/4″ foam between the bottom of the FAB an the top of the scoop. This will allow some space for the alternate air door mechanism, and will also allow for engine vibration. The FAB shakes with the engine, but the scoop shakes with the cowl.
Cowl Masking

Cowl Masking

Headrest Structure

Yesterday I located the oil cooler on the left rear baffle. Today I cut out some aluminum tubes to use as the supports that will keep the flanges from bending together when I tighten the bolts. Unfortunately, I ordered the wrong size of tube! It’s too small and the bolts won’t fit through.

Oil Cooler Bolt Tubes

Oil Cooler Bolt Tubes- too small!

I finished cutting off the other headset jack tab and primed both sides.
Evidence Removed

Evidence Removed

The landing light bracket will use the four corner screws to hold the brackets together, and the two large side bolts to attach that assembly to the structure in the nose bowl.
Landing Light Bracket

Landing Light Bracket

Landing Light Bracket

It’s a rare occasion when I can use universal rivets to attach a nutplate. Usually they have to be flush.

I worked a little bit more on the first headrest, making sure that he system is going to work before I make four of them. The idea is that these headrests will retract to the point where they are just slightly taller than the seat back. This is the only way that we could think of that would allow something to be tall enough to provide decent function (crash protection) but not in the way during operations with one or more empty seats. I copied the idea from a minivan.
Headrest Structure

Headrest Structure

Headrest Structure Attach

Headrest Structure Attach

In the picture above you can see three small holes in the short bracket. Those holes will get blind rivets, as will
additional holes on the top bracket.

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Hours Logged This Session: 3.7
Total Hours: 1883.75

Locating the Oil Cooler

While I was thinking about the aileron control cables, I realized that my previous location for headset jacks wasn’t going to work. I cut the old bracket off and this is what was left:

Headset Bracket Weld Bead

Headset Bracket Weld Bead

I used the die grinder and files to clean off the weld bead. It’s always frustrating when I end up making more work for myself, but such is the nature of building my own airplane I guess. I picked up where I left off last week with the landing light bracket, which involved using the rotary file in the dremel to finish enlarging the center hole. This is what I ended up with (after a few attempts to get the diameter correct on the back bracket hole)
Landing Light Sandwich

Landing Light Sandwich

The idea is that there is just enough thickness in the LED unit to allow for a tight hold when I attach the front bracket with screws. I’ll need to figure out a way to attach this contraption to the nose bowl, preferably in a way that still allows for some aiming adjustment later on.
At this point I have enough of the cowling done to be able to trim the baffles to their final height. I had previously rough-cut them so that they weren’t touching the cowl metal, so all that I needed to do was make a mark where I wanted to cut. To make that line, I poked a small hole about 1.5 inches from the end of a hotel room key. Any sort of plastic would do the job just as well, it’s just that I have a pile of hotel keys available. I stuck the point of a marker in the hole, then ran the edge of the card along the inside of the cowl metal. Some of the lines ended up on the front of the baffles, and some on the back.
Marking the Baffles

Marking the Baffles

Marking the Baffles continued

Marking the Baffles continued

I trimmed the left side so that I could know where I would be able to put the oil cooler. Tabitha came out later in the afternoon to make more window plans. She laid out the new shape in the upper left window and we worked together to cut it out.
Window Thoughts

Tabitha is thinking, looking at the old window shape. In this shape, the plexiglas is layered between the skin and a backing strip. We’re going to change the configuration to put the plexiglas between the steel frame and the aluminum skin, which saves a bunch of fasteners and allows us to enlarge the window a bit.

Bearhawk Front Window Skin

Trimming around the lock mount on the front window

While she worked on that I marked where the oil cooler will go.
Back left baffle Lycoming 360 oil cooler

First, here are the mounting holes.


Then I made marks for where the opening will be.

Note! This oil cooler mounting strategy proved to be inadequate in flight testing. The oil cooler is probably a little bit too small for this engine, but more importantly, it should probably be located back away from that cylinder a little. In the end I fabricated a mounting system that moves the cooler back about one inch. Also note that the ideal arrangement would be with the oil flow vertical. The vertical arrangement would give an outlet for trapped air to flow out of the cooler.
Then I cut out the hole for the opening.

Then I cut out the hole for the opening.

Cowl Hinge

Tabitha picked up where she left off on the cowl door hinge, exchanging clecos for rivets.

We’re both motivated to keep the project moving along.

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Hours Logged This Session: 7.3
Total Hours: 1883.75

Landing Light Bracket

This morning I sprayed the last coat of polyspray on the flaps, ailerons, and rudder. I came back to the hangar after lunch to debur the left door skin and start making the landing light bracket. For a while I wasn’t sure if I was even going to install a landing light. It certainly isn’t a required piece of equipment, and while it would be nice to have for flying at night, it’s not entirely necessary. There is some benefit for visibility to other aircraft, both in daytime and at night. While I was at Oshkosh I got a great deal on a AeroLED LED unit that I can put in the nose bowl, so that was a factor in changing my mind in favor of the light. The LED also has a built-in wig wag function (or in this case, perhaps more appropriately called a “wig”). The catch is that I have to come up with some way to mount it in the nose bowl. The unit is a standard PAR 36 size, so I started by ordering a bracket from Duckworks. The Duckworks bracket holds the front of the unit in place, and it was well worth the price, since it saved me a couple of hours of work. I used the fly cutter to make a hole in another piece of aluminum, which will support the back of the LED unit.

Bearhawk Landing LIght Bracket

This over-sized piece will eventually be the back of the LED support.

I’m not sure how the duckworks bracket was supposed to work exactly, but I found that it would work really well for me if I slightly enlarged the hole. I needed about 1/8″ more radius. I lined it up carefully in the drill press and used the fly cutter to make a significant part of the cut, then will use a rotary file in the dremel to finish the job.
Enlarging the Duckworks Bracket

Enlarging the Duckworks Bracket

Window Planning

Tabitha came out to the hangar today, so I took a break from the stinky covering. We worked together to create a cardboard template for the new left rear window. We also marked and cut the left lower front door skin, which we’ll replace with something transparent. Tabitha wants bigger windows, and having windows does enhance visibility, especially while flying solo. I was concerned about weight gain, but it turns out that .060 lexan weighs less per square foot than .032 aluminum does. .032 aluminum weighs .461 pounds per square foot, while .080 polycarbonate weighs .50 pounds per square foot, and .060 polycarbonate weighs .38 pounds per square foot.

Front Door Window

Front Door Window

We also made acommodations for the front door locks.
Bearhawk Window Planning

Tabitha is working on the cardboard template for the back left window. We had to design this window before we could determine the shape of the patrol door window, so that it will all flow together properly.

Cutting out the Window Hole

Tabitha’s using the snips to cut out the window opening

Cutting out the Window Hole

Here I am doing the same. We have to take turns because our hands get tired!

Covering Spray

Our seats are at the upholsterer, so I need to hurry up and finish the headrests. I cut out some 8×8 .032 aluminum squares to use as the face and top. I used the bench grinder to remove some of the larger bits of the weld bead from the exhaust pipe. Since the temperature has started to moderate a bit, I started with the spray coats on the ailerons, flaps, and rudder. The first step was to hang all of the parts from the ceiling. I hung a sheet of black plastic over the hangar door, with hopes of minimizing the UV exposure to the hanging parts. I sprayed a round of polybrush on the rudder, but the gun wasn’t quite working well. The atomization just wasn’t very good. I stopped there to let that coat cure, since I won’t be able to fix it until it does.

Back Seat Seatbelt Tabs

With the lower cowl in place I started preparing the outer fiberglass scoop that will cover the FAB and direct the intake air to the inlet. I found an RV builder who had a scrap scoop, which was quite affordable. I only needed a very small piece of the original, so any defects or mistakes higher up were not going to be an issue. I marked the edge and used the cutoff wheel in the angle grinder to get the edge pretty close.

Vans fiberglass intake scoop

This is how much fiberglass I cut off of the scoop.

Vans Scoop

Here is the final product, ready for the new fiberglass flange.

I wrote in a previous entry that the radius of the EMT elbows for the exhaust pipes was hard to adjust. Since the number 1 cylinder is closest to the cowling, I started working with it first. I needed a tighter radius, so here is what I tried:
Electrical Conduit Exhaust System

These saw kerfs allowed me to bend the pipe to a tigher radus. It was no trouble to weld the kerfs closed.

This is my second attempt on the number 1 pipe. On the last iteration I had the pipe coming out of the flange at an angle, which made it nearly impossible to get the nuts on. Next I made the seatbelt tabs for the back seat shoulder harnesses. I started with .125 4130 tabs that were 1″ wide.
Rear Seat Seatbelt Tabs

Rear Seat Seatbelt Tabs

Rear Seat Seatbelt Tabs

I shaped them on the grinder and welded them onto the cross tube over the cargo area.

A little bit of cleanup and paint will make that look much better.

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Hours Logged This Session: 5.25
Total Hours: 1883.75

Initial Prop Install

Today I connected the blue LED that will become the parking brake annunciator. Since the parking brake valve is just a check valve, it could be especially troublesome to land with it in the closed position. The brakes would apply normally, but they wouldn’t release! I’m planning to make this blue light come on any time the valve arm is not in the open position. I used a 430 ohm resistor and stuck the whole assembly into one of the little aluminum casings.

Bearhawk Panel Annunciators

Annunciators- Dynon Warning, Low Voltage, and Parking Brake

It’s time to start making the cowling so that I can build the intake and exhaust systems. The first step is to put on the prop:
Hartzell Propeller

The prop fits! It sure is a hassle to install though.

This allows me to check the nose bowl positioning again.
Bearhawk Nose Bowl Position

Positioning the fiberglass nose bowl based on the spinner location

Since most of the wiring is done I put the boot cowl pieces back in place for a little while. I definitely would not have wanted to do all of that wiring work with the boot cowl on! Back when I cut the side vents in the boot cowl I did it wrong and ended up with a bad shape. Here’s my solution:

Fixing my eroneous vent hole (not a metaphor)

I’ll add one more little D-shaped filler piece and fill the crack with smurf extract. When I put the right side boot cowl on I found a bit of a clearance shortage. The side vent duct is a squeeze between the boot cowl and the electrical distribution panel. Fortunately I think it will still work just fine.
Right Side Vent

Minor clearance shortage

While I had all of that back on I also set the new windshield in place just to see how it fits. I don’t think I’m going to have to trim it at all, which is very nice.
LP Aero Plastics

Windshield Trial Fit

Posted on
Hours Logged This Session: 6
Total Hours: 1883.75

Parking Brake Switch Wiring

This morning I made my first attempt at a parking brake indication switch. It didn’t turn out very well. I’d like to be able to adjust it so that it accurately indicates the valve status. It may take a bit more head scratching.

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Hours Logged This Session: 1.5
Total Hours: 1883.75

Parking Brake Control Bracket

I needed to make a new bracket to support the control cable in the new configuration.

Matco Parking Brake Cable

Here’s the new bracket before lightening holes

With Lightening Holes

With Lightening Holes

I removed the old brake lines, and while I was in the area, I replaced the remaining firewall tab clecos with bolts.

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Hours Logged This Session: 1.9
Total Hours: 1883.75

Reversing the Matco Parking Brake

Our spinner came with it’s original white paint, which matched the Husky that it came off of. I knew that we were going to have to repaint it one way or another, but we’ve both always preferred to have a polished spinner. I figured that I didn’t have anything to lose by stripping off the original paint and trying to polish the underlying aluminum. The chemical stripper that I used took the white paint right off, but the green primer didn’t respond to it. I used a fine scotch brite wheel in the die grinder to remove some of the green primer.

Hartzell Spinner

Almost naked spinner

I wrote before about my reversed parking brake control problem. These pictures show the solution. I removed the spring clip on the end of the valve arm and pulled it out. I stuck it in the other way around, thus inverting the valve’s operation. This makes so much more sense! In the picture below I left the old lines and it is even more obvious. I’m also glad to have a bit more clearance between the aluminum line and the grounding tabs.
Invertred parking brake valve

Inverted brake valve

Posted on
Hours Logged This Session: 2.9
Total Hours: 1883.75

Antenna Mounting

6/21 1015 ground shields, drill left com antenna, add tab to tail post 1235 2.4 hours
This morning I connected the rest of the audio shields to each other. I didn’t have any of the one-ended crimp-on terminals so I just used one half of a yellow crimp-on splice. I found a good spot for the VHF Communication antenna out past the fuel tank, and drilled a mounting hole for it and the grounding screw. I’ll put one just like it on the other side, which will allow for easy connection for the handheld VHF radio.

Left VHF Com Antenna

Left VHF Com Antenna in Wing

I wanted to come up with some method for stabilizing the VHF Navigation feedline in the vertical stabilizer. I added this tab so that I can have something to clamp the feed to.
Tail Post Tab for VHF Nav Antenna wire

Tail Post Tab for VHF Nav Antenna wire

Posted on
Hours Logged This Session: 2.4
Total Hours: 1883.75

Window Re-design

This evening Tabitha came out and we worked more on the left rear window design. We are making a cardboard template that will be the same size as the final lexan piece. This will give me something around which to fabricate a steel structure. The new window will be much larger than the original, on the bottom section in particular.

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Hours Logged This Session: 4.5
Total Hours: 1883.75

Troubleshooting the Audio Amp.

After some email help from Bob Nuckolls I was able to get the audio amplifier circuit working. I tested it by listening to music on the audio input. I’ll have to wait until everything is up and running before I can fine tune the volume resistors.

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Hours Logged This Session: 1.5
Total Hours: 1883.75

Powering Up the GPS

Today I brought out the Garmin 430 unit so that I could test my wiring. This is a bit of a stressful moment, since the unit is very expensive and I ran all of the wires by hand. I powered the circuit with fuses and used my meter to re-verify every single pin to be sure that power was only applied on the power input pins and that grounds were only continuous where they were supposed to be. With nothing else to test, I put in the box and turned on the switch.

Garmin 430 initial power-up

The moment of truth- powering up the expensive box on my own wiring!

Thankfully, it worked and didn’t start smoking. I ran a few initial coax cables for the antenna feeds, and designed a method for mounting the cat whisker VHF navigation antenna in the vertical stabilizer. I’d like to be able to remove the antenna once the covering is in place, so I will need to have a large enough hole in the covering to allow access to the mounting bolts. This H-shaped arrangement will give me a good hard edge to end the covering on, and a place on which to mount an aluminum hole cover.
VHF Navigation Antenna Mount, before prep and paint.

VHF Navigation Antenna Mount, before prep and paint.

The antenna that I found had a little bit of wear in the solder joints on the balun, so I fabricated a new one out of RG-58. I measured the original and made the new one to match.
New VHF Antenna Balun

New VHF Antenna Balun

Posted on
Hours Logged This Session: 6.5
Total Hours: 1883.75

Intercom Testing

It has been a couple of weeks since I’ve been able to get back to work. I installed the rear audio jacks and created the d-sub connection that I wrote about last month. Since the three non-pilot jacks all share a common audio source, I had to find a way to connect several small wires in a mechanically robust way. Here is the solution:

Combined wires for the Flightcom 403

Soldered D-sub for intercom wire consolodation

The wires go from the cabin jacks to a crimped d-sub connector. That connector plugs into this soldered piece, which is sort of like a mini bus bar for each channel. The three connections are for the audio left and right and ground.
I mounted the intercom box:
Mounted Intercom

Mounted Intercom

Intercom in Panel

Intercom mounted in panel

Then connected the audio wires between the Garmin 430 and the intercom. I wired the push-to-talk switches in the sticks, which allowed me to run the final wire for the intercom. I powered it up and everything works well. Never before has it been so much fun to talk to myself! I wish I could say the same for the audio amplifier circuit that I built. It keeps blowing it’s fuse, so I probably put something in the wrong place. I’ll email Bob N. and see if he has any troubleshooting suggestions.

Posted on
Hours Logged This Session: 4
Total Hours: 1883.75

HS34 Installation

Today was a long productive day in the hangar. I started by installing the HS34 to make sure that the bracket was in a good spot.

HS-34 in Place

HS-34 in Place

Here’s how the instrument panel looks as of today:
Instrument Panel Overview

Instrument Panel Overview

I finished the audio wiring for the front two jacks, and went home to escape the mid-day heat. Our windshield arrived today in a giant box. I ordered it through Mark at Avipro just a few days ago. The date of manufacture is 4 days ago, which makes it about as fresh as it could be. I opted for 1/8″ thickness and pre-trimmed. The smaller thickness will weigh less, and it should still be plenty adequate for our airplane.
Big Windshield Box

The windscreen comes in a big box!

Later in the evening Tabitha and I both came back out to enjoy the cooler temperature. She started by precoating the left aileron for taping.
Tabitha Prepares the left aileron for taping

Tabitha Prepares the left aileron for taping

We worked together on applying the tapes until she was ready to go home. I stayed for a few more hours and did more wiring.
Audio Out jack resistors

Audio Out jack resistors

Left Front Audio Jacks

Left Front Audio Jacks

Messy Intercom Wiring

The intercom wiring is messier than I would prefer for it to be.

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Hours Logged This Session: 8
Total Hours: 1883.75

Parking Brake Adjustments

Today I made a bracket for the parking brake valve. This will support the end of the cable.

Matco parking brake cable support

Parking Brake Valve Cable Bracket

I installed a cable control and found that I had a bit of a problem- it was backwards. I definitely want for the cable to be pushed forward when the parking brake is released, but in my first configuration it was the other way around. What I really needed was to flip the whole parking brake over. This would also solve the problem of the wacky curved brake lines that I wrote about earlier. Since the Dynon compass sensor is in the wing and I’ll need to be able to remvove the wings later, I needed to add a splice in each of the shielded cables near the wing root. I used a d-sub connector for both of the cables (4 conductors and a shield for each) and for the OAT sensor in the wing. In the end I’ll have the molex connector for the wing lights and the single d-sub connection for everything else. I made the connections for these cables at the instrument end, which completes the Dynon wiring. I used a little bit of rescue tape to build up the diameter of the bundle so that it will be more evenly supported where it exits the back shell.
Enlarging wire bundle

Small wires in a big hole.

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Hours Logged This Session: 4.8
Total Hours: 1883.75

Wiring the GNS430

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

Rudder 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

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.

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Hours Logged This Session: 5.8
Total Hours: 1883.75

Rudder Lacing and Taping

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

Bearhawk Rudder

Rudder Rib Reinforcements

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 Taping in Progress

Rudder Rib Stitching Done

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

Front Seat Area

Seat Position Adjustment

Seat Position Adjustment

Outboard Seat Track

Outboard Seat Track

Inboard 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

Dynon Manifold Pressure Sensor Back

Dynon Manifold Pressure Sensor Back

Once the epoxy cures I’ll trim it flush.

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Hours Logged This Session: 6.7
Total Hours: 1883.75

Covering and Wiring

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!

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Hours Logged This Session: 5.9
Total Hours: 1883.75

Wing Wiring

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

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

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.

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Hours Logged This Session: 7
Total Hours: 1883.75

Dynon Wiring

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

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

Dynon Serial Ports

Thermocouple Leads

Those brown wires are the thermocouple leads

D-180 Wiring

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.

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Hours Logged This Session: 3.4
Total Hours: 1883.75

Aileron Balance and Wiring

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

SPRL Fuel Valve Top

SPRL Fuel Valve

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

Tach Drive Cover

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.

Lycoming Tach drive

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

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

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

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.
Bearhawk Wiring

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

D180 Wiring

D180 Wiring

D100 Wiring

D100 Wiring

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Hours Logged This Session: 10.3
Total Hours: 1883.75

Installing the Alternator

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 I clipped the leads off of the old diode:

Damaged Ebus 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 improved Ebus Diode mount

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

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

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

Plane Power Case Mount Alternator Bracket

And the alternator itself:
Plane Power Alternator

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.

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Hours Logged This Session: 4
Total Hours: 1883.75

Making Smoke

After a few trips around town to find the right length of grade 5 bolts, I was able to install the last bolt for the alternator bracket.

I finished the main wiring for the electrical system, so I figured I’d turn on the master and see if it works. Since there aren’t any circuits connected the system is still pretty bare-bones at this point. Instead of turning on the master switch to energize the system, I used a manual connection of the battery lead. More specifically, I disconnected the positive lead from the battery, turned on the master switch, then touched the positive battery lead to the positive battery terminal. This allows for a very rapid disconnect, which turned out to be handy. As soon as I energized the system I got some smoke from the distribution panel, so I disconnected it quickly. After a brief investigation I found a fried ebus diode. It turns out that the mounting method I used did not provide sufficient insulation from the airframe ground. Hmm, that stinks, literally and figuratively. It should be an inexpensive fix though, since the whole diode package was only about $25.

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Hours Logged This Session: 1
Total Hours: 1883.75

Prop Governor Studs

Lately I’ve been fiddling with a Hartzell prop governnor that I got from another builder. The flange is designed so that the studs have to be just the right length, and my existing studs are too long. I spent a little while fiddling with it today before I finally decided to give up on the governor all together. This is in part because of the stud problem and in part because the splines on the governor don’t match the splines on my drive gear.

The Dynon EMS wire harness came with wires in place for every possible feature. I guess it’s easier to make them that way on a large scale. Since I know I’m not going to be using several of the inputs (fuel pressure, fuel quantity, etc) I removed those wires from the harness. I will probably be able to reuse most of them in other places, which is nice. Since I’m going to start wiring the avionics soon, I also made some wooden simulators for the Dynon boxes. I don’t have the boxes on hand yet, and the wooden pieces will make it easier for me to add the wires without making the final package too short.

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Hours Logged This Session: 3
Total Hours: 1883.75

P-leads and Wiring

I finished up the p-leads today for the Bendix mags. These mags require a special terminal, and I was able to find a used set of terminals in good shape. I used a single-conductor shielded cable, which was especially troublesome to strip and separate. The weave of the shield is very tight and it took a couple of attempts to get a good result. I added a bit of heat shrink to the empty shield right where the center conductor exits, and then another layer of heat shrink over the whole cable at that junction also. Hopefully this will be enough strain relief to keep the shield from breaking. You’ll also notice that I separated about a 4″ length, but cut the center conductor shorter. This is to allow for a cleaner installation, since the locations on the back of the mag are also staggered.

Stripped Shielded Wire

Stripped Shielded Wire

I added the outer threaded ring, then the metal piece, then the insulating piece. Then I added the little washer, bent the very ends of the conductor, and soldered the washer in place. Obviously it’s important for me to get the sequence correct here, since the other parts can’t go over the soldered end.
Mag Terminal Sequence

Mag Terminal Sequence

Bendix Mag Terminal Parts Together

Bendix Mag Terminal Parts Together

I crimped a ring terminal onto the shield, then used one of the screws on the back of the magneto to secure it. Here’s the whole thing:
Bendix Magneto P-Lead

Bendix Magneto P-Lead

The cockpit end was slightly different. I used 1/4″ fast-on tabs to attach the lead to the switch, but I also added a provision for the Dynon tachometer reading. The Dynon system is able to derive a tachometer indication by measuring the noise on the p-lead. The Dynon instructions specified the resistor value.
Dynon P-Lead takeoff

Dynon P-Lead takeoff

I crimped one end into the fast-on terminal and crimped a machined d-sub pin onto the other. This arrangement allows me to separate the wires going to the D-180, which may prove useful in future service. I used a female socket on one lead and a male pin on the other so that they are not interchangeable.
Cockpit end of p-lead

Cockpit end of p-lead

Cockpit end of p-lead

Cockpit end of p-lead

Next I connected the wire that goes from the starter switch to the starter contactor, and the wire that goes from the other terminal on the starter switch to the fuse block. This circuit works by providing 12 volts to the starter contactor terminal when it’s time to engage the starter, and that’s why it starts at the fuse block.
Starter Contactor

Starter Contactor

Starter Circuit on Fuse Block

Starter Circuit on Fuse Block

I also wired the battery contactor’s switch, the master switch. The battery contactor has a different design than the starter contactor. In the case of the battery contactor the switch lead is completing a circuit to ground. So the wire goes from the contactor to the switch, then to the ground tabs on the firewall. The contactor draws it’s current from the big terminals and thus doesn’t need a fuse.
Next I started on installing the alternator brackets. Since the bracket shares bolts with the engine halves, I will have to remove the current bolts and replace them with longer alternatives.
Lycoming Engine Bolts

These longer engine case bolts have the same grip length after adding the bracket

Shorten Bolt Threads

This bolt is a little bit long in the threaded portion. Before I cut it off, I thread on a die so that I can debur the threads more easily.

Lycoming Grade 5

The front two bolts are done. I'll have to go to the hardware store to get the back bolt. My engine builder says that grade 5 hardware is adequate here.

Since I found myself at a stopping point with the alternator bracket I went back to wiring.
Battery Terminal

Here are the battery leads, including a little boot for the positive lead.

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Hours Logged This Session: 4.4
Total Hours: 1883.75

Architecture Wiring

I sold a motorcycle and was able to buy some much-needed parts. The first is this Plane Power AL12-E160/C Alternator. This is the case mount unit since our engine doesn’t have the mounting boss. The parts look great!

Plane Power AL12-E160/C

Plane Power AL12-E160/C

Plane Power Brackets

Plane Power Brackets and Hardware

The other big part of my order was the probe package for the Dynon D180. This is an expensive package, but it comes with lots of goodies. I was surprised to see that the package included a pre-wired, color-coded 37-pin D-sub connector for the EFIS items.
Dynon EMS Probes
I’m using the Z13/8 electrical system designed by Bob Nuckolls. I started off my wiring with the leads that will make up the electrical system architecture.

Here are a few of the connections for the ebus relay.

I found one problem when I started to make the fuse links, which are very small wires connected to larger wires. Since splices are designed for the same size of wire, they wouldn’t do. Instead I used crimp-on “handshake” connectors, since they are available in different wire sizes. The whole finished product is not much bigger than a splice, and certainly as durable.
Splice Different Gauges

The small wire on the left uses a red connector, while the large wire on the right uses a blue. Clear heat shrink keeps the "handshake" connectors connected.

I have a few of the wires done now, with many more to go.
More Wiring

A few more wires

Shunt Wiring and Alternate Ebus Feed

Shunt Wiring and Alternate Ebus Feed

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Hours Logged This Session: 3.5
Total Hours: 1883.75

Battery Bus & P-Leads

Today I continued with more wiring. I finished the SD-8 ammeter wiring that I started yesterday, and made a cable for the starter:

Starter Cable

This clear double-wall heat shrink will preserve the label for a while.

I found a covered fuse block to use for the battery bus. Since it is on the engine side of the firewall I was worried about an uncovered block getting dirty. The only thing I don’t like about it is that each fuse feeds separately. To fix this I bent all of the tabs on one side:
Covered Fuse Block Modification

The top row of tabs will become the feed side.

Then I cut a piece of brass into a 1/4 inch strip and rounded the corners a little:
1/4" Brass Strip

This was from the same stock that I used to make the forest of tabs.

Brass Tab

The tab is just a little bit longer than the contacts.

I soldered the brass piece to the bent tabs, very carefully. I was able to get good melting without any of the plastic housing.
Soldered Tab

I also potted the back side of this with high-temp silicone, just to keep out contaminants and prevent shorts.

Next I started working on the P-leads for the mags. These bendix mags use a special terminal end.
Bendix Magneto P-Lead Terminal

This is the stub of the old p-lead terminal.

New kits are available to build the p-leads, but since I have these old ones I’ll just use the parts to make mine. The far right side is a soldered end that includes a small washer. I was able to melt the solder and extract the washer from the old ends. I used shielded wire and connected the shield to a ring terminal and grounded it on one of the screws on the back of the mag housing.

I’ve also been working on the wire conduit in the wing. I cut a notch to allow entry for the Dynon magnetometer cable, but that made a weak spot in the conduit tube. I cut a piece of aluminum tube for reinforcements:
Reinforcement for Plastic Conduit

Half of this tube will make a good reinforcement. I used a reciprocating saw to make the cut, but a bandsaw would have worked well too.

Reinforcement for Plastic Conduit

I roughed up the plastic and aluminum, then attached the reinforcement with JB Weld.

I added rubber grommets to each of the holes in the wing ribs, then reinstalled the conduit.

SD-8 Wiring

Today I continued with wiring the SD-8 and it’s components. I have a copy of the Z-13/8 drawing in the hangar, and I’ve been drawing lines on the diagram to note wires that are complete. First, I made a hole in the firewall for the alternator output wires.

Firewall Grommet

This grommet will fill a hole that is just big enough to get the connector through.

Firewall Hole

I chose this location in the firewall because it made for a nice short run to the alternator.

Then I ran the wires to the circuit breaker, which is part of the crowbar over voltage protection.
Circuit Breaker Wiring

The bottom circuit breaker is the 2A for the SD-8. the top is a 5A for the primary alternator's Crowbar OV protection.

Next came the wires to the switch.
Switch Wiring

The faston connectors at the back of the switch make the process easy.

Fuse links to the ammeter shunt

These wires are for the ammeter shunt. The ends include fuse links of 24-gauge wire.

The wires from the shunt go to a double pole switch that will provide a selection between the two ammeter measuring points.

Electrical Distribution Panel

I deburred the lightening holes in the electrical panel, and removed all of the sharpie ink from layout planning.

Electrical Distribution Panel

Deburred and Clean

Electrical Distribution Panel

Electrical Distribution Panel

Next it was time to get to work populating that panel. I started with the diode bridge for the SD8 circuit.
SD-8 Diode Bridge

SD-8 Diode Bridge

First up is the resistor:
SD-8 Wiring

I soldered the solid lead components instead of using the crimper.

Soldered ring terminal

Like this. Then I covered as much of it as I could with heat shrink.

Here’s the resistor for the capacitor:
SD-8 Capacitor

A little heat shrink will help limit shorts.

SD-8 Capacitor

SD-8 Capacitor

Here are most of the other components:
Electrical Panel

There are two problems here. First, I had to remove the jack on the middle of the right side. That was for alternator diagnostics, but with the Plane Power alternator that isn't available. Second, the ebus diode, just above the junction of the two fuse blocks, wasn't well enough insulated, so I changed the mounting later.

From left to right, top to bottom: Main bus fuse block, ebus diode, ebus fuse block, alternator diagnostic plug (later removed), SD-8 Diode Bridge, ebus relay, SD-8 Relay, SD-8 Capacitor, SD-8 Regulator, and SD-8 Crowbar overvoltage module.
And the back:
Back of Electrical Panel

The components also add a lot of stiffness.

I’m attaching that panel to the fuselage tubes with adel clamps, so I thought I’d make a copy of a tool to help install those clamps. The V on the end goes into the threads of the bolt that secures the clamps, relieving tension on the nut after compression. That makes a 3 hand job into a 2 hand job.
Adel Clamp Tool

Adel Clamp Tool made from thin stainless.

Here’s the panel in place. I didn’t realize at the time, but it’s going to crowd the duct for the right front seat passenger vent.
Panel in Place

Electrical distribution panel in place

Since the weather was nice I also cleaned and primed the steel straps that connect the rudder cables to the rudder pedals.
Rudder Cable Straps

Here the other side is ready to paint.

Wire Routing

I started out today by putting the control sticks back in. I drilled a hole in the bottom of the left stick that will allow the push-to-talk switch to fit through.

Bearhawk Control Stick Push To Talk

This is the bottom of the control stick. The black grommet will pad the wire and reduce the size of the hole, which must be big enough to accommodate the body of the push-to-talk switch.

Next I attacked the 0.025″ aluminum panel that I’ve spent the last few days making. I didn’t weigh it before and after, but hopefully it saved an ounce or two.

Electrical panel lightening holes

This part is clearly Swiss-made.

I was ready to add a few wires to the left wing conduit, but it made sense to do as much work as possible while the wires were convenient and outside of the airplane.
Dynon Magnetometer Wire

I stripped the end of the 4-conductor shielded cable and separated the conductors from the shield. This quad cable is much easier to work with than the single conductor wire that I am using for the p-leads.

I added a piece of tie-wrap to use for future wire additions, then added the magnetometer wire and OAT probe wires to the left wing conduit. Lastly, I took a few measurements to see if I’ll be able to find studs for the Hartzell prop governor.
Hartzell Prop Governor Flange

I'll never be able to figure out why they designed this flange this way.

This flange design seems problematic. Even if I can get the right length of studs, it looks like installation would be quite a hassle.

Window Planning

Tabitha came out today and we did some planning for the windows. With the top of the fuselage uncovered it was hard to realize how dark the back seat area would be with small windows. So we used a few blankets and such that we had around to serve the role of the covering material.

Bearhawk Window Testing

We used blankets to simulate opaque covering.

Tabitha put some plastic sheeting on the outside of the fuselage and used markers to draw a few different window layouts.

More Electrical Infrastructure

Today I picked up where I left off yesterday, adding a few more parts to the power distribution panel.

Populating the Panel

A few more items on the panel

Electrical Distribution Panel

It's getting a bit more crowded.

Next I started making a few parts to mount the audio amp and the low voltage warning.
Homemade Circuits

I decided to combine the two homemade circuits in an enclosure made from scrap aluminum.

Circuit Enclosure

This enclosure will provide mounting and short protection.

The next challenge was to cut a hole with the odd shape of the d-sub.
d-sub shaped hole

Here's how I cut an odd-shaped hole- drill the corners, then the dremel wheel to connect the dots.

The crowbar overvoltage module for the SD-8 doesn’t have any easy mounting options, so this is the best that I could come up with:
Crowbar Overvoltage

The clothespin holds the module while the JB Weld sets up, then I'll screw the small piece of aluminum to the distribution panel.

I also cut two more odd-shaped holes for the Dynon serial cables. These will be for firmware updates and that sort of thing.
Dynon Serial Holes

Two out of three- one for the D180, one for the D100, one to come for the HS34.

I allowed myself to become a bit distracted from electrical work to address a couple of other issues. First, the steel tabs that I made for the rudder cables were starting to rust. I took them off and dropped them into a bucket of phosphoric acid that I was also using to start prepping exhaust conduit parts.
Rusty Parts

Bare steel rusts quickly in the hangar.

I also installed the Dynon OAT probe. This is the probe version that connects to the D180, not the version that connects to the magnetometer. I wanted to put it somewhere with the minimum drag penalty and minimum damage risk, so I chose the spot right behind the wing strut junction. I figure that the air through there is going to be so turbulent that the drag penalty will be minimal, and it will be out of the way of birds and bugs.
Dynon OAT

Dynon OAT probe location

Next I drilled the control sticks for the push-to-talk switches.
Bearhawk Control Stick Wiring

This is just a pilot hole. The final hole has to be big enough to clear the switch.

Push-to-talk hole

This hole is right in the middle of the top of the stick. I'll cut a corresponding hole in the grip for the switch to protrude.

Today was a good day with lots of time in the shop. Several months ago I found that 4 hours was about all that I could work. Now it seems that I’m only limited by the need for food and restroom breaks, and weather extremes. I’d rather just be out there working all day.

Power Distribution Panel

Today a few more parts came in:

PWM Dimmers

These dimmers are for the LED cabin lights. I found a great deal at so I got 4. I doubt I'll use them all!

Alan stopped by and made some airplane noises:
Alan Tries it Out

Alan is planning on building a Bearhawk one day.

Since it was handy, I took a picture of my load analysis:
Bearhawk Electrical Loads

This highly technical chart sums up many hours of research!

I spent quite a bit of time with Bob N’s Z13/8 drawing and a handful of parts, trying to figure out how it all needed to go together. Bob’s drawing is a conceptual schematic, but it takes some effort to translate that to a practical layout. Here was one option:
Electrical Distribution Panel

I'm planning to put most of the electrical stuff in one place. I figured that the right side of the fuselage is a good choice, since it's close to the battery and battery contactor.

After a little bit more study I decided to change things up and center the buses around the tube that lies under the panel.
Distribution Panel Final Layout

This layout is to maximize the stiffness of the panel with regard to the underlying structure.

It’s enjoyable to do something as easy as sheet metal work for a little while!

Cabin Heat Valve

Today I stopped by to visit my new friend Alan Waters. I asked him to weld some flanges onto my adapted cabin heat box, but instead he offered for me to come over and do it myself. This was an awesome opportunity that I didn’t want to miss! This box needed an additional hole and flange, and one of the existing flanges was too large. My plan was to cut kerfs into the flange so that I could shrink it down around a 2″ tube, but Alan suggested that we just cut the old one off with his milling machine.

Carburetor/Cabin Heat Box

Removing the old flange

The Bridgeport milling machine was like an etch-a-sketch, with one wheel to control left-right and one to control front-back.
Bridgeport milling machine

After milling

Alan was showing me how to use his lathe, so we trimmed the ends of the tube flanges.
The Lathe

We used the lathe to make the tube end square. It wasn't really necessary, but it was fun.

With the pieces ready to weld, he set me up with some practice parts and his TIG machine. I hadn’t used a TIG machine on aluminum since I became comfortable with steel welding, but it is much easier than I remember. Well, until I touched the electrode to the aluminum, then it made a mess. Alan was very patient and talked me through several practice beads.
Aluminum TIG Welding

Here is a practice bead.

Aluminum Welding Practice

The top bead isn't mine, but you can see on the far left where I touched the tungsten to the aluminum.

Another Practice Bead

Here's Another Practice Bead

With a few hours of practice, I tried welding the part. I got distracted at one point and burned a big hole in the flange.
Mouse Hole

I was doing pretty well until I burned a hole in it. Alan fixed it for me.

Ready To Install

Now it's ready to install. We used the milling machine to remove some of the material around the hole that I made.

In the end the box is just what I need, and best of all, I learned a lot from Alan. I was also able to make a quick trip to the hangar in the afternoon. The picture below shows why I’d rather not use the crimp-on terminals that I got from the welding place.
Sloppy fit welding cable

I thought that the crimp-on end left too much space around the conductor.

While I was playing with those, Tabitha did a bit more filing on the window frame areas.

Governor and Carburetor

Today was a good day for staying close to the propane heater.

Snow at the airport

It was really cold at the airport today!

Hartzell Prop Governor

I got this Hartzell governor from Frank.

Hartzell Governor

I'm not sure why they designed the flange with so little clearance from the governor body.

Hartzell Governor

I didn't realize until later that the splines on this governor don't fit my engine.

Hartzell Governor

Making the circle...

Hamilton Standard Placard

The old Hamilton Standard placard made me wonder how many airplanes this governor has been on.

Hartzell and Woodward Governors

The Woodward governor is on the left, the Hartzell is on the right.

Hartzell Prop Governor Studs

The studs on the engine as of now are too long for this governor. It turns out that the drive splines are also not compatible, so I don't think I'm going to use it.

With the topic of the governor installation on hold, I turned my attention to the carburetor.
Carburetor and Throttle/Mixture Plate

I checked the plate to be sure that the bracket hole for the airflow was at least as large as the hole in the carb, and it was.

Carburetor Installed

Here's the whole thing bolted together.

Carb view from the bottom

View of the carburetor from the bottom

Lycoming 360 Intake Side View

Here's a side view of the carb installation.

With all of that done, I was ready to figure out where to route the engine controls through the firewall. I wanted to keep the throttle cable somewhat parallel to the bottom of the transponder rack, which is perpendicular to the face of the instrument panel.
Reference Marks on the Firewall

The end of the ruler points to a reference for the bottom of the panel.

Bearhawk Throttle Cable Hole

Here's the hole in the firewall for the throttle cable.

Throttle Open

The throttle is in the full open position here.

I finished installing the throttle cable, and it works smoothly. I’m at a stopping point with the mixture cable, in part because the hole on the arm is 1/4″ and the hole in the rod end is 3/16″.
I drilled the matching holes in the right rear engine baffle and the right side baffle.
Right rear baffle

The aluminum reflections make for confusing pictures!

Oil Dipstick Safety Wire

I needed to remove the oil dipstick, so I took this picture to be sure I get the safety wire correct when I reinstall it.

Dipstick Removed

With the dipstick out of the way, I was able to put in that little angle bracket just above the dipstick hole.

Left Rear Baffle Holes

I also drilled the holes on the left side. You can see that this piece is much thicker to help support the oil cooler.

Lycoming IO360 Baffle

I'll be able to trim off a little bit of the left rear piece where it overhangs the left side piece.

I wouldn’t have thought that there would be 35 pieces to the baffle kit, not counting fasteners and soft parts.

Baffles and Avionics Support

The new engine baffle piece that I ordered from Vans came in today, along with a plate for supporting the mixture and throttle cables.

New Parts

New Parts from Vans!

In the picture below you can see the difference between the new and old baffles. The old piece on top also has bends where I tried to make it line up with the right rear baffle. That whole operation was beginning to seem pretty clumsy.
Before and After Baffle

The old baffle is on top, the new one is on the bottom. The new one still needs some trimming, but not quite so much as the old one.

I’m planning to make two of each annunciator LED on the panel. The weight penalty will be very minimal, and I’ll have the benefits of redundant systems and improved visibility, regardless of which seat the PIC is in. I spaced them somewhat arbitrarily at 1 inch.
Instrument Panel Annunciators

Instrument Panel Annunciators

And the other side, for wire planning purposes:
Right Warning LEDs

Right Annunciators

I wrote in an earlier entry about wanting to create some support for the back (aircraft forward) of the Garmin racks. I re-purposed the old elevator trim push rod tubes to create a brace. I joined the two tubes together in the middle and made a template for the bend out of welding wire. I applied those bends to the new tube, yielding this:
Avionics Rack Support Tube

Avionics Rack Support Tube

I cleaned up the ends, added a crooked fish mouth to each side, and clamped the tube to the bottom of the 430’s rack. I added the sides of the boot cowl to help be sure that the instrument panel was in the right place.
Avionics Rack Support

Ready to weld

I welded both sides, cleaned off the old paint, and primed the whole thing. The first picture below is looking down:
Avionics rack support tube

Finished support tube

Avionics Support Tube

Looking across, from the left.

I ordered part number VA-149-360-PC KIT from Vans aircraft to use as a support for the throttle and mixture controls. This seemed like a good price, especially compared to spending a couple of days making one like it. The only problem is that there isn’t much room between the bracket and the firewall.
Throttle and Mixture Support

The Vans support bracket is about as long as it could be.

I’m looking forward to putting the carb on and scouting out the location for the air cleaner.
VA-149-360-PC KIT

Vans Throttle and Mixture Bracket, Side View

Tabitha also came out in the evening and worked to remove the last of the weld beads on her window removal job.

Posted on
Hours Logged This Session: 4.5
Total Hours: 1883.75

Making Electronics

Our Bearhawk is going to need two little circuits that I’m going to try and make. The first is a low-voltage warning module. They Dynon EMS has a built-in warning for low voltage, but this little circuit will be a stand-alone warning for a system that is fairly important. I used the Bob Nuckolls designed 9005 module. I ordered the circuit board for both circuits (and the e-bus diode) from Bob earlier this fall, and ordered the components from Digikey. I had to make a few substitutions due to availability from Digikey, but I was able to find all of the parts. I’ve had all of these parts for a few months, but today is my first working day that is just too cold for being in the hangar!

The low voltage module serves a simple role. It illuminates a flashing LED on the panel (in my case, two) whenever the battery is on, but the alternator isn’t. This is an indication to the pilot that he/she is running on limited stored battery energy instead of generated and therefore relatively unlimited alternator energy. The airplane will also be in this condition on the ground when the engine isn’t running, so it will help me remember to turn off the master after shutdown. I added all of the components to the circuit board, but I got one of the resistors wrong.

AEC 9005 Low Voltage Warning Module

Here it is, almost right.

Wrong Resistor

Here's the resistor that I switched.

Back of the LVM

Here's the other side

The second circuit is an audio isolation amplifier. This will consolidate the audio output of the various sources (GPS, Dynon, Ipod, etc) and provide a feed for the intercom’s single input. The board has provisions for resistors of different value, which will allow volume adjustments for each channel.
Audio ISO Amplifier

One side of the Audio ISO Amplifier

AEC 9009 Audio ISO Amp

The other side of the 9009 Audio ISO Amp

I wasn’t able to test the audio amp yet, but I made up a test rig for the low voltage module out of an old computer cable. It doesn’t work yet, but I’ve got some good leads on how to fix it.

Posted on
Hours Logged This Session: 7
Total Hours: 1883.75

More Panel Holes

I was able to get home for a day or so amidst lots of training. I thought about how to best fix the left rear engine baffle that I cut incorrectly last month, but decided just to order a new one from Vans instead. It was only a few dollars and will save a day’s work and produce a better finished product.

I also drilled holes in the instrument panel for the crowbar over-voltage circuit breakers and the 12-volt SAE (cigarette lighter) jack. I’m only installing one jack for now, but like many other things in the panel, I’m saving room for expansion. I came up with room for another two or so. I might want to have one on the main bus and one on the battery bus, such that I could charge and/or use devices even when the electrical system is completely off.

Bearhawk Air Vent Position

I needed to position the air vent so that I could lay out the location for the 12-volt jack.

Cigarette lighter

Here's a spot for one...

12-Volt SAE Jack

Here's where I put the jack for now.

And on the other side, circuit breakers.
Circuit Breaker Layout

I'm only expecting to have two circuit breakers, but I might as well keep some panel space open in case things change in subsequent years.

Here’s a better overview picture:
Bearhawk Instrument Panel

Instrument Panel Layout

Also, I had to adjust the modified flap handle so that it would slide far enough left to be in the right position. This involved a little bit of grinding and a little bit of bending.
Flap Handle Repositioned

The flap handle is back where it should be.

I filed and sanded the filler on the mount for the position lights too.
Wingtip Lights

It's starting to look better!

Cutting out the Windows

Tabitha has wanted to change the window layout ever since she saw an airplane with bigger back windows. Today she cut out the existing frames on the left side.

Tabitha Grinding

Tabitha is cutting out the window frames.

Tabitha Cutting out Windows

She used the die grinder with a cutoff disk.

Tabitha, Bearhawker

Tabitha, Bearhawker

While I was at Matt’s hangar he sent me with a length of spring to use for the rudder return springs. While Tabitha was working on the windows, I cut the spring in half with the Dremel cut off wheel.
Cutting Rudder Return Springs

Rudder return springs

I also took an overview picture of the instrument panel, since I hadn’t taken one yet.
Instrument Panel

Instrument panel layout so far.

Installing the Starter

After seeing the amount of stress that the Garmin racks would place on the panel, I started thinking about how I can add some bracing to the back. I spent a few minutes today checking to see if that support could be as easy as a piece of aluminum angle across the two diagonal tubes, but it looks like I’ll need to come up with something else. The height isn’t quite right for anything straight across.
Meanwhile I installed the starter and started tinkering with the engine baffles.

Starter Placard

Skytec Starter 149-12LS

Instrument Panel

Today I finished enlarging the center hole in the instrument panel and attached the two Garmin racks.

Garmin 430 and 327 Racks

Garmin racks in place.

Instrument Panel Switch Clearance

I cut some reliefs in the attach angles to make room around the holes for the switches

I added the Dynon trays, but did not yet cut the left flange off of the right tray. I’m planning to wait until I get the HS34 and its mounting hardware.
D180 and D100 Racks

D180 on the left, D100 on the right.

Next I enlarged the holes for the throttle, prop, and mixture.



I added a few more items to the panel layout, including the annunciators. To finish up, I sprayed a coat of polyspray on the side of the horizontal stabilizer with the patch.

Instrument Panel

I started off today by getting some silver polyspray onto the patches. Don brought up the instrument panel, so I started with the deburring process while I waited for the polyspray to cure. I added the ELT controller to the left side, since it is something that is low on the ambidexterity priority list.

ELT Remote

I started by adding the ELT remote controller.

ELT Remote

I need to find some screws that are small enough to fit into those little holes!

I attached the rack for the GNS430 and GTX327 together, then added aluminum angle pieces to use for attaching the racks to the panel.
Garmin Racks

The racks have built-in spacers for vertical alignment.

Installing Garmin Racks

The same screws that I'm using for the wing inspection panels fit into the racks without interference.

Somehow I gave Don Bandy the wrong dimensions for the middle hole. It ended up being a little bit short, so I trimmed a little off of the bottom.
Enlarging the panel cutout

This was my method for enlarging the cutout in the middle of the panel.

I left to go get ready for the EAA meeting. On my way out the door for the meeting I got a call from jetBlue with a class date in 2 weeks!

Seat Foam and Silver

Tabitha came out today and we glued the foam together for the back seat cushion. I had planned on a 3″ thick bottom cushion for the back seat, but with a little bit of testing we realized that the headroom would be limited with a full 3″ cushion. Instead, Tabitha carved out much of the 2″ foam to make the cushion 2″ overall. While she was working on that, I was putting together the paint shaker and stirring the polyspray.

Back Seat Foam

The little cut marks will disappear with the 1/4" layer of foam that we'll have quilted to the upholstery.

The silver polyspray was a lot of fun to stir! I could just stir and watch the little swirls all day long.
Stirring Polyspray

Isn't it just amazing to watch the swirls?

I sprayed the first round of silver and called it a day!

More Position Lights

I stopped by Laney’s fly-in towards the end of the event, but there were still a few airplanes left, including a new Maule. I liked the step on the landing gear, and perhaps it’s worth investigating.

Landing Gear Step Idea

While I was at Laney's fly-in I saw this Maule's landing gear step. I wonder if a similar step on the Bearhawk would allow me to reach the fuel filler from the ground?

In the hangar, Tabitha worked on getting the seats while I started roughing in the position light mounts. The epoxy between the foam layers was rock-hard and made for some complications with the shaping.
Position light plates with foam

These foam fillers shaped nicely. The epoxy between layers did not however.

Since the weather is starting to cool off, I spent some time with the iron on the horizontal stab and elevator. I wanted to dip my toe into the heat smoothing pool to see how it would go. If all goes well, I’d like to get all of the surfaces to the silver stage before the cold weather comes.

Posted on
Hours Logged This Session: 3.3
Total Hours: 1883.75

Positioning Position Lights

Here’s the antenna block that I was working on in the last session. I couldn’t figure out how to clamp it for drilling, and even if I did, I don’t think I’d have enough room between the elements to get in there and install the nuts and terminals.

VHF Nav Antenna Insulator

Here's another attempt at an antenna insulator. This one has the correct angle between the elements, but I don't have any way to drill the holes at the same angle, since my drill press only tilts to 45 degrees.

Meanwhile, I did make some progress on the wingtip mounted position lights.
Reference Marks for Position Lights

These are the marks that I made to locate the position lights fixture. Once the wings are on, I will be able to get the centerline accurately transfered to the other wingtip, and the chord positioning will be easy to measure.

I used a step drill to cut the holes, and verified with my marks that the holes weren’t wandering.
Aeroflash Position lights

There isn't really too much fairing to do, since the fixture sits pretty close to the tip.

Installing Aeroflash Position Lights

The aft hole is large enough to fit the molex connector on the other end of those wires.

I mixed up a batch of epoxy and attached three 1/4″ sections of blue foam on the back of each of the two aluminum mounting plates. I’ll file these down to match the wingtip contour after they have cured. While I had the epoxy out, i also stuffed a rolled up section of paper towel into the open end of the aileron balance tube and filled up the last 1/4″ or so with epoxy to seal the end.
Aileron Balance Tube End

Sealing the tube end with leftover epoxy

Tabitha came out for a few minutes and carved more seat foam today too. She worked on the back seat cushions.

Stainless Firewall Shields

Today I tried a Tony Bingelis technique for making shields for firewall pass-through parts like engine controls and wires. The idea is to provide an equal level of fire protection for areas that use rubber grommets. I started by choosing a “die” from my die collection, also known as a socket set. I’ve found sockets to be handy as dies before, such as in straightening a kinked tube by forcing the socket through the middle. The outer diameter of the socket should be as large as the major diameter of the grommet, which is why it is handy to have several sizes to chose from. I used a Forstner bit to make the female half of the die in some scrap wood. That hole was about 1/4″ larger than the socket. I cut out a square of .016 stainless that was about 3 inches square, and clamped up the wood, stainless, and socket in the vice. With moderate pressure from the vice, the socket bottomed out in the wooden die, leaving a wrinkled flange area in the stainless. I used the little anvil section on the vice and light hammer taps to flatten that part out, essentially shrinking the flange. The stainless forms beautifully, and within a few minutes I had it looking like this:

Stainless Firewall Shield

Here it's ready to trim. It is much easier to do the stretching/shrinking in this footprint.

I learned a few tricks in the process of making a few of these. First, start with a 3×3 square of material, even if you are going to trim it down to a much smaller size later. This makes the forming much easier, even though there is more waste. I haven’t tried it yet, but I’m hoping that this method will also work for two-piece shields. I’ll have to make two of these to get one two-piece shield, but I haven’t been able to find a commercially available option that has all of the dimensions that I need.

Three Shields

Here are a few more samples.

I also started making the aluminum plate that will serve as a mounting pad for the position lights. My plan is to attach this aluminum piece, then build up foam and fiberglass to make it all smooth and aerodynamic. This piece will have two nutplates, which will receive the two screws that the position lights require.
Position Light Mounting Plates

Position Light Mounting Plates

Position Light Mounting Plates

Both sides, ready for nutplates

I also spent a few more minutes trying out some VHF Nav antenna ideas, but I don’t have any real progress to report.

Copper Strips, Parking Brake

In the week since I last worked, the JB weld on the ANL mount cured nicely. I filed it flush with the back of the mount and then realized that it hadn’t occurred to me to find out if JB weld was electrically conductive. It turns out that it isn’t, which I was glad to discover.

I used a 1/16″ thick copper bar stock to make the electrical connections between the electrical components on the firewall.

Copper Bar Connections

For these short distances, the copper bar is a great alternative to stranded wire.

I also mounted the parking brake valve and the hard lines to it.
Parking Brake Valve

Parking brake valve installation

I’m hoping that the loops in the top won’t be too much of a source of air bubble problems- I’m planning on filling the system from the bottom.

Brake Lines

I spent an hour today installing the brake lines. I think that they’ll work fine with a little bit more support.

Brake Lines

Initial Brake Line Fitting

Priming and Wingtips

After spending a few minutes making holes in my aluminum welding practice pieces, I got back to productive work. I cleaned up the skylight parts and sprayed them with some temporary primer. I also trimmed the little grounding bus off of one of my fuse blocks, since I’m going to be using the brass forest of tabs instead. Finally, I used some aluminum screen material to block off the holes in the little rib that supports the aft end of the wingtips.

Wingtip Screen

The screen over the wingtip rib lightening holes will help keep the critters out of the wing.

Wingtip Screen

I used aluminum blind rivets with large heads to help distribute the load and prevent tearing of the screen.

I don’t know if the weight saved by the lightening holes is more than the weight that I added with the screen and rivets, but at least there are some flanges there to add some stiffness.

Seats and Populating the Firewall

Today I spent time adding more stuff to the firewall. While I was doing that, Tabitha was working hard on shaping the seat foam.

I added the nutplates for the battery buss, which is going to provide power to things that will be powered even with the master switch off. I finished installing the shunt for the primary alternator.

Z13/8 Parts Layout

On the left you can see the battery buss, on the right you can see the holes for the nutplates for the primary shunt.

Here you can see the brass grounding tabs.
Grounding Forrest of Tabs

Here I've installed the firewall grounding tabs and the primary shunt.

Cabin side of the firewall

This is what all of those nutplates look like from inside of the firewall, on the right side.

New Brake Line Entry

This is the new, higher location for the brake reservoir line, which will provide better toe clearance from the brake pedals.

While I was doing that, Tabitha was making good progress on the seats.
Front Left Seat Foam

The lawn chair makes a nice holder for the front left seat foam.

Tabitha, Seat Carver

Tabitha shows off her handiwork

I also started making some pieces of aluminum to try welding on.
Duct Flange

This was piece that I wanted to try aluminum welding with. This one didn't work very well, partly because the 3/16 holes and narrow strips along the sides.

I spent more time working on a mount for the ANL current limiter, but I decided that I didn’t like the progress.

Nutplates for Firewall

I don’t have any pictures for today, but it was still a productive session. I installed the last gusset for the seatbelt tab, and installed several nutplates for the firewall-mounted electrical accessories including the battery and starter contactors.

Today George Carter stopped by to visit too. I met George at the hardware store a while back and started talking about airplanes. I’m glad he was able to stop by and see the project! He has some pilot experience and spent several years in the Air Force. He seems to be an equal opportunity aviation fan that enjoys all matters aeronautical.

Seatbelt Tabs, Skylight Tabs

Here are the tabs that will support the shoulder harnesses for the front seat passengers:

Bearhawk Seatbelt Mounting Tab

It's hard to see the tabs in this picture, but they are tacked in place.

Most of the time today went to working on the flap handle and the seat foam, but I didn’t take any pictures. Tabitha is getting pretty good with the electric knife!

Welding Skylight Tabs

Since I used round tube for the skylight structure, I’m welding little tabs onto the tubes. These tabs will get nutplates and will hold together the aluminum-acrylic-steel sandwich.

Bearhawk Skylight Tab

Here's the first tab

I originally sized the tabs so that they would fit a standard nutplate, but then I realized that I really don’t need to install nutplates on the tabs that are accessible from inside the cabin. I’ll need to have someone sit in the cabin to hold the nuts during installation and removal of the skylight, but that should only happen every 5-10 years or more.
Bearhawk Flap Handle Modification

While I had the torch out I also welded up the flap handle.

Bearhawk Skylight Attach

In this picture about half of the tabs are on.

The flap handle also gets a reinforcement for the slot that the aluminum arc passes through.
Bearhawk Flap Handle Reinforcement

I cut this piece of steel out of a larger diameter tube, as specified on the plans. I didn't cut the slot until after I welded the part on- it's easier to hold onto it that way.

Since Tabitha was there, she took a picture for me.
Flap Handle

It's almost done! I just need to cut out the slot and add the reinforcement on the other side. The apron helps keep errant sparks from burning holes in my t-shirt. It took me a while to figure out where the holes were coming from!

Cutting a slot into a steel tube

I used the existing slot to guide the drill from behind for these holes. With the end holes drilled, the dremel makes quick work of the rest.

Tabitha also came out and cut more seat foam today.

Populating the Firewall

Today I started planning to add a few more items to the firewall. I’d like to make sure that I don’t try and put two things in the same spot, and also make sure that I can have maintenance access to items that need it. Tabitha also came out for a little while and cut more foam.

ANL Current Limiter and Shunt

Here are two of the firewall participants, the main alternator's current limiter, and one of the ammeter shunts.

The current limiter is sort of like a giant fuse for the alternator’s output line.
Battery Bus Fuse Holder

I'm going to use this covered fuse holder for the battery bus, because I like the idea of keeping the fuses and associated contactors clean. None of these fuses (or any of the others) are intended to be replaceable in flight of course.

The battery bus will power items that will have power available all the time, regardless of electrical system switch position. These items will include some of the interior lights and those types of things. I also spent more time on the brake line forward of the firewall. I’ll have more pictures of that later.

Posted on
Hours Logged This Session: 3.4
Total Hours: 1883.75

Seat Foam and Brakes

Tabitha came out today and started working on the seat foam while I made some of the rigid brake lines.

Tabitha's Seat Foam

In this picture, it looks like Tabitha is explaining to me about how it is going to be. This is the bottom of a front seat cushion.

While she was working with the electric knife, I installed some nutplates in the firewall. For such a big sheet, the blind dimple die is really useful.
Blind Dimple

This is the tool for making dimples in the middle of a big sheet, such as the firewall. The dimple dies have a hole in the middle that is just big enough for a nail, which goes into a pop riveter.

It’s very important to stay focussed with this operation. The tool only requires a soft squeeze with the rivet setter. On one occasion I was thinking about something else, and gave it a full pull, promptly breaking the nail.

Since we deciced to go with a 3-inch bottom cushion instead of a 4-inch, we had some extra 1-inch foam left. My preference was to make the top of the seat flat to help make the covers easier to sew, but she wanted to go this route to make the seats more comfortable. To settle the dispute, she agreed to make a wedge so that we could compare the two configurations and see if the benefits would outweigh the costs.

Experimental Wedge

Tabitha makes an experimental 1-inch wedge.

I also decided to move the fitting in the firewall where the brake line comes through. The first one is too close to the brake pedals, and I’m concerned that it might limit brake travel if the pilot’s foot is high on the pedal. The first location was arbitrary, so it’s no trouble to move it. I’ll just need to come up with something else to put through that hole, or perhaps a patch. If I can end up with just one wrong hole in the firewall, I’ll certainly be happy.
Bad Brake Line Location

This is a bad place to bring the brake line through the firewall, especially without a 90-degree fitting.

Another Angle- Brake Line

As you can see, with a straight AN fitting, the tube sticks way out there. With the left rudder pedal all the way down, the brake pedal gets closer than I would like.

Here’s a good view of the seat foam, including the lumbar support. The white foam in the seat back is two layers of a more rigid foam, which will hopefully help provide good lumbar support. The Avipro fames actually have a pretty good lumbar support built in. You can also see the “wedge” proposal on the seat bottom.
Bearhawk Seat Cushion

Tabitha's Seat Cushion Proposal

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Hours Logged This Session: 7
Total Hours: 1883.75

Brass Grounding Tabs

Today I started making the brass grounding blocks. My orders from Stein and All Electrics came in- great fun!

New Goodies!

New Goodies! D-sub crimper, brass tabs, assorted electrical bits.

More New Goodies!

More new goodies, including some BNC crimp-on connectors, and the parts to make the Bob Nuckolls alternator diagnosis jack.

The brass terminal strips were available from Stein for $1 each, so a few minutes of soldering and a $3 piece of brass from the hobby shop saved me $50 or so from B&C.
Brass Tabs

The tabs from Stein come in strips of 10 tabs each.

Brass Stock

Here's the layout on the brass stock


I used two large brass bolts instead of one brass bolt and two little bolts as on the B&C version.

Soldered Bolts

I soldered the heads of the bolts to the interior sheet so that I wouldn't need to hold them in place for tightening.

Soldered Tabs

Since the meco torch was handy, I installed a 0 tip and used it to provide the heat for soldering. Even with the tiny tip I still kept the flame several inches from the work and hand plenty of heat.

The flux looks pretty bad in the picture above, but after some time with a toothbrush and some rubbing alcohol it cleaned up well.
I also took apart the VHF Nav antenna that I picked up in the Aeromart at Oshkosh. It was very inexpensive, and I was planning to use just the conductors. I’m still trying to figure out how to make a mount that will work well on the fin.
VHF Nav Antenna

VHF Nav Antenna Parts

I installed the brake reservior on the engine side of the firewall with one of the holes in a support tab for the firewall.
Brake Reservoir

Brake Reservoir on the Firewall

My goal is to not have any bolts holding on just the firewall, since there are so many little parts that need to be mounted to the firewall too. I did need to shorten the tabs slightly because of the somewhat short reach of the -3 clip nuts that I had. I put the paper towel between the firewall and the tab so that I could use the dremel to cut the tab without scratching the firewall.
Shortening the Tab

On the left side you can see the paper towel pad.

I debated briefly about whether or not I wanted to have the reservior on the engine side of the firewall. The benefits would be ease of servicing and reduced possibility of interior leaks. The only drawback that I can think of is that the possibility of problems in the event of an engine fire. I decided that in the event of an engine fire I’m not going to be too concerned about the status of the brake reservior! The brakes will still work once or twice without the reservoir in the system anyway. I drilled a hole in the firewall for the line to pass through, then realized that the location of the hole was going to be too close to the brake pedals. I’m concerned that there is a remote chance that the fitting might interfere with the brake pedals, so I’m going to move it up a little.

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Hours Logged This Session: 3
Total Hours: 1883.75

Fuel Lines, Flap Handle

I finished making the wing fuel lines today and started on the fuel quanity gauges. I used files and emory cloth to debur the holes that Wade punched into the battery box yesterday, and used the band saw to rough cut the aluminum flap handle piece to shape. I used files and emory cloth to get it deburred and shaped to the final dimensions and it is ready to go. Tabitha came out and did more window mockups.

Unfortunately my pictures for this entry and the next few are gone, thanks to some hoodlums that broke into the hangar and stole my camera. The sheriff has arrested them, but they won’t say what they did with the camera. While they were there they had some fun with the dremel and grinding wheel and cut my perfect new flap handle aluminum piece in two. Wouldn’t it have been nice for them to do that to the old superceded one instead? My pictures won’t resume until 8-25.

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Hours Logged This Session: 3.5
Total Hours: 1883.75

Battery Box and Avionics

Today I finished the last fuel line that I can make without putting the wings back on.

Here's a shot of the bottom of the fuselage showing the fuel lines.

While I was at the hangar I also counted the pins on the Garmin racks so that I could make a shopping list for the d-sub parts. I think if I order 50 male and 50 female pins, I’ll have enough for all of the avionics. That’s counting on using some of the pins that I already have standing by.

While at Oshkosh I purchased a Vans battery box kit for the PC680, and today I started marking the top hold-down strap for drilling lightening holes.

Here are the locations of the lightening holes, as described by the Vans directions.

Today was a short day, but small progress is still progress.

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Hours Logged This Session: 1
Total Hours: 1883.75

Elevator Trim Pushrods

Today the river of airplane parts is flowing again with the arrival of my Oshkosh Aircraft Spruce order. I added the dimpled nutplates to the little boot cowl piece, and used my new fuel lube to install several NPT thread fittings that were on hold pending its arrival.

Here's the parking brake valve and it's NPT fittings with fuel lube.

And the fuel selector (which I subsequently decided not to use after all)

And the Gascolator

Since my repaired elevator trim pushrods didn’t bend so well, I also ordered more tubing to make new ones. This time I started with the bend, figuring that I could do the trimming and welding afterwards. This made much more sense than trying to get an accurately located bend after the ends were already in place. I tried making the bend on my imperial tubing bender, though it is certainly not designed for that kind of abuse. I used the specifications in the Beartracks issue to make a cardboard template, then put one arm of the tube bender in the vice. It took a fair amount of force, and I wouldn’t want to do it more than twice, but it worked pretty well.

Here's the bent elevator trim pushrod, ready to trim and weld the ends.

Isn’t it fun when all of the new parts come in?

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Hours Logged This Session: 2.5
Total Hours: 1883.75

Reinventing the Window

Another suitable title for this post would be “Defenestrating the Stock Window Design.”

Tabitha and I have been discussing windows ever since our cookout and during our visit to Oshkosh. She says that the existing stock windows aft of the front doors are too small and too few, while I contend that they are completed and require no more work. In return she says that’s not a good enough excuse for them not to be just as she wants them. While we were discussing the matter in the Avipro booth at Oshkosh, Mark very tactfully told her that making changes prolongs the completion date. I didn’t ask him to say that, though if I had thought of it in advance I would have orchestrated it for sure. She has offered to provide the labor to make the change, so she is going to start figuring out what the ideal configuration will be.

Tabitha made up a plastic sheet and marked it with the locations of the structural members so that she could try out some window arrangements.

The first proposal is in red, which makes it somewhat difficult to see in the small version of the picture. Click on the small one to see the full-size version instead.

While she was doing all of that I tried drilling a hole in the gascolator bolt for safety wire. I asked Bob whether or not the gascolator needed any safety wire, and he said that he was comfortable with it not having any, since the friction from the o-rings would provide a thread locking feature. He did say that there wouldn’t be any problem with drilling a hole to make a provision for safety wire, so that’s what I did. It’s easy, only took a few minutes, and is done. I was able to find some coarse bolts that were a little bit too long, so I shortened them and cleaned up the threads.

Here's the hole before deburring

With an adequate full-size drawing of the proposed windows done, we agreed that the existing baggage door skin will need to be replaced.

I also spent some time building the little access panel on the boot cowl again. I don’t remember if this was the last one or not, but I’ve made several.

Reinventing the same piece over and over again- Here I am in another iteration of the panel that I have made a few times. I've lost track of which version this was.

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Hours Logged This Session: 3.9
Total Hours: 1883.75

Fuel Selector Installation

Today my goals were to install the fuel selector and gascolator, and to run as many fuel lines as time and supplies would permit. As I mentioned last time, locating the fuel selector has been tricky. The best location interfered with the little trapezoid-shaped tab that came from the factory. That tab is made out of some pretty sturdy steel, so I called Bob to be sure that it wasn’t a structural concern. He said that it was not, so I removed most of it. I might need to remove more of it, though another challenge with the fuel valve is that the incoming lines must clear the cabin floor tubes. The valve may need some standoffs or shims to get the inlet fittings low enough, though the more I lower the valve, the more the bottom outlet becomes a problem.

Making room for the fuel selector

Making room for the fuel selector

I also had a thought to try making some shims for the fuel T fittings out of some plastic that I had on hand. I decided after the fact that I didn’t really like the way it turned out. I’ll look for some 1/4″ aluminum somewhere instead.

Trying a plastic shim

Here's the plastic shim attempt. It didn't work very well because the plastic compressed when I tightened the bolt.

I started to mount the gascolator, but realized that it was threaded with coarse threads. I wish it had been threaded with fine threads instead, so that I could just use one a couple of the AN bolts that i have on hand!

In October 2010 I asked Bob why he used coarse threads in this application. He said that generally it is not an accepted practice to use fine threads in aluminum for strength reasons. That explains it!

I finished most of the lines that I had enough material to make. Still to come are the hard lines in the wing and perhaps a few remakes. I ran the gascolator fuel outlet up to the lower left corner of the firewall, since that seemed like a good place to have the fuel line come into the engine compartment. I feel better about the service life of these lines than I did about the previous rubber hoses, especially in areas that are going to be hard to reach after final assembly.

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Hours Logged This Session: 9.1
Total Hours: 1883.75

Starting Fuel Lines

Since I’ll be on the way to Oshkosh shortly, I wanted to spend some time figuring out the fuel and brake systems again. This will allow me to buy the few remaining parts that I don’t have. I have had some 3/8″ .035 5052-0 line for a while, but I figured I should try bending and flaring some before I go to OSH in case I need to pick up more spares of that too. My first realization is that the 5052 work hardens really well- so well that I really only get to bend it once. If I bend it to 90 degrees when in fact I only needed 88 degrees, It’s pretty much impossible to bend it back to 88 again. This meant that I had quite a learning curve and made a few pieces of silver macaroni. I remembered the trick that Tony B suggested and tried making some templates out of welding rod first, and that helped.

One of the requirements of the fuel system is that everything flows downhill to the gascolator. Since the door jamb that the T fitting bolts to is sloped aft, this would create a low spot where water could be trapped.

Fuel Fitting Angle

This would be the fitting of the angle without any shims.

I wanted to try to eliminate this problem by making shims to angle the fitting closer to level.
A better angle

Here's a better angle for the fitting.

Another idea

This idea didn't work.

Aluminum shim attempt

Here's the making of an aluminum shim. This one turned out to be too thin at just 1/8 inch.

Shim concept

Even though these are too thin, you can see how they would work.

With that operation tabled pending some thicker aluminum, I started working on getting the fuel valve in the right place. This isn’t supposed to be hard, but it isn’t going well. As pretty and nice as the Andair valve is, the problem is that the outlet is on the bottom. Even with an angle fitting on the bottom, it is a little bit too tall. In order to keep a downhill slope from the valve to the gascolator, the valve has to be a few inches forward of the gascolator.
Locating the fuel valve

Locating the fuel valve

Another note from the future- I’ve decided not to use this fuel valve. There is another option that is much better suited to this type of installation. The other valve doesn’t have an outlet on the bottom, and the inlets are situated lower, so it will not protrude below the stringers.

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Hours Logged This Session: 5.7
Total Hours: 1883.75

Instrument Panel Layout

While we were on vacation with Tabitha’s parents, Tabitha’s dad and I spent some time working on the instrument panel layout. He’s going to try to cut it on one of his CNC routers, so we were measuring and researching the hole dimensions. If it works, this will save some time of cutting and filing and such.

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Hours Logged This Session: 3
Total Hours: 1883.75

Welding and Priming

The only parts that didn’t survive the move when we purchased the project were the tail struts. I haven’t been able to find them anywhere, and neither has Richard. This is unfortunate, since they are fairly expensive. I was able to buy another set from Mark, though he cautioned that they may need a length adjustment. After getting everything level for the tail pieces, I realized that one of the the struts was just a little bit too short. As you can see below, I removed the original end and welded in a new end that Mark also provided.

Adjusting the length of the tail struts

Adjusting the length of the tail struts

New end in place

I also added a small patch tab to the part of the tube where the old fitting was.

I never was able to understand why the two engine control tabs are mounted where they are. I am going to have three engine controls, and I’d like to have the prop control centered in the panel. Since these two tabs are situated around that location, it would be hard to use them. The solution was to cut them off, make a third tab, and put them where they needed to be.
Cut them off

Step one- cut the existing tabs off

Step Three- Put them where they should have been

Step Three- Put them where they should have been

Step 4- finish weld

Step 4- finish weld. Don't they look like little tombstones?

Shiny Tombstones

Shiny tombstones, ready to prime

I also cleaned up and primed several other welding areas. The bare steel rusts so quickly that it makes sense to prime these areas as soon as possible after cleaning them.
Control Stick Ends

Here are the cleaned and primed control stick ends

Panel adjustment area

Panel adjustment area cleaned and primed

After some more considerable measuring and head scratching, I noticed that when the elevator halves are joined at the middle, they don’t line up with each other.
Right Elevator

Right Elevator aligned with Stab

Left misaligned

...means that the left half doesn't line up with the left stab.

Elevator Trailing edges

Here is the same view of the trailing edges. Note that the left is lower than the right by a measurable difference.

I’m still not really sure about exactly what is going on here. The suggestions from Mark and others are to make sure that all of the pieces are installed correctly, but it certainly seems as though they are.

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Hours Logged This Session: 4.4
Total Hours: 1883.75

Test Fitting the Tail Pieces

Before I proceed with any of the covering steps, I want to be sure that I understand exactly how the tail goes together. To check all of this out, i tried a test fit.

Tail Pieces in Place

Tail pieces installed, not quite lined up yet.

I repositioned the engine lift over to the downhill side of the airplane so that I could level it left-right. Our hangar floor has a bit of a slope to it- about 18 inches over the 42 foot width.
Airplane Leveler

Here's my technique for leveling the fuselage left to right.

My first impression after adding the tail pieces is that something isn’t quite right. The left half seems to be slightly higher than the right half. It’s hard to get an accurate measurement of where the pieces need to be exactly, so I need to come up with some better methods. While I was doing all of this, Tabitha was finishing up the nutplates on the floorboards for the rudder cable guards.
Rudder Cable Guard Nutplates

Rudder Cable Guard Nutplates

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Hours Logged This Session: 8.3
Total Hours: 1883.75

Rudder Pedal Springs

Sometimes building an airplane involves taking three steps forward, sometimes it means taking a couple of steps back. Today I spent a little while adapting some springs for the rudder pedals, but I don’t really like them. I also spent a while making the third version of the boot cowl panel, and also made it wrong again. This is the couple of steps back day.

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Hours Logged This Session: 2
Total Hours: 1883.75

Rudder Pedal Geometry

In our last episode, I was moving the rudder pedals forward to address the potential over-center problem that Mark at Avipro brought to our attention. Back when Richard was building, the consensus was to locate the rudder pedals for ergonomics. Subsequent experience led to a new recommendation to locate the rudder pedals exactly as depicted on the plans. To meet those requirements, I ended up moving the pedals forward just about as far as they could go.

New Rudder Pedal Location

Here's the new location, and you can also see the old hole.

After moving the rudder pedals, I noticed right away that the brake cylinders would be touching the forward-most tubes when the pedals were at max deflection. I wanted to measure the rudder deflection so that I could see if the pedals would stop before reaching that point. To measure the rudder deflection off of a theoretical fuselage centerline, I needed to measure the angle formed by the fuselage sides so that I could subtract it from the desired total deflection.

Figuring out the angles

Measuring the angle of the fuselage sides so that I can create a template for measuring rudder deflection

Final Answer

Here's the final answer- 40 degrees on the template; 10 for the fuselage side and 30 for the deflection.

After all of that hassle, the final answer was that the rudder was at exactly the right deflection when the horn hit the stop (with no bolts in the tubes). Also, the brake cylinders do not contact the tubes at max deflection, but they are close!
Rudder Stops

Perfect deflection with no added bolts. For some reason I thought that I was supposed to have bolts in there- I guess not!

While I was thinking about it, I wanted to measure the rudder horn to see if it was the original design, or the temporarily different design. At one point there was a change in the rudder horn, then a few years later it changed back to the original design again. I believe that we have the interim horn size. Eric says that this change was simply one of control sensitivity, and that his is also the shorter interim length. The shorter length here means less pedal movement for the same amount of rudder deflection. I’m not planning to change the horn back to the original length, since I didn’t think that the rudder was too sensitive on Eric’s airplane, and since the change is optional.
Measuring the Rudder Horn

Measuring the Rudder Horn

With all of that head scratching done, I took a break to get a few things done at home. I came back later in the afternoon to start work on the steel tabs for the skylight structure. I wanted the option of using nutplates in the tabs, so I sized them with that goal in mind. (Mysterious note from the future: I subsequently decided not to use nutplates on most of the tabs, just because the skylight screws are going to be very rarely removed, and because access is easy with another person comfortably seated in the cabin)
Planning the tab size

Planning the tab size

Pile o tabs

Here's a pile of all of the rough cut tabs.

Since I moved the rudder pedals forward, I found the cables to be too short. My remedy was to make new steel attach straps. I used the materials and specifications from the Beartracks and Avipro assembly manual. As you can see in the picture below, I used a washer to draw the radius for the end.
Rudder Pedal Straps

Blanks for the new rudder cable straps

4 strap blanks

Here are the 4 straps- two for each side.

The next step is to drill the holes and install the straps.

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Hours Logged This Session: 4.8
Total Hours: 1883.75

Cable Guard Nutplates

Today Tabitha came to help. She installed nutplates in the floorboards for the rudder cable guards while I took care of a few loose ends.

Tabitha makes nutplates

Tabitha is installing nutplates


Here are the first few.

I was recently reading through the Beartracks newsletters and came up with a few things to check on. The first was the flat plate of steel that joins the two flap cables behind the aft bulkhead.

Measuring Flap Junction

I also checked to be sure that the flap junction plate was 1/8\

In the time since Richard installed the rudder pedals, there has been a potential over-center rudder pedal problem that has come up. I needed to move the pedals forward to eliminate this problem.

Measuring for Rudder Pedals

Measuring for Rudder Pedal Placement

While I had the rudder pedals out, I was also able to turn the bottom engine mount bolts back around. It isn’t possible to install them correctly while the rudder pedals are in place. In the picture I’m tightening the top bolt.

Engine Mount Bolts

Here I'm working on the engine mount bolts.

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Hours Logged This Session: 5.8
Total Hours: 1883.75

Elevator Patch and Cable Guards

Today’s efforts include a morning session of fabric work and an evening session of sheet metal work.

Richard had started the taping process on the tail pieces, but some are still in the works. Since one side still had exposed rib laces, I figured that I would check to be sure that they were spaced properly. Of course they were.

Rib Lace Spacing

I measured the rib lace spacing to confirm that it complies with the Polyfiber chart.

Elevator Overview

Here's a view of the elevator

Hard meets Soft

Since the aft edge of the lead weight is a hard spot on the soft fabric, I believe that it needs a reinforcement.

Preshrinking Fabric

Since the reinforcement is made from preshrunk light fabric, I built a wooden stand to use for the preshrinking.

Ready to Shrink

A quick lap with poly tack, 30 minutes of drying, and it's ready for the iron.

Shrunk and ready to cut

The iron really takes those wrinkles out!

The next task was to investigate the sound of something rattling around inside one of the elevator halves. I narrowed it down to the balance area, and made a cut in the fabric to investigate.

The offending piece of lead

Here's the culprit- a little piece of lead from somewhere.

I know it is counter-productive to cut off pieces of fabric before they are even completely applied, but I wouldn’t be able to live with myself if I knew that something was still in there. It’s much easier to repair now, before the aerothane starts flying.

Elevator Surgery

Fabric Removed, Ready to Clean

Lifting the Polyfiber Tape

A little bit of MEK and some rubbing made it easy to lift off the old tape.

Cleaned and Ready to Cover

Now I just need to recover the balance area.

First Comes the Fabric

First Comes the Fabric... (with adequate overlap per the polyfiber manual)

Stay tuned for the rest of the repair. This week featured especially moderate morning temperatures, which is why I’m able to do any fabric work at all in June. Even so, I’m limited to working in the mornings. Now skip ahead to later in the evening, when I came back out to the hangar to work on the rudder cable guards in the cabin.

Trimming the Aft Edge of the Rudder Cable Guard

Here I've trimmed the trailing edge of the rudder cable guard to match the angle that it forms with the aft cabin bulkhead.

What a nice fit!

What a nice fit! I'm going to replace that aft bulkhead with fabric instead of aluminum, but it will still fit nicely then too.

Left Side Guards

Here are most of the left side guards in place.

Right Side Guards

Here are the right side guards. Do you see the problem yet?

Rudder Cable Guard Interferes with Door Opening

As you can see from this angle, the aft cargo door opening coincides with the aft right guard. How am I going to fix this?

First, put the door on.

First, I should put the door on and see exactly what I'm working with.

This is how I'm not going to fix it

Here's a great idea that didn't work. I can't move the door sill up without shortening the door.

Here is where you can insert the picture of some serious head scratching. It’s time to get out some paper or card stock and try some different ideas. After a few more failures, here’s a promising possibility:

This looks better

The new and improved option.

The final result

This is the finished part.

While I was holding this part, I realized that I was unlikely to think up something like this theoretically. The only way that I was going to make something like this was to cut up some templates and mock it up on the actual airplane. I hate to waste shop time scratching my head, but sometimes that is the way it has to be.
Another View

Here's another view, just in case you are going to try to make something similar.

Working in these two separate sessions worked out well today. I find that in some cases my productivity suffers after 4 hours of continuous shop time, and during the hot part of the day I try to stay out of the hangar/oven.

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Hours Logged This Session: 5.1
Total Hours: 1883.75

Drill, Debur, Dimple, Nutplates

Today was a day with lots of hours and not a lot of pictures. I finished the work on the left air intake, which included dimpling the boot cowl and cutting countersinks into the plastic vent. I also dimpled all of the holes in the boot cowl skins that will get rivets, except for the firewall flange. I wanted to wait to commit to fasteners on the firewall flange until cowl time. I added some missing nutplates to the glareshield hatch (the corners that needed single lug nutplates) and started adding the nutplates to the lower boot cowl panels.

Install Nutplates

Here's a nice row of nutplates (in the wrong place)

Above you can see that I put the nutplates on wrong. I have made this panel 3 times now, so hopefully it is correct (speaking from the future again).

I also cut off some long strips of aluminum to use for the wingtips, and started preparing the stainless tunnel piece for it’s nutplates. It is so thin that dimpling is the only option for the nutplate rivets.

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Hours Logged This Session: 7
Total Hours: 1883.75

Engine Mounts and NACA Scoops

I’ve been watching the price of the engine mount rubbers for the past few months, and the trend seems alarming. In the 2008 Vans Accessory catalog, they were $40 per lug (for a total of $160). Today Vans sells them for $125 per lug, or $500 plus shipping! Yikes! I was surprised to see the cost go up so quickly. I was looking for some way to spend less, and eventually found that Jeppesen of all places sold them. Their price was well below anything else that I could find, at $88 per lug. My only explanation for this was that their price was outdated, but who knows. I was glad to save so much money. Here’s the data from the box:

Lord J-7402-24

Lord J-7402-24 Engine Mounts

Nobody seems to know how long the bolts need to be for attaching the mounts to the engine. I don’t really understand the mystery- the mounts have a center tube that gets compressed to the washers on either side. Now that I have them on hand I can measure the length of that tube and the end washers to come up with a grip length for the bolts. Here are some pictures of my measurements, in case you find yourself wondering how long the bolts should be.

This was just the uncompressed length, not very useful.

Washer Thickness

Here's the thickness of the end washer. It's just a little bit more than .1 inch

Measuring Again

Here's another somewhat useless measurement- the uncompressed gap between the two big pieces.

Here's the uncompressed length of the pair

Rubber Engine Mount Thickness

Here's a much more useful measurement- the thickness of the assembly once it is compressed.

Thickness of Engine Ear

This is the measurement that I took of the thickness of the engine mounting ear on the engine. This one isn't especially accurate, but is pretty close.

For the purpose of ordering bolts, my measurements aren’t especially accurate, since the bolts generally come in 1/16″ increments. I figured that the compressed rubber was 2.03″ and the engine lug was .93″. This makes the required grip length for the -7 bolts 2.96, not counting for any washers (and I’ll need at least one of those at 1/16″). The AN7-34 is 2 15/16″ (2.9375″), so I ordered the 7-35 with it’s 3 1/16″ grip length. That will allow for a washer or two but will keep the bolt’s threads out of the way.

With that bit of research done, I started working on the air intakes that will go on the sides of the boot cowl. These will provide fresh air for the front seats through an eyeball wemac type of vent on the instrument panel. I got the scoops from Vans, their part SV-1 at $6.25 each.

Vans NACA Scoop

Here's one of the scoops from Vans, along with a cardboard template that I made for marking the aluminum skin.

I wanted to make an aluminum backup ring so that the plastic part would be sandwiched between two layers of aluminum. The cardboard template made that step easy.
Aluminum Backup Ring

Here are the two rings and a nice view of the back of the SV-1

I drew a few lines on the boot cowl to try and figure out where I wanted to put the vent. My primary goals were to make the centerline of the intake horizontal in level flight, and to keep the intake lower than the outlet inside, so that water would be more likely to drain out if we were flying in the rain. I’m curious to see if this works. Note from the future! This vent installation is wrong. The hole is cut to the wrong shape- the aft portion of the vent should be straight across, not rounded.
Boot Cowl Layout

Here's the mark on the boot cowl sheet for where the vent will go. I almost oriented the vent backwards! This is the right side of the airplane, with the nose facing right.

Boot Cowl Vent Intake Location

Here's a more wide-angle view of where the vent will go.

vent on flat skin

Here's the boot cowl skin flattened out and ready for cutting the hole.

Ready to dimple

Now I just need to dimple the skin, countersink the plastic, and put everything aside until I'm ready to permanently attach the intake.

See note above- this is wrong. The aft side of the hole should be a straight line. I didn’t realize this until I was looking at Patrick’s RV in November 2010.

I got to the point of dimpling the holes for the first side and had to quit for the day.

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Hours Logged This Session: 4
Total Hours: 1883.75

Headset Jacks and Door Sill

I started out today by finishing something from last week.

Top Stringer Forward Attach

This is the forward attachment for the top stringer, looking up and slightly forward.

While I had the torch out, I also added a few more parts to the skylight area. First up were some plates for the headset jacks.
Headset Jack Plate

This plate will hold the headset jacks for the front and rear set occupant on one side.

This plate goes on the spanwise mini-bulkhead that I’m creating at the aft side of the skylight. This is what it looks like with a couple of the jacks installed temporarily.
Headset Jack Plate Populated

The switch is required to specify stereo or mono headsets. I've never seen an intercom that required such a switch.

Both Plates

The holes started out as small pilot holes, as you can see in this left-right before and after picture.

Headset Jack Plate Installed

Here it is after welding in place

This location will put the headset plugs and cords up and out of the way, behind the front seat passengers and ahead of the back seat passengers. Update from the future: This location doesn’t work. The aileron crossover cable interferes. Put the jacks somewhere else!

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Hours Logged This Session: 4.25
Total Hours: 1883.75

Repositioning Door Area Flange

Today was a two-part day. In the first session, I used a dremel tool to remove the weld on the vertical portion of the door threshold at the forward end. This was to allow for repositioning that piece so that it would attach properly to the aluminum piece that goes there. This also involved cutting loose the piece that I added on earlier.

This is the forward lower corner of the front door. I've removed the weld and the paint in the area so that I can bend the whole vertical piece out some.

This is the same piece that I added earlier in the year. This time I trimmed it and moved it inboard some to allow for the aluminum panel.

I also addressed a small scratch that I made on one of the engine mount tubes. I sanded the area with fine sandpaper to remove the scratch, then sprayed a little bit of temporary primer to keep it from rusting.

Engine Mount Touch Up

In the second session I added on the front tubes for the skylight, cut the chordwise tubes loose, bent them to a slight curve, raised the front piece up, and cut out some new stringer tabs. This is all work that I wrote about a few entries back.

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Hours Logged This Session: 3.5
Total Hours: 1883.75

Seats and Engine Mount

Today Tabitha came out again to finish squeezing some more wingtip rivets. We also tested the glue on the foams to make sure that it wasn’t going to dissolve them. The glue checked out OK, so we glued one of the bottom cushion combinations. Tabitha marked it for cutting and spent some time thinking about how all of that needed to be done.

Tabitha is trying out a few different seat foam combinations and marking them to cut.

While she was doing all of that I worked on more nutplates in the boot cowl/fuselage area. Danny stopped by, and he and I installed the engine mount.

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Hours Logged This Session: 5.5
Total Hours: 1883.75

Tailwheel Spring and Wingtip

Tabitha came out today too and we made some good progress. I was at a stopping point with the tailwheel spring because I didn’t have a drill that would handle larger bits. It had a temporary bolt in place of the AN-7 that is supposed to go in there. With the new drill I was able to get the hole up to size and reinstall the tailwheel spring.

I got this new drill so that I could use larger bits. All of my others have a 3/8\

Meanwhile, Tabitha was dimpling and squeezing the rivets for the wingtip flush mount strip.

Tabitha was dimpling and squeezing.

I also spent some time getting ready to install the engine mount, now that I have the hardware.

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Hours Logged This Session: 5.1
Total Hours: 1883.75

Seat Foam Ergonomics

Today Tabitha came out to help. With the seat pans finished, it was time to start thinking about cutting the foam for them. But first, the flooring supplies came in, both the foam padding and the top layer.

Here's the final color of flooring. It's the Nautolex Decko Dot in the charcoal color.

This is the 1/4\

The plan for the seats is to use one inch of firm tempur foam on the bottom, followed by urethane foam on top of that. I was initially planning on 1 inch of firm urethane followed by 2 inches of medium, for a total of 4 inches.

Mr. T tries out the back seat foam, but he says it isn't thick enough yet.

It looks like the 4″ cushion is going to limit the headroom, at least for me. We’ll keep the 1″ layer separate and use it when needed.

Here's a test of the 4\

Welding Goggles for extra effect

Here's a headroom test. Even without sitting up straight, there isn't a headset worth of space between my head and the ceiling structure.

Tabitha tries out the flap handle, demonstrating the need for inertia reels for the front two people.

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Hours Logged This Session: 2
Total Hours: 1883.75

Welding Skylight Tubes

I started cutting and adding in some of the new skylight tubes today.

Here is a new chordwise tube. Note that it doesn't really fit just right.

I cut a notch into the tube to make it match the mounting area.
Mysterious note from the future!
I learned in retrospect that the following picture shows a tube that is ground a little too much. It should have been a little bit taller.

Now it fits better.

Here you can see the pair.

Mysterious note from the future number 2:
The above and below pictures show another problem. I put the tubes in as straight tubes, and they should have been curved slightly. Can you see what I mean? They should probably match the curves in the channels at the wing root.

From this angle you can see the new spanwise tubes, and the problem with the chordwise tubes.

While I was there, I welded the seatbelt tube in place.

Here's the completed seatbelt support tube, ready for prep and paint.

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Hours Logged This Session: 4
Total Hours: 1883.75

Skylight Modifications

Today I finished the back seat covering. Now it’s ready for some airplane noises.

Here's the finished back seat bottom.

It's a front seat, in a seat. It and the engine mount are just having a chat.

Here are some details of how I sequenced the overlaps.

Since our back seat has the added headrest structure, I covered the back in two pieces.

I wrapped the front fabric of the seat back around the back side of the bottom tube.

After I finished the back seat I took a little lunch break. Fellow EAA 731 member Kevin Ball stopped by and we spent an hour or so talking about the airplane, then I went over to Bart’s to take a look at his avionics work and to return his bending brake. When I got back, I started preparing the ceiling structure for the skylight.

The first step was to cut the stringers off. I left them a little bit long for final trimming.

I also cut the old stringer supports down a little bit to effectively lower the roof line about 1/4 inch, after accounting for the thickness of the new tube that will be on top of it. I copied the spanwise tube sizes from the plans at station C (T3, 3/8 x.035), and the chordwise tube sizes from the existing tubes in that area (T2 5/16x.058). I chose that size since the spanwise tube at station C serves the same purpose as my new tube at station N- a forward border for the fabric and an aft border for the other than fabric.

I decided to run the skylight back to the aft spar, which is further back than Pat ran his. I'm planning to have three separate panels that each run the full length. This will help reduce the compound curves in that area.

Bob has also specified that another tube be added between station N and the x cluster for supporting the shoulder harnesses for the front seat passengers, if the shoulder harness is going to attach out in the middle of that big tube at station N.

Note the areas that I've cleaned for welding in the seatbelt support tube.

Since the skylight will move the forward end of the stringers aft, I'll need to cut off these tabs.

In this picture I'm cutting away the old stringer supports.

This is looking mostly forward at what used to be the tab that supported the stringer

Here's a nice overview. The two little vertical tubes that used to be stringer supports will now hold the spanwise and chordwise skylight tubes, and the new forward attach tabs for the stringers. The paint is gone in the middle of the large tube for the seatbelt support tube.

I also did some measuring to decide on how far forward to take the skylight. One certainty is that this is a lot of effort to make a big hole in the roof, and I’ll have to carry sunshades to cover it up for a lot of the time.

I still haven't decided on where exactly to end the skylight on the forward side. Here are some options, with the numbers reflecting the number of inches from the windshield track. This shot is looking down at the top of the fuselage with the nose to the right.

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Hours Logged This Session: 6.1
Total Hours: 1883.75

Welding, Casting, Covering

asting complete on 1, elt brscket on, control sticks done, cast 2, cover front seat bottoms and backs 1800 lunch?

With one aileron balance tube done, the second was easy. I’ll elaborate more on the process this time.

Here's the finished weight of the first lead tube. I will be able to drill some of the lead out once the aileron is covered to get a perfect balance.

I used a thick aluminum pan that Tabitha found at the thrift store, complete with a little pour spout. It was really perfect for pouring the lead.

I used tire weights that were really dirty. I would tilt the pan, and direct the torch at a tire weight. It was amazing to watch the bright silver liquid run out and leave the dirt, oxidation, and steel clip behind. A few passes with the torch helped be sure that all of the good lead was out. From there I would reach in and remove the nasties with needle nose pliers, putting them into a nearby rotel can. I would repeat this process until I had a fairly large puddle of bright lead, then I would reheat that puddle so that the whole thing was molten, and pour it into the tube. I would try to preheat the aluminum tube some too, in hopes that the lead would make it all the way to the bottom. Once the whole thing was cool and finished, I flipped it over and heated the other end. This caused all of the dirt and gravel to float up to the top, so I removed each of those with pliers. That left me with about a 1/4″ lip of aluminum as the lead settled into places that used to have little bits of rock in them.

I used a hammer to shrink the edge of the aluminum tube, so that it will help hold the lead in place more securely.

This would have been especially tidy if the whole tube was full, since then I could have the extra lead security on both ends.

Danny was telling me about an oil cooler that he didn’t use during his RV construction. Bob and others seem to think that it is adequate, and the price is great, so I think I’ll use it.

Oil Cooler donated by Danny

The control sticks are ready to repaint:

Here's the cap on top of the control stick, to support the push to talk.

I used the grinder to remove most of the weld bead around the control stick cap. This is to make sure that the grip will fit over the end, and this is certainly a non-structural piece, so I wasn't worried about removing the material.

I also finished the ELT bracket, except for cleaning and painting.

Here's the top of the ELT bracket, ready to weld to the bottom.

Here's the finished ELT bracket, ready to clean up and paint.

Today was a great productive day, and the weather was nice, so I figured I’d try a little bit of covering. I’m making the seat pans out of polyfiber covering, the same stuff as the exterior of the fuselage. The seats will be different from the airframe in that they won’t have any reinforcing tapes, UV protection, or color finishes.

I copied this idea from Oshkosh. The little cardboard disk helps reduce evaporation and drips.

Here's one of the front seat bottoms with the fabric on.

Today I finished covering the front seats, except for shrinking. I wanted to make this a priority so that I could get the seats ready for upholstery, which also involves cutting the foam cushions.

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Hours Logged This Session: 8
Total Hours: 1883.75

Back from Sun-N-Fun

It’s been a while since the last building entry, but I’ve been out of town more than usual. I just got back from Sun-N-Fun with a new list of ideas and a few new parts.

One of my SNF finds was these LED position lights. If I didn’t already have the aeroflash lights, I would have probably gone with a different setup, but since I do, I wanted to find some LEDs to replace the four incandescent bulbs. I had seen these before in the Aircraft Spruce catalog, and the guy who sells them to Spruce had a booth at the show. His price was a little better, so I got a set.

Here are the LED replacements for the position lights.

I took the cover off of the nav lights and took this picture.

Inside of the Aeroflash

This is the green LED in place

And the aft-facing white

Here's the whole assembly back together again. I replaced the green lens with a clear one, and was actually able to sell the original lens and bulbs to offset the price of the new parts.

On the red side I found that the gasket wasn’t properly installed you can see what I mean at the pointy end of the strobe insulator.

Notice how the black gasket doesn't quite fit right.

The white insulator wasn't quite right either.

When I put it all back together I put the gasket on correctly and also made sure that the white insulator was correct. I wonder if it came from the factory this way.
I realized that I should probably take some documentation pictures of the engine and accessories, because I always find myself with questions when I’m away from home.

The Starter...

...and the ignition wires...

...and the starter ring gear...

...and the carburetor...

...and the carburetor data plate...

I also found a baffle kit for sale second hand. This one wasn’t related to sun-n-fun, but I hadn’t had a chance to go through the kit to make sure that it was complete.

The plans for the Vans baffle kit are on one big sheet

There's all sorts of hardware in there

To change gears again, I finally had enough lead to fill the aileron balance tube. I ran safety wire from the corner of the bench to the tube, then leaned the tube slightly down and to the right as shown in this picture.

Aileron Balance Tube

This is a 1″ tube, which is larger than the 3/4″ tube originally designed in the plans. The diameter change is to improve the aileron if I recall correctly- it doesn’t really matter, since my ailerons have a 1″ hole in them. Back with the old 3/4″ tube, builders had to fill the entire tube with lead in order to get the required 5.5 pounds. I’m glad that another builder pointed out that the 1″ tube definitely does not need to be full. Without this tip I might have not thought about that until it was full of lead. I started to wonder if this uneven weight distribution would be a problem. I asked Bob, and he said to just leave the tube at it’s full length so that it will have more attachment points, and not worry about it. I’ll probably have to drill some of the lead out to actually balance the aileron. If I leave the 1″ hole open during covering, I will still be able to get a long drill bit into the lead. I can make small covers to pop-rivet over the 1″ holes when that is done. This will also come in handy if I need to recover the aileron later.

While I had the torch out, I figured I would also weld a cap onto each of the control sticks. This will make it much easier to mount a push to talk switch on the top. In this picture I’ve cleaned the paint off in preparation for welding.

Control Stick prior to welding

I also removed the paint for the ELT bracket

I don't remember where I got the idea for this holding fixture. It is 16 gauge copper wire and alligator clips. For tacking it works well, but since the clips are soldered it might not hold if it gets too hot.

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Hours Logged This Session: 5.3
Total Hours: 1883.75

ELT Antenna Bracket

Today I was in the mood for some welding. First, I noticed back when I primed the headrests that I had missed a problem with one of them. I had started to cut one of the horizontal tubes, then realized that I was cutting in the wrong place. This left a scored line around the tube, so I wanted to grind the paint off and run a bead around that score mark to remove the potential stress riser.

Fixing a problem with one headrest

Next, I needed to make a welding cart to hold my tanks. I started with this cheap harbor freight hand truck and spent an hour or so modifying it. I didn’t count this time towards Bearhawk building of course.

Starting point for a welding cart

With the tanks safely secured, I started on that ELT bracket.
Note: I’ve since removed this bracket and found a better way to do the same job. The problem that I encountered with this installation was that the fairlead fit a little too loose in the fairlead tube, and there wasn’t much clearance for the antenna feed connection. The better method that I came up with was to use an aluminum sheet piece on top of the stringers.
I started with the tube that will hold the fairlead plastic, and a short piece of tube that will locate that tube vertically.

Even with as much practice as I have, I still am not a pro. Note how I didn't get out fast enough with the torch at the edge of that thin 7/8\

My goal was to try and locate the top of the antenna plate just below the level of the stringers, just in case the covering had a little bit of sag between them. The reality is that since the stringers are so close together at that point, the covering probably won’t sag at all.

The ruler is just a straight edge to hold the bracket blank level with the stringers.

Here’s the blank after I’ve bent it. It’s going to be a tight fit with a 90 degree BNC adapter to keep the coax out of the elevator trim cable’s way.

ELT antenna bracket view from the top

Here's the top half of the bracket

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Hours Logged This Session: 3
Total Hours: 1883.75

Bending Cable Guards Again

I needed to bend the new aft cable guards again, so this time I took some pictures of the process that I described earlier. Thanks again to Brad and Joel for letting me use their machinery! The weather was nice, so I put the blanks into the car that Dad was driving down to the IPJ airport. His airplane was down there getting a new engine and he was helping them get it installed. He was going to be there all day, so I rode a motorcycle down there at around lunch time so that I could borrow their brake.

3-in-1 Sheet Metal Tool

3-in-1 Sheet Metal Tool

Theirs is the combination brake, shear, and roller from Northern Tool. I’d love to have one in my shop, but I probably wouldn’t use it enough to justify the cost. In fact, I’d rather have the larger version that could handle a 48″ wide sheet of aluminum, but even the cheap Chinese version is close to $1000 and 700 pounds- I definitely wouldn’t use that one enough to justify the cost! This one is very handy, but has some important limitations.
Bending Die with No Radius

This isn't enough of a radius for 2024-T3

The primary limitation is that the bending dies don’t have any radius. As you can see from this picture, they are quite sharp. Since the 2024-T3 Aluminum is so hard, it tends to crack if bent under these circumstances.
Fake Radius

Here's Bob's solution for adding radius to the dies

In this picture you can see the corrective action (as outlined by Bob in the early Beartracks) which is made out of some aluminum flashing. I used one piece on the bottom (just to prevent scratches from the sharp edges) and a handful of pieces on the top. If this were my own brake, I would modify the dies to have a 1/8″ radius permanently, but since it isn’t, I just use these pieces instead. The above picture actually also shows a blank in place and ready for bending. I bent the two pieces as before and enjoyed a fantastic spring ride back home. Everything is really starting to bloom and grow again, and the little two lane roads are full of lots of great yards and gardens to see.
Cabin Air Intakes

Here are the Vans cabin air intakes

Once I got back to the hangar I opened up a box from Vans that included the two air intakes for the cabin air and the countersunk nutplates for the boot cowl. Their price on the nutplates was better than spruce at somewhere around 50 cents each, and I’m going to use them for the parts of the boot cowl that aren’t riveted. The vents will provide fresh air to the two front seat occupants, and there’s no way that I would try to make them myself since Vans sells them for such a reasonable price.

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Hours Logged This Session: 2
Total Hours: 1883.75

Cable Guards and More Parts

Today I spent some time going through a big order of parts and hardware. This order included lots of stuff, including the rest of the screws for the wing inspection panels.

Bearhawk Wing Inspection Panel Screw Organization

This is my organization method for the wing inspection panel screws. Each panel gets one compartment. Can you guess which ones are for the fuel tank panels?

Dad was in town, so he cut out some new strips of aluminum for the aft section of the rudder cable guards.
Deburring with the scotch brite wheel

Dad deburrs the new cable guard blanks on the scotch brite wheel (which he gave me for my birthday).

I also ordered a foot of 7/8 .035 4130 to make fairleads out of.
Fairlead Tube

A new fairlead tube for the ELT bracket

Here’s where the new fairlead will go, just under the new ELT antenna bracket that I haven’t made yet.
Bearhawk ELT Bracket Fairlead

It goes here, mostly. This is the buklhead station aft of the rear cabin bulkhead.

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Hours Logged This Session: 3
Total Hours: 1883.75

Cable Guard vs Baggage Door

This was my first attempt at making a transition for the rudder cable guard. Since this piece was too short (see the left side of the picture) I figured it was expendable. I think that the best solution is going to be a combination of a piece like this one (but longer) and a door sill plate. I should be able to attach the two together.

Cable Guard at Baggage Door

Rudder cable guard at aft cargo door sill, looking down.

I also spent a while on the wingtips again. This course of action has not been worth the time that it has taken. I should have just filled the old holes and gone with the basic fiberglass over aluminum mounting method.

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Hours Logged This Session: 3.1
Total Hours: 1883.75

Rudder Cable Guards

Today I drilled and clecoed the rudder cable guards in place. The aft guards are too short. I tried to make them 24″ long each so that they would come out of a 48″ piece of stock. Since the aft bulkhead forms an obtuse angle with the floorboard, the cable guard needs to be longer on the top, and I didn’t account for that. The other complication is the back door on the right side. Since the door sill goes so low, I’ll have to figure out a way to make the transition.

Bearhawk Rudder Cable Guards

Rudder cable guards temporarily in place

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Hours Logged This Session: 2
Total Hours: 1883.75

Burn Testing Nautolux Decco Dot

I have been looking for some good material to use as a floor covering. Bob uses bare aluminum, and that method certainly has some merits. It is light, simple, and durable. Tabitha would rather have something that looks a bit more finished, but also something that dampens vibration a little bit better. She says that prolonged exposure of her feet to a vibrating structure like the floor will accelerate the development of arthritis and contribute to an overall mood of malaise and discontent.

I don’t really want to use something like carpet, because I know that it is going to be harder to clean than a solid surface. I don’t want to have to worry about getting into the airplane with slightly dirty shoes. I’d really like to find the airplane equivalent of linoleum, and there is a great example of it on the floor of our planes at work. It is thin, easy to clean, and super durable. It gets the foot traffic of lots of people, every other hour or so, every day, all day, and lasts years under those conditions. I asked a few of the mechanics about where it comes from, but they don’t know. Even if I could find who makes it, chances are good that it would not be available in the small quanitity and price that I would like to have.

A similar product is available for household floors, but it is 1/8″ thick and extremely heavy (pounds per square foot).

One of the email list members suggested that I try products intended for boat floors. This was a good lead, and soon I found Nautolux Decco Dot flooring. It has all of the good qualities that I like, and it is very light weight. I think that the entire floor would be under 5 pounds, perhaps even less. The bad news about the Nautolux is that it is a little bit too thin, such that it needs to be glued down to stay flat. It also doesn’t have much in the way of vibration dampening. I ordered a sample piece to try some burn testing on.

The whole idea of burn testing is a little bit silly in some ways. At first it seems like a really good idea to make sure that the interior materials have good qualities with regard to flamability. The unfortunate reality is that since the rest of the interior is made of aircraft fabric, the huge wall sections are certainly the weakest link. Having said that, I’m planning to burn a small piece of each proposed interior material, just to see if it is at least acceptable. Burn tests aren’t legally required for experimental airplanes of course.

Since the Nautolux is so thin, I figured that I could try to find some 1/8″ closed cell foam to use between it and the floor. This would help dampen vibration and noise, and also not add too much weight.

Decco Dot Sample Piece

I took the above piece and stuck it in the propane heater for an unscientific test. It started to burn, and when I took it away from the heater, the flame died down. That’s convincing enough for me, since it didn’t continue to burn brighter.