Electrical Parts & Weight

Today I started with an inventory of parts for the electrical system.

New Electrical Parts!

Getting new parts is so much fun!


I’m using several d-sub connectors for the avionics, so I set them all out and wrote notes about which one needs to go where.
D-Sub Organization

I labeled some of the d-sub connectors that I know I'll need.


More New Parts

Switches, LEDs, Terminals, E-Bus Diode, etc.


Molex Crimpers

These molex crimpers are nice, though the wire sizes are listed on the box but not the tool.


Fuse Blocks

One of these will be for the main bus, one for the ebus. The top of the picture shows my test lead for the low-voltage module.


Small Fuses

I ordered the small fuses from B&C since I couldn't get them locally.


Now it’s time to put some of those new parts to work! First, I installed the switches.
Right Row of Switches

The switches in this row are for lights.


The switches are divided by function, with lights on the right, and the others on the left. Both banks are within comfortable reach from the left or right seat.
Left Switch Section

These switches are for the magnetos, starter, and power distribution.


I spent a little bit of time getting the tip of my soldering iron reshaped and tinned, and fixed the AEC 9005 Low Voltage Warning Module. This is the one that I built per the Bob Nuckolls design. It wasn’t working after I first made it, but that was because I put a few parts in the wrong place. After I had all of that sorted out, it works great with my test harness hooked to the truck battery. This module is very simple and useful- it flashes a red LED whenever the master switch is on but the alternator isn’t. It’s important for the pilot to be aware of such a condition, because in flight it means that the alternator has quit and the system is consuming finite battery power. On the ground after shutdown it is a flashing reminder to turn the master switch off.

I wasn’t happy with the crimp results I was getting on larger electrical cables, so I’ve tried another method. The underlying problem is that the terminals are much larger than the conductor of the cable.

Improved large wires

The calipers are set to the OD of the 4 AWG copper wire. The terminal is an unmodified 4 AWG size, and this picture illustrates the difference.


Bob Nuckolls suggested that I stick copper wedges into the strands to tighten the fit, then crimp or solder. An alternate technique that I tried was removing material from the terminal to reduce its inner diameter. This provided a snug fit, then I soldered the able to make the joint gas tight.
Modifying oversized terminals

I put the terminal in the vice with very light pressure then used the Dremel to remove material.


Ready to Solder

I put a little flux on the copper conductor then squished the terminal in the vice.


This method produced a much better product.
Ground Cables

With a little heat shrink these ground cables are looking about done.


Engine Grounding Cable

This cable is surprisingly important, though it seems fairly minor.


Danny was borrowing a set of scales, so we figured since they were at the airport we should go ahead and weigh the Bearhawk as it is.
Bearhawk Weight

As of today, the weight is 885 pounds.


If I had a set of scales like this around all the time, I think it would be an interesting experiment to weigh the airplane weekly to see how it becomes so heavy. We’ll likely add another 400-500 pounds before we’re done. I also took a couple of overview shots since I didn’t have any good pictures with the wings on.
Bearhawk Front Overview

From the front right...


Bearhawk Left Side

... and the left.


These pictures will mean a lot when the airplane is finished.

Putting the Wings On & SD-8

After a year of watching, I finally found a good deal on an SD-8 standby alternator. Today Danny and I installed it on the engine. The last of the four nuts was a little bit tricky to get to, but we figured it out after a few minutes.

Lycoming Vacuum Drive

This is the spot where the vacuum pump would usually go.


I took a few pictures of how everything sits. I don’t see any clearance problems.
Bearhawk SD-8

Top view of the SD-8


SD-8 Right Side

... and From the right...


Since Don Bandy was in town and the timing was good, we decided to put the wings back on. Richard put the wings on once, but we haven’t had them on until now. A few of our local friends also came over to help, including Danny, Wade, and Kevin. I built a stand to put under the first wing to keep the fuselage from tipping over. Jim Woolf said that it wouldn’t tip over even without the stand, and he was right! That’s a bet I would have lost.
One Wing On

Wade evaluates our progress


Left Wing Extremists

Here's the left wing just before we put it on.


Since Richard already did the rigging and drilling, this installation was just a matter of lifting the wings and putting in the bolts. Even still, it takes a few folks to do it well.
On the Table

We set the wing on a padded table while we got Danny in place to put the bolts in.


Bearhawk Wing Bolts

The person at the wingtip, in this case Don, had the most important role. In the worst of circumstances we probably could have done the job with just 3- one person at the root, one at the tip, and one to put in bolts. Having more made it much easier though.


Personnel Positioning

Maybe it was Wade at the tip on this side!


Wing Strut

There's Don at the tip, while Danny and Kevin and I put the strut into place.


Tapered Bolt

I used a tapered, bullet-shaped bolt to clear the way for the airworthy version.


Wing Party

Left to right: Wade Kennedy, Kevin Ball, Tabitha Yates, Don Bandy, Bryna Riley, Chris Frye, Danny Hughes, and me.


With all of that done we went out to the Buffalo Wild Wings and ate a bunch of chicken wings. What fun!

Shaping Wing Light Mount

Today was a short day in the shop without any pictures. I started filing and sanding the superfil down to a nice smooth curve. I think I might have had some sort of reaction to the dust on my hands, so next time I’ll wear some gloves. I used 150 grit wet/dry sandpaper with water, since the blue dust clogs the paper when sanding dry.

Wingtip Light Mounts

I started today by filing down the fiberglass from yesterday.

Bearhawk Wingtip Light Mount

Here's yesterday's fiberglass trimmed down a little.

I added another layer of smurf extract to fill the voids in the cloth:

Superfil

Superfil is similar to Bondo, but it weighs less and has better dimensional stability over time.

My hangar neighbor Danny got his RV back from the paint shop recently too:

Danny's RV

Danny's RV, just back from the paint shop

Fiberglass on the Wingtip

The weather was nice today so I added a layer of fiberglass to the position light mount on the wingtip.

Bearhawk Wingtip Light

The position light mount has its first layer of fiberglass.


I also picked up some 1.5″ electrical conduit to use for exhaust pipes. Since they’re galvanized and welding zinc is bad for my health, I dipped the pipes into some phosphoric acid. The phosphoric acid will remove the zinc without damaging the steel base metal.
Phosphoric Acid Bath

The ziplock bag is just there to displace some acid and bring the level up higher.


Removing Zinc Plating with Phosphoric Acid

The acid has already started to dull the zinc, but it will take a few days to get back to bare steel.


I finished the second set of aluminum wedge shims for the fuel line too.
Bulkhead Fuel Fitting Shim

These aluminum wedges will eliminate a low spot in the fuel line where it passes under the front door jamb.

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.

Seats Ready for Covers

I started wet sanding the first silver coat today while Tabitha carved the last bit of foam. They are ready for transfer to Mississippi for covering. I also spent a little while carving down the wingtip foam to prepare for the first layer of superfill that I added to the wingtip for the position light.

Sanding Polyspray

This is what the polyspray looked like after sanding.


I forgot about the elevator trim torque tube and its corresponding sharp edge under the fabric, and sanded right through. It really does just take a couple of passes with the paper to cut the fabric! Now I’ll have to learn how to make a patch.
Hole in the Fabric

Here's my chance to try patching fabric.

Rough Cut Foam

The foam will hold the position light mount in place until I can build up enough filler and fiberglass to hold it permanently.


Test Fit

I installed the light fixture just to be sure that it all still fit properly, and it did.


Smurf Extract

The filler makes me think of the Smurfs, so I refer to it as Smurf extract.


That should be ready to sand/file on my next visit to the hangar.

Position Lights and Brakes

It was too humid this morning to spray the next coat of polybrush, so I worked on the wingtip instead. I mixed up a batch of epoxy and used it to attach the position light mount and the wingtip aluminum strip.

Attaching the Position Lights

I didn't have any paper masking tape, so I used a little bit of foil tape to hold the position light mount in place.


Wingtip Filler Strip

Wingtip Strip


I also made a short brake line for the left side and hung up some blankets to serve as drapes. Half of the front of the hangar is translucent, and I was concerned about unnecessary UV exposure.
Spray Booth

Here's my "spray booth" with most of the improvised curtains.

Finish Heat Smoothing

In two sessions today I finished the heat smoothing on the rest of the parts that are ready to go. I rigged up a way to hang the parts from the ceiling so that I can spray them all in one round.

Tail Parts Ready to Spray

I have a system of ropes, strings, and sawhorses holding the tail parts in place.


One strategy that I came up with for handling the problems with the wingtip-wing junction was to adhere a strip of aluminum that would overhang the junction. Today I got it ready for that operation.
Wingtip Aluminum Strip

Here's the aluminum strip, ready to adhere.

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.

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.

Battery Box Continued

As of today the fuel quantity gauges are done, and I drilled, countersunk, and primed the battery box and associated parts. Next time I’ll paint them and assemble the box so that I can add it to the firewall. Once again the pictures are missing until 8-25.

Posted on
Hours Logged This Session: 5.5
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.

Posted on
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.

Posted on
Hours Logged This Session: 5.1
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.

Posted on
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.

Posted on
Hours Logged This Session: 5.3
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.

Posted on
Hours Logged This Session: 3
Total Hours: 1883.75

Slave Labor

Dad helps drill some rivets while he's in town


Dad was in town today so he stopped by to drill out some rivets. Tabitha was also there with us. In the picture she is working on her practice toolbox from Van’s. She said that she should get to work on the real airplane since dad gets to work on the real airplane, and said that she doesn’t want to work on the toolbox anymore. I told her that’s fine, but that she can’t have my toolbox! The little practice kit really makes a cool little box. I spent the rest of the time helping the two of them and getting the shop straightened up.

Tabitha's Practice Toolbox

Posted on
Hours Logged This Session: 2
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.

Posted on
Hours Logged This Session: 3.1
Total Hours: 1883.75

Finished Right Wingtip Mount

Today I drilled the top mounting holes for the right wingtip and clecoed everything in place. I’m still going to have to do some work on the gap between the fiberglass and aluminum to try and get something that is rain tight. I walked over to Danny’s hangar to see how Vans solves the problem, and I really like their solution. His RV-7 has the outboard wing rib mounted about 1.5 inches inboard of the end of the skin, which allows that the fiberglass part fits under the wing skin. In this case, there are no waves at the fasteners because the wing skin spreads the load like a giant washer. Since the skin is only .025″ thick, from arms length it looks flush. If the inboard edge of the fiberglass isn’t perfectly straight, it doesn’t show, since it is under the aluminum. This would be a cool feature to incorporate for a scratch builder, but I can’t see how it would be practical to do this late in the game. Here are some pictures of the vans setup:

Vans Wingtip

Note that the fiberglass is under the wing skin

Wider Angle - From here there are no waves, and it looks flush because the wing skin is so thin.

At the Aileron it switches to fiberglass on top.



While I had the wingtip mounted, I wanted to see how hard it was going to be to remove the ridge that the wingtip had as a result of the mold. The fiberglass is pretty thick in that section, and I was able to file the ridge flush without getting through the white coat in all but just a few spots. With some filler and wet sanding, this tip will look great.

This is the ridge left during the manufacturing of the wingtip. The file takes it right off.

Here I am filing off the ridge, not straying too far from the propane heater.




Now I get to do it all again. I’m glad this isn’t a biplane!

Wingtips and Seats

I was able to get some good working time in today. The two areas of interest were the wingtip and the seats.

Back when I was at Bob’s this fall, I noticed that the fiberglass wingtips on his new Patrol LSA prototype were really smooth, with no waves between the rivets. I asked him how he did that, and he said that he put a protective piece of wood on the trailing edge (where the aileron would go) and used a ratchet strap to pull the wingtip tightly aft and down to the wing. Today since I was finished with the underlying AL support strip, I got out the ratchet strap and did some drilling.

Ratchet Strap on Wingtip

Here is the ratchet strap in place. I had to slide it left and right occasionally for drilling.

Hole Displacement

Here you can see the difference that the strap makes. The black hole on the fiberglass part used to correspond with the larger (center of 3) rivet hole. This picture is fairly close to the leading edge, and the strap is pulling towards the left side of the picture.

Hole displacement

Here you can see the old hole. Note how far the old hole is from the large rivet.

I’ll have to say that the ratchet strap did make a big difference, which was cumulative as I worked my way aft. There was probably a half-inch difference at the aft section. This is certainly better, but I’m still not all that pleased with the finished product. It still has some waviness.

Burned Hair

This is a picture of my burned hair, after reaching down to pick up something that was a little bit too close to the heater. Working on airplanes in the cold is a hazardous occupation!

Before I did any drilling, I wanted to make sure that the trailing edge of the wingtip was going to be parallel with the trailing edge of the rest of the wing. After all, if it was tilted, it would be acting like a miniature aileron all of the time. Since I’m trying for a flush mount, I had to trim the inboard side of the top of the wingtip so that the trailing edge would line up while the edges were flush with the skin.

Wingtip Alignment

Can you see how the trailing edge of the wingtip is now aligned with the trailing edge of the wing?

Trimming the Wingtip

In order to make that alignment possible with the flush mount, I had to trim about 3/16 of an inch off of one side.

Me trimming the wingtip

See, it is me doing the work.

After it started to get too cold to work in the hangar, I went back home to check on my chemistry project. I was wanting to weld some nuts onto the seat backs that would accept thumb screws. These thumb screws would hold the headrests in place, though for now the headrests are pretty snug as it is. I was worried about welding the zinc plated nuts and having zinc fumes, so I did some Googling. It turns out that zinc is very reactive and will dissolve in just about any acid. Steel also dissolves in most acids, which is a problem since the base metal of the nut is steel. Fortunately, phosphoric acid is one that will dissolve the zinc and leave the steel alone. This is handy, since I can drop the nuts into a jar and come back later without coming back to an empty jar. I left them in there for a few days, until they had mostly stopped bubbling.

Tapped Hole

I used a tap to cut threads into the tubes, so that I can use a screw to hold the nut in place during welding. These threads will also function in the final part.

First, I drilled and tapped the actual seat part. These threads were deep enough to hold a finger-tight screw in place, but certainly not deep enough for use in service. I threaded the nut onto the screw, put the screw into the seat hole, and lightly snugged the nut down tight to the seat part. This would help ensure that the threads would be lined up.

Nut Ready to Weld

The stainless screw is there to hold the nut in place and limit distortion. Note the dull luster of the nut after its acid dip.

I was reading the conversations on the Bearhawk email group about problems with welding nuts. Lots of folks were having problems with distortion of the threads during welding, so I took some of the advice of the more experienced welders to try and mitigate the distortion. For starters, I put a screw into the threads when I did the welding. Also, I tacked on four sides and tried to keep the puddle away from the middle of the nut as much as possible. Finally, I took the screw out as soon as I finished the weld, so that it wasn’t stuck there forever.

Nut Welded in Place

Here's the finished product, ready to blast and paint.


After the part cooled completely, I chased the threads one more time with the tap and everything was ready to paint.

Increase Wingtip-Aileron Gap

Today I was working on the wingtip mounting strip. I had originally put it in place with about a 3/16″ gap between the strip and the aileron, but I was re-reading Eric’s Building Manual and saw where he recommended a 1/2″ gap. This made a lot more sense, especially because it would be pretty stinky to have the aileron rubbing on the wingtip. So today I adjusted that gap, and spent the rest of the time drilling, deburring, and dimpling the holes on the wing side of the strip.

While I was working, I realized that in the past I would often work until I got to a stopping point. For example, in the case of this part, I would prep all of the holes, put in all of the rivets, and then go home. Then, next time i came to work, I would start on a new task. I realized that this is probably not the most productive way to work. Instead, I should not set the last 10-20 rivets, but leave the clecos in. That way, when I come back to work next time, I can walk in the door, turn on the lights (and my good friend the propane heater) and pick up the squeezer and get to work. By the time I’ve set all of the rivets, my mind is in the workshop mode and I’m ready to move on to the next task. This realization was certainly counterintuitive, but quite helpful nevertheless.

New Goodies

Today I spent an additional 1.5 hours on the wingtip, but the more exciting news is that an order came in from Wicks.

Seat Foam

Seat Foam and Invisible Cat

I ordered some 5052 Aluminum to make fuel lines out of, along with some foam for the seats. My plan for the seats is to use tempur foam for the bottom layer for its shock absorption, then to use regular seat foam for the rest. Wicks had the best price that I could find on a 1″ thick green cushion that was big enough for the seats.

Here our quality assurance department verifies the alloy of the aluminum fuel tubing by smell.

I also got some rivets for the doors. They are made of aluminum and have a nice large head to help spread the load evenly. I’m planning to use these AN fittings for the fuel quantity gauges. They have Flared ends on both sides, and one side has a bulkhead attachment. My plan (for now at least) is to set up the fuel quantity sight gauges outboard of the fuselage frame, on the inboard side of the root rib. This will eliminate the need for any flexible tubing.

Rivets and AN Fittings

The Wicks price was pretty good on aluminum pull rivets for the door and window skins. The 90 degree AN fitting is for the fuel quantity gauge.

I didn’t want to use tempur foam for the entire seat cushions for a couple of reasons. Cost and weight were two factors, since the tempur foam had more of each. Another reason was the recommendation of a professional interior guy that gave a presentation about how to build seats. Another Bearhawk builder named Dave Lenart recommended Rochford Supply for the foam. The higher density option is 4526, with the softer 3319. The 1″ thick harder stuff goes over the tempur foam, then the softer 2″ thick stuff goes on top of that. The seat back is 2″ 3319 by itself.

Seat Foam

The seat foam cushions came from Rochford Supply

Cinnamon Roll

Foam Cinnamon Roll


Posted on
Hours Logged This Session: 1.5
Total Hours: 1883.75

Flush Mount Wingtip Continued

Today I added more of the strip material that will hold on the flush mounted wing tip. It goes much faster in the straight stretches because I don’t have to cut relief holes for as many flutes. I put the aileron back on so that I could make sure that the gap was even and straight. I’m using .032 aluminum, which is specified in the Bear tracks for this use.

Wingtip Strip

This is the strip to allow for the wingtip flush mount on the tip rib.

Posted on
Hours Logged This Session: 3.5
Total Hours: 1883.75

Tabitha Visits the Hangar

Today Tabitha came out and started working on her toolbox practice kit. The weather was nice, so we opened up the hangar door and let some sunshine in. I made more progress on drilling out the rivets that held on the nutplates for the wingtip screws, and started making the first strip for the wingtip support.

Tabitha Squeezes Rivets

Tabitha Squeezes Rivets

Flush Mount Wingtip Support

This is the Flush Mount Wingtip Support. Note the 1/4\

I used the snips to cut into the 1/4″ hole, leaving the original hole as the inside of the new “V.”

Flush Mount Wingtip Supports

Each cutout matches a rib flute. I had to give the strip a little bit of a bend so that it would fit the airfoil shape more naturally.

Substitute Teeth

The wingtip support strip also makes a nice set of teeth.


Drilling Rivets

Today I finally got a nice middle joining angle for the two belly pieces, on the 4th attempt. It looks fine now. I spent the rest of the time drilling out rivets on the wingtip.

I really thought that attempt number 3 was going to be a good one, but I drilled the holes too close to the edge.

Insufficient Edge Distance

Note that the edge distance is way too short on the bottom strip.

Belly Joining Piece

This joining piece is more complicated than a joggle, but I think it will help give the entire panel some good stiffness.

Ready to Rivet

I drilled, deburred, and dimpled the holes, and now it's time to squeeze a few rivets.

Squeezing Rivets

Squeezing Rivets!

If I were starting with a fresh kit, I would have probably just planned to mount the wingtips by overlapping them above the wing skin. In this case, the holes in the fiberglass aren’t quite as I would like to have them. The end result is a little bit of waviness between the screws. There isn’t anything wrong with this really, in fact it is how lots of other airplanes look. But, since I’d like to try and smooth out the waves, I’m going to do it differently. Since the holes in the fiberglass are just slightly off, it would be quite difficult to attempt to drill new holes right next to them. To solve this dilemma, I’ve decided to mount the wingtips so that the fiberglass butts up against the wing skin, with a little support strip underneath.

Wingtip Holes

Here are a few holes after I've drilled the rivets out.

Drilling out Rivets

After drilling out a few rivets, it starts to get to be pretty easy.

Fuel Systems and Brakes

Today I finished welding the elevator trim pushrods:

Before and After

Before and After



I also took an inventory of the fuel system and brakes to figure up which fittings I’ll need and how much line to use. I went back to read the Beartracks and realized that Bob recommended 5052 Aluminum lines instead of the softer and much cheaper 3003. I asked him about this and he said that he certainly prefers the 5052 because of it’s superior resistance to fatigue cracking, but that the 3003 would work fine too. He said that the 5052 was still quite workable in it’s -0 condition. I also asked him about a primer, and he said that it really wouldn’t be necessary. He used to add them to his airplanes early on, but he says now days he doesn’t even bother, especially on airplanes with an electric starter. He said that the accellerator pump used during starting can substitute instead.

Answering Questions

I called Bob today and asked him about the AN210-3A vs -3B pulleys. He said either would work just fine.

I also asked him about the braided fuel line, which is something I’ve been waffling about for a while. The issue is that the current fuel lines are braided stainless lines instead of solid 3003 aluminum lines. The braided lines are popular with the race car crowd, but they are about much heavier per foot than the same size of Aluminum wire. In fact, the weight difference of 40 feet of 3/8′ is 1.76 pounds for the AL vs 5.8 pounds for the stainless. I don’t have any doubts that the stainless tubing is up to the task, since the pressure ratings and chemical resistance are great. I am worried about the longevity of the rubber line inside of the stainless tube. Is this concern well-founded? Probably not, but I really don’t know. By using these lines does it mean that the fuel system will only last 132 years instead of 250? or does it mean that the fuel system will only last 5 years instead of 50? Racecars aren’t built for the long term- they are built to be reliable for short periods but not for long periods- but that doesn’t necessarily mean that the fuel line won’t still last for as long as I need for it to.

I have consulted several expert opinions about the tubing, so I figured I might as well ask Bob what he thought. To summarize, he said that it should probably be fine, as long as the resistance to auto fuel was good (which I would say it is). He added that it was much more expensive and much heavier and thus couldn’t imagine why anyone would use it instead of the AL. Richard’s point was that it was much easier to install than the AL tubing. If I were starting from scratch I would have stuck with the AL tubing, but since the stainless is already paid for, cut to length, and installed, I will probably stick with it for now.

Hardware Patrol

Today I continued my hardware patrol.  I have been through the entire fuselage and the control stick and have replaced and/or noted what I’ll need to get to continue.  I can definitely justify the expense of a drilling guide since I have lots of bolts that are good candidates for drilling for cotter keys.

I changed the bolt on the trim wheel to one with a hole in the shank and feel much better about it.  I removed the doors since the hinge bolts were a little bit too short.  Rather than just swapping the bolts I just took the doors all the way off so that I could get in and out easier.  I made a few bolt changes on the elevator and flap controls to account for length and/or drilled bolts.  I also went through the landing gear bolts and installed the ones with the correct grip length, now that I know how to do that.  I didn’t have the proper drilled bolts on hand but I’ll have the gear off several other times and can replace them next time.

Using the torque wrench for the first time on the Bearhawk

Using the torque wrench for the first time on the Bearhawk

I like to keep the chainsaw handy for deburring aluminum and notching 4130.  Not really!  I also managed to dump out the little tackle box full of nutplates and washers.  I picked them up but haven’t sorted them back out yet.  I’ll probably try to use household tubs with tight fitting lids since the clear tackle boxes don’t stay segregated very well.  Either way it’s a waste of productive building time and I should try not to do such things.

Nuts and Bolts

Comparing the M4 to the Bearhawk

Comparing the M4 to the Bearhawk

This morning started out with a morning of Young Eagles flights.  I got to see Buck’s Maule M-4 for the first time.  He flew 8 of the 31 kids, which was pretty amazing considering that he only had 2 seats.  He said that the max gross weight is 2300 and the useful load is about 800 pounds.  He has the same engine that we will use, though we probably won’t have the same Hartzell CS prop.  His airplane is certainly beautiful, and I can’t wait to finish ours since it will be a very capable young eagle hauling machine.  For now I just helped out with the paperwork and logisitics.

Filing the Brake Pedal to fit between the tabs

Filing the Brake Pedal to fit between the tabs

In the last entry I was starting to install the right side brake pedals when I realized that I was going to need to relocate some tools from the clubhouse.  I loaded up my home-made work bench and took it over to the hangar, complete with an assortment of tools that I will hopefully not need in the clubhouse as much as I will need in the hangar.  I had to file the attach side of the pedals a little bit so that they would fit between the attach tabs.  

I started to mount them but realized that I didn’t have the right bolts.  I have several little boxes of bolts but was surprised that none of them were the right length!  Actually, I did have several that were the right length, but they were not drilled.  Since the brake pedals and cylinders are subject to rotation, 43.13 states that they must not be secured with self-locking nuts- that means a drilled bolt with a cotter key.  Since I knew that I was at least going to need those bolts, I figured I might as well go through the rest of the airplane and see what else I will need.  Shipping from the aircraft hardware stores generally isn’t free or even cheap.

"Reserving" the hardware anywhere that I can

"Reserving" the hardware anywhere that I can

I also started to notice that some of the bolts that I had were already comitted to parts and assemblies that were temporarily removed from the airplane.  For instance, the bolts that hold the flight control cables onto the control horns were not on the airplane, but were presumably in some of those little boxes of bolts.  I made a sweep of about half of the fuselage, adding missing hardware as a way to mark it as “reserved.”  In the process, I also saw some hardware that was not installed the way that I would have installed it, so I also resolved those minor conflicts.  For instance, the rudder stop bolts weren’t really quite long enough to stick through the nylon lock nut, so I switched them out. 

The longer bolts with 1, 2, 3 threads showing.  Correction- there shouldn't be any bolts here at all.  The rudder travel is correct without any bolts.  If it was not correct, the way to adjust the travel would be by tapping the holes and threading larger bolts from the front to back.

The longer bolts with 1, 2, 3 threads showing. Correction- there shouldn't be any bolts here at all. The rudder travel is correct without any bolts. If it was not correct, the way to adjust the travel would be by tapping the holes and threading larger bolts from the front to back

This was the case in several areas, and I also saw a few “subject to rotation” applications that I would have prefered to use with castle nuts and cotter keys.

This bolt should have a castle nut and cotter key per AC 43.13

This bolt should have a castle nut and cotter key per AC 43.13.

This bolt is too short since it doesn't have a thread protruding through the nylon.

This bolt is too short since it doesn't have a thread protruding through the nylon.

I worked for 3 hours today and made notes of which hardware I was definitely going to need, which included a few small pieces, and a few big ones, like the engine mount bolts.  I was somewhat surprised to see that I didn’t have any of those, since I figured that they would have been part of the Wicks hardware kit.  So, I went to the Wicks hardware list to look and see if they were originally included.  There on the list are some AN6-46 bolts, which are about the right length and in the right quantity (5).  So either the wicks list has changed, I have the bolts somewhere else, or I don’t have them.  I repeated this same process a couple of other times, referencing the Aircraft Spruce catalog for the grip length of each AN bolt, measuring what the grip length needed to be, and sorting through drawers to try and find the right stuff.  All the while I was making a list of things to buy so that I can make one order and get most of what I need.

I have several bolts that are the right size but undrilled, so I might try and find a bolt drilling jig.  For example, I have enough -6 bolts for the landing gear that I will probably not need anywhere else.

I also noticed that on the plans Bob calls for a pulley as AN210-3A, which is equivalent to MS24566-3A.  Yet, the wicks kit included only -3B pulleys instead of the -3A’s listed on the plans.  So far I haven’t resolved this discrepancy.  The Aircraft Spruce catalog says that the -a and -b pulleys are the same dimensions but have a different type of bearing in the center.  I suspect that they are interchangable but will probably have to call Bob or someone else to figure that out for sure.  The funny thing is that in a case like this I picture an attorney questioning a witness.  “Why didn’t you use the pulley specified in the plans?”  Maybe that’s an idea for the next episode of Law and Order.  I know it’s terrible to think of it that way, but that is the image that comes to mind in this case, and also quite often at work.

Some folks say that building airplanes isn’t as hard as people make it out to be.  This is quite likely true, and an experienced airplane builder can certainly separate

Organizing and Inventory

I’ve spent a few hours this week unpacking, building workshop infrastructure items, and taking inventory.  I’m almost done adding shelves, racks, and work tables that I’ve made out of leftover building materials.  One large corner rack is enough to store the ailerons, flaps, horizontal tail pieces, and most of the other parts. 

Since Richard had not yet ordered an engine mount I requested one from Mark at Avipro back in September and just now got around to unpacking it.  I was a little bit surprised to see that it had a fifth mounting lug, and I started to wonder if maybe it was actually a mount for the 540.  It turns out that they started adding the fifth leg on the 360 mounts too, so it was the right one.  I should add that I’ve been very pleased with the support that I’ve gotten from Mark, even though I wasn’t the one who wrote him a big check.  I asked him about getting a set of brake pedals for the right side in hopes that I would be able to catch up with him at Bob’s Picnic tomorrow.  It turns out that he wasn’t going to be going to the picnic but was glad to send me some for a small charge.  While I was unpacking I found that Richard had a set already, so I had to call Mark to cancel the request.  Anyone who can put up with that kind of trouble is worthy of respect and gratitude.

While moving the small boxes with hardware from the trailer I spilled a few of the drawers and had a handful of mixed hardware.  I spent some time sorting through all of the drawers and making sure that the labels matched the contents.  I certainly don’t want to buy hardware later that I acutally had in the wrong drawer. 

I’m getting to the point now where I won’t have any excuses not to work on the airplane!  I’ve spent several hours reading Richard’s Log and the Avipro Assembly Manual to try and see where we are going to start.  I have several good starting points in mind and have also made a list of “things to be sure to do.”  Likewise I have a list of “things to buy.” 

Today I also installed a few flourescent light fixtures to help combat the shortening daylight hours.  I’m sure that the guys from Alaska wouldn’t have any sympathy for me there.