Audio Problem Finally Resolved

Today was a good day for progress- I finally got to the bottom of the last audio problem. I isolated all of the inputs from the audio amp except for the music, which works fine. The circuit is designed to use resistors to control the volume level of each channel. I gathered from the directions that anything from 30-500 Ohms would be required. When I connected the Dynon audio to the iso amp, it was just super loud, to the point of being very distorted. I figured I would give the circuit a chance by using higher resistance, without regard for any norms about what should be required. I stuck in incrementally higher values until I made it all the way up to a surprising 3000 Ohms. At that level, the circuit worked fine. I reconnected the Garmin nav output and repeated the same strategy. You can imagine how surprised I was to find that it required 68,000 Ohms! With those very high value resistors in place, everything works exactly as it is supposed to, which is a big relief.

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

Audio Troubleshooting Still

The results of yesterday’s ground problem correction were good. Everything in the system works except for the channels that go through the iso amp. I took a break from troubleshooting to install the aft 12v SAE jack, and run a few cabin wires. I installed the dimmer for the instrument panel flood lights. The dimmer came from All Electronics, but is also available from Aircraft Spruce for about four times the price.

Pulse Wave Modulation Dimmer

Pulse Wave Modulation Dimmer


The dimmer has a sub-optimal wire connection method. The back of the dimmer is potted with some white rubbery stuff, so I removed the potting in the corner where the green terminal block was attached. I cut the leads off from the block, which liberated the block itself, then used the soldering iron and needle nose pliers to remove the remainder of the leads.
Dimmer ready for new wires

Dimmer ready for new wires


Then I soldered tefzel wires into the holes where the terminal block used to be. One wire comes in from the fuse (which is on the battery bus), then one goes to the central grounding point. The other two go to the front cabin flood light. The light in the back is controlled by a switch near the right rear passenger headsets, and it is on or off only, no dimmer.
The front light is selectable as red or white, with the switch that is right next to the light. I took the output from the dimmer to the center post of the switch, then took the red input from one end post and the white input from the other post.

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Hours Logged This Session: 10.2
Total Hours: 1883.75

Audio Troubleshooting Continued

The audio problem still continues. The good news is that today I have a better troubleshooting plan, thanks to the AeroElectric list. The most frustrating thing about this problem was that I just didn’t have a good plan for how to isolate the problem. One list member suggested pulling all of the pins out of the connectors, and assembling them one circuit at a time to try and isolate the problem. First I removed all of the wires coming into the intercom except for the front left seat. That didn’t fix the problem. Next I used little alligator clip test leads to connect the left front seat input on the intercom directly to the headset plugs, bypassing the aircraft jacks. The problem was gone! I reconnected the airframe microphone jack on the front left, and the test was still good. I reconnected the audio jack on the front left, and the problem came back. A little bit of investigation led me to the problem- the audio jacks weren’t grounded. This happened through a series of events. First, our project’s previous owner had connected the audio jacks without any ground wires. He was planning to ground them through the airframe, as was I. While microphone jacks must not be grounded to the airframe, audio jacks can be. Some time later, I learned that while the audio jacks may be grounded via the airframe, it’s better if they are not. When I learned that, I drilled the holes to a larger diameter and installed insulating washers like the ones on the microphone jack. The only problem is that I didn’t come back after the fact to add a ground wire connection. The good news was that the shielded audio cable had an extra conductor available, so I was able to add the ground by shortening the cables a few inches on each end. It took me several hours to perform this soldering surgery, but as of the end of today it’s all ready to plug in and test. I’m just glad to have it figured out.

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Hours Logged This Session: 6.6
Total Hours: 1883.75

Instrument Label Planning

This evening Tabitha and I both came out to the hangar so that she could see how the panel is coming together. We worked some on making a list of labels that we’ll need for the panel. I plan to use a label printer that we have on hand, at least at first. We may decide to make some changes to the labels, so I want to be able to make those changes in-house.

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Hours Logged This Session: 2
Total Hours: 1883.75

Audio Troubleshooting

Today the audio troubleshooting continues. First I swapped the power supply. My fancy battery charger has a “power supply” mode, so I had been using that for test power. Just in case that was related to the audio problem, I installed a temporary SLVA battery and tested again, with no change in results. I tried removing the plug from my audio amplifier circuit with no change. I didn’t have many other ideas for troubleshooting the audio right then, so I moved on to configuring the avionics to talk with each other. It was pretty neat to be able to see the course change on the 430 by turning the knob on the HS34. I connected a GPS antenna to a length of coax, then tossed the antenna out through the gap under the hangar door. After a few minutes, the GPS found itself, which was also quite rewarding.

First Fix

First Fix


I also finished replacing the ELT remote antenna, since it took me until now to get the replacement battery lined up.

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Hours Logged This Session: 2.4
Total Hours: 1883.75

Removing Masking Tape

Tabitha especially enjoys removing masking tapes, so we both came out today and finished removing the tapes from last night’s paint session. She compares it to unwrapping presents.

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Hours Logged This Session: .5
Total Hours: 1883.75

Spraying Blue on the Tail Pieces

This afternoon I was able to get the correct combination of software, drivers, and cables to update the firmware on the Dynons. The D100 had been in service before, so it was only a few versions old. The D180 was factory new, and the firmware was very old. I also updated the HS34. Then I cleaned out the paint booth and taped the horizontal tail pieces for blue paint. I sprayed those in blue, cleaned the gun, and left after dark again. Some of these paint nights tend to run pretty late.

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Hours Logged This Session: 6.5
Total Hours: 1883.75

Reinstall Intercom

I was feeling pretty good about my wiring, right up until I hooked up the intercom. All of the audio is just really weak. I did a little bit of troubleshooting before tabling that problem, pending more research. I installed the aft dome light, which will be able to serve either the baggage area or the back seat. When I installed the tab to support that dome light, I wasn’t planning on covering the ceiling the way that I did. In retrospect, I would have rather had the tab on the lower tangent of the tubes, rather than the upper. As it is now, the base of the light is under the fabric.

Dome Light

Dome Light


I also spent a little while pulling off the masking tapes from the last load of white paint parts.

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Hours Logged This Session: 2.4
Total Hours: 1883.75

Powering Up the Avionics

I started today by preparing and painting the tailwheel spring. I suspect that the paint will be somewhat short-lived on this part, but if it starts to come off, I’ll just paint it again. I cleaned off the light surface corrosion and applied a flat black rustoleum.

Preparing the Tailwheel Springs for Paint

Preparing the Tailwheel Springs for Paint


All of the tailwheel parts were ready to assemble, so next I put them together.
Tailwheel Assembly Parts

Tailwheel Assembly Parts


Assembled Tailwheel

Assembled Tailwheel


I also picked up a nice grease gun from Amazon to use on the various grease fittings.
Grease Gun

Grease Gun


When I mounted the tailwheel and spring, I used 39 foot pounds on the big bolt. Mark G had this bolt come loose once, so I made an extra effort to make sure that it was installed correctly. I found that I had to grind a slight bevel on the aft end of the spring to clear the weld fillets on the tailwheel body.
Installed Tailwheel Assembly, minus wheel and tire.

Installed Tailwheel Assembly, minus wheel and tire.


Next I reinstalled the instrument panel, with its fresh paint. That made a few easy tasks available, such as installing the annunciator lights, headset jacks, and switches.
Bearhawk Instrument Panel

Instrument Panel Progress


Back when I wired the Garmin boxes the first time, I separated the multiple power inputs to separate fuses. In retrospect Bob N. recommended that those two power leads be combined to a single wire and fuse, so I made that change. I installed each of the avionics boxes, connected them, and powered them up for a test in unison. Did you know that the ELT remote has its own little battery? I sure didn’t, until someone happened to mention it in passing. Since our ELT has been sitting on the shelf for a little bit longer than initially expected, I thought it prudent to replace the battery now.
ELT Remote Battery

ELT Remote Battery


I was glad to see all of the panel lit up, and no smoke released. I’ve been using this battery charger in its “supply mode” to power the electrical system for this sort of testing.
Bearhawk Instrument Panel

Bearhawk Instrument Panel


The intercom is the only remaining box that isn’t installed at this point. Tomorrow I’ll start with testing.

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Hours Logged This Session: 8.3
Total Hours: 1883.75

Painting White Pieces

This afternoon my Mom was in town again, so she helped by adding the masking paper to tail pieces. I use 3M fineline tape to mark the final edge, and then use regular cheap masking tape to hold masking paper onto that tape. It can be a little bit confusing sometimes to make sure that we mask the correct color section, especially since these are all smaller parts that are going to come together to make the final scheme.

Masking Paper

Masking Paper


While she did that, I added rivets back on to the inspection covers and reassembled the paint gun. The inspection covers came with universal rivets, but I took them apart to switch them to flush rivets.
Inspection Covers with Flush Rivets

Inspection Covers with Flush Rivets


This also allowed me to prime both sides of the retaining spring to help prevent corrosion. I also added rivets to the hinge on the door skin that will support the mouse door.
Mouse Door Hinge Rivets

Mouse Door Hinge Rivets


After a late lunch break I came back and painted white Aerothane on the inside of the door skins, the tailwheel fork, the tailwheel body, the elevator, horizontal stabilizers, and tiedown rings.

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Hours Logged This Session: 4.5
Total Hours: 1883.75

Rudder Pedal Changes

Yesterday’s efforts to strip the tailwheel fork were not fruitful. The abrasive that I was using was too fine and the coating was too tough. Today I was able to remove it with the die grinder and a scotchbrite wheel. I had previously painted the rudder pedal assembly, and while it turned out quite nicely, there was just an engineering change that suggested additional welding. I did that welding today, then prepped the welded portions for paint. In this round of priming I sprayed the other side of yesterday’s parts, plus the tailwheel fork, and the rewelded rudder pedals.

Posted on
Hours Logged This Session: 3.8
Total Hours: 1883.75

Another Round of Primer

The weather today was good enough for priming, and I finally have a big enough pile of parts ot make it worthwhile. I etched all of the parts and the instrument panel, then primed them.

More little parts to paint

More little parts to paint


On the items that will need both sides painted, I only painted one side today.

Still More Fuselage Reassembly

Today I tied up a few more loose ends of wires. I started with the ELT remote. The remote uses a cable that looks just like a phone line. I wanted to shorten it, so I clipped off the old end several months ago. This also made it much easier to fish the cable through grommets on the way back to the ELT. Today I crimped on a new end. Then I returned to the instrument panel and countersunk all of the holes that I drilled yesterday.

Countersinking the Dynon Trays

Countersinking the Dynon Trays


These angles hold the Garmin trays in the panel

These angles hold the Garmin trays in the panel


I riveted the trays to the panel with -4 rivets, then worked on the window frames. I deburred those and started making the covers for the inspection holes in the horizontal stabilizer area.
Front Stab Cover

Front Stab Cover


Right rear stab cover

Right rear stab cover


Both of these will need slots that will allow them to come on and off without removing the horizontal stab. Note from the future: I have since learned how to use a shrinker, and I could have made a nicer inspection panel by shrinking the edge a little. I also wish now that I had made the hole on the right side a little bit further up vertically, and/or made a similar size hole on the other side too. It turned out that connecting the elevator and trim mechanisms was pretty tricky with this arrangement.

Fuselage Reassembly Continued

It’s nice to have enough painting done so that I can start putting things together again. This morning I started with the firewall. When I painted the fuselage, I just balled up the wiring and wrapped it in a plastic bag. Today I untangled that big ball and started reconnecting the connections on the firewall. I disassembled the instrument panel, which involved removing the avionics racks from the panel blank itself. Those were drilled to #40 size and held together with clecos, so I drilled them to final size and deburred the holes.

I’ve never been very happy with Dynon’s mount for the HS34. The problem is that the holes are already drilled in the flange. The shape of the bracket makes it impossible to match drill the bracket to the instrument panel, which in turn makes it impossible to get a good hole location in the panel. If the flange were not drilled at all, then I could drill from the panel side and everything would match up. While I was at the Sebring LSA expo back in January, we had stopped by the Dynon booth to look at their displays, and I noticed that their display panel had a box-style mount for the HS-34. I was immediately excited and asked where I could buy one. It turns out that the mount is actually the one that they sell for the autopilot module, and I was able to order one.

Dynon's mount for the HS34

Dynon’s mount for the HS34


Dynon's mount for the AP74

Dynon’s mount for the AP74


The AP74 mount will require some modification in the back to make room for the connector, but I’ll do that later.

Reinstalling the Landing Gear

This morning I used a little bit of fuel in a steel bowl to clean the old grease out of the wheel bearings. Then I packed them with fresh Aeroshell grease and put the wheels back together.

Cleaning out the old grease

Cleaning out the old grease


Here's the bearing number in case I need it later

Here’s the bearing number in case I need it later


While I had the wheels in my hand, I checked to be sure that they would fit in the wheel pants that I picked up last summer at Oshkosh.
The tires fit in the wheel pants

The tires fit in the wheel pants


If only it were this easy!

If only it were this easy!


I’ll have to figure out a mounting bracket for them, but I might just wait until after the plane is flying.
With the plane back on its main wheels I pulled off the remaining masking tapes in the fuselage. Then I started working on a few remaining wires in the cabin. I cut out the inspection holes and installed the rear seat intercom jacks. I connected the static ports to a tee fitting in the middle of the fuselage and added some an adel clamp to hold it in place. Then I made an adjustment to where the ELT mounted. It mounts to a little piece of floorboard that sits aft of the cabin on the right side. I moved it as far aft as it would go, then riveted the bracket in place. That bracket had originally been attached with screws.

Preparing for Landing Gear Assembly

This afternoon I finished assembling the cargo door latch that I started yesterday. I also made a little aluminum plate that will cover the center of the mechanism, hopefully reducing the odds of getting a finger caught in there on a cold and windy night somewhere. Then I drilled the holes in the front cargo door to final size and deburred the holes in the frame.

I have noticed that when I had #40 holes in these parts, there were a few little bits of steel chips that I could hear
rattling around in the tubes. When I enlarged them to #30, the holes became big enough to evacuate those little chips by shaking the frame around with the holes pointed down.

Next I reassembled the main landing gear shock struts. I had taken them apart to paint the strut tubes, and to inspect Richard’s work. I figured it wouldn’t hurt to replace the automatic transmission fluid while I was at it, since the old fluid had been in there for a few years now. Isn’t it amazing how this 2-year project is going on 4? And to think, that’s after Richard had been working on it for a few years. I can completely understand why he decided to not continue with construction. One has to really enjoy this process in order for it to be worthwhile.

I set out all of the parts to reassemble the landing gear, in part to make sure that I had all of the right pieces, and in part just because it was fun.

Landing Gear Hardware

Landing Gear Hardware


Also, the axles had picked up a little bit of surface rust after being exposed for a while, so I polished them with a green Scotchbrite wheel in the die grinder.

Assembling Parts

One important mental changeover is switching from a temporary assembly mode to a more permanent assembly mode. In the past, I knew that anything that I put together was going to have to come apart again. Now I’m starting to assemble some parts that will probably be together until at least the first flight. Today I assembled the control sticks, rudder pedals, and rear cargo door latch.

Control Stick Assembly

Control Stick Assembly


I used the die grinder with a scotch brite wheel to clean the paint off of the part of the cargo door pins that will go into the fuselage holes. This should help keep them from binding.
Cargo Door Latch

Cargo Door Latch


I wasn’t able to paint today, but it was nice to take a break and do some relatively easy assembly, or I guess more accurately, reassembly, since all of these parts have been together plenty of times before.

Spraying the Interior

I’m thankful for being able to spend some serious hours in the shop this month. Today was a good painting day, at least in the afternoon, so I spent the morning wrapping up a few more prep tasks on the fuselage interior. I couldn’t come up with an easy way to mask the floor area. Then I had the idea of using the floorboards. After all, they are cut just to the right shape. I didn’t want them to get covered with overspray, so I masked them with a very thin plastic sheeting.

Floorboards as masking

Floorboards as masking


The fuselage was ready to spray, but it still wasn’t quite the warm part of the day yet, so I started preparing the horizontal stab and elevator for their white coat. Our paint scheme uses Bob’s measurements on the rudder and vertical stabilizer, but instead of painting the horizontals white, we put the same type of burst scheme on the top and bottom of those surfaces too. To make them look harmonious, I measured the overall perimeter of the rudder, then the overall perimeter of the elevator. Not surprisingly, they are actually very close to each other, within a few inches. I applied a small correction factor to the measurements, and assembled the tail pieces to lay out the stripes.
Something about this arrangement makes me think of DaVinci.

Something about this arrangement makes me think of DaVinci.


This is a really critical step, since the final paint scheme will fall where these tapes fall. I spent a couple of hours getting both sides of the stab done, then added paper to a couple of the pieces. I was out of time and paint booth space for today’s round, so I stopped there and sprayed Juneau White Aerothane on the interior, both trim tabs, and the left elevator. Then I cleaned the gun, which is a ritual that is becoming more and more familiar. I sit on the paint booth floor with my space man mask and white bunny suit and clean each of the pieces right away, since I won’t have any way to get the paint off of them after a day or two of sitting.

Prepping the Interior

The fuselage paint has had plenty of time to crosslink, so today I started masking so that I can spray the interior. I
didn’t spray it back when I was spraying the white on the outside of the fuselage, in part because we hadn’t decided on the interior color. In retrospect it would have been easier to spray all of the white at once.

Masking the outside of the fuselage

Masking the outside of the fuselage


A few other tasks today included putting wheels on the bottom of the fuselage rotisserie so that I can move it by myself. I don’t know why I didn’t do this sooner! I also prepared the wing tiedown parts so that I can paint them in the next round of primer.

Painting Little Parts

I’m taking advantage of this relatively warm weather to get as much painting done as possible. Today was a long but productive day that started with getting the ailerons and right flap safely stored in the ceiling.

Storing the painted parts

Storing the painted parts


The rudder is looking festive

The rudder is looking festive


I covered those parts with plastic to protect them from dirt and overspray that might escape the booth.
Yesterday I wrote about the Sprayfine gravity gun. Today I learned about the packing nut that seals the needle. It was leaking pretty bad on my last round and I had to switch back to the Graco gun. I noticed that several of the o-rings in the gun were not holding up well, so I wondered if the leak was from those. I called the company to ask their tech support folks. The most surprising aspect of that call is that the person who answered the phone also answered my question. There was no menu structure, no receptionist, just a knowledgeable person on the phone. He said that any o-rings in the gun should be removed, as it was designed to function without them. I’m not sure how it is that I ended up being the person to have to remove them, but I was just glad to get the gun back up and running with no downtime waiting for parts. It turns out I just needed to tighten the packing nut a little. The supplied wrench for removing the nozzle was designed to also work on the packing nut, but due to manufacturing tolerances the slot wasn’t quite big enough. I fixed that with a dremel, but soon found that the metal that the wrench was made of was a little too soft to be effective. Instead I just started keeping a small crescent wrench in the paint booth with the gun tools.
Starting the next round of prep

Starting the next round of prep


The next round of parts included the lower door frames, rear cargo door frame, one of the upper front window frames, some of the rudder cable guards, the rudder pedal assembly, the control sticks, the seat adjustment levers, the flap handle parts, one of the wing struts, and likely a few others that I’ve forgotten about. After painting an airplane, the number of parts becomes especially apparent!

Blue Paint for the Rudder

Today I moved the fuselage out of the paint booth. In the cool hours of the morning I finished drilling the rear cargo door skin holes to final size (#30) and prepared the rudder and right flap for painting this afternoon.

It looks great out in the sun, especially from this far away.

It looks great out in the sun, especially from this far away.


I also have a new paint gun to try. The previous coats have been with the Graco that came with the HVLP that I was able to borrow. The Graco gun is certainly nice, but is a suction feed cup, which is under the gun. By design, there is quite a bit of unusable paint with each batch. I found a reasonably priced gravity-fed gun to try. It’s sold under the “Sprayfine” brand from Turbine Products. After taking apart the gun, I can see that it is made with less quality when compared to the Graco. This is probably why it sells for so much less. For example, parts on the Graco were plated after machining, but several parts on the Sprayfine were plated and then machined. I deburred a few pieces so that they will be less likely to catch bits of paper towel as I clean the gun.

When it warmed up in the afternoon, I sprayed the blue paint on the rudder and right flap. The left flap wasn’t ready to paint yet because I have to stripe it when I stripe the left wing.

Spraying the Fuslage Blue

This afternoon the weather was finally good enough to paint again. I sprayed the blue coat on the fuselage, then removed the tapes to check for problems.

It looks great with the tapes off!

It looks great with the tapes off!


The paint ran under the tape a little at each point where the pinked edges intersected the tape seam. I was able to remove the larger part of these with MEK, since the blue had not yet cross-linked.
Bleeding under the masking tape at the fabric tapes

Bleeding under the masking tape at the fabric tapes


Just to exhonerate the 3m fine-line tape, the same thing happened under the vinyl registration number mask.
I also got a little bit of bleeding under the vinyl mask.

I also got a little bit of bleeding under the vinyl mask.


They end result is far from perfect, but it certainly meets my goals. I’ll just not be able to park right next to Dave or Georg!

Firesleeve Clamp Tool

Today was a short session, but I wanted to try out my new tool for installing the steel bands on firesleeve ends. It came from Aircraft Spruce, but is branded as a CV joint band tool. This is it from Amazon.

It works very well.

Door Frame Preparations

It has been too cold to paint, and I haven’t been spending many hours in the hangar. Today I finished cleaning up the tiedown rings, and started drilling the door skins and frames to final size. They were all drilled to #40, but I’m planning to use 1/8″ rivets to hold the skins on the frames, so I started drilling them out to #30. Today I did the right front top and bottom, lower left door, and started on the rear cargo door. The larger holes made it much easier to shake out the little chips of steel that were rattling around in there.

Making Tiedown Rings

I have always had some reservations about the durability of our Maule tailwheel, so when Georg was selling his lightly-used Bob-designed tailwheel for a good price, I was glad to buy it. Today I did a trial fit to the spring to make sure it would fit, then disassembled it. I’ll paint it white to match the fuselage, and to promote crack detection.

Tailwheel Assembly

Tailwheel Assembly


This wheel uses a 10-inch tire, so I took this picture so that I could remember the tire size, which is 10×3.5-4.
Tailwheel tire size

Tailwheel tire size


The tiedown rings are intended to mount to the bolt that holds the top of the strut to the wing. I started with mild steel 1/4″ rod, which I heated and bent around a piece of scrap steel that was about 1.5″ in diameter.
First Bend

First Bend


Rather than fight with a small piece of metal, I just added the second bend right on to the first. It was easier to do with more straight stock to hold on to.
Second Bend

Second Bend


I made the flat plates out of 4130, and as you can see, I left the 1/4″ rod a little bit long for the welding. That makes it a little bit easier to control the heat at the end of the bead.
Welded Tiedown Rings

Welded Tiedown Rings


I’ll still need to drill the holes, but that will have to happen on another day.

Posted on
Hours Logged This Session: 1.8
Total Hours: 1883.75

Wingtip Prep

It was too cold to paint today, but I was able to work on preparations for the wingtips. I filed some of the filler off, and also cut out the aluminum skin on the front cargo door for its window.

Fuselage Blue Prep Continued

This afternoon I continued with preparations to the fuselage for the next coat. This kind of work is more time consuming and tedious than I had anticipated. Since I’m painting in parts, I have to make sure that all of the stripes are located very precisely. We decided to use a pattern as follows: starting from the blue top, next we have a 2″ white stripe. Then there is a 3/4″ blue stripe, then all white. This pattern is very similar to Peter Stevens’s N27PS, and is essentially the standard “Bob” stripes minus one. I started by establishing the 2″ stripe, since I can measure everything else from there. My goal was to make the stripe parallel to the split of the front windows, and to have the stripe arrive at the engine cowling right at the air inlet.

Horizontal Stripe Reference

Horizontal Stripe Reference


As you can see in the picture below, I did quite a bit of head scratching to figure that all out. I temporarily installed the front windows to mark the location of the split. I used a copy of the early Beartracks issue where Bob lists his measurements for the stripes he used, and also had a copy of the 2013 Bearhawk Calendar handy so that I could reference Zane’s picture of N27PS.
Stripes get complicated

Stripes get complicated


I decided to use a paint mask from Higher Graphics for the registration numbers. Our numbers are a simple block style, which we chose to compliment the vintage-like lines of the Bearhawk. I didn’t realize it until I read Russ Erb’s observation about it, but the aesthetic cues of the Bearhawk fuselage and tail remind me of older airplanes. Maybe that’s part of why it looks so appealing to me. I’m sure I could have made the numbers out of tape, but using this mask kept the numbers all consistent and parallel. I located them with consideration for the horizontal stabilizer and cargo door, but still ended up with some of the last “B” on the cargo door. For a while it will be TP instead of TB. I followed the directions that came with the mask, and it all went exactly according to plan. First I sprayed the area with a mist of water, then I taped the top of the carrier sheet in place with the backing still on. That held the numbers in the right spot.
Applying the Mask

Applying the Mask


From there I was able to reach up from below and remove the backing, thus applying the adhesive of the letters and the carrier sheet onto the fuselage side. Once the letters were stuck, I just peeled off the carrier sheet and here is the result.
Right Side Registration Number Mask

Right Side Registration Number Mask


Left Side Registration Number Mask

Left Side Registration Number Mask


While this stage is tedious and quite consequential to the end result, it is also a phase with lots of visual progress.

Fuselage Blue Prep

Today I removed the masking tapes from the fuselage, and started adding paper to the front end of the fuselage for the upcoming blue painting. Here’s the result of the taping:

Vertical Stabilizer

Vertical Stabilizer


Registration Number Area

Registration Number Area

Spraying White on the Fuselage

This afternoon my Mom was in town, so we all came out to the hangar to get a few things done. They helped me move the fuselage into the paint booth. I later learned to put wheels on the front wood pieces, but back then it was still a three person job. After they left, I sprayed the white paint on the fuselage and one of the struts, and also did a little bit of touch up on th the elevator trim pushrod and main landing gear where I had missed some spots. I painted the bottom of the fuselage, the white stripes on the vertical stab, and most of the sides of the fuselage. My usual back-taping strategy was too complicated on the fuselage sides, in part because of the registration numbers and in part because of the horizontal stripes.

Spraying White Parts

Here’s a picture of yesterday’s masking work:

Vertical Stabilizer Masking

Vertical Stabilizer Masking


This afternoon I cleared out a few small parts to make room for the fuselage. Today’s parts include the main landing gear legs, shock struts, rudder, right flap, elevator trim pushrods, tailwire brackets, and the right hub cap.

Laying out Fin Stripes

Today we both came out so we could get the wing moved out of the paint booth.

Wing in the Sun

Wing in the Sun


Tabitha removes the last few tapes

Tabitha removes the last few tapes


Then we spent a while laying out the white stripes that will go on the vertical stabilizer and rudder. We’re using Bob’s measurements so that our stripes will match his, but even with those measurements it was still fairly difficult to get the tapes to sit where we wanted. The complex curves near the front base of the vertical stab make for some strange taping patterns.

Organizing

Today I organized the hangar for a while and finished cleaning up from the previous paint jobs. This included cleaning up the big piles of paper and masking tape and reassembling the paint gun. It has been surprising to me to see the amount of garbage that covering and painting generate.

Wing Blue Paint

Today was a fun day, removing the tapes from yesterday’s paint. It’s nice to see the two colors together with crisp lines.

Painted Right Wing

Painted Right Wing


Tabitha and my dad both helped. We also removed the tapes from the fuselage, since I won’t be spraying any more silver.

Spraying Blue on the Right Wing

Today I carried on with the spraying theme. I put the new tapes on the top of the wing in the morning, and then wet sanded that second coat of Polyspray. Later in the day when the temperature was back up I sprayed the final coat of Polyspray, then sprayed the blue paint on the right wing.

Fuselage silver is done

Fuselage silver is done

Second Coat of Polyspray

This afternoon I did a little bit more prep and sprayed the second coat of Polyspray on the fuselage, landing gear, rear seat back, scrap panel, and the patches on the tops of the horizontal stabilizer.

Wing white paint

Wing white paint


I also removed the tapes from the right wing and started taping for the blue coat.
Taping for the next coat

Taping for the next coat

Sanding the Fuselage

Today I had a visit from local EAA friend Skip. Skip is thinking about building a Bearhawk LSA and wanted to try some welding practice. While he did that I sanded the fuselage Polyspray, ironed down a few bits of tape that lifted, and in general got ready to spray the next coat.

White Paint on the Right Wing

As promised, I added paper and masking tape to finish preparing the right wing for spraying.

Ready for white paint

Ready for white paint


Then I sprayed the first of our Aerothane. I learned several things, some of which I’ll include here. First, I set up the fresh air box inside the hangar, near the HVLP turbine. This was acceptable, but it makes much better sense to put it outside and upwind. Next, the paint both that I built really isn’t big enough to comfortably paint the wings. It’s 10 feet wide, and the top arches are made with two 10-foot pieces. If I were to do it again, I would have made it wider, taller, and longer. Each bay should be 4 feet long, but I used 1/3 of 10 feet, since I was trying to minimize waste in the 10 foot lengths. Here are a few more lessons from later sessions that I’ll include here for easier organization and reference. First, standing or sitting on the fresh air hose will greatly diminish the flow of fresh air, and as such, is a bad idea. Also, the hose can become kinked if it gets twisted around very much. On the topic of diminished flow of fresh air, I also found out by experience that leaving the air compressor switch on is a bad idea. Since the paint booth uses two lights, a big fan, the HVLP turbine, and the fresh air box, our limited electrical circuit can’t handle much more. When I forgot to turn off the compressor, all was well until it leaked down enough to turn on. The lights dimmed, the fans slowed, and a few seconds later the breaker tripped and it all shut off. This is problematic in the middle of a paint job! Finally, it’s a good idea to keep plenty of extra clean gloves and rags in the booth, since the gun cleaning process usually consumes one or two.

Polyspray on the Fuselage

This morning Tabitha came out to help with laying out the masking tapes on the right wing. We are planning to only paint the areas that are going to show, so instead of painting the whole wing white and then masking off the blue areas, we’re going to mask off the white areas, spray white, then mask off those areas, and spray blue. This will require more labor and tape, but it will save weight and paint. Weight and paint are more expensive than labor and tape at this point. We applied the fine line tape, which establishes where the lines will be. Later I’ll come back later and finish with cheap masking tape and paper. I took the ends off of the wing struts so that I can paint them while I have the white paint mixed. After lunch I came back and sprayed the first coat of Polyspray on the fuselage.

Polyspray on the fuselage

Polyspray on the fuselage


This picture also shows the section of the back seat that I mentioned earlier.

Wing Paint Prep

While the Polyspray is drying a little I worked on wing preparations. I built the left wing rotisserie so that I could get the wing off of the rack, and made a few parts for the pitot tube mount. I’ll see if I can get my friend Alan to weld the aluminum parts, since that will make for a nice lightweight and simple mount. I started sorting parts into various buckets for painting the different colors. Now that the primer is on the right wing I installed the inspection covers. Our stripe scheme is going to be complicated enough that I’m going to paint with the panels in place. Finally I set up the fresh air supply and HVLP turbine and made sure that they both work.

Last Polybrush

The pile of empty cans is getting bigger and the pile of full cans is getting smaller! Today I did a little bit of touch up ironing and sprayed what will hopefully be the last of the Polybrush on the fuselage and landing gear.

Spraying the Fuselage

This afternoon I finished the last bit of heat smoothing in the interior. I had to add a little bit more reinforcing tape to one spot on the left side of the cabin where the large window is. That’s a complicated transition and a seam in the fabric makes it more complicated than it should be. The extra tape will help. I spent a few hours applying masking tape to the areas that I’d rather not have to clean off later.

Ready to spray

Ready to spray


Then I sprayed the first coat of Polyspray on the fuselage and landing gear.
First coat of Polyspray

First coat of Polyspray


I’m also spraying the exposed portion of fabric on the back seat, and a 3×3 foot swatch of spare fabric that I’ll prepare for emergency patches.

Interior Smoothing

I only had a few minutes to work today, but I was able to finish the smoothing on most of the interior. All that remains is the left side of the baggage area.

Fuselage Smoothing

Today I finished heat-smoothing the exterior of the fuselage and one side of the interior. I found that the iron shoe was getting pretty gummy with baked-on Polybrush, so much so that MEK wasn’t really getting it off. The green scotchbrite pad in the die grinder worked pretty well though, and left behind a nice polished finish. I also removed the elt bracket from the floor panel that goes aft of the rear cabin bulkhead. I’m planning to move it to the back of that panel, so that I’ll have a place for my feet in case I ever try to sleep in the cabin.

Repairing the Small Iron

One downside of using model airplane irons to smooth covering imperfections is that they really aren’t designed for that kind of pressure. I’ve damaged a few of them now. This wooden handled iron failed right in the very thin spot where the shoe top joins the handle.

Failure Point

Failure Point


To reinforce that area, I brazed in a small piece of steel tube that would fit inside of the cheap stamped and rolled handle.
Brazed Reinforcement

Brazed Reinforcement


I spent a little bit of time at the grinding wheel to clean it up:
Brazed Reinforcement again

Brazed Reinforcement again


Then I reassembled the iron and tried it out. It works much better now, since I can transmit plenty of smoothing force onto the covering without worrying about damage to the iron’s neck. Next I installed and top coated the few remaining fuselage reinforcement tapes. The next important task was to come up with some way to support the back end of the fuselage. So far I’ve just been resting the back end on the strong structural points, but that’s not going to be an option when I start spraying the covering products, since those areas will be wet. Instead I used some scrap 1.5′ square tubing to make a stick that will bolt to the tailwheel spring attach points.
I added a zig and a zag

I added a zig and a zag


Then added the spanwise brace that catches the AN4 bolts.

Then added the spanwise brace that catches the AN4 bolts.


This little tailspring substitute looks like it will work quite well.

Still More Fuselage Tapes

A full day of adding fabric reinforcing tapes to the fuselage has just about finished that process. I have just a few left to do.

Fuselage Bottom

Fuselage Bottom


Interior Ceiling, Fuselage is upside down

Interior Ceiling, Fuselage is upside down


After applying the last of the 1″ wide reinforcing tapes, this is how much I had left on the roll.
Not much extra!

Not much extra!


Fuselage right side

Fuselage right side

Priming the Right Wing

This morning I added some fabric tapes to the right side of the fuselage, then prepared for a round of priming.

A few small parts

A few small parts


One big part

One big part


Since we have a complicated striping pattern, I’m priming the access hole covers now, so that we can apply the top coats with them in place.

Wing Masking

Since I’m not planning to paint the wing root, tip, or trailing edge areas, I added some masking paper and tape to block them off.

Masked wing root

Masked wing root


Masked trailing edge

Masked trailing edge


I finished the metal prep on the top of the wing:
Still wet, but very clean

Still wet, but very clean


Then I moved it into the paint booth with some help from Tabitha, Danny, and Jeff. I finished the day with a little bit of heat smoothing on the main landing gear legs.

Wing Preparation

Today I continued with paint prep for the right wing, while Tabitha worked on more fuselage taping.

Right Wing Prep

Right Wing Prep

Wing Rotisserie Continued

Today we were both back out at the hangar. Tabitha continued with adding tapes to the fuselage, while I continued with getting the right wing onto the rotisserie. Here’s what one end of the rotisserie looks like. The double 2x4s stick into the wing by at least two center ribs to spread out the load. The lag bolt in the center is long enough to go through the double chord-wise 2x4s.

Wing Rotisserie

Wing Rotisserie


Here's the other side, though I still need to cut off the too-long spanwise 2x4s so that they will clear the a-frame.

Here’s the other side, though I still need to cut off the too-long spanwise 2x4s so that they will clear the a-frame.


The wings sure are dirty! This is a picture of the bottom even.
Dusty wing

Dusty wing


I taped the inspection holes to keep the various solutions out of the inside of the wing.
Temporary hole covers

Temporary hole covers


The process is to first wash it with the Polyfiber alkaline cleaner and a fine scotchbrite pad, then a phosphoric acid-based etching compound. The biggest hassle has been removing the residue from the plastic adhesive that had been on the aluminum to protect it from scratches. There were several very small spots that became obvious after etching, since they were still shiny when the rest of the aluminum is dulled slightly.
Clean wing bottom

Clean wing bottom


Here’s a before and after on the top of the right wing.
Half clean wing top

Half clean wing top


While I did that, Tabitha worked on taping the right side of the fuselage.
Tabitha taping

Tabitha taping


Eventually Felicia came out for a visit too.

Eventually Felicia came out for a visit too.

Wing Rotisserie

Tabitha came out today to help get the right wing ready to go on the rotisserie. That involved riveting the tip rib back onto the skin, since I recently drilled those rivets out to remove the flush mounting strip.

Tabitha the riveter

Tabitha the riveter


My strategy for getting the wing onto the rotisserie was to start with it on sawhorses.
Wing goes here

Wing goes here


She helped me move it there, then started working on the fuselage top tapes while I worked on the rotisserie.

Paint Booth Details

Previously I wrote about building the paint booth, but today I added the airflow system. There was an old furnace under our house that had a nice big blower. I spent some time under there with the reciprocating saw and extracted it for the paint booth.

Dusty Blower

Dusty Blower


A couple of 2×4 scraps and a stub of electrical wire brought it back to life.
It works!

It works!


My plan is to use that blower to pull air out of the booth, and this large stand fan to force air in.
First I tried just pointing the fan at the filters

First I tried just pointing the fan at the filters


The airflow was pretty good with having the fan just pointed at the filters, so I didn’t bother with anything else. I stopped by the Sherwin Williams store to pick up some paint can lids with pour spouts (nobody else seems to have them) and looked in the clearance corner. They had this nifty stick-on zipper for $10, which seemed worth a try.
Adhesive zipper

Adhesive zipper


I wish I'd gotten two!

I wish I’d gotten two!


The hole in the end won’t be big enough to get the large pieces like the wings and fuselage in, those movements will be fairly infrequent. Next I marked the lines and precoated for tapes on the top of the fuselage.
Ready to tape

Ready to tape


It’s not easy to mark a line parallel to a curving stringer! Fortunately accuracy isn’t super critical for these lines.

Inspection Rings and Tapes

Note from the future: I had to add several more rings than you see here. For example, I had to add another hole in the top of the cabin, another three or four holes in the tail area, another on each landing gear leg, and that’s not to mention that I forgot to account for the elevator trim horns all together. If you are deciding where to put rings, I would suggest making a visit to a flying airplane with a similar configuration to yours to take detailed notes about where they need to be.

The elevator halves join behind fabric, and I think it will be much easier to get in there to install and inspect those bolts if I have an opening that’s larger than the usual ring. I made a larger rectangular ring for the right side, but used a standard round ring on the left. The round ring will use a spring cover, while the right ring will use nutplates and screws.

Custom Inspection Ring

Custom Inspection Ring


I also embedded a small piece of aluminum in the tail. I’ll rivet the dataplate to this plate after painting.
Data Plate Mounting Pad

Data Plate Mounting Pad


Left Rear Inspection Rings

Left Rear Inspection Rings


The interior will need inspection rings near the headset jacks.
Interior Inspection Hole and Tapes

Interior Inspection Hole and Tapes


More Interior Tapes

More Interior Tapes


Tapes, tapes, and more tapes!

Fabric Taping

Now it’s time to start down the long road of reinforcing tapes. I started with the round doilies for the inspection rings. I found a good deal on some of these fancy pinking shears:

They cut a continuous line and are very well suited for these shapes.

They cut a continuous line and are very well suited for these shapes.


Danny stopped by and tried them out, and liked them so much that he cut out all of the doilies for me. Next I started on the lengthwise tapes.
Left Fuselage Side

Left Fuselage Side


While the fuselage tapes were drying I started on the landing gear leg.
Left Landing Gear

Left Landing Gear


More Tape Detail

More Tape Detail- Note: Don’t copy my ring placement. I ended up having to add several more later.


The 1-inch tapes that I’m using on the stringers are very hard to keep straight. The stringers aren’t straight though, so using wider tapes might be counterproductive.

Posted on
Hours Logged This Session: 6.7
Total Hours: 1883.75

Building the Paint Booth

It will be time to start painting soon, so I built a paint both out of plastic and PVC pipe. I used 10-foot lengths of PVC electrical conduit, which was cheaper than the white stuff. I found a roll of plastic that was 10-feet wide, so that made for easy layout.

Paint Booth

Paint Booth


Update- The booth isn’t quite big enough. The 10-foot width is ok, but it really needs to be longer. I used 1/3 of a 10-foot piece for each of those bays, but I should have used 4 feet instead. That would have added an extra 40 inches to the booth. Afterwards I spent a few minutes to finish the rib stitching. My big bucket of covering supplies is slowly diminishing, and now I’m putting the rib stitch needles and thread away for the last time.

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

Polybrush on the Fuselage

It’s finally time to start putting some new colors on the fuselage. I wiped the fuselage fabric with MEK and then brushed on a coat of Polybrush.

It's Pink

It’s Pink


It's Pink from this angle too

It’s Pink from this angle too


Next I applied the reinforcing tape to the VS ribs.
Ready to measure for rib stitch

Ready to measure for rib stitch


Plastic Reinforcing Rings

Plastic Reinforcing Rings


Rib Stitching Done

Lower Rib Stitching Done


I finished the lower rib, and will pick up with the upper rib next time.

Visitor Day

I hadn’t planned to have so many visitors today, but it sure was nice! I started out early in the morning with the rest of the remaining fuselage cementing. Skip stopped by in his Kitfox and visited for a little while. I had sent a message out to our EAA chapter members to invite folks over who wanted to learn more about covering. Jack took me up on the offer and I put him to work on one of the landing gear legs.

Jack cements the fabric on the right landing gear leg

Jack cements the fabric on the right landing gear leg


Left landing gear ready to shrink

Left landing gear ready to shrink


I worked on the left landing gear leg while Jack worked on the right, and it didn’t take long to finish them both. We shrank the covering on those legs, and Jack started working on the first coat of Polybrush while I shrank the fuselage.
Jack applies the first coat of Polybrush

Jack applies the first coat of Polybrush


Then fellow Bearhawk builder Hari stopped by from out of town for a visit. Hari was able to take some pictures of our
progress and give us an update on his. Other visitors that afternoon included Jim, Danny, Paige, and Bradley.
Bradley flew in for a visit

Bradley flew in for a visit


The weather was perfect, which might have been part of why so many folks came by. I was able to finish the shrinking on the fuselage, which is looking very nice.

Still More Cementing

The new can of cement came in so Tabitha and I resumed our covering. While Tabitha finished the fuselage edges I started to prepare the horizontal stabilizer for a new patch. This was an area that I’ve patched before, but needed to patch again after grinding off the sharp edge on the elevator trim mechanism.

First, I drew a circle

First, I drew a circle


Then I used MEK to remove the coats around the patch area

Then I used MEK to remove the coats around the patch area


Here are the sheets of polycarbonate for the windows and skylight

Here are the sheets of polycarbonate for the windows and skylight


The landing gear legs have a brake line that hides under the covering, so I installed the brake lines in both.
I'll have access to remove the lines later, but it's easier to put them in now.  Note!  in this picture, they are upside down.

I’ll have access to remove the lines later, but it’s easier to put them in now. Note! in this picture, they are upside down.


Tabitha works on cementing the left side of the fuselage.

Tabitha works on cementing the left side of the fuselage.


Those dark blue gloves are extra thick ones from Harbor Freight, which work much better than the regular ones.

Cementing Continued

This covering stuff takes a while! Today I worked until I ran out of cement (two quarts so far in the project). I installed a piece on the lower right side under the cargo door. Since I’ll have to order more cement, I spent time today to make sure I have enough reinforcing tapes too.

Envelope Continued

Today we continued with cementing the envelope.

Cementing the right side of the fuselage

Cementing the right side of the fuselage


Once the bottom was cemented for most of the back end, I did some preliminary shrinking on alternating sides of the seam to help smooth out the most severe wrinkles and make sure that we’d be able to get a good final shape.
Preliminary shrinking on the VS.

Preliminary shrinking on the VS.


Scrap Panel

Scrap Panel


I’m planning to finish this scrap panel with the whole process up to the final coats. That way we’ll have something to cut small patches from later on.

Installing the Envelope

Most of the fuselage fabric is in a one piece envelope from Jim and Dondi at Aircraft Technical Support. The envelope is made of two pieces of heavy duty fabric, sewn together so that a seam runs along the leading edge of the vertical stabilizer and the left top stringer. The best way to start was to locate the seam along the leading edge of the vertical stabilizer.

Note the clothespins on the leading edge of the VS

Note the clothespins on the leading edge of the VS


Then we draped the rest of the envelope close to where it was supposed to be, and gradually moved it closer to the final position.
Front of the Envelope

Front of the Envelope


As we pulled the edges down, these clothespins would have to come off

As we pulled the edges down, these clothespins would have to come off


Next we pinned the trailing edge of the VS

Next we pinned the trailing edge of the VS


One possible shortcoming of the envelope is that it’s just barely big enough to cover the right side of the fuselage. For someone who doesn’t have the cargo door, this envelope wouldn’t work. Of course Bob’s prototype is the only one I’ve seen without the cargo door.
Right side of the Envelope

Right side of the Envelope


Felicia checks out the progress

Felicia checks out the progress


Looks good!

Looks good!


We started cementing at the leading edge of the vertical stabilizer, then the trailing edge.

Fuselage Covering

This morning I finished cementing the belly fabric in place. I shrank the fabric to 225 degrees and it looks much better.

Shrunk Belly Fabric

Shrunk Belly Fabric


With the distractions of the rest of the fuselage hidden by the fabric, I see that the stringers aren’t quite straight. I probably managed to bend the standoffs a little while handling the fuselage. At this stage it was easy to fix- I just reached in from the sides of the fuselage and gave the stand-offs a little tap with a hammer. That made the stringers look much better too. Next I added the rib stitching to the cabin roof:
Reinforcing tape in place, stitch holes punched

Reinforcing tape in place, stitch holes punched


Stitching in place

Stitching in place


Here's another shot from the nose to show the progress.

Here’s another shot from the nose to show the progress.


I left the area behind the tailwire attachment point open to allow for airflow in the fuselage. To help deter mice and the animals that eat mice from getting in through that opening, I added a swatch of window screen.
Tail vent hole

Tail vent hole


Looking up at the inverted fuselage

Looking up at the inverted fuselage


I used a little dab of fabric cement to hold the screen in place.

Shrinking Interior Covering

I started off by installing those two remaining triangles in the cabin area roof. Those were the last pieces of the interior, so I started shrinking those areas to make sure that it was all going to work. I didn’t shrink the ceiling pieces yet, since they aren’t stitched. Next I started cementing the belly piece, which is a single strip of heavy-duty fabric.

Belly Piece and Interior

Belly Piece and Interior


Belly Covering

Belly Covering


The rotisserie arrangement sure is important at this stage!

Interior Covering Continued

Today I continued with the fabric covering for the interior. I divided the cabin area roof into four sections, with the first being as shown below:

Cabin area ceiling

Cabin area ceiling


I didn’t account for my back seat shoulder harness tab when I did this piece.
Shoulder harness tab

Shoulder harness tab


When I do the other side I’ll cut a small slot and slide the fabric over the tab during installation. On this side I’ll have to cut a pretty big hole to make room for the tab. It will be hidden behind a big reinforcing patch anyway.
Starting on the other side of the rear ceiling

Starting on the other side of the rear ceiling


Done with the cargo area ceiling

Done with the cargo area ceiling


This section of the roof is a concave shape- the only one on the airplane. That’s why I’ve arranged the covering into these triangle shapes. The next pieces will require some stitching to keep the panels from pulling off when I shrink them later.
This is what we came up with for the left rear window

This is what we came up with for the left rear window


Left rear window continued

Left rear window continued


The area around the front of those two big triangles gets a little bit weird because of the overlaps.
A wide piece of tape will cover this void, hopefully.

A wide piece of tape will cover this void, hopefully.


Next roof piece

Next roof piece


I’ve marked this triangle to fit in on the front section of the ceiling. This piece will go on as an overlap joint with cement, since there aren’t any tubes to wrap around.

Interior Covering

Today we were both out at the hangar to get started on the fuselage fabric covering. The first step was to cover the interior, since some of the interior pieces need to overlap under outside pieces.

Interior Covering

Interior Covering


Alan stopped by for a visit and some supervising.

Alan stopped by for a visit and some supervising.


We started with the easy pieces and went from there

We started with the easy pieces and went from there


This process of covering the interior is more time consuming than I would have thought.

This process of covering the interior is more time consuming than I would have thought.


After our work session I read back through Eric’s manual and saw that he was also bogged down a little with the interior covering. One tool that helped with trimming around the tubes was a little pair of scissors that I ordered from China. They have small, pointed blades that are spring loaded to the open position.

Wing Repair Continued

Picking up where I left off last time, I finished the wing repair

Ready to Rivet

Ready to Rivet


Ready to prep and paint

Ready to prep and paint


While I had the air drill over on that side of the hangar, I also removed the metal strip that I had installed in the wing tip to allow for flush mounting of the fiberglass tips. At this point it just makes more sense to use the much simpler overlap method instead.

Anti-Chafe Tape

There are a few more things that I need to have done before we can start covering. For example, the lower fuel lines that cross under the front door sills need to be in place.

Left Lower Fuel Line

Left Lower Fuel Line


I installed those lines and added a nutplate for a clamp that will support the right rear vertical line.
Fuel line tab

Fuel line tab


With our covering strategy I don’t think I’ll need to have the vertical lines in place prior to covering. I routed the rear passenger headset cables and tied them neatly in place. I added the anti-chafe tape to a few spots on the fuselage that seemed like good candidates for it, and I started repairing the hole in our wing root.
Wing Root Repair

Wing Root Repair


How did I end up with a hole in the wing of an airplane that isn’t even flying yet? I’ll tell you- I cut that hole. I was thinking of a way to get airflow to the back seats, and copied an idea that I saw on another airplane. Then, after I had the hole cut, I saw something in the Avipro manual about not putting big holes in the .032 portion of the wing skin. So I called Bob, who confirmed that there really shouldn’t be such a big hole there. He said that I should patch it with a doubler underneath, using -4 size flush rivets spaced 1 inch apart. In the picture above you can see the beginnings of just that. I used a square and a ruler to lay it all out, cut out the hole to a rectangular shape, then match drilled the skin and the doubler.

Covering Prep

This morning I mixed up a batch of epoxy, which I used to laminate a strip of unidirectional carbon fiber to the inside of the wingtip. Hopefully this will keep the scalloping down.

Wingtip Carbon Fiber Strip

Wingtip Carbon Fiber Strip


Carbon fiber looks like a snake

Carbon fiber looks like a snake


Top carbon strip

Top carbon strip


Antenna feedline and ELT remote cable

Antenna feedline and ELT remote cable


I also used the epoxy to secure the wooden ribs to the vertical stabilizer steel rib.

Nutplates that will be burried in covering

Nutplates that will be burried in covering


Here are a few more nutplates that are easier to get to now than later. These include the front strip on the lower sides, plus the back of the skylight hole. I only have a few more things to do before we can start covering.

Posted on
Hours Logged This Session: 5.2
Total Hours: 1883.75

Wooden Ribs

There is some discussion in the Avipro building manual about adding spacers to the ribs. I made these out of poplar on the bandsaw and belt sander.

Wooden rib shims- I ended up not using the top set

Wooden rib shims- I ended up not using the top set


I thought these turned out pretty well.

Posted on
Hours Logged This Session: 1.1
Total Hours: 1883.75

Installing Stringers

I was glad to be done with painting for a little while, and ready to start reassembling things! I sanded the filler on the wingtip and applied a coat of gray automotive primer to check the progress.

The first coat of paint tells many tales

The first coat of paint tells many tales


I think it will do.

I think it will do.


I installed the stringers with long blind rivets. These were all aluminum and are very lightweight.
They were also fast to install.

They were also fast to install.


The other side

The other side


Here's the part number and specs from McMaster Carr

Here’s the part number and specs from McMaster Carr


This shot shows the notch to clear the fuselage tube.

This shot shows the notch to clear the fuselage tube.


Since we’ve decided to use the Dynon pitot tube, we’ll need to route static lines from the back of the fuselage. These static ports came from a kit that I got from Avery while we were in Oshkosh. The little aluminum plates will hold the ports in place.
Static Ports

Static Ports


Inside (left) and outside (right)

Inside (left) and outside (right)


Mounting holes ready to countersink and dimple

Mounting holes ready to countersink and dimple


Countersinking and dimpling done

Countersinking and dimpling done


Here's how the ports mount to the stringers.

Here’s how the ports mount to the stringers.


I put them close to an attach point so that they wouldn’t wiggle as much.

Next I routed the VHF navigation antenna feedline from the vertical stabilizer. I put a joint in the line so that we can replace the antenna if it doesn’t work, or if it quits working in a few years.

VHF Navigation Feedline

VHF Navigation Feedline


Here's the best way I could find to secure the coax cable

Here’s the best way I could find to secure the coax cable


I also did a few more pre-covering jobs, such as adding nutplates to the areas that are going to be harder to get to after covering.

Posted on
Hours Logged This Session: 5
Total Hours: 1883.75

Priming Small Parts

The new can of catalyst arrived today, but I couldn’t get the top off. The neck broke free from the can and was spinning with the lid. I poked a hole in the cap and forced the cap and neck off in one piece. I had a clean empty can from another product and was able to transfer the catalyst to that can.

Priming Small Parts

Priming Small Parts


I prepped the fuel tank bay cover and sprayed it and a few other odds and ends, and a few touch up spots on the fuselage.
Fuel tank bay cover

Fuel tank bay cover


Rudder cable covers

Rudder cable covers


That should wrap up the fuselage painting and start the clock on our 7-day waiting period for covering.

Posted on
Hours Logged This Session: 1.8
Total Hours: 1883.75

Cleaning Stringers

This morning I shaped some of the filler from yesterday.

More Filler

More Filler

Over the past few years the stringers have gotten pretty nasty, and the texture of the paint was a little rough, so I cleaned them with some fine sandpaper. Now they are clean and smooth. This should help prevent catching and fraying the fabric when we put it on.
Clean Stringers

Clean Stringers


The stringers have taken a little bit of a bend already. If I were starting fresh I’d use the heavier stringers that Mark G. sells.

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Hours Logged This Session: 2.5
Total Hours: 1883.75

More Priming

I went out today to touch up a few more paint spots, but when I reached for an unopened can of catalyst I was surprised to find it was empty! Unfortunately it leaked sometime in the past couple of years, so I’ll have to take a break from
painting until I can get more.

Painted Tubes

Painted Tubes


Instead I worked on the wingtip filler and the position light mounting pad.
More filler on the position light pad

More filler on the position light pad


A little filler on the wingtip leading edge

A little filler on the wingtip leading edge


I’m starting to wonder if I’ll be able to get all that I need from the first can of filler!

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Hours Logged This Session: 2.8
Total Hours: 1883.75

Priming Continued

When I got back to the hangar today I found a few spots where the paint was a little thin. I also saw that the texture under the paint was pretty rough in areas where the sandblasting started and ended. I sanded those spots in areas where they would show, then sprayed another coat.

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Hours Logged This Session: 6.9
Total Hours: 1883.75

Sand Blasting

Funnel Top

Funnel Top

We had a great time at Oshkosh as usual. We saw several old friends and met new ones too. It was hot, as you can see in this picture:
Hot Ladies

Hot Ladies


I found a great deal on a set of Cessna style wheel pants. I’ll have to make the inboard brackets, but that shouldn’t be too hard. I also picked up a different nut to support the outboard side.
Wheel Pant Axle Nut

Wheel Pant Axle Nut


It was finally time to sandblast the fuselage, so I made arrangements to rent a 180 CFM compressor and pressure pot.
Diesel Compressor

Diesel Compressor


The pressure pot was very simple, but it had one serious inconvenience. The top is shaped like a funnel, which makes it easy to load, but it’s very hard to empty. The previous renter had been using a different type of media, but I didn’t know what it was or how coarse it was. I dumped out what I could, and just ran the nozzle out into the air until my quartz started flowing.
Sand Blast Pot

Sand Blast Pot


As advertised, it was a hot and miserable job. I only blasted the areas where I had removed paint previously. In retrospect, I probably should have removed more, because the transition from old paint to bare metal ended up showing through the new paint. I started setting up at 12:00 and was done by 15:30. When I was done I turned the fuselage over several times to make sure I didn’t miss any spots. I moved it back into the hangar and took the compressor back, since I was paying by the hour. I used a total of 150 pounds of medium quartz. I was back in the hangar by 17:40 and sprayed paint until after 10:00pm. Those tubes sure are tricky to paint- there are so many different angles that have to be covered. I used almost two quarts of EP420 to get it all covered, and most of that ended up as overspray.

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Hours Logged This Session: 8.2
Total Hours: 1883.75

Wingtip Light Mount

I stopped by today for one more measurement to make sure that the landing gear alignment is within tolerance, and it is. I cleaned up the hangar in preparation for round 2 of sandblasting, and applied a coat of smurf extract to the right wingtip position light mount and the stringer that required a relief cut. It’s time to go to Oshkosh soon, so building will be on hold for another week or two. Next time I’ll have a few more parts and plenty more motivation, though at this point I’m not facing a shortage of either.

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Hours Logged This Session: 1.5
Total Hours: 1883.75

Final Gear Alignment

Today was the day to bend the landing gear to fix the alignment. Here’s a picture of the measuring jig:

There's one small problem here

There’s one small problem here


Can you spot the problem with this arrangement? The right side sawhorse is in the way of the right axle. It’s going to be hard to get in there with the BATPISS to bend the axle. BATPISS is Russ Erb’s acronym for the bending lever. I forget what it stands for, but you’ll probably have no trouble finding it with a google search. I used a 1″ piece of black pipe that’s about 10 feet long. I put a snug-fitting piece of 4130 inside the axle, then put the black pipe inside of that. I dusted off the trigonometry to figure out how much travel I needed to have at the end of the bar to get the toe-in angle correct. This was really rather pointless, because the pipe flexed quite a bit. Part of what makes this job so complex is that the wheels need to be off while heating up the landing gear junction, but they have to be on to measure to see if the angle is correct. That means heating the junction, bending until it seems about right, waiting quite a while for the cluster to cool, reinstalling the wheel, and measuring again. Fortunately I only had to go through that cycle twice per wheel. I used a giant rosebud tip on the industrial OA torch that had a terrific flame- I didn’t take a picture, but it’s about 1/2″ wide and 4″ long.

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Hours Logged This Session: 2.7
Total Hours: 1883.75

Gear Alignment Continued

Today I was able to try measuring the main landing gear alignment with more sturdy steel angles. When I was shopping for them, I tried to find the straightest two in the store. The tiles on the store floor made a nice straight edge. Just to be sure that I didn’t have any bends in the angles, I repeated my measurements with several different configurations, and they all came up the same. The right wheel needs just a little adjustment, and the left wheel needs quite a bit. Felicia stopped by to see how things were going:

Felicia sizes up my measurement

Felicia sizes up my measurement


She says it looks like a lot of trouble. It is!

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Hours Logged This Session: 2.25
Total Hours: 1883.75

Main Landing Gear Alignment

Today I was able to start in earnest on the main landing gear alignment. I used three tiedown straps per side to make a rigid mount for the fuselage. One strap runs from the firewall station to the floor tiedown (which is right about where it would need to be to serve as a wing tiedown). Another strap runs from the tiedown to the tailpost. A third runs from the tiedown to the top of the fuselage, near the rear wing attach bolt. The same pattern is on the other side, so I was able to end up with a very sturdy fuselage position. The final strap runs from the top of the vertical stabilizer to the ceiling, and holds the tail up to a level attitude. One challenge of doing these measurements on a dirt floor is that it’s hard to make marks. The best solution that I could come up with was to use two sheets of plywood, attached to each other with 2×4 lumber. This simulated floor allows me to make a chalk line for the fuselage centerline. Fortunately I’m working in the part of the hangar where we put extra gravel so the left-right level is pretty close even on the bare floor. I removed the tires from the wheels and put the wheels back onto the axles, then positioned the main landing gear so that the wheels were spread apart as described in the information from Bob. In the process of trying to measure the toe-in angle, all that I’ve been able to determine is that the thin little aluminum angles that I have been trying to use just aren’t going to work. I need to get some beefier steel angles that will not flex when I try to measure with them.

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Hours Logged This Session: 3.5
Total Hours: 1883.75

Soda Blasting

This is the third and final day in my bachelor building binge. The girls have been out of town and my goal was to press on to get the fuselage primed and ready for covering. Unfortunately this hasn’t worked out for a few reasons. The first is that I’m out of reducer for the expoxy primer. This stinks, because I need to paint the fuselage right after it’s blasted. My original plan was to go rent a compressor and sand blaster today, but earlier this week I was talking with a friend who asked if I had looked into soda blasting. Soda blasting uses baking soda as a blasting media with equipment that seems very similar to sand blasting. The soda is not as harsh as sand, which means less likelihood of blowing holes in the thin steel tubing. I figured I should at least get a quote, which came to $100. That was less than I was going to have to spend to rent the other equipment, and that’s not to mention that I wouldn’t have to do the miserable job of the blasting.

I met the friendly blaster early in the morning and moved the fuselage out into the sun.

Ready for Soda Blasting

Ready for Soda Blasting


Soda Blasting in Action

Soda Blasting in Action


While he did that, I made some minor adjustments to one of the stringers. This one is the upper left sringer, which rubbed on one of the diagonal fuselage tubes. I cut a little relief out of the stringer with the Dremel:
Take a bite out of stringers

Take a bite out of stringers


Then I added a little dam of aluminum to help seal the area

Then I added a little dam of aluminum to help seal the area


The idea is that I’ll fill this hole with some epoxy to seal the bottom, then top it off with some Superfil.
Epoxy first

Epoxy first


Meanwhile, the kind blasting gentleman was through, and I was able to learn the second main reason why I wasn’t going to be able to prime today- the soda blasting wasn’t harsh enough. I don’t think it’s the fault of the operator, but rather the process. Soda blasting just isn’t suitable for prepping welded steel tube structures.
Soda Blasting Results

Soda Blasting Results


Note the little bits of oxidization in the low spots.

Note the little bits of oxidization in the low spots.


These were too hard for the soda to remove, but sandblasting would have yielded fresh, bare metal. I think the process is very well suited for paint removal- the blasted areas looked just like they did before I painted them with a temporary primer. This was a disappointing setback, but these have still been very productive days. I took the rest of the afternoon off and came back later in the evening to prepare for the landing gear alignment project. I would have preferred to get the alignment done before the blasting, but time constraints wouldn’t allow that this week. With my new delayed schedule, I can return to the preferred order and get the alignment done next. The first step in aligning the gear is getting the fuselage positioned at the right height and level in all dimensions. Then I need to secure the fuselage in that position so that I can make reliable measurements, and presumably be able to bend the landing gear without having the fuselage moving around. To start, I installed augers in the floor to use as tiedowns. These are in the right spot to serve as wing tiedowns later on.
Installing anchors in the floor

installing anchors in the floor


I also spent some time locating and adhering the position light mounting pad to the left wingtip.
Wingtip Position Light Mount

Wingtip Position Light Mount


I left the hangar in the wee hours of the morning, somewhat defeated, but only reminded that deadlines and goals need to be flexible with this kind of project.

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Hours Logged This Session: 4.1
Total Hours: 1883.75

More Disassembly

Today I carried on with the disassembly, in a marathon building session that would indicate that Tabitha is out of town. I took out the control sticks, elevator bellcrank, rudder pedals, headset wires, and other things like that.

Getting back to bare bones

Getting back to bare bones


The wiring was going to be too much trouble to take out completely, so I just balled it all up and wrapped it in a trash bag.
Protected wire bundle

Protected wire bundle


I removed the landing gear legs and set the fuselage on sawhorses. I welded on a tab to support the fire extinguisher, which will mount on the floor just in front of the main carry-through structure. Since we’re planning to leave the wing root section uncovered in the fuselage, the wing root fairing doesn’t have anything to collide with where it meets the fuselage. I added a few tabs there to allow for a vertical portion of the wing root fairing, which will seal the gap. I started with a long strip, then welded the end of the strip in place. Next I trimmed the strip off to determine the length of the tab. This made it much easier to hold the pieces in place for welding.
Weld the tab on, then cut it to length

Weld the tab on, then cut it to length


Here's the finished row of tabs

Here’s the finished row of tabs


Next I modified the landing gear trailing edge to allow for larger tires.
Here's the original arrangement

Here’s the original arrangement


Here's the desired arrangement, before welding the lower section

Here’s the desired arrangement, before welding the lower section


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

Here’s the final product, ready to blast and paint.


With both of those done, I needed a way to get the fuselage around by myself. This is what I came up with:
1-man wheelbarrow fusleage transport

1-man wheelbarrow fusleage transport


The fuselage is resting on a 2×4 that sits on the wheelbarrow. There is a strap that runs under the wheelbarrow handles, which makes it possible to lift the rear end of the wheelbarrow by lifting the tail.
I tied the front down for stability

I tied the front down for stability


I tied the front down for stability

I tied the front down for stability


these will make up the front portion of the rotisserie, which is a necessity for the next few building steps. I learned several months later that it was not a good idea to use the airworthy AN bolts. The moisture in the wood led to a little bit of corrosion on the bolts.

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Hours Logged This Session: 11.5
Total Hours: 1883.75

Taking it All Apart

My last session in the shop included putting almost all of the parts on the airplane, and my last entry here included flying in Dave’s Bearhawk. From those two highs, it’s time to carry on with progress and see a few lows. First I dug through my tubing scraps and was pleased to find one that will fit nicely inside of the axle. This will help when it is time to bend the axles to align the wheels. Next I marked and trimmed the fiberglass fairings that cover the junction of the lower strut end and the fuselage. Since I’m not planning to have the wings on for a while, this is good to do now.

Lower Strut Fairing

Lower Strut Fairing


Next I cut the aluminum on the right upper front window frame to match the steel where the lock cylinder will go.
Right window lock mount

Right window lock mount


With those things done, I started taking things apart. After about 6 hours of work, this is what it looks like:
Almost all apart

Almost all apart


Wade and Danny helped with getting the wings and engine off. Tomorrow I should have everything removable off of the fuselage to prepare for blasting and painting.

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Hours Logged This Session: 11
Total Hours: 1883.75

Dave Lenart Visit

Today was a real treat- I was able to catch up with Dave in Vermont to spend some time talking about his Bearhawk. The weather was perfect and it was a great way to spend the morning. Dave let me pick his brain with all sorts of questions about his construction. We’re using almost the same engine and prop, and we both came upon kits that were already started. We both also started building at around the same time, which doesn’t say much for my building speed! Here are a few photos of flying in Dave’s airplane, and of the pancake breakfast in Rutland, VT

Magnificent Vermont

Magnificent Vermont

.
Bearhawk Cabin Visibility

Bearhawk Cabin Visibility


Dave's Bearhawk

Dave’s Bearhawk


Dave’s airplane performs very well, and it helps validate my decisions on engine and prop choices.
Blueberry Pancakes!

Blueberry Pancakes!


Tailwind

Tailwind


This picture helps me remember where we were.

This picture helps me remember where we were.


Polished airplanes sure are pretty.

Polished airplanes sure are pretty.


High Visibility

High Visibility


Studying the Maule

Studying the Maule


Maule wing root fairing hole

Maule wing root fairing hole


I wonder why Maule put this hole in their wing root fairing? Water drainage?

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Hours Logged This Session:
Total Hours: 1883.75

Photo Session

This morning I reinstalled all of the sheet metal on the front end, especially the tunnel and lower boot cowl. This is all part of the plan to make sure that I don’t have any interference problems.

Lower front sheet metal

Lower front sheet metal


With those parts and the cowl on, I rolled the airplane outside for a few photos. It looks so close to being done, but it’s still so far from flying!
Bearhawk Before Covering

Bearhawk Before Covering


Bearhawk Before Covering


P1020910


Axle Nut Width
I also measured for the size of the wheel axle. This is the first time that I’ve needed to take the wheel off, and I’m not sure about what the best tool is going to be. The nut is 1-3/4 inches, but it’s recessed inside the wheel so that it’s not really accessible by a wrench or socket. I’m not sure whose idea that was. I did more initial checking of the main landing gear alignment and have come to the conclusion that I’m going to need some better measurement methods if I’m going to get repeatable results. I tried using some 1/16″ aluminum angles that I had on hand, but they’re just too wiggly.

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Hours Logged This Session: 3.1
Total Hours: 1883.75

Antenna Planning

I was only out for a little while today, but I cleaned up the hangar and measured for a few of the coax cables. I was planning to use RG-58, but it turns out that some of the low-cost cable that I found wasn’t very good quality. Additionally, Bob Nuckolls has a pretty good deal on some RG-400 equivalent, and his pricing is very good. In some cases it will work out better to have a 90-degree end, which he offers as an option.

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Hours Logged This Session: .5
Total Hours: 1883.75

Adjust Seatbelts

I found a great deal on a set of seatbelts on eBay. These are military surplus Amsafe units that were stocked by the military for off road vehicles. These are almost the same as the ones that I use in airliners, with the only difference being that these don’t have a release option for the shoulder harnesses only. The buckles are 5-point, but the eBay auction only included the parts for the 4-points. I’ll have to buy a few extra parts to make these work just as I’d like, but hopefully in the end it will mean a significant cost savings over the other options, and a much nicer finished product. I started with the front seats. When I bolted in the lap belt and buckled it up, this is how much slack was left over:

Front Seat Slack

Front Seat Slack


Obviously that’s not enough. While I’m not as skinny as I used to be, I’m still fairly skinny by comparison, so we’ll need more adjustment here. The solution is to put the shoulder harnesses in as lap belts, since I’ll be replacing the front shoulder harnesses with inertia reels anyway. The only problem with that plan is that the left lap belt is permanently attached to the buckle. This seemed like something that I could overcome, so I started taking the buckle apart.
First I removed the Amsafe logo in the middle, exposing the allen bolt.

First I removed the Amsafe logo in the middle, exposing the allen bolt.


Here's what's underneath.

Here’s what’s underneath.


To get the buckle out, I loosened the 6 torx bolts, then pressed down on the latch from above. Then I put the shoulder harness buckle in instead:
Shoulder Harness Becomes Lap Belt

Shoulder Harness Becomes Lap Belt


Now I just need to round up a few more buckles and some inertia reels.
As I mentioned in a previous entry, the threaded-end mixture cable that I was planning to use wasn’t going to work. I was able to trade with a local EAA Chapter member for a bare-wire mixture cable, so I put it in today to make sure it was going to work. I also got a good deal on a pair of aluminum eyeballs, though they were 1/8″ holes. I enlarged the holes to fit the mixture and throttle cables.
Enlarge Eyeball Holes

Enlarge Eyeball Holes


I used a letter B bit for the final hole.
Here they are in place

Here they are in place


While I was there I did a few other minor things, including a preliminary check of the landing gear alignment and installation of the quick release pins for the back seat.

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Hours Logged This Session: 4.3
Total Hours: 1883.75

Tech Counselor Visit

This afternoon our technical counselor came for an official visit. It’s still very early in the process, but it was certainly good to get his input now when it’s still easier to change things.

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Hours Logged This Session: 1.5
Total Hours: 1883.75

Seatbelt Tabs

This morning I made and installed some mounting tabs for the front seat belt crotch straps. I used 1/8 inch 4130 steel.

Seat belt tab blanks

Seat belt tab blanks


I removed much of the metal to save weight.
Shaped Blanks

Shaped Blanks


I had a hard time coming up with a good mounting method that would put everything in the right place. This is the best that I could come up with.
Tab mounting location

Tab mounting location


A while back I shorted the SD-8’s ammeter shunt while I was working on something under the cowl. After a discussion with Bob Nuckolls on the AeroElectric list, I decided to replace the fuse link that was there to protect that shunt. He recommended a fuse instead of a fuse link, since that’s what’s in the Z13/8 drawing now. I ordered this fuse holder, which uses a gasket that is very similar to the weatherpack connectors.
Waterproof ATC Fuse holder

Waterproof ATC Fuse holder


It’s a good thing that I replaced the fuse link. Here’s what it looked like when I took it out of the fiberglass sheath.
Overloaded fuse link

Overloaded fuse link


Afterwards I killed a few minutes by peeling more of the protective plastic off of the wing skins.

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Hours Logged This Session: 2.4
Total Hours: 1883.75

Brake Lines

When I changed the configuration of the parking brake valve, my old brake lines became obsolete. I made new ones today out of 1/4″ 5052 aluminum tubing.

New Hard Brake Lines

New Hard Brake Lines


I also reinstalled a few more of the floor panels in the front part of the cabin.

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Hours Logged This Session: 2.9
Total Hours: 1883.75

Final Fuel Lines

Tonight I finished making the last of the fuel lines, hopefully for the last time.

Looking up at the fuel lines from belowFinal Fuel Lines

Looking up at the fuel lines from belowFinal Fuel Lines


Final Line Routing

Final Line Routing


I put the stainless steel tunnel in place and it looks like it just barely touches the fuel valve:
Fuel valve interference at tunnel

Fuel valve interference at tunnel


I haven’t decided yet if I’m going to try to make a bump in the tunnel or try to secure the valve to the tunnel. The first option is the most appealing so far. While I was at the hangar, I also weighed our new fabric aft cabin bulkhead and our old aluminum bulkhead to see how much weight we saved. The fabric weighs 11 ounces, and the aluminum weighs 3 pounds 1 ounce. Yikes!

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Hours Logged This Session: 2.3
Total Hours: 1883.75

Fabric Aft Cabin Bulkhead

Back when we picked up the seats we had Russell save us a yard or so of the tweed fabric that he used. This will make a fabric version of the aft bulkhead, which will be lighter and quieter than the current aluminum version. My mom was in town to visit, so we put her to work on the sewing machine.

Sweatshop

Sweatshop


I thought it turned out pretty well, and a nice 10″ Bearhawk patch was the icing on the cake.
Aft Bulkhead

Aft Bulkhead

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Hours Logged This Session: 2
Total Hours: 1883.75

Mounting the Fuel Flow Transducer

I’ve decided to put the FT-90 Gold Cube fuel flow transducer aft of the firewall, between the gascolator and engine. It will end up being right under the pilot’s left foot. The wires come out of the top, so I made a bracket that will provide some space between the floorboard and the cube. I wasn’t able to find much in the way of installation instructions for the FT90. What I did find explained the orientation (wires up) and suggested flex lines going to and from the sensor. I wondered if this would be necessary in a case where the sensor is rigidly mounted, so I emailed the manufacturer and asked. They said that the flex lines were intended to dampen vibrations that could cause erratic readings. Since I’m not sure if I’m even going to be able to use this sensor due to the flow issues, I’m going to install it for now with hard lines since they are available and more durable. If I get erratic readings, then I’ll know that replacing those lines with flexible alternatives will be the first step towards fixing them.

Fuel Flow Sensor Mount

Fuel Flow Sensor Mount

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Hours Logged This Session: 3.25
Total Hours: 1883.75

Measuring for the Seatbelts

Now that the seats are in I was able to measure how long our seatbelts will need to be. I used the form from the Aero Tuff website. A few entries ago I made the oil cooler lines. Today I applied some high-temp RTV to the ends to help keep the oil and debris out. I’ll add the special stainless clamps once I can find someone who can loan me the tool that they require.

Firesleeve Rolled Back

Firesleeve Rolled Back


High Temp Goop

High Temp Goop


Ready for a Clamp

Ready for a Clamp


Oil Lines Installed

Oil Lines Installed


I also repositioned the fuel valve one last time, I hope.
Fuel Valve Location

Fuel Valve Location


I was concerned about having it in the way of grabbing the flap handle, but after sitting in the seat and making a few practice grabs, I found that for the first couple of flap settings my hand didn’t go to the end of the handle anyway.

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Hours Logged This Session: 4.5
Total Hours: 1883.75

Installing the Seats

I only had a few minutes free today, but I had to take out the seats and see how they looked in the airplane. They fit just as they were supposed to, and it was nice to see them back home again. Back when I made the headrests I intentionally left the vertical pieces a little bit long, so today I trimmed them to fit and put the headrests in.

Bearhawk Seats

Seats Installed

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Hours Logged This Session: .7
Total Hours: 1883.75

Picking up the Seats

Today and yesterday I have been driving over to Mississippi to pick up our seats from our upholsterer. When I was younger I flew model airplanes with Russell Wood, and he’s been an upholsterer for a long time. Since our seats were already in Mississippi, I dropped them off with him a few months ago and he did his magic. I think the finished product is much better than it would have been if we would have done it, and for likely a similar price in the end.

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Hours Logged This Session:
Total Hours: 1883.75

Oil Hose Pressure Testing

I purchased some surplus reusable hose ends from B&B Aircraft Supplies a few years ago at Oshkosh, so I figured I would use those. They were new and very inexpensive ($5 each), but I didn’t know much about them. It turns out that they were Stratoflex 676 fittings. A few hours of research turned up that they are designed to work with Stratoflex 156 hose, which is a braided stainless type of hose. I ordered a few feet of hose from the Sacramento Sky Ranch and assembled the lines. Since I was operating on intuition instead of instruction, I thought it would be prudent to pressure test the lines before installing them.
With an afternoon to kill in Charlotte, I sat down with Google maps and started calling hydraulic shops around the area. The first few weren’t set up to do any testing at all. One would test them at their hourly shop rate of $100 per hour, with an estimated test time of 1.5 hours. Another would test them for $35, but wasn’t sure when they would have time to do it. Eventually a shop put me in touch with Rick White, at Brown and Miller Racing. On the phone I asked Rick if he was set up to test lines, and he said “Sure.” Did he have 1/2″ 37-degree flare fittings? “Of course.” How long would it take? “A few minutes. You can come back into the shop and watch.” When can you do it? “When can you be here?” That was all of the convincing that I needed. The only problem was that I was in Matthews and he was in Concord, and it was 4:00. Their closing time was 5:00, so I headed over there directly. I arrived at 4:45 to find a very polite and accommodating Rick. He showed me his test bench and explained how it worked. It uses a specially filtered water to apply a specified pressure anywhere up to 5,000psi, then closes the valve to check for loss of pressure. He tested the lines up to 500 psi and they held fine, which was a relief. It’s always nice to have my own work validated! I also needed a flexible fuel line for the firewall-carburetor connection. Rick priced a fire-sleeved Teflon line with crimped-on ends at just under $30. Then, he made it with his fancy machinery (and pressure tested it) in about 3 minutes. In short, I was impressed with his capabilities and amazed with the level of service he provided, even though I walked in the door a few minutes before closing time. If you are in the area and need to test some hoses or have non-PMA hoses made up, I’d recommend giving Rick a call at 704-793-4319. His shop is next to the Charlotte Motor Speedway is certainly worth a visit.

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Hours Logged This Session: .5
Total Hours: 1883.75

New ELT Antenna Bracket

Back a few years ago when I made and installed the antenna bracket for the ELT, I never got around to putting in a fairlead bushing. Now that I have, it’s a pretty loose fit. This is the third strike against this setup, with the incorrect height and limited cable clearance being the other two. So with three strikes, it’s out.

Old ELT antenna bracket is out

Old ELT antenna bracket is out


The new bracket is just a trapezoid of .032 aluminum that will share fasteners with the stringers.
New, much simpler ELT bracket is in

New, much simpler ELT bracket is in


By putting the antenna off to one side slightly, I was able to eliminate the interference issues with the feedline and the elevator trim cable.
Lateral Offset

Lateral Offset


Here’s a nice wide-angle picture of where we are these days.
Overview and messy hangar

Overview and messy hangar

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Hours Logged This Session: 4
Total Hours: 1883.75

Preliminary Control Rigging

With the flap cables in place, I was able to work on adjusting the flap rigging. I adjusted the pushrods until the flaps came up to zero degrees under spring tension. I started to adjust the aileron cables and realized that my loop is just a little bit too short, and I’ll need to make a new version of one of the back cables that’s about 3/4″ longer than the current one.

Tabitha stopped by to say hi and Felicia says "Oh Dad, why aren't you done with this yet?"

Tabitha stopped by to say hi and Felicia says “Oh Dad, why aren’t you done with this yet?”

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Hours Logged This Session: 1.6
Total Hours: 1883.75

Oil Cooler Lines

A few days ago when I finally got the right oil filter installed, it became pretty obvious that the straight AN fitting that I was going to use for the oil cooler line wasn’t going to clear the filter. I swapped it out for a 45-degree nipple instead, which works much better.

AN823-8D Fitting

AN823-8D Fitting


I made the second oil cooler line out of the remaining piece of stratoflex, and started to think about measuring the deflection of the flight controls.

Posted on
Hours Logged This Session: 1.3
Total Hours: 1883.75

Fuselage Features

I mentioned yesterday that I was going to add a fairlead for the elevator trim cable at the aft end of the skylight. This morning I welded that tube on, and while I was there, I also welded on tabs for the front and rear flood lights.

Elevator Trim Cable Fairlead

Elevator Trim Cable Fairlead


Aft Flood Light Tab

Aft Flood Light Tab


Those will be LED spotlights on the battery bus. The light fixtures are adjustable so that the rear white light can point to the baggage area or to the back seat. The front is red and white, and I’ll install a dimmer on the instrument panel for it. With our new rear left window arrangement, the lower stringer interfered with the diagonal steel tube. I cut a small relief out of the stringer, and it looks like a small bite mark.

Posted on
Hours Logged This Session: 2.8
Total Hours: 1883.75

Control Cables and Fuel Lines

In the last entry I mentioned that the lower right fuel line was going to need an extension. This morning I added that extension and made a line from the fuel valve to the gascolator. Next I routed the upper flap cables, made new rudder cables, and routed the elevator trim cable. It became immediately obvious that the elevator trim cable was going to need to occupy the same space as the aileron cable. If I had put the aileron cable turnbuckle somewhere other than in the middle of the cabin, this wouldn’t have been an issue. Bob Barrows says that an offset of the aileron turnbuckle is usually enough to provide clearance. If not, it would be acceptable to split a few inches of 3/16″ Nylaflow tube and attach it to the aileron cable with some Pliobond. I think I’ll follow the path of Bearhawk builder Gavin Chester and add a fairlead just above the junction. After a break for dinner I came back to the hangar and made the left front fuel line again. This latest version looks like it will work just fine. I installed the elevator and trim tabs again so that I can verify the operation of their associated cables and such. Back when I was covering the horizontal stabilizer I sanded through the covering at the outboard end of the elevator trim torque tube. I was worried that this was going to be an ongoing problem, so I cut an access hole to see what was going on. Here is the view:

Sharp Edge

Sharp Edge


This would explain the issue. Ours is welded on instead of bolted on, and I’m not sure if that’s something that Avipro did at the factory or our previous owner did. In any case, the welding seems like a good idea, since the bolt would have been inaccessible without a hatch. My plan is to dress the edge a little, then put a patch on the hole before painting the color coats. I was going to have a patch there anyway since I had the sanding issue, but this way we’ll have less chance of abrasion once we’re operating the airplane.
Dull Edge

Dull Edge


Now a little bit of primer on the steel, and a little bit of MEK to remove the old patch, and it will be ready to repatch. I’ll be able to spray the area when I have the equipment out to spray the fuselage and landing gear later this summer.

Posted on
Hours Logged This Session: 10.3
Total Hours: 1883.75