7.2 Nose Gear Installation (Door mechanism)

This entry is part 1 of 39 in the series 07 - Landing Gear

This is an area that’s been bugging me since day 1. The main gear doors a attached to the gear legs. But the nose doors are hinged. They are brought up by means of a rather complicated hydraulic system. Here’s a picture of a completed plane.

This picture is looking aft at the canard bulkhead. The greenish looking pipe going down is the nose gear leg. The opening at the bottom is the space that the nose gear comes through when it retracts. You can see the rear hinge arms of the nose gear doors (they’re white). Those doors are closed by a hydraulic cylinder (gold at the top center partially behind the large red flexible duct) which pulls up on a pair of arms that extend down to the door hinges. The hydraulic cylinder is activated by a switch (off to the right near the bottom of the cylinder) that gets triggered when the nose gear is up.

I’ve seen a couple other builders that used this method. After some investigation, I found the guy who builds these.

I asked the builder who came up with this if he could build one for me. But his fabrication guy was unavailable. So Malcolm told me he had built one that it’s in a plane nearby. A call to Terry Miles had me stopping by to take some pictures and measurements.

Same view as the previous picture but with the Hangar 18 mechanism.

The spring is so that when the gear bounces a little while in the up position, the doors will stay closed.

Some fabrication I can do. But I’m not a welder and I don’t have a milling machine. So Lynn, my current A&P put me touch with a guy who put me in touch with a guy who does metal work. I sent him my drawings and measurements. In return, he sent me:

Here are those parts installed.

Now I have to get the linkage and spring so I can drill for the pins to fix the arms in place.

7.7.1 Main Gear Legs (Painting)

This entry is part 33 of 39 in the series 07 - Landing Gear

The main gear legs don’t have to be painted. Neither do the gear wells. But it would look so much nicer if it’s not bare fiberglass. The gear legs are going to be hit by small rocks kicked up be the tires during takeoff and landing. So regular paint would look pretty bad after just a couple takeoffs and landings. Malcolm suggested Zolatone paint. It’s “splatter” type of finish that takes abuse without showing and doesn’t require prefect finishing prior to painting.

So I ordered a quart and started shooting. This stuff is a pain to shoot! If my gun had a larger nozzle, it would probably be easier. As it was, every now and then the nozzle would get hopelessly clogged and I would have to clean it out. What could have taken 15 minutes with the correct nozzle took about 90 minutes.

Gear well:
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Gear leg
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Finished and reassembled.

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6.9 Overhead Fresh Air Plenum Painting

This entry is part 35 of 42 in the series 06 - Fuselage

Many builders cover the A & B pillars and overhead fresh air plenum. I decided to follow Andy Millin’s example and and use paint for those surfaces. He used a satin finish on his plane.  But the amount of finish work required to get a good result was rather daunting.  So I selected a texture that did a much better job at hiding sins.

So after very little finishing work I sprayed the plenum. The results were very nice.

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Inside wiring for the lights

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And a quick lighting test.

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15.2.2 Window Trim

This entry is part 4 of 9 in the series 15 - Interior

The kit comes with interior trim pieces for the windshield and rear windows. Apparently, these were made from molds that don’t exactly match the windows. Which means that they require a lot of work to get them to fit and even then, they don’t. So I decided (on the advice of other builders) to make my own.

Here’s the right rear window. The plexiglass is covered so it doesn’t get scratched during building.

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I covered the window area with duct tape. Here’s the right rear window.

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Then I covered the edge with four layers of BID.

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This is the windshield with the layups around the edge.

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Top is the factory left rear window trim and bottom is mine.

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In the middle is my one-piece windshield trim and the two-piece factory trim. The windshield trim doesn’t need to be one piece but it’ll be easier to trim it to fit than try to make it bigger.

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6.0 A-Pillar Beam (Overhead Switch Panel)

This entry is part 36 of 42 in the series 06 - Fuselage

The overhead switch panel is the beam which joins the A-pillars across the top. Just like the B-pillar beam, I added a couple BID of carbon fiber inside and out to increase the strength. Next, I had to decide how to join it to the A-Pillars. Here you can see that it doesn’t quite line up.

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I could mount it as is and transition it or I could cut it down. As I’m taller than the average person, leaving it as is mean that it hangs lower. This COULD become a visual obstruction. It also means a bunch more work where it transitions to the A-pillar. On the down side to cutting it to fit is that I’ll have less room to work with when installing switches.

So I cut it down until if was even with the A-pillars. Then like I did with the B-pillar beam, I made a flange out of carbon fiber uni using the foam rubber trick. Here’s the result on the pilot side (the nylon tube is for routing wires).

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 Before permanently installing the beam, I needed to cut an opening and create a flange for where the switches would go.

Once again, here’s the beam before the opening:

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And here it is after:

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Closeup of the flange and nutplates:
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With a blank aluminum panel in place:
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Closeup of the panel:
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To mount the beam, I used structural adhesive on the inside and a couple layers of carbon fiber uni on the outside of the seam and BID along the front and rear.

This is the beam after mounting and during filling.

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Stuff you don’t think of until it’s (almost) too late.

Andy Millin came up with an absolutely brilliant thought. Rather than run the wiring for the plenum lights all the way from the front to the aft wall of the cabin, then up to the plenum, then forward to the lights; Why not create a tunnel between the inner and outer skin of the roof from the switch panel to the plenum? It’s only 4 inches instead of 20 feet! He did his BEFORE installing the overhead beam. But where there’s a will, there’s a way.

I drilled two holes; one where the forward edge of the plenum will be and the other behind the switch panel.

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Then I started tunneling. Using a sharpened clothes hanger and some other MacGuyver-type tools, I was able to break though. Then I inserted at length of nylon tubing.

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Then I filled the area around the tube with epoxy/micro.
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Once the micro cured, I cut the tubing flush.

6.9 Overhead Fresh Air Plenum Modification

This entry is part 15 of 42 in the series 06 - Fuselage

Plenum Modification

The front of the overhead plenum tapers down to the roof. Here’s this picture again where you can see what I mean.
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It occurred to me (after painting the darn thing) that doing the interior is going to be a challenge. Most of the ceiling is covered with a thin flexible board (almost like cardboard) which is covered with fabric or vinyl or leather or whatever you want. But what to do at that taper?

So I decided to lop it off and square is up. After that, I had to paint the area and blend it in with the existing paint.
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13.5.2 Cabin Lighting

This entry is part 53 of 67 in the series 13 - Electrical / Instruments

First I built my overhead courtesy lights. Click here for a refresher.  I even etched my own circuit boards.

Then I decided to add an “all on” feature which required a circuit board redesign. For version 2, I had the circuit boards etched by a company that specializes in that work.

Then I decided that I wasn’t happy with my dimming choice.  There’s a good chance that I’ll want to dim these lights. My plan was to connect a potentiometer (variable resistor) to the supply side. But LED’s are weird little ducks. With incandescent lights (24 volt, for example), they begin to glow with about 1 volt and get brighter with increasing voltage up to 24 volts. So to dim incandescent lights, you connect a pot (short for potentiometer) that allows you to adjust the voltage going to the lights.  This works just like the dimmer in your house.

But like I said, LED’s are different. First, they’re current driven instead of voltage driven. But to keep things simple, we’ll approach this from the voltage side. The second (and this is what caused my current problem) is there operating range. The LED’s I chose were 3 volt LEDs (I reduced the voltage to the LED’s using a fixed resistor). But here’s where the dimming problem came in. These LED’s don’t start to light until about 2.4 volts. So with the pot installed, you turn it and nothing happens for the first 3/4 of a turn and then the slightest movement of the knob causes a huge difference in brightness for the remaining 1/4 turn.

So I had to educate myself with how to power and dim LED’s. So I started looking for dimmers. I found a guy that makes a bunch of stuff for the experimental aircraft market. He makes a dimmer called EGPAVR (Extraordinarily General Purpose Adjustable Voltage Regulator). With it, you can define the lower and upper voltage levels for your lights. So I picked up a couple and started testing my new design. One other modification I made was to increase the number of LED’s in each fixture. You can always dim or turn them off, but you can’t make them brighter than max brightness.

Here’s my test setup. The LED’s are on the breadboard. The EGPAVR is to the right. A variable resistor used to determine the fixed resistor values is to the right of the EGPAVR and I have two meters to monitor the voltage and current levels.

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Once I had the values for the fixed resistors determined, I designed my new circuit boards and sent them to be etched. When they came in, I disassembled the old lights and got to work.

The new PCBs

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Each card and circuit boards for two light fixtures.

Marked for cutting.

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And after cutting.

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Here the light fixtures ready for assembly.

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Circuit boards have been mounted to the back and holes drilled.

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Resistors and diode inserted.

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LEDs mounted.

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And finally the wiring harness and connector installed

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6.3.2 Front Seat Assembly

This entry is part 37 of 42 in the series 06 - Fuselage

The seats consist of a pan (the part you sit on), a seatback and a hinge. The front seats use a new adjustable hinge which lets you change the angle of the seatback. The rear seats have a fixed angle.

Here are the three parts for one of the front seats. There’s also a rail (not pictured) that the seats mount to which allows you to slide the seat front-to-rear.

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Now the this adjustable hinge is new and it doesn’t fit to the seat pan very well.

 Here’s the approximate position of the hinge on the seat pan.

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 But the hinge is wider than the seat pan.

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Notice the space between one the hinge arms and the seat pan? If I were to screw it in place the hinge would bind.

 The gap is exactly 1/8″. And I just happen to have some extra 1/8″ stock laying around so I made a pair of spacers.

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 I used structural adhesive to bond these to the sides of the seat pan. Then I marked the holes, drilled and tapped them.

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 The seatbacks have been redesigned to work with the new hinge so no modifications were needed there. It was simply a matter of drilling and tapping the holes. Then I put everything together.

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Next I had to mount the finished seats to the rails. Four holes are drilled in the seat pan that go through to the rails. Once I located and drilled the holes, then I started thinking about how to attach the pan to the rail. I could use bolts and nuts, but then I wouldn’t be able to remove the pan from the rail once it had foam and upholstery. And I’ve spent enough time fussing on my current plane about stupid engineers who design things without thinking about someone needing to take it apart later.

So here’s what I did. I cut some 1/2″ aluminum into 1.5″ squares.

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Then I cut an opening in the top (inside) layer and dug out the foam to make a recess.

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Then I put the aluminum hardpoint in the recess with structural adhesive.

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And then cover the hardpoints with a layer of BID. Once it cures, drill and tap the holes.

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Now the seat can be removed from the rails.

6.9 Overhead Fresh Air Plenum Installation

This entry is part 16 of 42 in the series 06 - Fuselage

Now that the overhead beams are installed, the modification to the front of the plenum is done and the lighting for the overhead air plenum is finished, it’s time to install the plenum itself. I had to cut away the side where it meets the overhead beam to the B-pillars. Then I spread structural adhesive and riveted the plenum in place. Most builders probably leave it at that, but I put down a 1 BID layup.

Here’s the plenum after the 1 BID layups had cured.

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Then it’s finishing time. Most builders cover the A-pillars, B-pillars, beams and plenum with some type of upholstery (leather, vinyl, cloth, etc).  But since I decided to follow Andy Millin’s lead and paint these parts, it was time to get to work. As much work as the plenum was, it was EASY compared to these surfaces! The plenum was on a workbench. The surfaces I was working on how were not so easy to work with.

But eventually it was time to paint.

Here’s the result:

B-pillar and part of the plenum

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Closeup of the plenum with the map light.

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Hand hold on the pilot’s side A-pillar.

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Overhead switch panel (with sample switch).

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