Center Panel Section Arrives

The fuel tank was still holding air after two days so felt confident to move on and get things ready for the final instillation. One uncompleted task involved installing six nutplates on the flange of the T-1211 fuel filler neck.  Last fall, the filler neck was mated with the turtle deck skin and match drilled to the holes in the turtle deck … but the nutplates were never installed at that time. So to finish off the fuel filler neck, nutplates were screwed in place and the nutplate rivet holes were drilled into the flange on the T-1211 filler neck. Because the fuel filler neck will reside under the turtle deck skin, the nutplate rivet holes in the flange require countersinking for flush rivets. After the countersinking was completed, the nutplates were riveted onto the flange on the fuel filler neck with AN426AD3-4 rivets.

Using the pneumatic squeezer to rivet nutplates ono the T-1211 fuel filler neck.

The instrument panel’s center section finally returned from powder coating … but prior to installing any of the instruments, it was necessary to remove the powder coating from the inside of all the cutouts and holes. The AP and Knobs panels would not fit in the cutouts nor would the screws go through the holes …. So a lot of time was spent using jeweler’s files to remove the powder coating. By the time the powder coating was removed, there was only enough time left to install the AP & Knobs Panels modules. One thing I did NOT do was install the nutplates that would normally be used to install both modules. By not doing so it saved me a little room, clearance wise, mostly at the top edge of the center panel … however, by doing this it required the use of the smaller MS21042-06 lock nuts which fit well (barely). The main reason for using MS21042-06 nuts is because the AP & Knobs panel modules were offset to the left from their normal center mounting to make room for the backup airspeed indicator. By doing so, it placed the modules more into the curve of the panel, so it would have been necessary to grind a little material away from the ears on the nutplates to clear the upper forward fuselage skin when it gets installed. Rather than fuss around doing a bunch of custom fitting of nutplates, using the MS21042-06 locknuts in lieu of nutplates was a no hassle solution.

Both the AP Panel & Knobs Panel modules are now installed in the center panel … tightening the last screw while holding the MS21042-06 locknut with a 3/16 wrench.

Did not quite have the time to mount the backup airspeed indicator but will do that first thing during the next work session. Unfortunately, I forgot to take a photo of the backside showing the mounting hardware …. Will try to remember to do that and post the photo here later.

Fuel Tank Pressure Tested & T-01219C Vent Line Fabricated

While waiting for the center section for the instrument panel to come back from powder coating (should be this week), decided to move on to the last remaining task involving the fuel tank prior to instillation, which involves pressure testing the fuel tank. To complete the task, Van’s has the builder attach the fuel filler neck onto the fuel tank with a piece of hose and two hose clamps then place the fuel cap into the filler neck. Van’s plans has the builder cap off the fuel tank’s vent fitting and place a Schrader air valve on the fuel return fitting and use a balloon on the fuel outlet on the fuel tank. I did not like the idea of using a balloon so decided to use a 0-60 inches of water gauge instead. I deviated a bit from the plans in that the gauge was placed on the fuel vent fitting on the top of the fuel tank and the two fittings on the bottom of the fuel tank were capped off.


The regulator on the air compressor was turned way way down so air trickled out of the hose and the fuel tank was pressurized to 24 inches of water in about 8 seconds or so. For those interested in using an inches of water gauge for the pressure test, 1 PSI equates to approximately 27.7 inches of water … so by pressuring the fuel tank to 24 inches of water, I was under the Van’s 1 PSI limit.


CAUTION: When Van’s says not to pressurize the fuel tank more than 1 PSI they mean it! Even though the pressure was under the 1 PSI limit, the fuel tank was visibly bulging a little.


At first the tank would not hold pressure so the first thing I looked at was the fuel cap and filler neck attachment. (When Bernie and Mike K. helped with the assembly of the tank, we were careful to assemble the fuel tank with as much care and attention to detail as possible, so I would be truly shocked if the tank itself leaked). A leak detection liquid was used and it did not take long to determine the hose clamps needed to be really cranked down before the fuel tank would hold pressure.

After tightening the hose clamps on the filler neck, the tank began holding pressure. One can still see the aftermath of all the bubbles that were created by using the leak detector liquid.

The fuel tank is holding pressure at 24 inches of water.

Looking good after 15 minutes, the gauge is still holding at 24 inches of water.

While the fuel tank was left to pressure soak a bit, did a little cleaning and putting away of tools and parts trays from the bench to make room for the next task of making the T-01219C vent line for the fuel tank. This is the line that will run from the vent fitting on the fuel tank and pass through the hole in the upper right corner of the baggage bulkhead where it is inserted in the T just aft of the bulkhead.  I immediately ran into a small issue where the dimensions shown for the “1:1” drawing of the T-01219C did not match the measurements called for on the drawing. The drawing measured as follows:  The 2 1/6" dimension measured 2", the 6 5/32" dimension measured 6" and the 2 1/32" dimension measured 1 31/32". Decided to make the vent line using the printed dimensions shown on the drawing and did not use the drawing as bending template. If the vent line ends up being too big, I’ll return from the future and amend this post. The vent line only has two bends (95 and 50 degrees), so it will be a piece of cake to remake if the line needs to be made smaller.

The T-01219C vent line with the 95 and 50 degree bends completed … ready for one end to be flared to mate with the vent fitting on the fuel tank.

By bending to the printed measurements, one can see the vent line is a little longer than the actual “1:1” drawing.

Using the Parker Rolo flaring tool to flare the end of the T-01219C vent line that will attach to the vent fitting on the fuel tank.

Completed T-01219C vent line … hopefully, I did the right thing by making the vent line to the printed dimensions on the drawing as opposed to using the drawing as a template … time will tell.


After putzing the hanger for another couple of hours and meeting the new neighbor in the adjacent hangar it was time to close the hangar door and head home …prior to leaving, looked at the pressure gauge and it was at 21 inches of water. So in four hours the pressure dropped 3 inches of water. I’ll know tomorrow, but I believe the pressure drop is due primarily to the air temperature which had been slowly dropping throughout the late afternoon/early evening.

Approximately 4 hours later, the pressure in the fuel tank has  only dropped 3 inches of water. Guessing this has more to do with the temperature in the hangar steadily dropping from the afternoon’s high temp thus reducing the pressure inside the fuel tank.

Autopilot Disconnect Switch Readied for Instillation

After doing a little more dressing of the wiring in the instrument panel, decided to do a little prep work on the autopilot disconnect switch. When fabricating the separate mounting bracket for the controls, the mounting hole for the AP disconnect switch was not drilled. At the time, I was planning on only using one of the switches on the Tosten control grips to disable the autopilot. However, have decided to go ahead and install the AP disconnect switch for a couple of reasons … one being the control panel will conform to other RV-12’s and by having the AP disconnect switch installed, it will be a convenient location for wiring the autopilot disconnect wire from one of the switches on the Tosten control grips.

When installing the optional AP Panel module, the Autopilot connector on the AV-50000A Control Module is replaced by a new wiring harness that comes with the AP Panel kit. The white F452 wire from that harness is the autopilot disconnect wire and is attached to pin 1 of the Molex connector for the AP disconnect switch. Pin 2 is the black ground wire for the switch. Pin 3 is the yellow/purple cockpit lights power for the internal LED in the disconnect switch and pin 4 is the yellow/green cockpit lights – wire for the LED light. When the AP disconnect switch is pushed, the switch places a ground on the white F452 autopilot disconnect wire … so this will be a convenient point to attach the autopilot disconnect wire from the Tosten control grips.

The autopilot disconnect switch. Pressing the AP disconnect switch places a ground on the white wire which trips the autopilot off. … this will be a good wire to mate with the autopilot disconnect wire coming from the switch on the Tosten control grip.

The white wire in my hand is the F452 autopilot disconnect and will be wired to pin 1 of the Molex connector.

The female .093 Molex connector pin on the white F452 wire was cut off and replaced with a new female pin along with the addition of the AP disconnect wire from the Tosten control grips. The two wires were both crimped onto the connector pin and will be inserted in position 1 on the Molex connector. When crimping the connector pin, I was not able to see the wires in the connector and discovered the yellow wire pulled back a little and the strain relief did not capture the insulation on the wire. Decided to use a tiny piece of heat shrink tubing on the wires to aid as a strain relief. Plus all the wires will be snugged together with wire ties so adding the heat shrink was probably unnecessary but makes me feel a little better. The overall diameter is small enough that the heat shrink should not interfere with inserting the pin in the Molex connector.

The yellow wire is the AP disconnect wire from the switch on the Tosten control grips … that wire was crimped along with the white F452 AP disconnect wire. This pin is now ready to be inserted into position 1 on the Molex connector for the AP disconnect switch.

The AP disconnect switch requires a 1/2" hole drilled into the mounting bracket for the controls. Typically, the center panel section has a tiny hole that gets enlarged to 1/2" when the auto pilot is installed. In my case, the DOG Aviation RV-12 uses a modified separate mounting bracket for the controls, so needed to make my own hole by drilling a lead hole then used a step drill to enlarge the hole to 1/2" to accept the AP disconnect switch.

Using a step drill to create a 1/2" hole in the controls mounting bracket for the AP disconnect switch.

The AP disconnect switch temporarily installed in the newly drilled mounting hole … it fits.

Readers may be wondering what the blue tape with the red marks is being used for. While working with the mounting bracket for the controls, each one of the controls was test fit into its respective hole (after some powder coating was filed away from each hole) so measurements could be taken to determine how much room is taken up by the mounting hardware. Measurements were made to determine how much space remains for engraved labeling. I was so pleased with the way the labeling turned out for the fuel pump and landing light switch that the decision was made to make similar engraved labeling for the controls as opposed to stick on labels ... so measurements were taken and drawings were made for the engraver.

Fuel Pump & Left Landing Light Switch Wiring Completed

Finished up the wiring for the two panel switches today beginning with the left landing light power wire. Frequent readers of the DOG Aviation blog may recall a few weeks ago I contacted Van’s about the current rating of the unused extra power circuit (pin 14) available at the connector on the back of the AV-50001 Power & Switch module and received the reply that it is was rated to 5 amps, so decided to use this location as the power source for the left landing light. However, the pin 14 extra power circuit is an unfused circuit so went to an automotive store and purchased an inline fuse holder. Doing the calculations for the fuse value resulted in needing a fuse just a little over 3 amps so the next size larger was used and a 4 amp fuse was placed into the fuse holder.


I would have liked to have placed the inline fuse holder nearer the AV-50001 module, but it would have made getting at the fuse very difficult should it ever blow. A compromise was made and the fuse holder was placed just ahead of the left landing light switch’s “C” terminal. To finish off the wiring for the fuel pump switch the wire going to the fuel pump was attached to terminal “1” on the switch.

Completed wiring for the fuel pump and left landing light … a 4 amp fuse was placed in the fuse holder which can be seen in the left side of the photo.

Fuel Pump & Left Landing Light Switches Installed

Those that have been following the DOG Aviation blog know installing panel mounted switches for the fuel pump and left landing light has been in the works. Wanted to have nice labels made for the switches as opposed to using a Dymo style stick-on label. Decided to use the same style of label material Pete used in his gorgeous RV-9A (www.myrv9.com) which is a two color layered plastic .020 thick that when engraved exposes the color below …. flat black with white underneath was chosen.


The goal was to have the engraver cut the rectangular slots for the panel switches into the label material so the two switches could be installed onto it. This required the need to create a scaled detailed drawing for the engraver, but I did not have software in the new home computer I trusted to get the scaling correct. Mike K.’s wife Kim came to my aid and helped me create a scaled drawing using her sewing machine software …. yep, that is right, sewing machine software. Once I had a scaled drawing to work from that had the correct switch positioning and scaling, I was able to modify it for engraver.  Thanks to Kim, I was able to obtain the correct scaling for the switches.


One of the down sides of the sewing software is that lines are thick because they represent stiches, but that was easy to fix using picture editing software at home. Once the drawing was converted to a single line a font was chosen that is a close match to the font on the ignition switch module. This was taken to the engraver who understood what I was trying to achieve and did an outstanding job of creating the label for the two panel switches. A special thanks to the employees of Engravers Edge for creating exactly what I was looking for.

The label for the two panel mounted switches that will be installed above the ignition switch module.

Even though the bezel on the two switches will keep the label in place, the decision was made to place a really sticky tape on the backside of the label … so the label needed to be installed correctly the first attempt. To aid in the alignment of the label while sticking it in place onto the instrument panel, the two switches were inserted from the back side of the panel so they could be used as alignment guides. Because the plastic for the label is a two color plastic the sides show as white so a black permanent marker was rubbed along the edges to blacken them prior to installing the label onto the instrument panel.

The two switches were inserted from behind the panel and used as an alignment guide for positioning the engraved label.

Fuel pump and left landing light switches installed along with the engraved label.

For those fellow builders that are interested in the switches being used, they are the same type used by Van’s in the Fuse and Switch module. The switches are manufactured by Otto and are from the K1 series. Otto manufactures a plethora of switches in this series with long part numbers and each letter in the number means something like momentary on, or steady on, terminal style, LED or no LED, LED voltage rating, color of LED lens, etc. The part number for the Otto switch in the K1 series that has off to steady on operation, with a 12 volt LED and green lens is:  K1ABAPCABA.

The Otto K1ABAPCABA rocker switch is from the same family as the switches Van’s uses in the Fuse & Switch module.


Below is a diagram I made of the back of the switch and a schematic of the internals.

Drawing of the back of the Otto rocker switch and internal schematic.

Wiring of the switch is straight forward. Using the wiring for the fuel pump as an example the “C” terminal is the voltage source to the switch … the power comes from pin 29 of the fuselage connector which would normally go directly back to the fuel pump. Terminal 1 goes to the load … in my case the wire to the fuel pump. Terminal 3 is the ground for the internal LED in the switch which can be wired directly to ground … or, as I have done, wired so the LED can be dimed for night flying by using the Cockpit Lights – wire from pin 18 of the Options connector. The SkyView controls the lighting level by using a varying resistance on the ground wire for the panel and  cockpit lighting, so I intercepted the Cockpit Light – lead and ran it to terminal 3 on the two panel switches, then on aft to the cockpit light.

The white/yellow wire comes from pin 18 of the Options connector which is the Cockpit Light – wire and is connected to terminal 3 (LED ground) of both switches. The yellow/green wire is the wire that continues aft to the cockpit light mounted on the roll bar and will supply the ground for the cockpit light. Of note, the fuel pump switch is on the right and the left landing light switch is on the left.


As can be seen in the above photo, most of the wiring for the switches completed during the work session except for two wires. All that is left to do is connect the wire to the fuel pump and connect the power for the landing light after adding a fuse to the circuit.  Had it not been for spending a huge chunk of time searching for the .092 Molex connector pins (mentioned in the previous post) during the afternoon the switch wiring would be completed.

Riveting Of Tail Cone Nutplates Finally Completed

Bernie came by the hangar today to give me a hand with riveting the last two rivets for the nutplates closest to the upper surface of the stabilator. My original plan was to use a rivet gun to set the remaining two rivets … but upon much closer analysis, we decided that would be risky. The problem stemmed from the stabilator’s mounting bracket being very close to the rivet hole that the rivet gun could possibly easily begin banging on the bracket.  Decided to just use a pop rivet instead … both nutplates have one solid rivet in them, so the nutplates are not going anywhere. Ended up using CCR264SS-3-2 rivets in the place of the AN426AD3-3.5 rivets.

The rivet closest to the upper skin of the stabilator received a CCR264SS-3-2 pop rivet. Felt this was safer than pounding the rivet because of the close proximity to the stabilator’s mounting bracket which can be seen in the photo just below the rivet.


After finishing up with the tail cone, was showing Bernie how the autopilot disconnect was going to get wired and realized I did not have any Molex .092 connector pins. I had pins for the .063 connectors but not the larger .092 connectors. So a fair amount of time was spent this afternoon trying to locate pins locally. After locating the connector pins,  began working on the wiring for the two rocker switches for the fuel pump and the left landing light which will be covered in the next post.

Riveting Of Tail Cone Fairing Nutplates Completed – Almost

Over the past few days there have been just a couple of very short work sessions, but have been able to finish dimpling all the nutplate rivet holes on the tail cone. Fortunately, access was good and all twelve nutplate rivet holes on the lower portion of the tail cone were dimpled using the pneumatic squeezer.

Riveting tail cone fairing nutplates onto the lower portion of the tail cone.

For riveting the nutplates, I choose to use a no hole yoke because it offered more clearance for riveting the nutplates on the upper portion of the tail cone in the vicinity of the rudder horn and rudder cables … it worked out quite well.

The no hole yoke sets the rivets without the use of a die on the yoke and is also shaped differently so it offers more clearance.

All the nutplates on the lower portion of the tail cone are now installed.

The four rivet holes that needed to be dimpled using the C clamp will need to be riveted using a rivet gun because of clearance issues. Of course, one could always remove the vertical stabilizer and the stabilator and there would not be any issues. I have elected to work around them so will use a rivet gun and bucking bar to set the remaining four rivets … the two rivets closest to the vertical stabilator and the two rivets closest to the upper skin of the stabilator.

Using the rivet gun and bucking bar to rivet the nutplate rivet closest to the vertical stabilizer.

Was able to finish off setting all of the rivets for the nutplates with the exception of the two closest to the stabilator. Because of the location, did not feel comfortable attempting to do this by myself, so will enlist Bernie to give me a hand later today to set the remaining two rivets thus putting this chapter of the build to rest.

Dimpling Tail Cone’s Nutplate Holes Presents Challenges

Although a relatively short work session did made some forward progress on the nutplates for the tail cone’s fairing despite running into a few clearance problems. Work this session involved drilling the rivet holes for the six nutplates that secure the upper half of the tail cone’s fairing. The drilling of the nutplates for the upper half of the tail cone’s fairing was accomplished using the same drilling methods covered in the previous post for the lower half of the fairing.

This portion of the tail cone’s skin is flat, so drilled the nutplate holes from the outside using the angle drill outfitted with a #40 drill bit.


After all the rivet holes for the nutplates were drilled, they need to be marked for positioning then removed for deburring and dimpling … this was done one nutplate at a time so labels did not need to be made. Marks were placed on one of the nutplate's rivet holes in the tail cone's skin and the corresponding rivet hole on the nutplate to identify positioning for reassembly. I quickly ran into issues when attempting to dimple the nutplate rivet holes closest to the vertical stabilizer … the pneumatic squeezer could not get onto the rivet because the squeezer’s yoke interfered with the rudder’s horn. I tried a couple of different yokes to no avail and a hand squeezer …. shy of removing the rudder (not an option), nothing seemed to work. After a little brainstorming, came up with the idea to set the dimples using a C clamp.

Because there was not enough clearance to use the pneumatic squeezer for setting the dimple in the nutplate rivet hole closest to the vertical stabilizer, opted to use a C clamp to compress the dimple dies together. Although a little scary, took it slow and this method ended up working out quite well.

After using the C clamp to squeeze the dimple dies together, the dimple was checked with a rivet … this rivet is sitting flush with the skin … time to move on. The red marking denotes nutplate positioning for reassembly.


Working from the top down, the nutplate rivet holes in the tail cone were dimpled along with the corresponding nutplates. All was going well until reaching the lowest rivet hole closest to the stabilator. Even with the pneumatic squeezer sitting on the skin of the stabilator, there was not enough room to get the dimple dies close to being squared up … so resorted to using the C clamp again to make the dimple.

The C clamp was once again enlisted to create a dimple … this time for the nutplate rivet hole closest to the stabilator.

Did not have the time to finish off all the dimpling so will finish that off during the next work session. I can see now riveting the nutplates onto the tail cone skins at the tight spots may present a challenge … sure all the tail feathers could be removed to allow for unobstructed access, but would prefer not going that route if I can find other methods that work.