All Roads Lead To Prep & Prime

At this point in the build everything that can be worked on to continue assembly of the RV-12 seemingly requires something to be primed. The rudder pedal assembly receives a wiring bracket during instillation … that bracket needs to be primed. The electrical connectors for the wings need to have their mounting brackets and cover plates primed so the connector instillation can be completed. The side skins could be installed now but one of the stiffeners that mates with the side skins needs to be primed.

To complete the wiring to the instrument panel, the tail cone needs to be installed so the electric trim motor wires can be run through the fuselage up to the panel  … but I’ve been dragging my feet on that knowing there has been a modification in the works for the tail cone at Van’s. That modification was just released earlier in the week and was immediately ordered by the DOG Aviation procurement department. That modification, which will be discussed in the coming days, consists of a stiffener rib that will be installed in the tail cone … of course, the rib also needs to be primed.

All roads lead to primer. That being the case, headed up to the hangar and retrieved most all of the parts that need primed except fuel tank components. Figure it’s time to deburr and prep a bunch of parts for primer to make the hassle of cleaning the HVLP spray gun worthwhile. Looks like the next few days will consist of deburring and preparing parts for a primer session later next week after the monsoons end.

Parts needing to be primed. Foreground left are parts holding up progress, foreground right are parts separated today on the band saw ready for deburring. Background is mostly cover panels and flooring ready for deburring.

Aircraft Specialty Brake Lines - Matco Parking Brake

The RV-12 kit as shipped from the factory has no provisions for a parking brake. I understand Van’s is trying to keep builder costs down and to a lesser degree, perhaps weight. However, one would think in today’s day and age there would at least be a parking brake option ... sadly none is offered. A parking brake is not complicated, in fact, it is simplistic ... it is just a valve attached to a pull lever. To set the parking brake, the brakes are applied and the parking brake’s lever is pulled. This rotates a valve that prevents the applied pressure to the brakes from releasing … thus keeping the brake pads compressed onto the rotors, keeping the brakes applied.

While at this stage of the RV-12 project, since the RV-12 is being built under E-AB rules, feel it would be totally daft on my part not to incorporate the instillation of a parking brake while access is easy. Yes, there have been some inventive designs for control stick gust locks which incorporate pushing on the brake pedals as part of the rudder lock. This is fine, but hardly worth the time and effort needed to dig out the gust lock from the baggage area, install and adjust it just to make a quick fuel stop ... or to go inside a FBO for a restroom break ... or to procure refreshments. The Matco PVPV-D parking brake comes to the rescue.

Photo of the Matco PVPV-D dual parking brake valve.

One of the reasons the brake lines have not been installed yet on the rudder/brake pedal assembly was due, in large part, to wanting to install better quality brake lines on the RV-12 other than the plastic tubing Van’s supplies with the kit. From following the forums, I knew Aircraft Specialty as working on offering a brake line kit for the RV-12 made from Teflon hose covered with stainless braid and coated with clear vinyl. Sign me up! The DOG Aviation procurement department contacted Steve at Aircraft Specialty and requested a brake line kit that will connect to the Matco parking brake planed for the RV-12. This was around the beginning of May if I recall correctly and Steve told me they were putting the finishing touches on a kit and that the brake lines were currently being fitted onto a test RV-12 to verify fit.

As it turns out, DOG Aviation has taken possession of Aircraft Specialty’s first complete RV-12 brake line kit for customers desiring Vinyl coated, Teflon and stainless brake hoses which will interface to the Matco PVPV-D parking brake. First impressions …. the kit contains extremely high quality hoses complete with all the fittings necessary.  The quality of the materials and workmanship is outstanding. Steve even screwed the fittings onto both ends of every hose so there was no question as to which fitting should be used with a particular brake line. A nice touch and shows good consideration for Steve’s customers. Of course, it will be many, many months until the hoses are filled with fluid so won’t know if they will leak … but judging by the way they look, seriously doubt there will be any issues.

The complete RV-12 brake line kit offered by Aircraft Specialty … Teflon hoses covered with stainless braid and coated with clear Vinyl. The two larger diameter hoses on the left with red caps are the brake lines that will run down the landing gear legs to the wheel brakes. In the center is the Matco PVPV-D parking brake assembly.

Because the bulkheads are already assembled and the bottom skin installed, it did not seem prudent to take a chance on attempting to increase the diameter of the holes in the bulkheads to accept through fittings for the brake lines. Too much can go wrong at this point making the risk far overweigh the reward. As such, the DOG Aviation RV-12 will still have a small section of plastic brake line running from the Matco parking brake through the center tunnel to the fittings for each gear leg’s brake line. This will be OK because this line does not move and is not exposed to the sun or elements. I suppose most current RV-12 owners retrofitting their RV-12’s will do the same thing.  The main thing is all of the brake lines that connect to the moving rudder/brake pedal assembly or are outside the aircraft’s fuselage and exposed to the elements will be the new Teflon hoses covered with stainless braid and coated with clear Vinyl.

Installing one of the hose fittings into one of the Matco master cylinders using Loctite 567 thread sealant.

Completed rudder/brake pedal assembly now ready to install. Note: For completeness, the not yet installed round brake fluid reservoir was included in the photo so the reader can see how Aircraft Specialty’s brake lines interface to it.

Also of note … the above photo shows the Matco parking brake valve and how the two brake lines with yellow caps will attach to it. The Matco parking brake will be installed sideways near the top of the F-1217A right tunnel rib just below the tunnel’s cover plate.  The exact position will be determined after the rudder/brake pedal assembly is permanently mounted ... but it appears it will be located above the cross brace.

Nav/Strobe & Landing Light Shielded Cables Terminated

It is amazing how much work a pet can create … case in point, our rescued cat. It started last summer and was pretty much like watching scenes from a Looney Tune’s Tweety Bird & Sylvester cartoon. What self respecting cat can ignore being taunted by a multitude of tweeting Sparrows perched in the bushes just outside the porch's screens? or pesky flies just asking for it? not to mention  turf disputes with other trespassing cats! Well, the very, very old porch screening has not been much of a barrier for a laser focused cat on a mission ... and subsequently, numerous holes and rips have been created in the tired old metal screening. You can see where this is going … yet more time spent away from the RV-12 project replacing all the porch screening with a more robust “pet resistant” (at least in theory) screening. This has turned out to be yet another one of those projects which has become a time sucking abyss. However, in between rain storms and the need to get off ladders, some forward progress has been made on the RV-12.

In preparation for the switch being installed to control the electric fuel pump, the red wire that powers the fuel pump was removed from pin 29 of the fuselage connector using a pin removal tool. The plan is to install a new wire from pin 29 to one of the recently purchased rocker switches and hopefully have enough wire length to secure the removed wire which runs to the fuel pump onto the rocker switch without making any splices. At this point, it looks good .... the final switch position on the panel will be determined later after seeing how much room there is once all the panel goodies are installed.

Inserting the pin removal tool to release the fuel pump wire from position 29 of the fuselage connector.

The electric fuel pump wire with removal tool after the wire was removed from position 29 of the fuselage connector.

After the electric fuel pump wire was successfully removed from the fuselage connector, a replacement 18 gauge red wire was prepared. This new wire  will run from pin 29 of the fuselage connector to the yet to be installed panel rocker switch for the electric fuel pump. The male and female connector pins can either be soldered or crimped … I chose to use a special crimping tool made especially for crimping these connector pins. The tool has four crimping fingers which push into the barrel of the connector pins. As the tool is squeezed, it creates four dimples around the circumference of the connector pin’s barrel … thus compressing the barrel onto the wire. It is very easy to use … insert a stripped wire into the barrel of either a male or female connector pin, place the wire and connector pin into the hole in the crimping tool until the connector pin bottoms out in the tool ... then squeeze the ratcheting handles until the handles release. Presto! A completed crimp.

Inserting the wire with pin into the special ratcheting crimping tool.

Completed wire with the newly crimped male connector pin which will run from position 29 on the fuselage connector to the yet to be installed fuel pump rocker switch.

With the exception of installing the extra switch to power the left landing light, the wiring at the instrument panel end of things for the shielded cables being installed for the landing lights and the navigation/strobe lights is now completed. The two shielded cables were prepped and the 18 gauge wires were terminated with female pins and installed into the appropriate positions on the options connector. Unlike the fuselage connector, Van’s already shrunk the heat shrink around the wires going into the options connector. I did not want to make any cuts in the shell of the connector so decided to strip back the shielding on the two cables so the shielding ends just before the shell of the connector.

Stripping back the shielding with a pair of flush cutters.

Heat shrink tubing was placed over the separate 18 gauge wires for added protection where the wires enter the shell of the connector and also where compressed under the strain relief. A second larger piece of heat shrink was placed over the cables where the shielding was terminated to make a smooth transition.

Upper cable is the completed wire prepping. The bottom cable shows the heat shrink on the separate wires prior to sliding the larger piece of heat shrink over the transition area.

Female connector pins were crimped onto the ends of the four wires and the wires were inserted into their correct locations on the options connector … followed by reinstalling the connector’s shell.

The completed options connector with shielded cables installed for the navigation/strobe lighting plus the right landing light power and Wig-Wag power for both landing lights.

A separate 18 gauge wire was pulled through the wire grommets from the instrument panel to the electrical connector for the left wing. This wire will be connected to a yet to be installed rocker switch which will control the left landing light’s steady on power. This idea has been strategized in previous posts on the topic.

RV-12 Panel Switches Sourced – A Duh Moment

Admittedly, not much big progress has been made on the RV-12 as of late. Aside from a little work here and there, have not spent any serious time in the shop and have been doing other things while enjoying the long anticipated warm weather.

With the changes in the wiring mentioned in a previous post, panel switches will be needed for the left landing light and additionally a switch for the electric fuel pump. Preferred not installing plain old toggle switches, so the search was on to find rocker switches that match the RV-12's panel switches. A big thanks to RV-12 builder Dave at Schmetterling Aviation for taking a very good photo of his instrument panel from above that clearly shows the panel switches are soldered onto circuit boards. After seeing that, decided not to attempt ordering the switches from Van’s because I preferred not to etch a printed circuit board just for two switches, so began searching for switches that are similar but non congruent … in that they should look identical but have either screw or spade terminals.

Return fron the future. Correction – My assumption that the rocker switches are soldered onto a PC board is NOT correct. It was pointed out to me that the Otto part number I came up with below for the RV-12 rocker switches is indeed the actual part number Van’s uses for the RV-12’s SPST rocker switches. I revisited the photo mentioned above which I based my solder assumption on and upon a MUCH closer inspection, one can see that female spade connectors are soldered onto the PC boards and the male spade connectors on the rocker switches just plugged into the female connectors. Gee, wish I would have known that a couple of weeks ago, for it would have saved me many hours of research.

The Van’s Air Force forums were searched for a lead on the switches … found a few threads pertaining to finding a source for the switches but it appeared nobody had ever posted a vendor source. I spent hours to no avail searching on the Internet for rocker switches that looked like those installed in the RV-12’s panel. Finally, I decided to call Stein (a supplier for some of the parts on the RV-12) and was told he does not supply the panel switches, but thought they may be made by “Auto”.  So I began spending hours doing new Internet searches for “Auto” rocker switches … here again, to no avail basically only seeing automotive type switches.

Then finally the “duh moment” … I ran across a switch manufactured by a company called Otto.  Duh !!! Stein didn’t say Auto … he said Otto!!! Got on their WEB site and was pleased to find what appears to be exactly the same panel switches as used on the RV-12’s instrument panel.

The elusive rocker switch manufactured by Otto that appears to be an exact match for the RV-12 except this single pole single throw version uses spade connectors and not printed circuit solder connections.

The Otto K1 single pole single throw rocker switch with spade terminals and 12 volt green LED light.

Otto makes rocker switches available as either a single pole (K1) or double pole (K2) switch. The letters after the K1 or K2 designate the connection type, switch color, LED light voltage, ect.  The part number for the Otto single pole rocker switches ordered by the DOG Aviation procurement department is K1ABAPCABA. Otto has a PDF file on their WEB site describing the multitude of available combinations for their K1 & K2 rocker switches but here is what the long part number means for the switches ordered.
K1 - Single pole rocker switch
A - Quick Connect standard spade leads
B - Actuator color of black
A - Switch action … on in “A” position, off in “C” position (single pole single throw)
P - Light type … 12 volt green LED
C - Lens color position “A” Green
A - Lens color position “C” None
B - Light/circuit location … Dependent light on in position “A” wired to terminals 1&3
A - Legend and orientation … None

Finding a distributor for the switch also proved to be challenging as well … some wanted a ridiculous minimum order, but it appeared Mouser did not. However, since I wanted a spare, I ordered three from Quist Electronics in Minnesota because they were a few bucks cheaper per switch than Mouser. Return from the future - also or what it is worth, a fellow builder informed me that Van’s charges $14 for the switches which is what I paid for them from Quist.

The schematic for the switch is similar to the one bellow. I tested the switch by placing 12 volts on the center terminal and a ground on terminal 3 … when the switch is placed in the “A” on position, the LED lights and 12 volts is placed on terminal 1 which will be wired to the load … in my case that will either be the left landing light or the fuel pump.

Internal schematic of the Otto K1 SPST rocker switch.

Wiring The Lighting System – Off The Reservation

For the most part, this post will document the instillation of shielded cables for the lighting system and IS NOT representative of the typical RV-12 wiring. Background: At the time Van’s selected AeroLED’s as the vendor for components in the RV-12 lighting kit, AeroLED’s did not suggest installing shielded wire for their navigation/strobe lighting … apparently the strobe lighting system was found to generate some electrical noise, so now the AeroLED’s Web site suggests wiring their nav/strobe lighting using shielded cable.

Because the DOG Aviation RV-12 is being built as E-AB and not E-LSA, the decision was made early on to take advantage of the flexibility building E-AB offers and install shielded cable for the navigation/strobe lighting … so the wings were wired accordingly when built. In addition, because a second landing light was installed in the left wing for Wig-Wag operation, decided to also run shielded cables for the landing light circuits as well, just in case the Wig-Wag mode also generates a little electrical noise … this is most likely total overkill (a trait I’m known to exhibit at times).

The deviation from Van’s wiring - the plan is to run two 18 gauge 2 conductor shielded cables from the instrument panel to the blue electrical connectors on the fuselage for the wings ... one cable for navigation & strobe power and the second for landing light and pulse (Wig –Wag) power.  Admittedly, working with shielded cable has its unique issues and there are more than a few ways to install the cables. Ultimately, the instillation method decided upon creates a lot of extra work, but think I’ll be happy with the results.

In a nut shell, the right landing light will wired per the plans from the instrument panel connector to the blue electrical connector, except shielded cable is being used. However, the additional left landing light that was installed will receive its steady on power from a separate panel switch, but its Wig-Wag operation will be on the Van’s supplied switch … this will be accomplished by way of running an 18 gauge shielded wire from the pulse power wire (Wig-Wag) on the blue electrical connector on the right side of the aircraft to the blue electrical connector on the left side of the aircraft. This will allow the left landing light to receive the pulse power for Wig-Wag operation yet remain off when the right landing light is steady on. The reason this is being done is to not overtax the electrical system’s power draw. The additional 2.6 amps the landing light draws will eat into the safety margin of the RV-12’s electrical system a little more than I would like. As mentioned in previous posts, Wig-Wag operation does not increase the current draw because only one landing light is on at a time. If ever flying at night, the separate switch on the instrument panel can be used to turn on the left landing light during short final. Of course, all this complicates the wiring somewhat.

Grounding shielded cable – when installing shielded cable, to be effective the shields should only be grounded at one location on the cable … which opens up lots of possibilities. For good or bad, the decision was made to ground ALL the shielded cables being installed for the lighting system to one of the previously established ground points on a seat rib near the center of the fuselage aft of the F-1203A bulkhead.

A solder sleeve with a grounding wire attached and the prepped area on one of the shielded cables for the landing light circuit.

For those not familiar with solder sleeves, they come in various sizes, with and without wires pre-attached … I used both styles and photos that show all black wires were wires I added to a bare solder sleeve. Basically, solder sleeves are a special heat shrink material containing a ring of a solder that melts in the center of the sleeve. The outer Tefzel coating is carefully removed from the cable exposing the shielding for the solder ring inside the solder sleeve. The solder sleeve is slipped into position over the exposed shield and a heat gun is used to shrink the solder sleeve and finally after a while the inner solder ring will finally melt fusing the wire to the stranded shield and thus creating a grounding point. Friends – you have to get it really hot with the heat gun before the center ring melts … amazingly, the Tefzel can take the heat.  After each solder sleeve was installed, an ohm meter was used to verify the ground wire made good contact with the cable’s shield and that the two conductors were not fused to each other or to the ground shield. All was well with all the cables.

The solder sleeve after being heated with a heat gun.

For the navigation/strobe power wires, decided to fabricate a "T" just aft of the F-1203A bulkhead so the nav/strobe power can be feed from there directly to the left and right electrical connectors. Working with shielded cables and the need for grounding complicates matters a bit, but was able to make a neat splice in the minimum length possible with great results. The shielded cable from the instrument panel was run through the existing wire run to the aft side of the F-1203A bulkhead.  The end of the cable was prepared for butt splices and solder sleeves were used to establish a ground point for each cable.

Verifying the measurements for the solder sleeve and butt splices on the 18 gauge two conductor nav/strobe power cable.

The nav/strobe cable going to the left wing was prepared in exactly the same fashion as above and placed in one end of the butt splice along with the cable from the instrument panel and crimped.

Nav/strobe cable from the instrument panel along with the cable going to the left blue fuselage electrical connector crimped together in the butt splices.

Completed "T" the shielded cable going to the right blue fuselage electrical connector added to the butt splices. Note all three cables have solder sleeves for grounding the sheilding of each cable. 

A larger diameter piece of heat shrink tubing was placed over the butt splices to finalize the nav/strobe “T”.

To complete the landing light Wig-Wag wiring a wire needs to be run from the master out on the right landing light to the slave in on the left landing light (think Wig-Wag sync). Additionally, to complete the wiring for the strobe lights, a strobe sync wire needs to be run between both strobe lights. Neither of these wires will carry current because they are in essence data lines, so a 22 gauge two conductor shielded cable will be run between the right and left blue electrical fuselage connectors.

The installed nav/strobe "T" in its final position. All of the black ground wires still need to be tied down to ground. Two of the three solder sleeves used on the other shielded cables can also be seen here and their ground wires also need to be tied down to the single point ground as well.

The Poor Man’s Standoff

Ever have one of those daze when nothing seems to go as planned and the seemingly simple turns into a time sucking abyss? Well today was one of those daze at DOG Aviation.  All that was left to do for the headset & auxiliary audio out jacks was to crimp two pins onto the left and right audio wires for the aux out jack then plug the wires into the micro Molex audio connector. Crimping the pins was easy enough but dressing the cable to my liking was a challenge.

The Van’s supplied audio wire going to the micro Molex connector for the headset audio is somewhat long … as is the wire harness from the headset jacks. No problem … just wrap them up and wire tie them right? Well, no matter how I tried to wrap the wires they would seemingly rub on something somewhere … a rib, the floor pan or the bottom skin. Perhaps folding the shielded audio cable may have worked, but did not really want to do that.

The seat ribs have some machining holes which, after fussing with the wires for quite a while, I decided to utilize for making a poor man’s standoff from vinyl tubing and wire ties.  I can’t take credit for the idea of using tubing to create a standoff, but have seen it successfully used by other builders … so made a mental note of the idea. Short pieces of vinyl tubing create the standoffs and a wire tie is looped around the wire to be mounted and then the cable tie is fed back through the vinyl tube, through the hole in the seat rib and cinched up. It sounds easier than it is in practice. Fortunately a good job was done smoothing the lightening holes in the seat ribs because it was necessary to fish my arm in through the holes to grab and pull the wire ties tight.

Forward vinyl tube and wire tie standoff made to keep the headset audio wires away from the seat rib.

Looking closely the aft vinyl and wire tie standoff can be seen adjacent to the micro Molex connector.

Admittedly, it is not the most attractive solution, but it does work well … plus it will keep the audio wires away from the lighting power wires that have yet to be connected to the blue electrical connector for the wing. At least now none of the headset’s audio wires are touching any of the aircraft’s structures.

Soldering Optional Auxiliary Audio Out Jack

Thus far all the wiring connections on the RV-12 have been either connectorized or crimped … however, the optional Radio Shack 274-249 1/8" stereo jack for auxiliary audio out requires soldering.  The Van’s drawing shows the auxiliary audio out jack needing to have two 47K ohm resistors attached to the jack, one on the tip and one on the ring connections … this requires soldering. For those new to soldering, the rest of this post is intended to provide helpful tips to hopefully alleviate your fears and help you produce good quality solder joints. For the most part, soldering small electronic components and connectors does not require a huge soldering iron … this is one arena where bigger is not better … a 25 watt soldering iron is more than sufficient for these small parts. For the soldering of general purpose electronic components, I have always had good luck with the Weller SP-23 (25 watt) solder iron outfitted with a cone tip. The cone tip is versatile in that the very tip can be used to apply heat to a small component or the entire edge of the cone can be used to apply a lot of heat when soldering larger surface areas.

A vice grip is used to prevent the small jack from moving. The two 47K ohm resistors are ready to be soldered onto the 1/8" stereo jack’s tip and ring soldering lugs - note the heat shrink tubing ready to slide over the solder joints once the soldering is completed.

Soldering electronic components is easily accomplished if five basic steps are followed.

1.  Soldering iron tips need to be kept clean and tinned ... often. Tinning is the process of melting solder on the tip of the solder iron when it first heats up to create a thin coating of molten solder over the entire tip. This helps to quickly transfer the heat into the work and allows the solder to flow quickly. I can’t overstress the importance of having a freshly cleaned and tinned solder tip. Some use damp sponges to wipe the tip onto prior to applying the tinning this practice is good for long soldering sessions … but for small soldering jobs, I just wipe the tip with a paper towel, immediately re-tin the tip with solder, shake off the excess solder onto a paper towel and then quickly solder the work.

2.  I won’t go into solder formulations but all you need to know is DO NOT USE ACID BASED plumbing solder or paste fluxes or solid solders when soldering electronic components. When soldering electronic components, ONLY USE solders containing rosin cores … my preference, 22 gauge solder or smaller because I find large diameter solders can tend to let a lot of rosin run out of the center core at times before the solder melts and this can become annoying and problematic.

3.  Commit - get in – solder - get out … you do not want to overheat the items being soldered. One of the worst thing you can do is dabble the soldering iron … by that I mean don’t lift the soldering iron off the work then place it back on the work … so on and so forth. Commit - hold the soldering iron on the work, flow the solder in and get off the work. Dabbling creates solder blobs and often contributes to creating cold solder joints, typically characterized by a dull or powdery silver appearance … not good.

4.  If at all possible, try making a solid mechanical connection prior to soldering and try to prevent the item(s) being soldered from moving. In the example for this post, the jack was secured in a vice grip - the resistors's leads were tightly bent around the solder lugs on the stereo jack and the 20 gauge wire was tightly wrapped around the resistor’s lead prior to soldering. It is acceptable to LIGHTLY tin stranded wire to help it hold its shape when attaching it onto another item.

5.  Let the solder flow into the connection. Commit and place the freshly tinned tip of the soldering iron firmly onto the work with light steady pressure and immediately try to feed a little solder into the location where the soldering iron is touching the work to begin melting the solder. The molten solder will aid in quickly pulling the heat from the soldering iron into the work and once the flow begins, keep feeding the solder until the item is satisfactorily soldered (but not to the point you are creating a large blob of solder) then quickly remove the soldering iron from the work. Also, while the solder is flowing, by dragging the tip of the soldering iron across the work one can spread the solder on the work … helpful when trying to fill an eyelet or soldering a long wire splice. When soldering stranded wire, consider placing the tip of the soldering iron under the wire, then feed in a little solder and once the solder begins flowing, transition the solder so it feeds in from the top of the wire directly above the soldering iron tip … for long splices move the iron across the bottom of the wire while following and feeding in solder along the top of the wire.

As always when learning a new skill, try experimenting and become comfortable with your soldering iron by soldering few pieces of scrap wire together until you get the hang of it. By following the five tips above you should have yourself making quality solder joints with very little practice.

The heat shrink tubing slid over the solder joints on the stereo jack and shrunk. Next the 22 gauge wire is wrapped around the resistor lead and ready for soldering.

After the 47K ohm resistors were soldered onto the tip and ring terminals on the 1/8" stereo jack, the heat shrink tubing was slid over the solder joint and shrunk with a heat gun. Next a 22 gauge wire was wrapped around the leads from the resistors and soldered.

The 22 gauge wire is now soldered onto the resistor leads and ready for more heat shrink tubing.

Heat shrink tubing was slid up the wire to cover the entire exposed resistor lead that the 22 gauge wire was soldered onto. After the heat shrink tubing was shrunk onto the resistor leads, a larger diameter piece of heat shrink was slid over the resistors to cover the small amount of exposed resistor lead where the heat shrink was slid over the solder connections at the stereo jack terminals.

Heat shrink covering the 22 gauge wire solder connections on the resistor leads.

Completed stereo jack with 47K ohm resistors and the 22 gauge wire solder connections all covered with heat shrink tubing.

Blog viewers may be asking themselves why just one piece of heat shrink wasn’t used to cover each resistor entirely? It very well may have been OK to do so. However, I though the heat shrink tubing being used was rated at the typical shrink ratio of 2:1 so was not sure if a diameter large enough to slide over the bodies of the resistors would shrink down enough to make a tight connection around the resistor leads. As it turns out, I forgot the DOG Aviation purchasing department had procured some high-grade polyolefin heat shrink that has a shrink ratio of 3:1 … but doing it with three pieces made a nice tight encapsulation of the resistors.

Auxiliary audio out 1/8" stereo jack mounted on the right floor pan.