Friday, May 23, 2014

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.

Tuesday, May 20, 2014

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.

Sunday, May 18, 2014

Interior Cockpit Light Mounted

It was good to get back into the shop today after such a long time away from the RV-12 project.  Found myself just staring at all the unfinished wiring trying to become reacquainted with the organized chaos and decided to finish off the mounting/wiring of the interior light.

The mounting bracket for the interior light was never machine countersunk last fall during the primer/interior paint marathon. There were three holes that needed to be machine countersunk for the flush pop rivets that are used to install the light. It would have been best to do this prior to painting, but care was taken not to mar the paint. The bigger issue was preventing the rivet holes from becoming elongated … so a piece of scrap hinge material was drilled and used behind the bracket to prevent the countersink bit from drifting and enlarging the rivet hole.
Machine countersinking the three mounting holes in the cockpit light’s mounting plate … note the hinge material used behind the hole to prevent the countersink bit from drifting.
Riveting the cockpit light onto the cockpit light bracket.

After the cockpit light was riveted in place, the previously installed wires run inside the roll bar were butt spliced onto the two wires for the cockpit light.

The plans give the builder the option of installing an external audio out jack (not included) for piping audio to external devices. At first though I would not install this option … but after seeing how cool Pete’s Go-Pro video camera is and how good the audio sounds, had a change of heart. A trip to Radio Shack secured a 1/8" stereo jack # 274-249 and two 47K ohm resistors required for the instillation.
Drilling the right floor pan directly under the existing headset jacks.

The plans instruct the builder to drill the hole for the aux audio out jack to 1/4" but that seemed a little large for the shaft of the Radio Shack jack so the hole was drilled to 15/64" and a very small amount of tweaking with a reamer produced a nice snug fit.
1/8" stereo jack with the two 47K resistors that will be soldered onto the tip and ring connections on the 1/8" jack and wired to the left & right audio connections on the micro Molex connector for the right headset jacks.

The resistors need to be soldered onto the jack and a brief search for a new soldering iron tip was not fruitful. The old soldering iron tip has been melting the blue plastic film and is now no longer acceptable to attempt a quality solder job. There is a new tip in the shop … just need to locate it tomorrow.

Tuesday, May 13, 2014

My First Flight In Pete’s RV-9A

The lull in activity at DOG Aviation has been due to visiting San Diego to attend the wedding for a son of a long time friend.  While in California, just had to visit Pete and see his now one year old RV-9A. After a late afternoon arrival at Pete’s house we endured late Friday afternoon rush hour traffic and made the trek to Chino airport.

Unfortunately, I moved away from California just shy of the final completion of the RV-9A … so after spending years helping Pete pound rivets and assembling components, it was wonderful to finally have an opportunity to go flying in our handiwork.  Pete was just in the process of finishing up his annual inspection on the RV-9A and all that was left to do was perform an engine compression check and put the cowlings back on the airplane and go flying.
Pete’s freshly vinyl covered RV-9A with the cowlings off waiting for the engine compression check.

It was quite a shock to see Pete’s plane painted yellow with white wings …. No not painted, it is vinyl wrapped!!!  While Pete had the airplane out of service for the annual inspection, Pete had the RV-9A wrapped in vinyl as opposed to having the airplane painted. Pete had been keeping this under wraps, so to speak, until after the annual was completed so he could fly the RV-9A up to Big Bear to take official completion photos for his Blog using  the mountains as a scenic backdrop.
Pete and his marvelous RV-9A.

After the compression check was completed, we buttoned up the cowlings and while the sun was still high enough over the horizon to be legal we took the RV-9A up for a few laps around the airport.
Pete towing the RV-9A out of the hangar for our sunset flight around the airport.
The RV-9A ready for our short flight of making a few laps around Chino’s traffic pattern.
In the pattern at Chino turning down wind.
The RV-9’s instrument panel in flight.
Pete’s “RV grin”.
Turning for a short final on Chino’s 26L runway.
After flying the RV-9A, Pete (and I) had an even bigger “RV grin”.

WOW!!! Pete’s RV-9A truly flies great!!! It is so smooth, it is just amazing. Just an awesome flying airplane!!!