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.