Trimming The W-1222 L&R Wingtip Extensions

While waiting for the replacement brake line fitting to arrive, decided to move forward and begin working on the wingtip extensions. The basic RV-12 does not have wingtip lights unless the optional lighting kit is ordered … which it was for the DOG Aviation RV-12. Longtime readers of the Blog may recall the wing lights have been already installed long ago along with installing the wiring for the navigation and strobe lights … which will attach onto each wingtip via fiberglass W-1222 L&R wingtip extensions. As is typical for the fiberglass pieces that Van’s provides, the extensions are larger than necessary and require being trimmed down to scribe lines. A Dremel tool outfitted with a cutting wheel was used to make the rough cuts close to the scribe lines.

Using a Dremel tool outfitted with a cutting wheel to remove excess material from the W-1222-R wingtip extension … the material was trimmed away close to the scribe lines.


Each of the wingtip extensions have a tight S curve which was tweaked with the Dremel outfitted with a sanding drum. The outboard portion of the extensions have a flat mounting surface for the navigation/strobe light’s mounting brackets. The flat mounting surface on each of theW-1222 wingtip extensions has an oval scribe mark which denotes an area where material needs to be removed  … this will create an oval cutout for the Molex electrical connector for the navigation/strobe light wiring to pass through.

“Dr. Sander” how is the patient doing? “After lots of sanding, step one of the procedure is completed … as can be seen, it’s the completed trimming of the W-1222-L&R wingtip extensions to the scribe lines. The extensions will be mounted on the outboard ends of the wings to provide a mounting surface for the navigation/strobe lights. The oval cutout created in each fiberglass extension is for a Molex electrical connector and associated wires to pass through”. The S curve mentioned above can be easily seen adjacent to my left elbow.


Reading ahead through the instillation instructions, discovered that the wings will need to be flipped over after a few holes for Clecos are drilled so a mixture of flox can be applied to each extension which will apparently fill a void between the extensions and  the wingtips. So will need to enlist the help of one of the ground crew members in the near future.

Amassing Parts To Balance The Rotax Engine’s Bing Carburetors

Now that the Rotax 912ULS engine has been run, at some point in the near future it will be necessary to balance the two Bing carburetors. This procedure is quite familiar to anyone who has owned a multi-carburetor car or motorcycle and has tinkered with the carbs. In a nut shell, the carburetors are adjusted so the vacuum on the intake manifold of each carburetor is the same at mid throttle and idle.


There are a myriad of gages available on the market that will do the job, including some digital displays that are really cool. Depending on how out of sync the carbs are, readings could vary a lot ... but expect the readings to likely be under 18 inches of water. After syncing the carburetors GUESSING the readings will end up be around 11 inches of water at 2,500 RPM and around 15 inches of water at idle. In fact, two long tubes containing an equal amount of water in each tube can even be used (if done carefully using slow RPM changes, especially when going from a high RPM to low a RPM) because the vacuum measurements are made in inches of water so using tubes much longer than the expected vacuum should help guard against water ingestion should one want to go that route ... I prefer the more costly dry approach in this instance.


While waiting for the new replacement 90 degree brake fitting, decided to work a little on making my own carburetor balancing fixture. Two quality gauges were chosen that read from 0 to 30 inches of water. The gauges will be screwed directly into a valve. The purpose of the valve is to create a dampener ... because if the vacuum fluctuates enough, it will cause the needles on the gauges to “bounce”. To alleviate the “bouncing”, the valves can be slowly closed off until the needle on each just gauge steadies out allowing meaningful carburetor adjustments to be made.


The Rotax 912 maintenance manual describes four methods that can be used to attach the vacuum gauges onto the engine … three of which involve removing/plugging various combinations of  hoses on the balance tubes. The last time I tried to mess with a balance tube hose, it needed to be replaced because it was destroyed trying to remove it, so I’m not keen on any of those methods. The fourth and most appealing method to measure the vacuum is to remove a 6 mm plug in each of the intake manifolds and screw a tube into the port that a hose coming from a vacuum gauge can be attached onto. While simplistic enough, this poses a problem here in the Americas because where do you go to find a M6 threaded tube with a hose barb on the end of it? I thought about finding a long M6 bolt, cutting the head off and drilling through the center of it … but that seemed like a lot of fussing around.


Then it came to me … go to a foreign car parts place and ask for a M6 brake bleeder valve. They are already hollow and have a hose barb on them already. M6 brake bleeder valves are used on VW’s and early models of BMW’s for sure … although I think M7 is more common these days. Anyway, I found some. Wade at the foreign car parts shop took the time to look up what I was looking for since I did not have a specific car year or model to give him. In the process, discovered he too was a pilot so we got along just fine. Wade was able to hook me up with M6 brake bleeder valves and also gave me some small rubber O rings to make a good seal when the valves are threaded into the intake manifold.


Because the tip of a brake valve is solid and pointy, the plan was to cut off the pointy part of the valve with a Dremel outfitted with a cutoff wheel then run a #40 drill down through the center to enlarge the small center hole a little bit. The result is perfect and should work great!

About to use the Dremel outfitted with a cutoff wheel to remove the pointy end on the M6 brake bleeder valve to reveal the hollow center.


After the tip was removed from the M6 bleeder valve reveling the hollow center, I noticed the hole was a little smaller than I desired so a #40 drill bit was run down through the center of the valve to enlarge the hole a little.

The setup for making the “home brew” carburetor balancing fixture. The meters will screw into valves that can be adjusted to dampen the meters if necessary. The valves will have a hose barb fitting for connecting to the hose between the valve and the M6 bleeder valves screwed into the intake manifolds.  The uncut M6 bleeder valve can be seen to the right of the one my finger is pointing towards which is the one I cut the tip off. The small O rings were added and will make a good seal when the fitting is screwed onto the intake manifolds.


I’m thinking of mounting the meters and valves on a piece of aluminum so the parts are not lose and may even try figuring out a way to read the meters with the engine running while inside the cockpit. I have a few ideas on that, but have not worked out the details as of yet.


For fellow builders that like to do it yourself, the big takeaway from this post is it appears that M6 brake bleeder valves can be easily modified to be used as an interface between the vacuum meters and the intake manifolds. If there are any unforeseen issues discovered with this setup, I will return from the future and amend this post accordingly.

Working On Resolving Leaky Brake Fittings

Since completing the instillation of the rear window on Wednesday, have continued working on various small tasks that needed attention … the first of which, completing the trimming of the right & left flaperon’s inboard skins to obtain the required 1/8" clearance between the flaperons and the fuselage during full deflections of the flaperons.


Another area on the wings that required attention was in the vicinity of the F-1204R side covers for the blue electrical connectors. Unlike most of the other inspection covers on the RV-12, these covers do not seat into a joggle, so they protrude out from the side of the fuselage. The first time the clearances for the wings were measured, the F-1204R side covers were not installed, so it was necessary to remove a little material on both wings to obtain the required 1/8" clearances. A Dremel tool with a sanding drum was used followed by hand filing and smoothing with a 3M sanding block. I did not take any photos because photos of the process have already been posted in recent posts.


While the wings were off, decided to work on the brake fittings on the master cylinders that were discovered to be leaking after the engine run. The master cylinders and pedals are accessible with the wings off by leaning in over the canopy rail. For easier access, a bungie cord was used to pull up on the rudder pedals so the master cylinder was within easy reach. Bernie was available to lend a hand with draining the brake lines by opening up the bleeder valves at the calipers and capturing the brake fluid in a vessel while I pumped fluid out of the reservoir and brake lines by hand pumping the master cylinders. The fitting that was looked at first was the one that was physically dripping … which was the left brake master cylinder on the pilot’s side.

The pilot’s side master cylinder for the left brake has a leaking 90 degree fitting as can be seen here. This fitting was actually dripping a bit.


The fitting was removed counting the turns … it was in three turns. The fitting was lubed with fluid and clocked tighter and tighter by loosening then tightening the fitting progressively tighter until it had around a quarter turn or so left to go. At this point, the fitting was removed, and the threads carefully cleaned with solvent until they appeared free of fluid and debris, then Loctite 567 thread sealant was applied to the fitting and the 90 degree fitting was reinstalled and tightened to four turns without self-destructing … now the fitting is REALLY tight.

Snugging down the brake line to the pilot’s left master cylinder after tightening the 90 degree fitting one additional turn tighter. After this, a torque wrench was used to obtain the final torque on the fitting. Hopefully, one turn tighter will solve stop the drips because the fitting will never make it another full turn.


At this point, it was one down and two to go. The other leaks were on the co-pilot’s right master cylinder. They were not a physical dripping yet, but the fittings were definitely beginning to weep … so figured may as well fix it now.

Both the fittings on the co-pilot’s right master cylinder are showing signs of weeping.

The first fitting tackled on the right master cylinder was the upper 45 degree fitting … here again it was removed counting the turns and it too was three turns in. The same procedure as used above was used to work the fitting into the master cylinder one more turn and the brake hose was connected. However, when working on the 90 degree fitting on the bottom of the master cylinder began to run into issues. That fitting was screwed in 3 ½ turns to begin with. Using the previously mentioned procedure to progressively work the fitting deeper into the master cylinder discovered at the 4 turns point there is so much resistance that I feared if the fitting were to be made any tighter, it will either crack or break off in the master cylinder. I also suppose it may be possible to place the male 90 degree fitting in a die and screw it in tight and try seeing if another ½ turn can be obtained. However, have decided to first try another new 90 degree fitting and a different type of thread sealant that hopefully will do a better job of filling the voids in the threads … especially if I can’t get the new fitting to go in any further than the original one. So will have a little setback while waiting for the parts … but there are other things yet to do.

The RV12’s Rear Window Instillation Completed

Yesterday, in spite of the heat, high humidity and mostly calm air which really kicked up the temperature inside the DOG Aviation hangar, the decision was made to move forward and install the rear window with the help of young and agile Blake. Blake has been doing the trimming of the bushes and weeding of flower beds at the house for a couple of years now. Blake, being thin and agile, was the perfect choice for crawling into the cockpit and assisting with the installation of the rear window. In spite of the heat and humidity in the hangar, Blake still was excited about doing the job.


With Blake’s assistance, the rear window was positioned on the turtle deck skins and roll bar … after some fussing around, we were finally able to get the holes in alignment so screws could be inserted. Admittedly, I did not put any fuel tank sealant on the rear window in the area of the fuel tank’s filler neck. My thoughts on this are … Van’s now has the new Plexiglas window available which was not available at the time the finishing kit was ordered.  The Plexiglas is preferable because it won’t craze when (not a matter of if) fuel gets on it. However, figured may as well use the polycarbonate window that was shipped with the kit until it begins having issues with crazing … at which time, it will be very easy to remove since it will not be glued in place with hard to remove fuel tank sealant. The molded Plexiglas window is my preference.

Blake pushing down on the rear window to seat it onto the roll bar which helped align the holes as I inserted screws.

Basically, after placing screws in all the holes, the screws were drawn tight in two steps. Blake turned the nuts on the inside of the baggage area with a nut driver until he felt the resistance change as I held a Philips screwdriver on the screw heads on the outside. Once all the screws were somewhat snug, a second pass was made using fingertip snugness so as to not create any cracks in the window.

After the window was positioned, Blake’s job was to place washers and nuts onto the screws and then use a nut driver to gently snug them up.

Completed instillation of the RV-12’s rear window.

******* IT’S ALIVE !!! *******

Yesterday afternoon the Eagle took its first breath of fresh air mixed with 93 octane Sunoco premium auto fuel and sprang to life in a somewhat spectacular fashion … leaping forward and bouncing, all the while being barely tethered by the brakes.

Prior to taking the wings off to trim a little more metal from the right flaperon the decision to start the engine was an impromptu one at best. It was a nice afternoon, winds were calm, the firewall forward portion of the instillation was completed, fuel tank was almost full so we rolled the DOG Aviation RV-12 outside and went for it.

The eagle ready for the first signs of life … the passenger, apparently not so much.

All of the minor issues encountered were of my making due to lack of adequate preparation because this was so spontaneous. For starters, the first couple of turns of the prop where the engine did not fire was due to not pulling the choke lever out. Next, I had a little (correction, a lot) more throttle than necessary when the engine fired up so the RV-12 began moving forward. Not having the seats or seat backs installed in the cockpit meant my legs were fully extended while standing on the brakes. The daftest move was not wanting to hurt the engine by pulling the throttle back until I could figure out where the RPM readout was on the display. The Rotax engine should not be idled less than around 1,400 RPM and ideally 1,800 … so I wanted to make certain that by pulling back the throttle I would be above the 1,400 minimum. But because I was fixated on making sure there was plenty of oil pressure first (there was 58 psi), it took quite a little while to scan the EMS display data to find the  RPM readout … (its on top of the screen) …  if it would have been a snake, it would have bit me before I found it.. (Time should have been spent locating the tach on the display prior to starting the engine).

Here is a video Mike began taking of the of the “event” with his phone as I yelled “clear prop”, closed/latched the canopy and preformed the amateurish first start-up of the Rotax 912 ULS engine in the DOG Aviation RV-12.

Photo of the first engine run.

The video was stopped just prior to shutdown which was performed with much more precision by pulling the throttle back then switching off the right ignition, waiting a second and switching off the left ignition for an instant stoppage of the engine.

A post-run inspection of the engine reveled no apparent oil or coolant leaks, but it was not really run long enough to know for certain …. although, at this point, it looks encouraging. What was not encouraging is the two small leaks discovered in the brake system … one a little weeping of fluid the other actual drips. Two of the four 90 degree fittings with NPT threads that screw into the master cylinders are weeping/dripping … actually, one fitting dripped a few times the other shows signs of weeping fluid. The drips ARE NOT coming from the Aircraft Specialty Teflon brake lines and associated fittings … rather the fittings they connect onto which are threaded into the body of the master cylinders. This will require draining all the brake fluid from the system, and removing the brake lines attached onto the fittings so each fitting can be removed for inspection, reapplication of thread sealant and hopefully one more complete turn can be obtained when reinstalling the fittings.

After the engine run, the RV-12 was rolled back into the hangar and Bernie assisted with removing the wings so the right flaperon could be filed down a little more and the wing skins tweaked at a few locations.

Ten minutes after the engine run was completed the DOG Aviation was back in the hangar with the wings removed so a little more filing away of excess material on the wings can take place.

Removing excess material from the right flaperon so there is a 1/8" inch of clearance between the fuselage and the flaperon during full deflections.

Finished up removing material from the right flaperon but there is a little material that needs to be removed from the lower skins on both wings where the F-1204R side cover assemblies reside.

Tweaking The Fit Of The Eagle’s Wings

The instillation of the spar pins used to keep the wings secured has been a bit of a struggle both timed the wings have been mated to the fuselage. The first time when marking for the required 1/8” clearance between the wing skins and the fuselage, it was noticed the lower wing skins were touching the doublers that were installed on the sides of the fuselage … at the time it was thought this was probably the cause of the tight spar pins. Nope.


After removing excess material prior to mating the wings for the second time it was discovered the spar pins still were way too tight. Analysis of the situation with a mirror showed the right wing needed to go in just a little further so the bushings could align perfectly. Looking at the retainer block showed there was no clearance and it appeared the retainer block was preventing the spar from going in just a tad further. Thinking perhaps the rubber seals were causing an issue they removed but the spar pins were still way too tight.  The decision was made to remove the wings and sand 1/32" of material from the bottom of the block in the hopes it would allow the wings to be inserted just a tad bit further.

One of the two white F-1204R retainer blocks attached to each side of the center section. It appeared as though this retainer block was preventing the right wing from going inward just a tad further, so it will be removed for trimming along with the one on the right side. At this point the spar is tapered so removing just a tiny bit of material will allow the spar to be inserted just a tad further.

A line was marked on all four sides of both F-1204R retainer blocks so a 1/32" of material could be evenly removed from each of them.


The F-1204R retainer blocks were placed on a piece of sandpaper and sanded down while rotating the block often to make sure it was being sanded evenly. Material was slowly sanded away until the 1/32" red line was gone. The retainer blocks were reattached onto the center channel and the wings slid into the center channel. Ultimately, sanding a 1/32" off the F-1204Rretainer blocks solved the problem. The left wing was installed and both spar pins were inserted to hold the wing in position but not pass through the bushings. Next the right wing was slid into position and an instant difference was noticed, in that, one could feel the alignment was much better and after a little pushing and rotating of the spar pins they slid into the bushings of on the right spar. At this point it would have taken a soft faced mallet to seat the pins the rest of the way, now I was able to tap on the spar pins with the palm of my hand to fully seat them. Finally, a good fit!!!


Gee, before taking the wings off again to do a little more clearance filing on the right flaperon and to reinstall the gap seals, why don’t we roll the Eagle out of the hangar and start the engine? Sounds like all the makings for a big announcement in the next post.

Angle Of Attack Indicator Tubing Connection Finalized

Prior to installing the wings a couple of days ago the final routing of the Tygon tubing used for the AOA indicator was finalized. The Tygon tubing and Luer Lock quick disconnect connectors were purchased through McMaster Carr were covered in the following post many moons ago.


http://www.dogaviation.com/2012/12/left-wing-wiring-and-aoa-plumbing_21.html


The Tygon tubing for the AOA was routed behind the left electrical connector and coiled long ago … the tubing makes its way to the ADAHRS mounted in the tail cone. A hole large enough for a tiny grommet was drilled in the F-00032 side cover for the blue electrical connector just aft of the connector as can be seen in the following photo. The grommet was snapped into the hole and the Tygon tubing was routed through the hole and a Luer Lock quick disconnect was attached to the Tygon Tubing. The DOG Aviation procurement department also purchased protective caps for the Luer Lock quick disconnects so when the wings are off the fuselage, the connectors and Tygon tubing can be protected from dirt or insects.

A 3/16" hole was drilled into the F-00032 side cover aft of the blue electrical connector and a tiny SB-178-2 grommet was inserted so the Tygon tubing would not ride on the sharp edge of an aluminum hole. The one half of the Luer Lock quick disconnect can be seen here.

This photo shows the protective cap placed on the Luer Lock quick disconnect to protect debris from entering Luer Lock fitting when not mated to the Tygon tubing coming from the left wing.

Tygon tubing at the left wing root with Luer Lock quick disconnect attached along with a protective cap. After this photo was taken, a wire tie was used to support the tubing in place of the pull string it is currently on.


One of the reasons the wings came off again is because there were a few tight spots between the flaperon and fuselage … plus, the spar pins were VERY tight. After careful analysis, it appears the F-1204R retainer blocks could use a little trimming which will be covered in a future post.