Sunday, July 31, 2016

Chipping Away At The Small Stuff

With the DOG Aviation RV-12 nearing the end of the build, there are really no big tasks left to complete … however, that said there is quite a mound of small tasks that need to be knocked out to get ready for the air worthiness inspection only a week away. Quite a few tasks have been completed but the two that required a little tweaking are mentioned below.

Decided it was time to install the two shin whackers (the steps) which are passed up through an elliptical slot in the fuselage skin and bolted in place using AN4 bolts. I discovered the clearances were a little tight for both steps (probably due to the powder coating on the steps) which required filing away a little material from the fuselage skin. Came up with the idea of using O rings on the steps to protect them from being scuffed as opposed to placing  an anti-slip covering over the powder coating which would hide it's beauty. Two years ago some rubber O rings were installed as an experiment to see how well they would hold up ... not well they cracked, so switched to Neoprene O rings and they seem to be holding up well after over a year. Not sure how well these will hold up in actual use … if they don’t, will cut them off and switch to a traditional non-skid covering.
Installing the powder coated left shin whacker (step) was just a matter sliding the step up through a cutout in the fuselage skin and securing it to the F-1202F bulkhead using two AN4 bolts … once the opening in the fuselage skin was filed a little larger. A close observation will reveal neoprene O rings have been placed on the step so shoes don’t mar the powder coating. (I also have  some O rings for the hollow tube as well).

One of the items I had been putting off was trimming the aft edge of the canopy  on the left side. I have known about this for quite a while and had been putting it off but have now finally gotten around to tweaking the fit. This was a self-created issue, in that, it seemed having the canopy slightly skewed allowed it to fit better on the canopy frame…  so I went with that knowing the aft edge on the left side would likely touch the rear window, and it did. Coarse sandpaper was used to remove a little material from the aft edge of the canopy so the canopy could be closed without touching the rear window. Once the optimum fit was achieved, the aft edge of the canopy was sanded more using progressively smoother sandpaper until the edge was polished smooth.
Sanding some material away from the aft edge of the canopy on the left side so the canopy doesn’t touch the rear window when closed.

Saturday, July 30, 2016

Instillation Of Navigation/Strobe Lighting Completed

It has taken a little longer to get the navigation and strobe lighting instillation completed  than expected (mostly due to not being at the hangar) but Thursday it finally all came together … although there was a small bump in the road I’ll mention later. During the last couple of short work sessions the wires were stripped back and male .062 Molex connector pins were crimped onto the wires then placed into the Molex connector body. Because the DOG Aviation RV-12 is using shielded cable for the nav/strobe power leads (which is a modification), the cable for each wing tip light was stripped back and the shields were connected to the ground wires that attach onto the outer wing tip skin ... this was accomplished by using heat shrink solder sleeves and removing a band of insulation from the ground wire so the solder sleeve could make contact when heat was applied to shrink and melt the sleeve.
Wires attached onto the Molex connector for the left wing’s navigation/strobe lights.

After the wires from inside the wing were connected to the Molex connector for each wing, the W-1222 wingtip extensions were prepared for final assembly. The assembly instructions call for using a thin coating of fuel tank sealant on the flange of the wingtip extensions that will sit on the W-1204D wingtip closeout skin … this requires masking off the area so when the tank sealant oozes out while riveting, it won’t make a huge mess. A really thin strip of tape also needs to be cut and placed on the edge of the W-1222 extensions between the rivet holes and outer edge of the part. My circuit board etching tape would have been very handy for this, but it was 75 miles away at the southern Outpost ... so I resorted to cutting thin strips of electrical tape with scissors.
Electrical tape was placed on the wing’s skin leaving about a 1/32” gap between the tape and the W-1222 wingtip extension. One can also see thin strips of tape were placed between the rivet line and the outer edge of the extension.

At this point the W-1222 wingtip extensions were slathered with a thin layer of fuel tank sealant and riveted in place.
The W-1222 wingtip extension riveted in place onto the left wing. The fuel tank sealant can be seen as the dark area under the flange the rivets are set into.

Unfortunately, when installing the nav/strobe lights, I discovered that the oval slots on the extensions cutout for the Molex connectors were too small for the body of the Molex connector attached to the wires coming from the nav/strobe lights to pass through. The Molex connectors from the wings passed through the slots just fine, but the Molex connector housings on the ends of the wires from the nav/strobe lights are larger … so they would not fit through the opening in the extensions until the slot was made a little larger. It was a little disheartening to discover this after riveting the extensions onto the wings, but the issue was easy to resolve spending 10 minutes on each wingtip extension with a couple of jeweler’s files. Note to fellow builders: Check that the body of the Molex connector that is wired to the lights passes through the slot in the F-1222 extensions prior to riveting the extensions in place.

The physical instillation of the navigation/strobe lights onto the wingtips is a snap (once the Molex connector body can pass through the slot on the W-1222 extension). After the Molex connector body is passed through the slot in the F-1222 wing tip extension and the housing for the light sits directly over the bracket, it is then pushed aft to lock it in in place on the bracket. To secure the light housing onto the wing tip, there is a small set screw that screws into a hole on the aft edge of the light’s housing which tightens up against the bracket preventing the light from moving forward and unhooking itself from the bracket.
Photo of the completed instillation of the navigation/strobe on the left wingtip. My finger is pointing to the hole for the Allan set screw that secures the body of the light onto the bracket.

One item I forgot to take a photo of was the use of a wire tie to secure the Molex connectors together. The Molex connector used is for five wires but only four positions are used for the nav/strobe lighting. I used the ScotchBrite wheel to shave about 1/64 inch from the edge of a small wire tie so it could be passed through the unused hole in the connector and tightened. This will prevent the Molex connector from separating on its own. I also pulled  out the spare slack of the pull string that runs through the electrical grommets in the wing and tied the pull string onto the Molex connector so it would not get lost in the wing.

Sunday, July 24, 2016

F-1222 Wingtip Extensions Prepared For Final Instillation

After letting the flox mixture cure overnight, the remaining two #30 holes were drilled into the F-1222 extensions, through the cured flox and into the W-1204E wing tip ribs. Upon drilling the two holes in each extension, they were removed and the clay plug was removed and that area cleaned up … although not necessary, some of the excess blobs of flox were cut away with a Dremel tool.
Drilling the second of the two #30 holes that needed to be drilled into the W-1222 extension, through the flox and into the W-1204E wingtip rib.
The W-1222L wing tip extension after removing the clay plug and trimming away some of the excess flox. Now knowing what the end game is supposed to look like, far less flox could have been applied to the part.

Looking at the above photos, one can see there is no flox on the outer edges of the extensions. When the extensions are Clecoed in place, I noticed there was a small area where there was somewhat of a gap between the extension and W-1204E wing tip rib right at the forward edge of the extension. Not wanting to stress the fiberglass when it is riveted, after all the countersinking coming up next was completed, a small amount of flox was added to that area on both extensions and they were Clecoed back in position to let the flox cure overnight.

There are three mounting holes that need to be drilled into the W-1222 extensions for the mounting bracket for the nav/strobe lights. There are tiny dimples molded into the W-1222 extensions to help position the mounting brackets for drilling. The mounting bracket is centered as best as possible over the dimples and clamped in position for drilling using a #27 drill bit. After each hole was drilled, a screw was placed in the hole to help hold position. Once the three mounting holes are drilled to #27, the W-1222 extensions require machine countersinking.
The mounting bracket for the left nav/strobe light is clamped in position on the W-1222L wing tip extension and ready for match drilling using a #27 drill bit.

With the mounting holes for the brackets now drilled, per Van’s instillation instructions, the W-1222 wing tip extensions require some machine countersinking for all the holes common to the outer surface of the W-1204E wing tip ribs using a #30-120 degree bit for the flush rivets that will be used in this area. Because the DOG Aviation RV-12 is using flush rivets on all the outer surfaces, in addition to machine countersinking the required rivet holes mentioned above, all the remaining rivet holes in the W-1222 wingtip extensions were also machine countersunk for flush rivets.
Machine countersinking the line of rivet holes in the W-1222L wingtip extension common to the W-1204E wingtip rib using a #30-120 degree countersink bit.
Completed instillation of the mounting bracket for the nav/strobe lights on the W-1222R wing tip extension.

At this point, I drove home to get a small hand held vacuum that could be slipped in through the access hole in the wing tip so all the metal chips from the drilling could be removed from inside the wing. By the time I got back to the hangar and finished with cleaning up the debris from inside the wing, it was getting a little late to continue on … so mixed up a small batch of resin and flox and applied it to the previously mentioned area where there was the small gap, Clecoed the extensions in position and left them to cure overnight.

Saturday, July 23, 2016

W-1222 Wingtip Extensions Floxed

In order to finish off the repair of the leaky fittings on the brake master cylinders, it was necessary to bleed the brake lines once again. This time, Bernie and Mike K. were able to lend assistance yesterday morning with the brake line bleeding chore. The left and right brake lines were filled with fluid from the calipers up using the same pump oiler and method used before.  However, this time around it appeared the brakes were still a little spongy, so with most of the air out of the lines we switched tactics. I got inside the cockpit to pump on the brake pedals as Mike continually added fluid to a tube connected to the brake fluid reservoir while Bernie worked the bleeder valve at the caliper and monitored for air bubbles coming out of the line. The whole process took us a while, but the brakes appear to be quite solid now and so far, the fittings on the master cylinders are remaining dry.

With the brakes functional again, it was time to get back to working on the W-1222 wingtip extensions for the navigation & strobe lights. The next step for installing the W-1222 wingtip extensions involved flipping the wings upside down which Mike helped me do. With the wings upside down, a batch of resin mixed with flox is applied to the inside edge of the W-1222 extensions to fill the void between them and the W-1204E wingtip ribs. Prior to applying the resin/flox mixture, the areas around the wing that could come in contact with the flox are to be covered with wax … as is typical at DOG Aviation, this was taken one step further, in that the contact areas were covered with clear packaging tape and then Vaseline was smeared onto the tape as the release agent. There is also an area on the W-1222 extensions that needs to be protected from the flox so a nut can be installed later in the assembly process … Van’s suggests using a plug of modeling clay to protect the area from the flox, which was done.
A plug of yellow modeling clay is used to protect a location that will be used for a nut to secure the mounting bracket for the  nav/strobe lights. Looking closely at the area my finger is pointing to, one can see the line of the packaging tape which was rolled over the outer edge of the wing tip. Another strip of tape was used on the other side of the wing adjacent to the outer edge. Prior to applying the flox, the packaging tape was slathered with Vaseline so the extensions can be removed to work on the electrical connector and the mounting bracket attachment after the flox mixture cures.

After applying the flox mixture to the inside edge of the W-1222 extensions that will contact the W-1204E wingtip ribs, the extensions are secured onto the wingtips using Clecos. It appears the main reason flox is used here is to fill a void between the W-1222 fiberglass extensions and the W-1204E wing tip ribs … because after the flox mixture cures, it is necessary to drill two more rivet holes through the extensions and into the W-1204E wingtip ribs … that area can be seen between my fingers in the photo below.
After the resin/flox mixture is applied to the inside edge of the W-1222 wingtip extensions, the extensions are secured onto the wing using Clecos to hold position as the resin/flox mixture cures. After the flox has cured, the area between my fingers will receive two #30 holes for rivets.

Prior to leaving the hangar for the day, I wanted to get a little more done so the ELT antenna and bracket was installed. This has remained off for access, but now that the fuel tank and rear window are now installed, figured it was time to mount the ELT antenna. Nothing out of the ordinary here so no photos were taken since this was covered earlier this year ...  it was just a matter of installing three screws and attaching the antenna wire to  the connector on the base of the antenna.

Now that the flox has had time to cure overnight, the first order of business today will be  drilling the two#30  rivet holes, then remove the extensions to continue with the mounting of the bracket for the navigation & strobe lights and the electrical connections.

Friday, July 22, 2016

Brake Fitting Replaced & Instillation Of W-1222 Wingtip Extensions Begins

Despite getting a late start at the hangar yesterday, was able to get a couple of things done. The new brake 90 degree brake fittings arrived so the first task of the work session was to install the fitting onto the co-pilot’s master cylinder. I’m pretty sure I could have used the old fitting but because I was really torqueing on it to attempt to get the last 180 degrees necessary decided it best to just try another fitting. Along with the new fitting decided to use a medium bodied thread sealant that has been recommended as being a good product for this task called TiteSeal. It is available in both a light weight and medium weight formulation … for this task the medium weight formulation was chosen.
TiteSeal medium weight sealant compound. Far as I know, this 1 lb can is the smallest quantity that can be purchased … enough for the entire RV-12 fleet many times over.

Between replacing the fitting and using the TiteSeal, hopefully the leaking at the master cylinder will be cured … time will tell. Moving on, went to work on fitting the W-1222 wingtip extensions onto the RV-12’s wings. The fitting process for the W-1222 extensions begins with drilling four #30 holes through the fiberglass and into the W-1204E wingtip ribs. The W-1222 wingtip extensions were placed on the outboard edges of the wings and the two forward and two aft holes for the extensions are #30 drilled into the F-1204E wingtip ribs. The hole locations are marked on the fiberglass as tiny dimples to set the drill bit on. After the four holes are drilled, the extension is removed for deburring and then Clecoed back in place so the lower flange on the W-1222 extension can be drilled into the W-1204D closeout skin.
After positioning the F-1222-R wingtip extension on the right wing and securing it with tape, the two leasing and two aft hole locations marked on the F-1222 extensions are #30 drilled into the W-1204E wingtip ribs.
Completed drilling of the F-1222R wingtip extension.

Looking at the above photo where the flat mounting surface is one can see there a large span with no rivet holes drilled at this time … this is because there is a void behind the fiberglass that will require filling with a resin/flox mixture. After the flox hardens the remaining two rivet holes will be drilled but the process requires flipping the wings over so will need some ground crew assistance for that.

Thursday, July 21, 2016

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.

Monday, July 18, 2016

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.