Friday, October 30, 2015

Anti-Servo Trim Motor Installed

The first task of the day was installing the safety wire for the anti-servo trim tab’s hinge wires. There are two small holes in the center of the aft spar on the horizontal stabilator that are used to capture both trim tab hinge pins with safety wire.
The safety wire for the hinge pins is run through two holes in the stabilator’s aft spar and looped over the hinge pins for the left and right anti-servo trim tabs to secure them in place. Note: The discolored metal is not corrosion ... it is from the SanChem metal treatment (similar to Alodine but eco friendlier) that was done to the inside of the skins.
The safety wire for the hinge pins is twisted tight on the forward side of the stabilator’s aft spar.

The trim motor assembly is attached onto the tail cone’s aft bulkhead using a long AN3-35 bolt and a couple of spacers. Nothing difficult, but everything is a tight fit and the work is done from under the horizontal stabilator, so it takes a little finessing to get all the components in place.
Placing the trim servo motor tray in position so the mounting bolt and spacers can be installed.

One thing of note:  Builders should pay close attention to the AN3-10A bolt called for attaching the trim servo push rod onto the horn on the trim tabs. The bolt is just a little too long as can be seen in the photo below, so it will be necessary to add an additional washer or use the next size shorter bolt. The DOG Aviation procurement department purchased an assortment of bolts just to have on hand so will likely need to look in that parts bin. The short term fix will be adding an additional washer, but during the first annual plan on replacing the bolt with a shorter bolt.
As can be seen in the photo, the AN3-10A bolt called for in the plans is a tad long .. the nut would have bottomed out on the unthreaded shank of the bolt.
Adding an additional washer took up enough space so the nut did not run out of threads while being tightened.

Return from the future: I did not like the way the bolt looked because there were more threads showing beyond the nut than the one to three threads the "standard" calls for. Decided to rearrange the washers on the bolt for a better instillation. The resulting instillation used an AN960-10 washer under the head of the bolt and in addition the AN960-10 washer that goes under the AN-365-1032 lock nut, I added an additional AN960-10L washer. The AN960-10 washers on either side of the MM3 bearing were left undisturbed. The result is a perfect fit and the instillation looks much better now.

Results after adding an AN960-10 washer under the head of the bolt and adding an AN960-10L washer under the nut.

Having the trim motor in place and connected to the anti-servo tabs it was time to operate the trim motor through its range of motion to check for free operation of the horizontal stabilator along with checking clearances. All was well.

Of note to other builders: I did not play around with the micro connector as suggested in the plans for a location to place voltage on the trim motor’s white wires. Instead, applied the power at the end of the servo cable in the instrument panel. Reason for this was two fold … first, did not want to mess with applying power to the pins of the delicate micro connector at the servo motor end and possibly damage one of the tiny pins. And secondly, I had not yet operated the trim motor to determine which of the two white trim motor wires ran the trim tab up or down when a positive voltage was placed on it … and this information is needed when installing the trim cable’s wires into the connector. Now I know and marked the wires accordingly. Also, did not bother using a bulky 12 volt battery … a 9 volt transistor radio battery works just fine to operate the trim motor throughout its full range of motion a few times.

After cycling the trim motor a few times and checking for clearances and freedom of movement, the plans instruct the builder to use two wire ties to secure the trim motor cable onto the servo tray. The first wire tie just loops through the small hole adjacent to the wiring connector and the second wire tie is to loop through the first wire tie and then around the servo cable to hold it in place. Doing this holds the wire just fine … but doing so also draws the cable onto the edge of the metal servo tray. Not wanting the servo cable to ride against the servo tray, decided to create a standoff by cutting a small piece of vinyl tubing and looping the wire tie through the tubing. The first loop of wire tie is run through the hole as per the plans and the vinyl standoff was attached onto that loop.
My finger is pointing to the standoff made by using a small piece of vinyl tubing to keep the servo cable off the servo tray. This is a much better way (IMHO) of securing the cable to the servo tray than the method called for in the plans.

After verifying the anti-servo trim tab was working correctly and all the clearances were good, moved onto installing the tail cone’s fairing for final drilling. The fairing needs to placed in position and then centered as best as possible between the stabilator’s skin so the final drilling of the fairing’s mounting holes into the tail cone can be completed. The goal stated in the plans is to have the fairing centered as best as possible and then verify there is at least a 1/8" clearance between the fairing and the stabilator.  In my case, it will involve filing/sanding away some aluminum from the stabilator skin. The loss of clearance and ultimate interference is mostly along the aft portion of the fairing as can be seen in the photo below.
The sides have close to the specified 1/8” clearance between the fairing and the stabilator skin but the same can not be said for the aft portion of the tail cone fairing.

The above interference should be easy to address with the aid of a sanding drum on a Dremel tool and a little filing at some point in the near future.

Thursday, October 29, 2015

Horizontal Stabilizer Installed – What Worked – What Didn’t

The Rotax 912 engine needs to come out of the box very soon … prior to installing the engine, the carburetors and intake manifold need removing in order to install the FF-1207 fiberglass cooling shroud. I would prefer doing that work on a work bench but the second workbench has the horizontal stabilator sitting on it. So prior to digging into the engine, wanted to get a couple of tasks completed. First, I plan to paint the FF-1207 fiberglass cooling shroud prior to installing it. However, the fiberglass was really rough and porous, so a mixture of epoxy resin was thinned with Acetone and slathered onto the cooling shroud to soak into all the nooks and crannies … this will create a much smoother surface for the paint and hopefully better visual appeal. After the shroud was coated with the thinned resin, it was placed into the hot box to cure. Now it has dried and is looking for the most part, very smooth … so thinning the epoxy with Acetone worked great for getting rid of all the roughness.
After a mixture of epoxy resin was thinned with Acetone, it was slathered onto the FF-1207 cooling shroud to fill in all the roughness of the glass weave.

Second, and more importantly, I need a workbench freed up so the engine can be placed on a sturdy surface while working on it, as opposed to working on the floor … and that meant installing the horizontal stabilator to free up the workbench it is sitting on.  The plan: Tilt the tail cone down to meet with the level of the horizontal stabilator, roll the workbench into position and bolt it up. I told Bernie about my plan to make a wooden block with a V notch so the front tire would not roll and then place wood underneath it to lift the wheel and drop the tail cone so I could keep the stabilator on the workbench and only need one helper. Bernie came up with the great suggestion of using a cement block he had and letting the wheel sit in one of the holes. This worked great to meet my low workbench … in fact, had to also add one piece of 3/8" plywood under the block to get it perfect.
The nose wheel placed in the hole of a cement block to lower the tail cone worked perfectly. Thanks for the idea Bernie.
Tail cone lowered to meet with the level of the horizontal stabilator sitting on the workbench.

So far so good … next the long counterweight arm was slid into the sockets on stabilator and bolted in place. This makes the stabilator want to roll from all the weight and from this point on things became a challenge and an exercise of patience. The workbench was rolled forward until it almost touched the tail cone and the stabilator was slid forward and aligned with the bearings as best as possible.

Now for what did not work. I was hoping there would be enough access to install the bolts and washers from up above. This is where the wheels fell off and that proved to be pure folly because there is not much room to work yet alone see while bent over the top of the horizontal stabilator. At one point I climbed up onto the workbench and although the view was better it was truly difficult to even get the bolt started yet alone worrying about the washers. Finally got a bolt through the bearing on the left side without any washers just to hold positioning.

Getting back on track, it was determined the task would be far easier to complete if done from below, so with a bolt holding positioning on the left side I commandeered Mike’s creeper from the hangar next door (thanks Mike T.) and accessed the situation from bellow. Seemingly there was more room when Mike K. rotated the stabilator a little and held it so I was able to easily get a bolt fed through the inboard washer. To hold the washers, a wooden pop sickle stick was filed to have a curve on the end that matched the washer, then masking tape was used to adhere the washer onto the stick. From below the view was better and could see to easily get to the bolt in the hole, then using the pop sickle stick, placed the washer in position and slid the bolt through the washer and ultimately into the bearing when Mike K. gently moved the assembly around. I had not glued the outboard washers as suggested in the plans but found that using the stick to hold the washers the outboard washers were easily slipped into position … however a thin strip of metal was needed to push on the edge of the washers to position them correctly so the bolt would capture them.

Having the bolt and washers for the right side bearing in place, it was determined that repositioning the workbench only underneath the left side of the stabilator would give me more room to work on the bolt and washers for that side. Mike moved the stabilator until a neutral point was found that allowed me to remove the bolt that was temporarily slid through the bearing to hold position. The pop sickle stick trick was employed again and with a little patience the bolt and washers were in place. For those builders interested in the washers used … the inboard washers ended up being AN960-416 and the outboard washers were AN960-416L.
A proud moment - the horizontal stabilator is finally installed. Could not have done it without Mike K.’s help. Thanks Mike!

To finish off the horizontal stabilator instillation the anti-servo tabs were installed. The hinges need to have 3/4" of the end bent to 90 degrees … this is so the hinge pins can be safety wired onto the stabilator.
Using a seeming tool to bend the end of the anti-servo tab hinge pins to 90 degrees.

Installed the left anti-servo tab first and while installing the right side, discovered the hinge pin needs to be installed from the bottom. The hinge pin for the first anti-servo tab installed can be inserted from the top or bottom … however, which ever anti-servo tab is installed last the hinge pin needs to be inserted from the bottom. Ask me how I know.
Installing the hinge pin for the left anti-servo tab.
Installing the hinge pin for the right anti-servo tab - tghis needed to be done from below by deflecting the anti servo tab up to get clearance.
Completed tail feathers for DOG Aviation RV-12.

Tuesday, October 27, 2015

Stabilator and Rudder Fairings Finished

Builders building their RV-12 as E-LSA can disregard this post. Yesterday, tackled one of the unfinished tasks on the tail feathers which was to install the vertical stabilizer and rudder with fairings.  Back when bonding the foam block onto the canopy arm, some of the left over flox mixture was used to bond thin strips of aluminum onto the inside of the rudder and vertical stabilizer fairings. This was done because the DOG Aviation RV-12 is being built with flush rivets on the external surfaces and to keep a consistent look, the rivet holes will need to be machine countersunk to accommodate the flush rivets. Countersinking the fairings will leave the fiberglass thin so the thin strips of metal will allow the rivet to set on metal without the fear of crushing the thin fiberglass resulting from the machine countersinking.
The two thin strips of aluminum were bonded onto the inside of the rudder fairing so the rivets can set onto metal instead of thin countersunk fiberglass. Two aluminum strips were also added onto the vertical stabilizer fairing as well.

The fairings were placed onto the tail feathers and match drilled. Care was used not to push in too hard on the drill bit so the thin metal strips would remain bonded onto the fiberglass.
Match drilling the rudder fairing - carefully not pushing hard so the metal strip inside stayed bonded to the fiberglass.

After the rivet holes were drilled into the vertical stabilizer and rudder fairings, the rivet holes were machine countersunk. Because the joggle built into the fairings prevented the countersink cage from sitting flat on the fairings, the cage needed to be removed and the countersinking was done by hand. (The joggle can be seen in the first photo if looking closely). A little scary, but care was taken not to get carried away by using short spurts of the drill and low RPM’s.
Machine countersinking the rivet holes in the rudder’s fairing using a #30 120 degree countersink bit. Note the countersink cage is removed so the countersink bit could be placed square to the rivet hole.

The last remaining item prior to final assembly was to dimple the rivet holes for the vertical stabilizer fairing (the rudder was dimpled during assembly long ago). The small step stool I was using would not cut it … I did not feel comfortable holding the pneumatic rivet squeezer high above my head so searched around and Ed, a gentleman on the field who buys and restores airplanes, was kind enough to loan me his step ladder. Thanks Ed.
Standing on Ed’s step ladder while making the 120 degree dimples with the pneumatic squeezer held at eye level felt a lot more comfortable than holding it high over my head.

While dimpling the vertical stabilizer, I could not easily get square to the aft hole on each side (because the rudder was installed) so used the dimple dies that have a nail hole through the center of them that Bob Avery at Avery Tools made for me long ago. A hand rivet puller is used with these dimple dies to draw up on the nail which compresses the dies into the metal.
The custom made 1/8" 120 degree dimple dies Bob Avery made special for the DOG Aviation RV-12 project.

Although the dimple dies above have not been used regularly, they have been used successfully quite a few times to create dimples in tight places during the construction of the DOG Aviation RV-12 … they work great. Builders doing flush rivets on their RV-12 will want these dimple dies.

After the rivet holes for the vertical stabilizer’s fairing were dimpled, the fairing was secured on the stabilizer with Clecos. The fairing was sanded down until there was clearance between the rudder’s fairing and the vertical stabilizer’s fairing throughout the rudder’s full range of motion. Once happy with the clearances the vertical stabilizer’s fairing was riveted in place.
Riveting the vertical stabilizer's fairing in place using flush rivets in the place of LP4-3 rivets.
Completed instillation of the vertical stabilizer fairing and rudder fairing.

Sunday, October 25, 2015

Thur, Fri, Sat - Dodging Rain, Painting, Prep and Primer

Dateline Thursday: Was able to squeeze in a spray session between fast moving rain squalls to apply a coating of interior JetFlex paint onto the fuel tank and three small parts that were missed when painting interior paint last fall.  Those of you that have used a spray gun know there is quite a bit of time involved in setting up to spray parts … Bring out the plywood and a saw horse to create a table off the pickup’s tailgate. Attach the air regulator to the gun, schlep out the air hose and spray gun holder, adjust the air pressure, bring out the paint, stirring sticks and disposable paint cups for the spray gun, solvents (water and ammonia solution for the waterborne JetFlex), Acetone (gets rid of the film left behind from the ammonia solution), paper towels, etc. … etc.

After donning all of the safety garb, grabbed a screwdriver and was about to open the can of JetFlex paint and it begin to sprinkle. Darn … (not the actual word used). Quickly hustled everything back into the hangar before the sky cut lose.  After the rain passed, I waited a little longer and continued deburring firewall forward parts.

A second attempt was made … and guess what? Just before I was about to thin the paint, more sprinkles. More choice words and once again schlepped everything back into the hangar waited for the much harder rain to subside.   Before making a third attempt, I broke out the cell phone and looked at the radar on my Garman Pilot App and could see there was one more quickly approaching squall line then what appeared to be about an hour window of opportunity. After the squall passed, and the roof stopped dripping, schlepped everything outside for the third time and what turned out to be a successful attempt. Had just enough time to spray two coats of paint onto the tank and the three small pieces then place the wet parts back into the hot box to dry. Just as I was finishing with disassembling the spray gun for cleaning and had most of the gun in solvent … it began to sprinkle. Fortunately, got everything quickly back inside the hangar before the sky cut loose again.

Dateline Friday: Finished deburring parts and scuffing them up with a Scotch-Brite pad. After looking at the plans, it appears the parts that make up the drip trays for the carburetors required some trimming. The pieces used to make up the drip tray for the right carburetor required even more trimming. Part of the upper outboard flange on the FF-01226A drip tray is to be removed and a new rivet hole drilled.
The upper outboard flange on the FF-01226A drip tray for the right carburetor (lower in photo) requires trimming and a new rivet hole needs to be drilled … as can be seen compared to the left drip tray.

Both of the FF-01226B drip tray stiffeners require a sliver of metal to be removed from the bottom edge of the stiffeners and, in addition, the FF-01226B drip tray stiffener for the right drip tray requires more trimming … by way of removing a section of the upper portion of the stiffener.
The upper portion of the FF-01226B drip tray stiffener that will be used on the outboard side of the right carburetor’s drip tray assembly (top stiffener) also requires trimming as can be seen in the photo.

After trimming the above parts, the edges of the remaining firewall forward parts were sanded smooth and then all the parts were scuffed with a maroon Scotch-Brite pad to prep the parts for primer.

Dateline Saturday: All firewall forward parts that were receiving Akzo primer were thoroughly cleaned with Acetone and placed in a plastic bin.  Once again I found myself forced to find a window of opportunity between intermittent afternoon rain showers to achieve what will likely be the last spray session for the season. Although none of the pieces were large, there were quite a few pieces to paint, so I knew I would need close to an hour and a half window taking into consideration the 30 minute induction time required for the Akzo primer.
Firewall forward parts deburred, scuffed with a maroon Scotch-Brite pad and cleaned with Acetone … ready to prime.

It began to rain 10 minutes after the above photo was taken … and it rained off and on all afternoon. By 3:40 pm it stopped raining and it appeared there was a big enough window of opportunity so mixed the Akzo primer and during the 30 minute induction time, schlepped everything outside and set up for the spray job using the HVLP spray gun.  This time the timing was perfect, got all the parts quickly coated with primer and placed in the hot box, just finished cleaning the spray gun and had carried most everything back into the hangar when it began raining again.