The Dog Aviation RV-12 Receives Stabilator Tips Fairings

One of the only complaint most RV-12 owners have had about the RV-12 is purely cosmetic …  it has to do with the unfinished look of the horizontal stabilator’s outboard edges. Quite a few years back the owner of a RV-12 decided to do something about the unfinished look of the stabilator and made a mold to create stabilator fairings for the RV-12 made from rugged ABS plastic. Early on during the building of the RV-12, the DOG Aviation Procurement Department purchased a set of the stabilator fairings for the RV-12 … yet another project that required completion prior to the RV-12 heading to the paint shop.

As can be seen in this photo, the outboard sides of the RV-12’s stabilator just simply has an unfinished look …. Hopefully, the ABS tip fairings will give the DOG Aviation RV-12’s stabilator a much needed finished look.


Before going through the steps for the instillation procedure for the ABS stabilator fairings, it bears mentioning that when Van’s introduced the upgraded fuselage for the new RV-12iS, Van’s designed a fiberglass tip fairing for the RV-12iS’s stabilator. Fortunately, for owners of the original legacy fuselage, such as mine, Van’s has provided a pathway for installing the new stabilator tip fairings. Installing the Van’s tip fairings involves removing the stabilator’s outboard ribs and replacing them with new ribs that create clearances for the fiberglass tip fairings. I elected not to install the Van’s tip fairings because the ABS stabilator tip fairings were purchased long ago … plus, solid rivets were used to rivet the ribs onto the stabilator’s spar box which would increase the difficulty level of removing the existing ribs a tad. Truthfully, the Van’s tip fairings are probably the better solution because the fairing slides under the stabilator’s skin which is a better solution compared to the ABS tip fairings which are just butted up against the outer edge of the stabilator.

A photo from Van’s WEB site showing the newly developed stabilator tip fairings for the RV-12iS. It is hard to see from this photo, but Van’s stabilator tips slide under the stabilator’s skins and can be installed on legacy RV-12’s by installing new outboard ribs on the stabilator.

The ABS stabilator tip fairing kit purchased for the RV-12 consists of two metal mounting plates, two ABS tip fairings, a bag of mounting hardware containing screws, rivets and tinnerman nuts (which I’m not a big fan of and will likely change out for a threaded version) and instructions.


The ABS stabilator tip fairings are fairly easy to install. First a mounting bracket is temporarily attached to the outboard edge of the stabilator using the existing tooling holes on the outboard ribs. The mounting plate is temporarily “pinned” in place on the outboard ribs using rivets. The rivets are not set at this time …. they are only used to temporarily “pin” the mounting bracket onto the stabilator’s outboard ribs. With the mounting plate “pinned” onto the outboard end of the stabilator there are two holes in the mounting plate that are to be used as guides for drilling two holes into the outboard ribs.

Looking closely at the above photo one can see the mounting bracket is “pinned” to the stabilator using two rivets and one Cleco. Tape was added to make sure the template does not move. Below my finger are two holes in the mounting bracket which need to be used to match drill into the stabilator’s outboard rib.


After the two holes in the mounting bracket are drilled into the stabilator rib, a line is drawn at every tab where the stabilator’s skin meets the tabs. After placing marks on the tabs where they meet the stabilator’s skin, the mounting bracket is removed from the stabilator and each tab is bent using the previously drawn line as a reference.

Photo of the mounting bracket after all the tabs have been bent.

The mounting bracket is once again temporarily “pinned” onto the outboard ribs of the stabilator and the ABS tip fairing is slid over the now bent tabs tabs for a trial fit. Odds are it will be necessary to sand some material off the edges of the tip fairing. In my case, material needed to be removed from the front and aft portions in order to obtain a tight butt fit with the stabilator. I found it quite easy to sand the fairing quickly by placing some sticky sandpaper on the workbench and sliding the fairing across the sand paper until enough material was removed from the ends that the center of the fairing just began losing material. At that point there was a nice straight edge to work with.

Looking at the above photo the viewer can see material was removed from the forward and aft portions of the fairing by sliding the edge of the fairing back and forth across the sandpaper. I continued sanding until streaks began to appear in the clean center area of the sandpaper at which time the edge was totally flat.

Trial fit after sanding. The upper portion of the fairing has a nice, tight, almost perfect butt fit to the stabilator as can be seen here. The fit on the underside is not quite as good as it has a slight gap in spots but not enough to be of concern so, I decided to move on.


After fitting removing and sanding the fairing tip a few times to achieve a good fit, the ABS fairing was removed so the mounting bracket could be riveted onto the outboard edge of the stabilator.

The stabilator fairing mounting bracket primed and riveted in place on the stabilator’s outboard ribs.

Once the mounting bracket is installed, measurements need to be made so the mounting hole locations on the tabs can be marked onto the stabilator fairing to obtain locations for drilling the mounting screw holes. This was accomplished by placing masking tape along the entire edge of the fairing and sliding the fairing onto the mounting bracket just enough so the mounting holes are visible.  Before making any marks, care must be taken to insure the forward tip of the fairing is in line with the leading edge of the stabilator. Center lines for the mounting holes are transferred onto the tape on the fairing. In addition, measurements are taken from the stabilator skin to the center of each tab’s mounting hole and marked onto the tape to obtain the exact drill locations for every hole. You only get one shot at this ... so it is necessary to make careful measurements prior to drilling the holes.

Tape is placed along the edge of the stabilator fairing and the fairing is slid over the tabs but not so far as to cover the holes in the tabs.  Measurements are made and marked onto the tape denoting the location of each mounting hole that needs to be drilled.


With all the locations for the mounting holes now marked onto the tape, the fairing is pushed all the way onto the mounting tabs and butted up against the stabilator. More tape is applied to prevent the tip fairing from moving during the drilling process. Next the mounting holes are drilled into the stabilator tip.

After taping the stabilator fairing tight to the stabilator, the mounting holes were drilled into the tip fairing.

Just realized a photo was never taken of the completed stabilator prior to moving the RV-12 to the paint shop. But below is a photo of the fairing setting on the mounting tabs which is representative of the finished look.

This photo was taken just prior to drilling the mounting holes into the fairing. It is representative of how the fairing looks when installed on the stabilator.


All and all installing the ABS plastic stabilator tip fairings went fairly fast and the end result looks quite good. Think most would agree, having the stabilator tips installed on the RV-12 certainly looks WAY better than the original look.

The RV-12 Receives Another EAA Tech Counselor Inspection

Knowing an EAA tech counselor visit was scheduled for Saturday, Friday was spent playing with the tail cone fairing and connecting the stabilator control cables. The previous post showed the tail cone fairing sitting roughly in position … so Friday the positioning of the tail cone fairing was tweaked a little then the fairing was drilled and Clecoed to the tail cone. The plans call for a minimum of 1/8" of clearance between the tail cone fairing and the skin of the horizontal stabilator … there was no position that achieved that without the need to do some filing so I picked a position that offered a good compromise.  After all the holes were drilled, the fairing was removed. The holes need to be final drilled to #27 and nutplates need to be installed … but placed that on hold due to the upcoming EAA tech counselor visit.

I wanted to have the upper and lower horizontal stabilator cables attached to the two horns on the stabilator so the horizontal stabilator would be totally functional for the inspection. This required connecting the aft end of the upper and lower stabilator cables onto the horns on the horizontal stabilator. Nothing special here, just a little grease, one bolt, three washers, a castle nut and a cotter pin per each cable attachment.

The upper and lower stabilator cables in the tail cone make up the aft half of the stabilator cables. Because each upper and lower stabilator cable is comprised of two sections … a forward and aft cable, the aft cables need to be joined together to the forward cables using a special threaded barrel. One end of the barrel has a ring grove machined into the metal which denotes that end of the barrel has reverse threads … this end needs to point aft. Following the directions in the plans, the forward and aft stabilator cables were connected together by getting on a creeper and rolling under the fuselage to reach in through an inspection access hole and threading the barrel onto the threaded ends of the cables. Following a sequence in the plans, each barrel is turned until the slack was taken out of the cables. I stopped at this point because the DOG Aviation procurement department still needs to purchase a cable tensiometer to finalize the tensioning on the cables. However, at this point I had a working horizontal stabilator which completed the instillation of the flight controls for the EAA tech councilor visit on Saturday.

The grove on the aft end of the adjustment barrels for the stabilator cables can be seen if looking closely. This grove denotes reverse threads and needs to face aft. Also: The cables in this photo are not fully adjusted yet … so they do not have the proper amount of threads showing, nor are the locking clips installed.

Saturday, the EAA tech counselor visit went quite well and no work corrections were pointed out. Jim the EAA tech councilor and his friend Don a fellow EAA chapter member came down from the Cleveland area to give the RV-12 a good looking over and gave it a clean bill of health. For being a small plane, both Jim and Don were impressed with the level of sophistication and complexity of Van’s RV-12 design.

Jim the EAA tech counselor in the foreground and his friend Don in the background looking over the DOG Aviation RV-12 project.

While there was extra muscle in the hangar, decided the time was right to lift the Rotax engine box out of the crate and unbolt the engine from the box so the engine could be set on the workbench. Prior to installing the engine on the firewall there are a few tasks that are required to be performed.  These tasks can be completed much easier if the engine is setting on a workbench.

The right side of the Rotax 912ULS engine. The mechanical fuel pump (two orange hoses attached to it) is just aft of the prop flange and the starter can be seen on the bottom left of this photo with the red label on it.

Front view of the Rotax engine … behind the flange for the propeller attachment is the gear reduction unit, the black oil filter is on the bottom left.

Left side of the Rotax engine. Just above and to the left of the Bing carburetor (center far right) one can se what looks like a silver radiator cap … which it is. This is the cap for the small black coolant reservoir.

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.