The Eagle Receives A Rudder Trim Tab

During the second test flight where the RV-12 was flown for over an hour and away from the home field’s traffic pattern, it was noticed there is a yaw component that needs addressed. To keep the airplane flying without yaw, it required a constant pressure on the right rudder. This is not unusual for a RV-12 without rudder trim … in fact, I would say it is the norm. As mentioned in a previous post, this was expected because I can’t remember seeing any RV-12’s at Oshkosh that didn’t have a trim tab or a wedge on the left side of the rudder. Van’s now has a trim tab available for the RV-12, but unfortunately it came out after the DOG Aviation RV-12’s rudder was completed.


A few weeks ago I ordered a bunch of goodies for the RV-12 such as a canopy cover, sun shade and a trim tab which will be installing now before the temperatures plummet … I wanted to use AKZO primer which is temperature sensitive, so instead of flying more at this time, we are spraying paint. The part number for Van’s trim tab for the RV-12 is R-01220 … the trim tab comes predrilled and pre-bent for the amount of trim that is typically needed at cruising speeds to achieve flight without yaw.

The pre-bent R-01220 trim tab and associated AD-41-ABS rivets used for instillation.

Installing the R-01220 trim tab on a completed rudder requires the removal of one rivet … the lower aft rivet on the left side on the rudder. Prior to removing the rivet and begin drilling, decided to prime the mating area first because the temperatures were forecasted to get much colder than would be suitable for the Akzo epoxy primer to cure properly. The trim tab was held in position and a line was traced around the trim tab so the area could be masked off and sprayed with primer along with the mating surface on the trim tab.

After placing the trim tab in position, a line was traced around it to denote the area that would require masking and scuffing with a ScotchBrite pad.


A one ounce batch of primer was mixed up and the RV-12 was rolled outside and the primer was airbrushed onto the rudder and trim tab along with a couple of other small parts that I want to install in the future.

Akzo primer was airbrushed onto the surface of the rudder where the trim tab will be installed.

As mentioned above, the lower aft most rivet on the left side of the rudder requires removal so the mandrel requires being pounded out so the rivet can be drilled and removed. Those following the DOG Aviation Blog know flush rivets were used during construction, so the rivet being removed is a flush rivet … this will require dimpling the corresponding hole in the trim tab. All the remaining holes that will be drilled will NOT be dimpled because the rudder is now built and there is no access. Also, the rivets are so close to the trailing edge that there is not room for the dimple dies … so the trim tab will only receive one dimple where the flush rivet is being removed and the remainder of the rivets will not be flush.

My finger is pointing towards the only rivet that requires being removed. This rivet hole is used to orientate the trim tap in the correct position while match drilling the remaining holes into the rudder. Because a dimple already exists here, the trim tab will be dimpled only at this location.


Not wanting to just pound on the rudder with a hammer while the rudder was on its stop, decided it best to ask for assistance … so asked Bernie if he could come by the hanger for a few minutes to give me a hand. Bernie held a rag covered block of wood on the right side of the rudder on the rib opposite of the rivet being removed. I used a hammer to pound out the mandrel in the center of the rivet using a mandrel from another rivet that was tapered on the end a little on a Scotch-Brite wheel. Once the mandrel was removed, the head of the rivet was drilled until it popped off so the remaining portion of the rivet could be pushed in clear of the rivet hole. After the rivet was successfully removed, the F-01220 trim tab was secured onto the rudder with a Cleco so the bend line on the trim tab could be aligned with the aft edge of the rudder. Once in position, the trim tab was taped in place so it would not move while drilling.

Match drilling the rudder trim tab to the aft left side of the rudder. Notice the drill has a drill collar. It was adjusted to only allow the drill to penetrate just a little deeper than the skins so the drill bit would not hit the opposite side of the rudder.


After drilling, the rivet holes in the trim tab and the rudder’s skin were deburred. To install the R-01220 trim tab, the lone dimpled hole received a flush rivet and the remaining nine rivet holes received the AD-41-ABS rivets supplied with the trim tab.

Using the hand rivet puller to rivet the F-01220 trim tab onto the RV-12’s rudder. The lower left hand rivet is a flush rivet because the rudder was already dimpled at this location … the remaining nine rivets are AD-41-ABS rivets.

Completed instillation of the F-01220 rudder trim tab on the DOG Aviation RV-12.

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.

A Day Filled With Misery At DOG Aviation

The first task of the day was finishing the installation of the cotter pins on the bolts for attaching the rudder cable to the rudder horn. The joy of standing back and admiring the completion of the rudder instillation was very short lived … 15 minutes max.

The next task was installing the cables and pulleys that are used to connect the control column to the stabilator. The necessary hardware was rounded up along with the forward stabilator cables and pulleys.

These are the two F-1247A forward stabilator cables that ruined my day in more ways than one.

Shortly after the above photo was taken, while attempting to install the first F-1247A cable, the feeling of joy and pride quickly diminished to feelings of total disbelief … self loathing, anger, and dismay. I had installed the right rudder cable into the wrong holes in both center channel bulkheads. Really??? DUH!!! It sucks … really sucks, because after figuring out how to reroute the cable without removing the entire rudder cable instillation, it was realized when attempting to connect the rudder cable onto the rudder horn the newly created F-1258 links are now to short because the correct holes for running the right rudder cable are lower … thus taking up more cable which will require a longer links.

Fellow builders can chuckle … it is not catastrophic … but the mistake will require remaking the F-1258 rudder links for the right side. Fortunately, the postage will cost more than the part … so it is not an expensive mistake. I think two factors played hand and hand with the mistake … first- normally only the holes in the center channel for the rudder cable have grommets and I placed grommets in all the holes. Second - the drawing showing the rudder cables and stabilator cables can be misleading if the builder is not very careful because the rudder cable switches positions aft of the center channel as can be seen in the following photo of the plans.

Note the blue markers point to the right rudder cable in a high hole. At the center channel the pink markers point to the rudder cable in a low hole.

Guess I must have referred to the above drawing too quickly and only noted the rudder cable position where the two blue markers are. Apparently, when running the cable forward from there, I used the same high position when traversing the center channel. Obviously, a senile delinquent moment!

With the right rudder cable now rerouted through the correct grommets, began trying to install the two forward stabilator cables … this proved to be another time sucking abyss and also raised some concerns, which will be addressed in the next post.

RV-12 Rudder Cable Rigging Completed

Continuing on with the rudder cable rigging from the previous work session, the previously marked F-1258 links were removed from the rudder cables and the center point of the hole location marked on the tabs were center punched and drilled. Prior to drilling, a marked F-1258 link was placed on top of an unmarked link and a bolt was placed through the holes to hold alignment. The pair of links were then clamped and drilled out to #12 as a pair. The same procedure was used for the other pair of F-1258 links.

One marked F-1258 link is center punched and placed on top of an unmarked link and the pair is clamped so the holes will be drilled as one.

A small lead hole was drilled first, then the hole was stepped up a couple of times …. drilling the hole to a final size of #12.

After drilling, the result is one pair of long F-1258-L links and another pair of short F-1258-R links. The excess metal needs to be removed and the cut end of the link is given a radius … I used the pre-made end of one of the links as a template to draw the curve for the cut. The links are steel, so would suggest using a hack saw and a grinding wheel to make the radius. Out of habit, I almost began using the band saw to make the cuts … then, fortunately, remembered the links are steel, so used a hack saw to make the cuts. Cutting steel on a small band saw will quickly take a toll on the band saw’s blade.

The finished F-1258-L&R links … the longer links will attach to the left rudder cable and the shorter links will attach onto the right rudder cable.

Here is where I made a slight deviation from the order of assembly in Van's plans. Van’s instructs the builder connect the aft end of the rudder cable onto the rudder horn first, then crawl into the cockpit to attach the cable and newly created cable links onto the rudder pedal horns. I felt it would be advantageous to have more cable play while attaching the links onto the rudder pedal horns … especially while being all scrunched up working in the cramped confines between the tunnel ribs. So I attached the rudder cables and F-1258-L&R links onto the rudder pedal horns first while string was still attached to the aft ends of the rudder cables so they could not be pulled into the tailcone. Once the F-1258 links were bolted up, moved to the tailcone and connected the aft end of the rudder cables onto the rudder horn. Had no issues … just sucked it up and endured the pain while working between the tunnel ribs. I absolutely dread working between the tunnel ribs because I know it is going to hurt.

Completed rigging of the forward end of the left and right rudder cables and F-1258 links.

The aft end of the rudder cables connect directly onto the rudder horns. I had an easy time of installing the hardware onto the rudder horns. I did keep the rudder locked in position (as described in the previous post) until both rudder cables were attached.

Installing the bolt and one of the washers that go above and below the rudder horn.

Completed rudder rigging … the aft end of both rudder cables are now attached onto the rudder horn finishing the rigging of the rudder cables.

For those with keen eyes … please don’t send Email's about the missing left and unset right cotter pins on the rudder cable’s mounting hardware. I just had to leave the hangar to attend Holiday festivities and could not stay a moment longer. Will install the cotter pins first thing during the next work session.

Rigging Of The Rudder Pedal Cables Continues

Now that the rudder cables have been pulled through the tailcone it is time to begin rigging the rudder cables. In essence, what is about to transpire is the rudder pedals are going to be locked and the rudder cables will be temporally attached directly to the rudder pedals … then pulled taut by pulling aft on the F-1258 cable links temporarily attached to the aft end of the ruder cables. When the slack is pulled out of the cables, the links will be clamped in place on the rudder horn and the hole in the rudder horn will be used to mark the F-1258 cable links for drilling. After the holes are marked and the F-1258 links drilled, the links will be moved forward and permanently installed onto the rudder pedal horns. Smart people at Van’s … it is far far easier to take the slack out of the cable and mark the links for drilling at the tailcone end … as opposed to doing this while all scrunched up between the center tunnel ribs.

The rigging process begins by temporarily attaching two of the four F-1258 cable links (that have a center line drawn on them) onto the aft ends of the F-1239 rudder cables. The rudder cables are pulled forward and temporarily attached onto the horns on the rudder pedals. Maks sure to keep a string tied onto the rudder cable at all times to prevent it from dropping onto the tailcone.

F-1258 link with center line temporarily attached to the aft end a rudder cable.

The rudder cables were pulled forward and temporarily attached onto the rudder pedal horns. Blue masking tape was used to hold the bolt in position on the rudder pedal horns so I could screw the nut on one handed.

Next a rudder stop needs to be fabricated. The plans give instructions on how to make a the rudder stop using wood from one of the Van’s shipping crates. The rudder stop is used to lock the rudder pedals in a neutral position.  So I had to put aside the metal working tools and break out the jig saw to become “Samurai Woodsman” and cut up some wood from a shipping crate to fabricate the rudder stop. A 6" strip of plywood was removed from the lid of one of the shipping crates, then cut into two pieces 16 1/2" inches long. The remaining scrap of wood was cut to 5 1/2" to form the "H".

Cutting the 5 1/2" piece of wood that creates the center of the “H” … the two larger strips of plywood in the foreground have already been cut to length.

The two long pieces receive cutouts at both ends. One of the cutouts will slip over the rudder pedals and the cutout at the other end will sit on the F-1202F bulkhead. The 5 1/2" piece of wood is used as a center spacer to nail the two longer pieces onto … forming a “H”.

All three pieces ready to be nailed together to form the “H” shape of the rudder stop. Note duplicate cutouts were created on the two longer pieces of wood.

Results of playing “Samurai Woodsman” with the jig and band saws. I cheated a little as the center piece should be 6" high … did not want to cut another piece out of the plywood so the center is a little shorter than the plans call for … no big deal it is only used to keep the two larger pieces spaced parallel. The “H” looks like the plans (except for the short center piece of wood) … so time to put away the “Samurai Woodsman” tools, clean up the saw dust and put the rudder rigging stop to good use.

The rudder pedal rigging stop is installed on the pilot’s side … the forward portion of it sits on top of the left and right rudder pedals. The aft portion of the rudder pedal stop sits on top of the F-1202 bulkhead. This locks the rudder pedals in the neutral position so the slack can be pulled out of the cable and the drilling location marked onto the F-1258 cable links.

The fabricated rudder pedal rigging stop installed on the pilot’s side.

The plans instruct the builder to center the rudder then pull back on the F-1215 cable links to remove slack from the cable … while pulling back on the links a clamp is to be used to secure the links onto the rudder horn. I was doing this by myself and was making the rudder move either by pulling the slack or while clamping with one hand. After a few cycles of frustration, decided to just lock the rudder by using strips of wood clamped onto each rudder horn to prevent movement while the rudder cables were pulled aft and clamped onto the rudder horn. Measurements were taken from the center of the holes in the rudder horn to the tailcone’s aft bulkhead and equal position was achieved at around 2 3/8" (if memory serves me correct). The clamping worked out great!

Rudder locked in a neutral position by using two strips of wood clamped onto the rudder’s horns.

View of how both sides of the rudder was clamped in a centered position.

Closer view of the left side of the rudder horn clamped in a centered position.

By having the rudder locked, I was able to pull all the slack out of both rudder cables and clamp them onto the rudder horn by myself. Once clamped in position, the hole in the rudder horn is traced onto the F-1258 links. Of note, this process will create long and short F-1258 links. Not to worry … this is because the arms at the rudder pedals are offset … so this process is creating long and short F-1258 links to accommodate for that difference.

The F-1258 links for the left rudder cable will become the long links.

The F-1258 links for the right rudder cable will become the short links.

By this time it was getting late so did not finish drilling the links … so that will be the first task during the next work session.