Saturday, May 18, 2019

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.