Apologize for the long delay between posting Part 2 and Part 3. The weather made a drastic change with many days of rain followed by a quick temperature plunge and snow. Not being too keen on working in a cold damp hanger or dealing with the loud noise levels from rain hitting the all metal roof, I decided to wait out the rains and unseasonably cold daytime temps and wait for a day with more favorable temps to finish up … which took far longer than anticipated.
The two previous posts Part 1 & Part 2 covered the steps necessary
to perform the needed modifications to the WD-1207 & WD-1208 stabilator
horns and preparing the stabilator for the new hinge bracket assemblies and new
HS-01231C hinge gussets. Here in Part 3, the steps used to complete the
instillation of the new bearing bracket assemblies and new hinge gussets to complete Service bulletin
18-02-02 will be covered.
As mentioned in Part 2, the decision was made to use all solid rivets
for the three rivets that attach the HS-01231C stabilator hinge gussets onto
the flanges of the inboard hinge bracket assembly. This involved a little more
extra work than I anticipated but everything worked out quite well.
Assembly of the bearing brackets begins by bolting the outboard hinge
bracelet assemblies to the stabilator. This is a final instillation so all new
AN3-4A bolts were used because the bolts are being screwed into nutplates and
every insertion wears the threads down a little. These bolts will likely never
be removed again so figured bolts are cheap just may as well replace them with
Because of my desire to install all AN470AD3-3.5 rivets in the flanges
of the inboard bearing bracket, it becomes the sticky wicket during reassembly
… in that, the inboard bearing bracket assemblies pose a problem for riveting
because the bolts for the HS-1210 stabilator stops need to be removed along
with the bolts for the bearing bracket mounting bolt for to allow access for
the rivet squeezer’s yoke. (Note to fellow builders/owners … if not installing
the aft AD470AD3-3. 5 rivets and using the LP4-3 rivet called out in the
service bulletin, there will be no need to remove the bearing bracket mounting
bolts during riveting). Guessing this is why Van’s instructs the builder/owner to
use a pop rivet at this location. To save wear and tear on the nutplates, I
decided to cheat a little and used short AN525-10R7 screws to temporarily hold
the inboard bearing brackets for riveting).
As can be seen in the photo below, the inboard bracket assembly was
mounted with the temporary use of AN525-10R7 washer head screws in lieu of the
regular bolts. The HS-01231C hinge gusset was secured onto the stabilator with
#30 Clecos and the inboard line of AN470AD3-3.5 rivets were set in place to
assure positioning. A Cleco clamp was used to hold the HS-01231C hinge gusset
firmly down on the flange of the inboard bearing bracket. Note the bearing stop
bolt is in position and a standard nut was temporarily used to snug up the
assembly to assure proper positioning during riveting.
The HS-01231C hinge gusset is secured to the stabilator with Clecos ready
for final riveting. Note the AN525-10R7 washer head screw used temporarily to
keep the inboard hinge bracket positioned during riveting. Also note the bolt
for the hinge stop is also in position and temporarily snugged down with a
standard #10 nut (not in view).
To accomplish the actual riveting, the pneumatic rivet squeezer was
outfitted with the “no hole yoke”. I found during bench testing it offered more
surface area than the standard yoke with a flat rivet set. There is not a lot
of excess room to reach the aft most rivet so felt the “no hole” yoke was the
best choice since there is one in the tool box. I also discovered the aft most
rivet needed to be accessed from the front and not the side in order for the
squeezer to be properly squared to the rivet head during riveting. The first
step in the riveting process was to rivet the forward most AN470AD3-3.5 rivet
as can be seen below.
Using the pneumatic rivet squeezer outfitted with a “no hole” yoke to
set the forward most AN470AD3-3.5 rivet that attaches the HS-01231C hinge
gusset to the flanges of the inboard bearing bracket assembly.
At this point, to gain access to the remaining two AN470AD3-3.5 rivets
that need to be set, it is necessary to remove the bolt for the HS-1210 hinge
stop and the bolt for the inboard hinge … which is why I used the short AN525
screw. (Actually, I had given this quite a bit of thought while waiting for the
weather to improve and thought the much smaller head of the AN525 screw would
allow access for riveting … not so, because the clearances are very tight. Even
using the AN525washer head screws there was not enough clearance for the yoke
of the rivet squeezer to access the rivet properly). With the hardware out of
the way, the next rivet squeezed was the aft most AN470AD3-3.5 rivet.
Using the pneumatic rivet squeezer outfitted with a “no hole” yoke to
set the aft most AN470AD3-3.5 rivet that attaches the HS-01231C hinge gusset to
the flange of the inboard bearing bracket assembly. Also note the center rivet
was left sitting in the hole to assure positioning just in case the HS-01231C
hinge gusset tried moving a little … it didn’t.
The last AN470AD3-3.5 rivet set on the inboard flange was the center
rivet. After setting the three AN470AD3-3.5 rivets on the inboard flange of the
bearing bracket assembly, a new AN3-4A bolt was screwed into the bearing
bracket assembly and torqued to specifications (20-25 inch pounds plus the
running torque of the nutplate). At this point, the remaining #30 holes in the
HS-01231C hinge gusset received pop rivets. Because flush rivets were used on
the skins of the stabilator during the construction of the DOG Aviation RV-12,
those rivet holes common to the stabilator skins received flush rivets and the
remaining holes received the standard van’s LP4-3 low dome pop rivet. Most
builders/owners can ignore the last comment because your RV-12’s used the LP4-3
rivets exclusively on the stabilator skins. When riveting of the HS-01231C
hinge gusset is completed, the bolt that secures the HS-1210 hinge stop was
final installed using a new AN365-1032 lock nut.
Gee this was just so much fun … let’s repeat the process again three
more times for the remaining three HS-01231C hinge gussets that need to be
Setting one of the five flush rivets in the HS-01231C hinge gusset. Note:
These flush rivets are unique to the DOG Aviation RV-12 … most all other builders/owners
will be using the standard Van’s LP4-3 rivets to secure the HS-01231C hinge
gusset to the stabilator assembly.
Completed riveting of the two HS-01231C hinge gussets onto the top side
of the stabilator … time to flip the stabilator over and begin riveting the
After all four HS-01231C hinge gussets are riveted in place, the last
remaining chore before the stabilator can be bolted back onto the RV-12’s tail
cone is installing the WD-1207 & WD-1208 control horns onto the stabilator.
Assembly is straight forward, in that, each control horn is first bolted in
place and then the HS-1232 stabilator horn doubler is riveted to the HS-1211
spar cap. Once bolted, the position of the control horns won’t change … so
prior to bolting the WD-1207 & WD-1208 control horns all the LP4-3 rivets
were placed in the HS-01232 stabilator horn doubler but not set. With all the
LP4-3 rivets sitting in place on the HS-01232 stabilator horn doubler, four new
AN3-4 bolts were installed to secure each control horn to the stabilator spar
box. This is followed by setting all the rivets securing each HS-01232
stabilator horn doubler to the HS-1211 spar cap which completes the service
Using a torque wrench to final torque of the AN3-4A bolt that attaches
the WD-1208 stabilator horn to the stabilator spar box. Note all the LP4-3
rivets are sitting in the HS-01232 stabilator horn doubler prior to tightening
the four bolts that secure the stabilator horn to the spar box.
Using a hand rivet puller to rivet the HS-1232 stabilator horn doubler
/WD-1208 stabilator horn assembly to the stabilator spar cap.
Completed riveting of the HS-1232 stabilator horn doubler /WD-1208 stabilator
horn assembly to the stabilator’s spar cap.
If the instructions in the service bulletin are followed correctly, you
will find yourself with four leftover AN960-10L washers. This is because the
original plans called for an AN960-10 washer to be placed under the heads of
each of the four bolts that secure the four HS-1210 hinge stops and an AN960-10L
washer under each of the four AN365-1032 nuts. Following the service bulletin,
during reassembly the AN960-10 washers that were under the head of the bolt are
moved to under the nut and the thin washers are NOT reinstalled. I’m guessing due to the extra thickness of
the two thin HS-01231B brackets installed during the service bulletin Van’s
decided it was cheaper to eliminate the thin washers as opposed to requiring
The two bolts the arrows are pointing to will not be reassembled with washers
under the head of the bolts. (The same applies to the other hinge bracket
assembly not in view). Instead, the AN960-10 washers that used to be under the bolt
heads are moved to under the AN365-1032 nuts. The thin AN960-10L washers (which
used to be under the AN365-1032 nuts) sitting on the table are NOT reinstalled.
Completed Service Bulletin 18-02-02 on the stabilator assembly ready for reattachment no the RV-12’s tail cone. After completing the entire service bulletin decided it may be a good
idea to place a dollop of torque seal on the heads of all the bolts and nuts.
Bolting the stabilator back on the RV-12’s tail cone was NOT a piece of
cake it requires lots of patience. It was hard to do the first time during the
initial build … but with the addition of the box around the hinge bracket, it
increases the level of difficulty. In full disclosure, I did not crazy glue the
washers in place first … because others have reported they tend to fall off
anyway, so I figured why bother and used a thin metal ruler with masking tape
to hold the washers during insertion between the bearing bracket and bearing. What
helped out the most after fighting with it for quite some time and ultimately ended
up being a workable solution was to forget about the washers at first and just
get the stabilator aligned enough so the bolts to go through the bearings. Then
once both bolts are inserted, pull back one bolt and insert the necessary
washers as the bolt is being reinserted … then do the same to the other side.
Unfortunately, I will likely need to remove the stabilator again in the
spring for painting. My plan is to use the two old AN4-12A bolts and grind down
the threaded area on the bolts to form a slight taper so the bolts will help self-align
the parts as the tapered bolts are being inserted. Will likely also remove a
little material (not much) from the shank of the bolt so it will be easier to
slide then in and out of the bearing brackets and bearings. Once these bolts
are used to “pin” the stabilator in place … then they can then be removed one
at a time so the actual threaded AN4-12A bolt and appropriate washers can be
As mentioned in Part 1, the upper and lower stabilator cables were
removed from the stabilator horns without loosening the adjusting barrels. So
to aid in reinstalling the stabilator cables, I made a tool out of a piece of
scrap aluminum and cut out a slot with a rounded bottom. A hole was drilled
near the end of the piece of scrap metal so a used bolt and nut could be
attached to make it easier to pull on the tool. Just place the tool over the
cable and pull back so the bolts can be reinserted.
A scrap piece of bent aluminum with a slot cut in it with a rounded
bottom will hold the stabilator cable while it is being pulled taunt so the
cables can be reinstalled on the stabilator’s horns.
The homemade cable pulling tool in place on the upper stabilator cable
for a proof of concept test. All was well but the tool was tweaked a little to
remove sharp edges and allow it to capture the cable just a little further aft.
In summary, Service Bulletin 18-02-02 requires a lot of time to install
… it is NOT a 2 hour job. If one wants to take the extra time, it is possible
to not drill into the HS-1211 spar cap when match drilling the WD-1207 &
WD-1208 stabilator horns to the HS-01232 stabilator horn doublers. It is also possible
to use all AN470AD3-3.5 rivets on the inboard line of rivets securing the
HS-01231C hinge gussets to the inboard hinge brackets for a more uniform look.
Oh, I have not installed the upper & lower tail cone fairings yet, but be
aware they will require a small amount of trimming to make room for the
HS-01231C hinge gussets … so fellow builders/owners make it a point to check
that after completing Service Bulletin 18-02-02.
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