The last couple of days at DOG Aviation have
been spent doing metal prep and priming of the stabilator skins along with some
of the tail cone components. I had hoped to prime some of the tail cone skins
as well, but quickly realized that the logistics of storing wet 9 foot long
pieces of aluminum in addition to the two large stabilator skins prevented that
from happening.
Although getting a late start today, significant
progress was made on the final assembly of the stabilator. The ribs that were
cut per the plans fit well and did not require additional tweaking.
Placing the stabilator skeleton into the left
stabilator skin.
Aligning the ribs was a slow process, but went
well and without any unforeseen issues. Here again as with the other empennage components,
having dimpled skins and ribs really helps hold the position of the ribs once
the positioning gets close to correct.
Using a finishing nail punch to help align the
holes for the Clecos.
Jan holding the right stabilator skin open for me while placing the stabilator skeleton into the skin.
Once the skeleton assembly is inside the right stabilator
skin, the Cleco process is repeated. Once both left and right skins have been Clecoed,
the whole assembly is flipped over and the other side is Clecoed to prepare for
riveting. Much to my surprise, all the aft ribs were already aligned and the
forward ribs were mostly aligned except for two and they were very close.
Having spent the time to flute the ribs perfectly flat (well close) really paid
off. The pool noodles worked well yet again ... this time they were used to keep the weight off the underside
Clecos ... the noodles are just tall enough to keep the Clecos off the bench.
Once the top and bottom of both stabilator skins
are Clecoed, it was time to begin riveting the skins to the stabilator skeleton.
However, there is a row of rivets at the outboard trailing edge of each side
that does not receive rivets at this time on both top and bottom of the
stabilator. Later there will be small aft skins that attaches there, so those
holes are to be marked for NO riveting.
Marking the holes not to be riveted with blue
painters tape.
Setting the first rivet of the final assembly into the spar
box.
The riveting on one side all finished and the
stabilator is ready to be flipped over to complete
the riveting. The noodles
worked great to keep the underside Clecos off the bench.
The remaining few holes in the right stabilator
skin that could not be dimpled with the C-frame were finished off first thing
today ... then work began on dimpling both sides of the left stabilator skin. Each
skin required a little over two hours … Admittedly, it is a time consuming labor
of love, but the end product makes all the extra effort worth while. One of the
main reasons the dimpling took so long is because the C- frame had to be moved
for every hole. Usually you keep the C-frame stationary and move the skins, but
because the stabilator’s skins are made from one pre-bent big piece of aluminum,
it was safer to keep the skin propped up on pool noodles and move the C-frame
so it took quite a bit of extra time positioning the C-frame for every hole.
Dimpling the last hole in the stabilator’s left
skin using the hand pop
rivet puller and the dies that have a hole in them for
a nail.
Finished right
and left stabilator skins … all dimpled and waiting for primer.
While in the dimpling mood, decided to prep the stabilator
skins for dimpling by removing the blue protective film along the rivet lines
and from the inside of the skins so they will be ready for priming.
Removing the blue film from the rivet lines on
the right stabilator skin.
Noticed on a couple of other builder sites the
suggestion was made to use a tube to remove large areas of the blue film by
rolling the film onto the tube. I had a
piece of 1 1/2” PVC tube that Van’s used as a shipping tube for the replacement
hinge to replace the one I accidentally drilled extra holes into many weeks ago.
The tube technique works great! … my hat goes off to the person who came up
with that idea.
Using a PVC tube to roll up the blue plastic
coating on the stabilator skin.
The PVC tube made easy work of removing the tenacious
blue protective film coating.
After the blue film was removed from the
stabilator’s skin, the dimpling process began using the C-frame. The first two
holes at the leading edge of the skin along with a small row of holes at the aft end will
be done by hand using the pop rivet tool which uses the dies that have a hole
in the center for a nail to be pulled by the pop rivet tool.
Using the C-frame to dimple the stabilator’s
right skin for flush rivets.
Allowing the skin to hang off the edge of the
bench under its own weight so the
leading edge bend opens up as little as
possible during the dimpling process.
So far the dimples look great! Will finish off
the right skin tomorrow by dimpling the few remaining holes with the hand pop
rivet tool and dies then do the same process on the left skin.
After completing the task of breaking the edges
of the F-1279 L&R skins (a step which was omitted from the plans) work
began on the stabilator’s aft skins.
Removing blue film to prepare the edge of the
F-1279-R for the Cleaveland edge breaking tool.
The plans call for match drilling the stabilator’s
aft skins to the ribs so the ribs were numbered to assure correct orientation for
final assembly. Just as before in the anti-servo tabs, the last trailing hole in
the ribs are not drilled. This is because the same rib can be installed facing
inboard or outboard … because the trailing holes in the skins are offset slightly
to prevent the rivets from hitting each other at the narrow point in the
trailing edge, it is necessary to match drill using the trailing edge holes in the skin as a
guide.
Match drilling the stabilator’s aft skins to the
ribs.
After match drilling and deburring the aft skin
and ribs it was time to break both of the skin’s leading edges and then dimple both
aft skins and the four ribs for the 120 degree flush rivets being used on the
RV-12. Three dimpling methods were used depending on access. Pneumatic squeezer,
hand pop rivet tool and dies with a hole in them used with a nail, dies and a
C-clamp for the trailing edge hole where things are really tight.
Dimpling the ribs using the hand pop rivet tool.
Dimpling the last hole at the narrow end of the
rib requires the C-clamp and dies.
Dimpling dies C-clamp setup.
Was able to dimple all the holes in both aft
skins and their ribs without any issues. Next up is dimpling the stabilator’s
main skins then on to primer.
Dimpled ribs and aft skins and the tools that
were used to make the dimples.
The seemingly easy task of breaking the edges on
the tail cone skins ultimately turned out to be an all day chore … nothing hard
mind you, just time consuming. Before breaking the edges on the skins, a soldering iron was used to remove the blue plastic
from the top and bottom area of the skins to
be broken. While at it, the blue plastic coating was also removed from those areas
where there will be an overlap so they can be primed. That added up to over 160
feet of plastic that needed to be removed. After the plastic coating was
removed, the rivet holes that were punched into the skins at the factory needed
to be deburred, thus assuring the rollers on the edge breaking tool would not
get hung up on the burrs …. figure 9 skins at well over 100 holes per skin
needing deburring, it takes time.
Melting the plastic for removal with a soldering
iron. Gee, that pool noodle came in handy yet again.
Deburring the holes so the edge tool rolls over
the holes smoothly.
While preparing the skins, I quickly realized
the plans omitted mentioning anything about breaking the edges of the F-1279
L&R skins. Looking at the plans, it appeared to me as though the edges of
the F-1279 L&R skins should also be broken. I spent quite a bit of time
looking at the plans and could see no good reason why not to break the edges on
the F-1279 skins … so made up my mind I was going to do so. However, it was
getting late so set those two skins to the side and got on the computer just to
make sure breaking the edges would not cause a problem. I went to the Van’s
Forums and did a little research and discovered another builder had wondered
the same thing and called Van’s about it, he was told to go ahead and break the
edges of the F-1279 L&R skins … it was just an omission from the plans. The
omission is really no big deal, at the end of the day it is purely cosmetic.
Breaking the edges went smooth without any
problems. I did follow another builder’s tip I read about and sprayed a little
WD-40 on a paper towel and rubbed down the edges before using the Cleaveland
edge tool. I think it made the process easier. Holding onto the bolt for the top roller in
addition to the handle helps keep the tool in proper alignment, plus aids in
pulling the tool down the length of the skin.
Breaking the edge with the Cleaveland edge tool
was smooth and easy.
Top tailcone skin after breaking both edges … it
is like a big soft noodle.
Return from the future: The portion of the top
skin between the F-1210 far aft fuselage frame and the aft bulkhead the plans
say to add extra break really needs it … especially the last 12” to 14”. If you
are planning on dimpling your RV-12 for flush rivets as I am doing, hold off on
dimpling the F-1278 top skin until the top skin is test fit onto the tail cone
assembly. Once dimpled, you can not add more break.
Today the plan was to break the edges of the
tail cone skins as per the plans. However, realizing that idea was a bit premature,
decided it prudent to spend a few hours deburring all of the tail cone skins
before breaking the edges.
Finding places to keep all 9 of the tail cone’s
9 foot long skins was the biggest challenge as all the pieces were fished out of the
shipping crate one by one for deburring. Most all of the skins were fairly
smooth to begin with and required very little major filing … but hand filing in the
nooks and crannies was required along with running the Scotch-brite wheel down
all the edges.
All of the skins except one have a built in J stiffener
and are fairly easy to handle … however, the top skin has no built in stiffeners
and moving it around is akin to handling a 9 foot long wet noodle … it even droops
over both edges of the bench.
Filing the edges of one of the tail cone’s bottom
skins.
Deburring one of the tail cone’s side skins with
a pneumatic
grinder using a small Scotch-brite wheel.
The stabilator hinges are drilled using the
opposite end of the template used for drilling the anti-servo tab hinges. The
plans call out not drilling two holes on each hinge so that location is covered
with blue tape. If the marking was done right, when rotating the hinges around the
two blue tape marks should line up.
Hinges are a mirror image of each other so the
tape marks should line up if one of the hinges is flipped around.
Drilling stabilator hinges using the drilling
template.
Drilled and deburred stabilator hinges.
After the hinges are drilled, they both get
mounted on upper and lower flanges of the right stabilator skin. The two holes that
were omitted on each hinge using the blue tape will now get match drilled using
a hole in the skin as a guide. In addition, one additional hole is also match drilled
using the stabilator skin’s inboard third hole in as a guide.
Left and right hinges Clecoed to stabilator skin
ready for match drilling three holes on each
hinge. The two holes omitted while
drilling with the template and one additional hole.
Match drilling stabilator hinges using the
stabilator’s skin holes as guides.
Not having anything left to do on the stabilator
before priming, decided to work on some of the tail cone parts. There is a J
stiffener which comes with three stiffeners that need do be separated. The part
was to long for the band saw so used a metal snip to cut one of the attaching
tabs but had to use a cut off wheel to cut the tabs where the “J” curve is.
Using a metal cutoff wheel to separate the three
J stiffeners.
One of the first items in the tail cone plans
calls for breaking the edge of the tail cone’s top, bottom, and side skins. I
have a new tool for doing this sold by Cleaveland Aircraft Tool … but have
never used this type of edge breaking tool before. So thought it would be a
good idea to bone up a little and play a bit on a spare piece of aluminum
before turning myself lose on the tail cone skins.
The Cleaveland edge breaking tool has two
rollers … one of which (the roller on the right) has a small taper on the lower
portion of the wheel which can be seen in the following photo. The small taper
on the wheel when rolled down the outer edge of the metal places a small few
degree downward taper on the skin’s outer edge. The purpose for this is to help make tight
joints where skins overlap each other. Without the small “break” on an overlapping
joint, the riveting process has a tendency to pull the skin upward slightly along
the rivet line. Breaking the edge prior to riveting helps keep the skin snug to
the surface being overlapped.
The tendency is to over adjust the tool. The
tool is easy to adjust … basically slide
the very outer edge of the rollers over the material to be broken and adjust
the tool so the rollers just touch the material. Once adjusted, start at the
edge to be broken and make sure the edge of the metal to be broken is riding
along the raised ridge or guide on the far inside of the wheel and pull the
tool smoothly and evenly along the edge to be broken. Do not tilt the tool up
or down … just drag it straight back and let the tool do the work. It pulls fairly easily but I read on one
builder’s site that putting a little WD-40 on a rag and lubing the metal with a
thin coat helps. Will give that a try tomorrow.
The Cleaveland edge breaking tool … the tapered
roller which creates
“the break” can be seen on the lower portion of the right
roller.
The break can be seen clearly as light under the
straight edge at the outer edge of the skin.
