It has been a couple of weeks since the last
post … due in part to taking a few days away from the project after the
fuselage inventory was completed, coupled with waiting for tools and materials as
well as with dealing with a yet to be resolved interior/exterior color theme.
Just before the fuselage kit arrived, I attended
an EAA pancake breakfast at the airport I had hoped would become home base for
final construction and phase one flight testing of the RV-12 … only to find out
the likelihood of finding a hanger (or shared hanger space) is practically
zilch. The possibility still exists for
using the EAA’s facility for assembly, but after assembly there is apparently
no place there to shelter the aircraft. So being just a little depressed about
the situation, decided to take a few days away from the project after the
inventory was completed.
Components making up the RV-12’s center section.
After studying the plans and looking more
closely at finished RV-12 aircraft, it became very apparent there were a few issues
which created an instant dilemma, beginning with the first piece of the fuselage
puzzle … the F-1204 center section as seen in the above photo.
Primer & interior paint … basically, the
shop only had a very small quantity of the Akzo epoxy primer remaining.
Unfortunately, Akzo can only be purchased in 2 gallon batches (1 gal epoxy, 1
gal catalyst). I had not ordered more earlier because the under the floor pan
components would only require at most a pint of primer (if that), so research
was being done on finding another primer that would work well with interior
paint. Ultimately, this proved to be a waste of time because builders have
reported on the forums of good success using the Akzo primer with Sherwin-Williams
Jet Flex water reducible (which is an interior paint made to Boeing
specifications) as long as the Akzo is top coated in 24-48 hours. I really like Akzo primer so one problem
solved … another batch of Akzo was ordered (there will still be a lot left over
perhaps to pass onto another builder). Jet Flex interior paint is available in
solvent based (which is NOT Isocyanate free (think Bhopal India disaster) and
requires a fresh air respirator) and water reducible which can be sprayed using
a good organic vapor filter on a respirator … so I’m inclined to give the Jet Flex water
reducible a try based on other builders good experiences with the paint.
Knowing the Akzo primer must be top coated within
24-48 hours opens up another can of worms … what color will the exterior of the
airplane be? Should the interior paint color tie into the exterior color scheme?
What is the exterior color scheme? Oh … what about interior upholstery appointments
and seat belt color choices? Was hopeful all these decisions could be dealt
with later by kicking the can further down the road for the time being (much
the same as Congress does) … but as it turns out, the RV-12’s center channel assembly
is visible and will require primer and interior paint.
Some builders spray the fuselage interior after
assembly (but it is hard to get the paint evenly into all the nooks and crannies)
and some prior to assembly. Some builders who have painted the fuselage
interior after assembly have said, if done again, they would probably paint
prior to assembling the parts. I’m inclined to paint prior to assembly because
none of the rivets are set with a rivet gun which will mar paint. Unfortunately,
parts are riveted onto the F-1204 center channel in the very first step of the
plans, so a command decision is required … and soon. DOG Aviation has already received
a few color chips with more on the way, along with interior samples as well.
Although not doing any assembly yet, forward
progress on the fuselage has begun. The aft portion of the RV-12’s F-1204 center
channel required being match drilled to the holes in the F-1204D center section
aft bulkhead. Clecos are used to secure the center section and aft bulkhead onto
the bottom skin for horizontal alignment and clamps are used to snug the two
parts together for drilling. The match drilling consists of drilling 73 holes and
after drilling, two of those holes are enlarged with a #11 drill bit. The
center channel is 5/16” thick and is on a slight angle so the DOG Aviation
procurement department purchased a drill guide to aid in drilling straight
Drill guide with drill bit inserted.
Drill guide viewed from the bottom. The V on the
bottom allows the drill guide to center a hole in round tubing as well.
Because the center channel material is so thick,
if the holes are not perfectly square, the heads of the solid rivets going into
the holes will not set perfectly flat. Sure a piece of hard wood with a hole in it would work,
but did not have any lying around the shop and a thick chunk of it costs almost
as much as a drill guide.
Using the drill guide to match drill the first
of 73 center section holes
in the aft bulkhead … starting in the center and
Making progress slow but sure … lots of holes
still left to drill using the drill guide.
Completed match drilling of the F-1204 center
channel to holes in F-1204D
aft bulkhead - all 73 holes completed, plus two
holes enlarged to #11.
After the holes were drilled in the center
section, the components are disassembled for deburring. Deburring the outer
portion of the center channel was a snap using the Avery deburring tool.
However, that tool is too long for use inside of the center channel. At first
the bit was unscrewed and spun by hand (as done before) but doing 73 holes this
way … my fingers were getting sore just thinking about it! There had to be a
better way. After a little brainstorming, hit upon an idea that proved to work
great! The angle drill is a seldom used tool in the drawer and appeared to have
the same thread size as the deburring tool bit. So simply screwed the deburring
bit in and went to work easily deburring all the remaining holes in the center
channel. It is always satisfying to successfully repurpose a seldom used tool
with great results.
Using the angle drill to deburr the holes inside
the center channel.
Admittedly, color choices and interior decorating
is not my forte. So while struggling with those issues, work will continue on
fuselage items that will need to be done eventually anyway, such as separating parts
on the band saw, filing, deburring, smoothing edges, etc. Some parts such as
the ribs under the seat and floor pans could also be primed at this time since
they will not receive a top coat of interior paint.