Not much time was spent in the cold shop today but
did accomplish the test fitting of the stall warning assembly on the left wing.
The instructions have the builder make a 5” ground wire which is attached onto
one of the stall warning assembly’s mounting screws. The assembly is then
mounted onto the W-1208-R nose rib that has two plate nuts on it.
After the stall warning assembly is mounted onto
the rib, the W-1202-L wing skin that has the slot on the leading edge for the
stall warning vane is carefully set in place and Clecoed to test the fit. The
vane should move freely and not bind on the sides of the slot in the skin.
Guess I got lucky because there is no binding and the vane is centered.
Stall warning assembly and ground wire attached
onto the W-1208-R rib
that has the two nut plates. Photo taken prior to micro-switch
adjustment.
Close up of the stall warning vane sticking
through the slot in the W-1202-L wing skin.
This view shows how far the stall warning vane
protrudes from the leading edge of the wing and also its slight downward angle. It’s been reported the protruding vane has quite an
appetite for the pants and legs of unsuspecting souls.
Before working on the RV-12 today, I was filling
the tires of DOG Aviation’s support vehicles (without gloves) so by the time the stall warning
assembly was mounted and the W-1202-L skin set in place, my hands were chilled
to the bone so will move onto adjusting the micro-switch/vane assembly during
the next work session after the hands thaw out.
New Years Eve was spent rearranging the shop a
little by putting away a folding table which was used as a catch all table. Now
the snow blower can be moved from the middle of the shop allowing access into
the large box that contains the wing skins. The left wing’s middle skin is
needed for testing the fit where the stall warning micro-switch/vane assembly passes
through a slot in the leading edge of the skin.
Wanting to get the New Year started off on the
right foot by making some forward progress on the RV-12, assembled the stall
warning micro-switch/vane assembly per the instructions. Winter in the shop is not fun … trying to assemble
all the small hardware with gloves on was impossible but doing it with numb
fingers was only marginally better. Should have fired up the heaters but
figured it was hardly worth it for the small amount of time I planned on
spending in the shop … although my hands and feet disagreed with that assessment.
The assembled stall warning sub assembly ready
to be mounted onto
the W-1208 nose rib previously prepped with mounting plate
nuts.
The wiring tools ordered by the DOG Aviation
procurement department came in New Years Eve and consists of an automatic wire
stripper along with a ratcheting crimping tool made by Tool Aid with seven changeable dies ... the part number of the Tool Aid kit is #18960. The crimping
tool will crimp a host of connectors …. . both standard sizes of open barrel Molex
connector pins, standard and miniature insulated
and non-insulated ring and spade crimps, Weatherpack terminals, coax cable,
even spark plug connectors. Return from the future: Subsequently another die set #18937 was needed for the small .063 Molex open barrel connectors and open barrel connector pins for for tiny wire.
Wire strippers and Tool Aid ratcheting crimping tool with
seven dies for various wire terminals.
The last item needed before riveting the skins
onto the rib skeleton is the shielded cable for the strobe lights … which should
be here Friday according to the shippers tracking info. After that the only
hold up should be my tolerances to working in the cold holding tools that feel
like blocks of ice.
In spite of surviving the end of the Mayan calendar,
Christmas hustle & bustle, and the first winter storm of the season
requiring the use of DOG Aviation’s emergency snow removal equipment, RV-12 construction
at DOG Aviation is about to resume. The project has been in somewhat of a
holding pattern waiting for a micro-switch, some wire and tools. Now the micro-switch is here but still waiting on the shielded wire for the strobe light
wiring which was ordered a week ago and will be needed real soon.
About that the replacement micro-switch for
the stall warning assembly ... behind
the scenes, DOG Aviation’s research department is constantly looking into
modifications that improve on the already excellent RV-12 design. One such
modification pioneered by Joe (the RV-12 builder in Michigan who came up with the AOA
modification) is to replace the stall warning micro-switch with one having a
slightly longer arm … this makes fine tuning the stall speed warning alarm much easier.
I ordered a new switch from Mouser which requires much less force to operate, it
is Cherry part number E22-50KL. The replacement Cherry switch is the exact same
switch electrically as the original, it differs physically in that the roller
arm is moved forward to give a better mechanical advantage.
Is this modification really necessary?
Truthfully, … nope. That said, to me it makes good sense because once the wing
is assembled, adjustment access through the small inspection port is well, at
best, challenging so at $4 and change for a micro-switch, why not go for it if
it makes fine tuning the stall warning easier?
I ran two mounting screws through the two
micro-switches in the photo bellow to keep the switches in alignment so it is
easier to see the subtle difference between the original Cherry switch shipped
in the parts from Van’s and the replacement Cherry switch purchased from Mouser.
The original micro-switch from Van’s is on the
bottom and the replacement micro-switch purchased from
Mouser is on the top.
One can easily see the slightly longer arm on the replacement micro-switch.
Twas the night before Christmas, when all
through the shop not a rivet was stirring, not even a pop; Well you get the
idea … Merry Christmas from DOG Aviation!!
Earlier in the day, in an effort to move forward
with the project no mater how small the task, a small amount of time was spent machine
countersinking the VA-195A mounting plate for the stall warning indicator’s
micro-switch. The mounting plate has two holes that accept #4 screws used to
mount the micro-switch for the stall warning indicator system. These two holes are
drilled out to #30, then machine countersunk using the 100 degree #30
countersink bit until the #4 screws set flush into the VA-195A mounting plate.
Machine countersinking the two holes on the
VA-195A mounting plate which
will accept the #4 mounting screws for securing the
stall warning micro-switch.
The VA-195A has another hole that receives a #8
screw which also requires machine countersinking … this hole is drilled out
using a #19 drill and machine countersunk using a #20 countersunk bit. This #8 screw
will be both a mount and pivot point for a vane that has a downward bend where
it protrudes through a small slot in the wing’s leading edge and into the airflow.
The theory behind this assembly is simple … under
normal flight conditions, because the vane is bent downward, the wind will push
down on the vane preventing the vane from rising and tripping the micro-switch.
However, when the angle of the wing becomes higher (as when approaching a stall)
the airflow will get under the vane, lifting it, thus tripping the micro-swich
causing alarms to sound in the cockpit.
Finished VA-195A mounting plate, machine
countersunk and ready for assembly.
One option that was purchased along with the
wing kit was a lighting kit which consists of navigation lights, strobe lights
and position lights all in one unit for each wing, along with a landing light
for the right wing, all manufactured by Aeroleds.
The parts do not look like they will be a piece
of cake to install … but the instructions appear to be concise enough to allow
for a hopefully smooth install. Van’s includes 18 gauge wires for wiring the
navigation light power, strobe light power and strobe sync lines to the
Aeroleds lights. One discrepancy I noticed immediately on a schematic in one of
the Aeroleds boxes is the use of shielded wire. I know I’ve read about builders
mentioning they can hear a little noise in their headsets when the strobes are
on. Installing the strobe wiring using shielded wires as opposed to running
unshielded wire may really help keep strobe noise out of the electrical
system. A call to Aeroleds confirmed my
thoughts and they have 3 conductor shielded cable available so will probably
place an order for that today.
Before any wiring begins in earnest inside the left
wing, I want to have all the components together to see if there is plenty of
room in the grommets that will be placed in the ribs for wire runs …. May have
to go to the next size up because of the shielded wires and plumbing I plan on
installing.
Pluming in a RV-12 wing you may be asking? Yes,
for the AOA indicator of course!! (Similar to a reserve lift indicator). One of
the features built into the Dynon SkyView which Van’s elected not to utilize because
of the RV-12’s removable wings, is an AOA (angle of attack) display. A builder in Michigan (Joe) did the research and
pioneered a working method where a small piece of tubing is connected to a port
strategically placed at a 30 degree point under the leading edge of the wing.
When the RV-12 approaches a stall, the tube’s air pressure changes and the
SkyView analyzes that pressure change and displays a bar scale with increments
in green, yellow, and red (falling out of the sky). Quite a few builders on the forums have modified
their RV12’s to take advantage of this very useful display function (which adds
another element of safety) and all have been very very pleased with the
results. Since the RV-12 is being built
as E-AB and not E-LSA, I will install the AOA plumbing now.
Just a hand full of small inexpensive parts are
needed to install the AOA hardware.
The parts consist of: … Center in the photo - 1/16”
ID Tygon tubing ( I chose tubing rated at Shore 64 because it is firmer than
totally soft but still considered soft), below the tubing is a threaded 1/8” NTP
male adapter which will screw into the ADHARS for the SkyView and allows the small
Tygon tubing to be attached. Upper right
- a female Luer Lock, Lower left - a male Luer Lock. Luer Lock connectors are a
¼ turn release connector and will be placed at the root of the wing for easy
disconnect during wing removal. On the
left side of the photo there are Luer caps: Top – female caps, Bottom – male caps.
The caps are for protecting the tubing from contamination when the wings are
removed and are really not necessary … I noticed them while placing the parts
order and they seem like a good idea so picked them up as well. The 1/8” NTP
adapter was the only item available as a single unit all the Luer connectors
were in bags of 10 but they are very cheep. All total think the parts were
around $20 from McMaster-Carr. (Not including the Locktite 243 which is for
installing the stall warning micro switch).
At a strategic location under the leading edge of the wig, in the bay with the inspection plate, the tubing
is connected to a drilled hole for a port which can be a rivet similar to the static port rivets (mandrel driven out)
or a sports ball inflating needle as the original author of the modification
used. Builders have had great success with either method. One good thing about using
a ball filling needle is where the threads protrude the wing skin, a cap can be
screwed onto the threads (where an air hose would normally go) to protect the
tubing from insects and dirt. while the plane is on the ground.
Those following the Blog will notice there have
been a few days of non activity since the wing skeleton was completed. This is due
in part to waiting for materials needed to move forward, coupled with a bit of a
mental pause on my part.
After finishing the left wing skeleton, the next
steps in the plans regarding instillation of components for the stall warning indicator
were quickly perused to see what would be involved. My eye caught two items
which placed the brakes on the build… the first was Locktite 243 thread sealant
which the DOG Aviation procurement department desperately tried locating
locally, to no avail I might add, so an online order was placed.
The second item was a reference to machine
countersinking two screw holes in a mounting plate for #4 screws. A moment of
total mental pause!!! Countersink for #4
screws?? … The procurement department never ordered a countersink bit for #4
screws!! Build time was now diverted to research time to find a vendor for #4
countersink bits plus another side issue I’ll mention later. (Cleaveland
Aircraft Parts does carry them).
The moment of clarity … Yes, I would have needed
to wait for the Locktite 243 anyway but after SLOWLY rereading the instructions,
the first step is to final drill the mounting plate screw holes to #30 …. DUH!!
Don’t need a special countersink bit for #4 screws, I can use the countersink
bit with the #30 tip I already have. Issue solved.
Taking advantage of an unseasonably warm day,
decided to remove the right wing spar from the crate and use the airbrush to prime
the factory mounted rib clips as was done on the left spar. That was followed
by changing the oil in the snow blower so it will be ready for action if the
snow slated for the end of this week becomes substantial. Once all side the
chores were completed, work resumed on completing the left wing skeleton
beginning with riveting the remaining two nose ribs.
Using the close quarter pop riveter to attach a W-1208-R
rib at the
third rib clip in from the root of the wing using LP4-3 pop rivets.
As mentioned previously, the second and third
ribs from the innermost rib require riveting using LP4-3 pop rivets where the
web of the ribs attach to the rib clips … this is because the adjacent rib
clips interfere with the body of the pneumatic squeezer preventing proper
access.
Finished third rib in from the root of the wing
... AN470AD4-4 rivets attach the aft
flange onto the left spar and LP4-3 pop
rivets attach the rib’s web to the rib clips.
Using the rivet gun and bucking bar to rivet the
aft flange of the lone
W-1208-L nose rib onto the left spar using AN470AD4-4
rivets.
Because of the extra support needed for the wing
walk area, the rib spacing is closer near the root of the wing. Unfortunately,
this closeness prevented the pneumatic squeezer from having good access and
almost prevents the pop riveter from having access. My standard pop riveting
tool did not come close to fitting between the ribs. Fortunately, the close
quarter pop riveter worked, but just barely and not without flexing the
neighboring rib so the riveter’s handles could be opened enough to allow the
riveter to get a second grip on the rivets … the rivets never pop during the
first squeeze and require the riveter getting a second grip before they pop. It
was really a chore getting Clecos in and out so needless to say, it was a fight
to set the pop rivets in this area of the wing.
All ribs now riveted onto the RV-12’s left wing
spar.
Better view of all the ribs riveted onto the
left spar ... note the closer spacing of the nose ribs for the wing walk area.
The left wing’s stub spar assembly is the last
component to complete the left wing’s skeleton. The stub spar assembly is
riveted onto the nose of the inner most six ribs.
Attaching the stub spar assembly onto the W-1208
nose ribs with Clecos in preparation for riveting.
Access for the pneumatic squeezer was good
enough to allow riveting the stub spar assembly onto the W-1208 nose ribs using
solid rivets. AN470AD4-4.5 rivets were used to rivet the stub spar assembly
onto the nose ribs …. in those areas where there was a doubler plate, AN470AD4-6
rivets were used. This was another one of those cases where the 4-6 rivets were
slightly to long and the 4-5 rivet was much to short.
Using the pneumatic squeezer to set the last
rivet attaching the stub spar assembly
onto the W-1208 nose ribs and thus completing the left wing skeleton.
With the stub spar assembly now fully riveted, the
RV-12’s left wing skeleton is completed.
Final tally … out of the 151 rivets holding the
nose ribs onto the left spar and stub spar assembly, only 12 ended up being
LP4-3 pop rivets due to clearance issues with the pneumatic squeezer.
