was not a hard process, but it took a lot
of time. The big
steps, fitting the flap
to the fuselage and installing the pushrod, were both a series of
measuring, removing, trimming and repeating.
But I would rather take it slow and end up
with a good fit than move too
fast and end up with a big gap because I removed too much metal.
Fitting to the Fuselage
To begin the process
of hanging flaps, I set the ailerons in
the trail position by installing the W-730 bellcrank jig. I also checked that the
tooling holes in the
wing tip and aileron lined up. Then
installed the flaps, sliding the hinge pin in from the inboard side of
flap. An alternate
method that might be
a little easier if you have help is to make two small hinge pins. Have your help hold one
end of the flap and
slide the pin in a few inches while you do the same on the other end. Since you just need the
flap in position to
check for fit, you really don’t need to install the entire hinge pin.
I started this step
marking and trimming the top skin
with the cutout template from the plans.
Then I repeatedly installed the flap, looked
at the fit, marked where it
needed more trimming, removed the flap and trimmed.
I got pretty good at installing the hinge
pin, and found that a shot of WD-40 made a huge difference.
did most of the
trimming with a cutoff disk on an angle
grinder. I then
polished the edge with the
course scotchbrite pad on the grinder.
Once I was down to minor trimming, I used just
the course scotchbrite
pad. I didn’t
bother with final edge
dressing until I was done with all the trimming.
The aft end of the flap with the tight bend
radius was a little tricky to trim.
used the scotchbrite pad as far aft as I could, but finished the aft
round files and emery cloth.
Trim just enough
the top skin of the flap from
scraping the side while the bottom skin of the flap lightly touches the
Now mark and trim the
bottom flap skin to match the F-826
and F-827 skins. I
used a cutoff wheel
with the flap on the bench to initially cut the large piece off. Then I cleaned up the edge
scotchbrite wheel. I
did the final
trimming to make the edge parallel to the F-826 and F-827 with the flap
installed, using just the scotchbrite pad.
This made hanging flaps go a lot faster.
If you haven’t already
set the ailerons to neutral, you will
need to do it now before you install the pushrod.
Installing the Pushrod
started with the pushrod the length called for in the
disconnected the WD-806 flap
control from the motor so I could move the flap up and down by hand. I installed the pushrod by
just pushing a
bolt into the holes; I didn’t bother with nuts just yet. Then I moved the assembly
through the up and down
motions until the pushrod touched the skin.
Then I marked where it touched, removed the
pushrod, trimmed and
re-installed for another check.
I used a rotary file bit
on the angle grinder to do most of
the trimming in the holes. Then
I used a
piece of emery cloth to smooth and dress the edges.
I repeated this process
on one side until I could move the
flap assembly through its full range of motion.
Then I did the other side of the airplane.
completing these hanging flaps steps, ensuring everything fit without
interference, I then connected the
WD-806 to the flap motor and ran it full down.
I adjusted the down stop on the motor until
the bottom of the WD-806
stopped ¼” from the floor as called for in the plans.
Then I connected the F-847 pushrod to the
WD-806 and the flap. I
checked that the
flap was between 40 – 45° down, and adjusted the
length of the pushrod if needed.
Then I ran the motor
until the flap was full up, and
adjusted the up stop to get the flaps to just touch the belly skins. As I ran the flaps up, I
moved very slowly, ensuring
the pushrod didn’t scrape anywhere.
actually had one spot that I had to trim again.
I wanted to run the flaps
full up and down a few times to
check everything, but I wasn’t sure how many times in a row I could run
flaps without overheating the motor.
I only ran them one direction and checked for fit.
In the full up position, I checked that the
flap was flush in trail with the aileron and flat on the bottom of the
and full down, I checked that it was between 40 - 45°. Then I waited a little
while before I ran them
the other way.
from Hanging Flaps
to Final Assembly
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