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Wingtip Fitting 1 September
2010: Fitting the wingtip. This was one of those "grab a quick hour to
work on the Kitfox" days. Because of that I did not take any photos. I
trimmed the edges according to the instructions in the builders manual. On
the day I ordered the kit I remember sitting in the office at Kitfox
Aircraft talking to John McBean. When I mentioned that I intended to read
the builder's manual before I receive the kit he made it clear to me that
there will be things that I will not understand until I have the parts in
my hand. Today brought all that home to me. I couldn't envision what the
instructions wanted me to do until I grabbed the part and stuck in on the
end of the wing. The instructions became immediately clear to me.
 4
September 2010: My workstation. During past projects I've discovered
the hard way that if you're going to do a good job from an awkward
position you have to make yourself as comfortable as possible. I'm
drilling upward into the end rib. This is as comfortable as I can get and
I'm hoping for the best.
 
Drilling and clecoing the aluminum mounting strips
  Positioning
the wingtip with zip ties
   The
mounting holes are carefully spotted and then drilled and clecoed. You
will notice that the aft end of the wingtip extends beyond the trailing
edge. This has to be trimmed.
 I've
allowed enough overlap at the forward part of the wingtip to accommodate
the layers of fabric that will eventually be over the spar. A guess on
my part.
  Trimming
the tail. I dug out my old dovetail saw and cut the tail flush with
the trailing edge. After that I filled it with epoxy.
 5
September 2010: Enlarging the mounting holes. I drilled out the holes
to the exact size of the mounting screws. The black clecos only
approximate the correct size so, where I could, I used the screws backed
with hardware store nuts to keep the wingtip in exact position as I
drilled.
 Drilling
the rivet holes for the nutplates.
 I
used a rivet squeezer to dimple and set the solid flush rivets.
 A
"Well Duh!" moment. It should have been obvious that the last nutplate
on the top would conflict with the one on the bottom. But I installed them
anyway. One has to go. As you can see I removed the one the bottom and I'm
mulling over what I want to do.
6 September 2010: The mounting strips are complete.
Shaping the trailing edge: I'm fully aware that if I cut a "V" on
the outside edge I could have the wingtip terminate in a sharp edge but I
feel that my arrangement is more robust and won't hurt so much when I
run into the wingtip with my head.
 The
builder's manual says, "Carefully countersink the capstrips on the
wood ribs for the flush head pop rivets." Past experience tells
me that using a power drill is dangerous with thin plywood. I choose to do
this
by hand. The riveting will wait until the fabric is in place and before
the final taping.
11 September 2010: Fabricating the Fabric Reinforcement Plates.
First, it's confession time. I cut the first piece the wrong size and, as
Murphy would have it, I cut it too small. So, before I make the parts for
the left wing, I'll have to give John and Debra a call for an extra piece
of aluminum. These plates are to reinforce the fabric around the lift
strut brackets.
Another on of my makeshift jigs. This one allows me to make the
inside cut.
  The
finished parts.
12 September 2010: Flaperon
Assembly
   I've
decided to work on both flaperons. I started by installing solid,
round-headed rivets along the trailing edge. The assembly manual suggests
flush rivets but, since the airflow at the trailing edge is typically
turbulent, I see no advantage to flush rivets. I stabilize the flaperon
with shot bag scuba weights and use my rivet squeezer.
 15
September 2010: Riveting is finished. I've turned off the flash to
allow the rivets to stand out in the shine of the aluminum skin.
  19
September 2010: Drain holes. The slots on the upper skin that
accommodate the hinges will allow water to enter. For this reason drain
holes are drilled into the bottom skin. They are located at a very thin
part of the airfoil. For that reason I've placed a drill stop very "high
and tight" on the bit.
 Installing
the Inboard End Ribs.
25 September 2010: Flaperon tips. The kit provides a block of foam but
the builder's manual offers the option of using balsa. I chose the balsa.
 I
held a block of balsa against the end and drew around the outline of the
flaperon. With Sketchup I generated a curve and transferred it to the
balsa.
   I
started the shaping process by carving "facets" with a wood rasp. I then
rounded them to the final shape with sandpaper. Finally I glued them in
place. There is still a bit of work to do to achieve a final finish.
   26
September 2010: Spotting
the location of the flaperon mass balance weights. I located and
drilled the rivet holes for the mass balance weights. Since control
surfaces with the counterweights installed are awkward to handle I will
wait to do the final installation just before painting.
 28
September 2010: Making the Flaperon Clamping Fixtures. These are
necessary in order to be able to align the control horns. I was able to
find 2X2 stock made of tulip poplar.
  I
countersunk the mounting screws. After that I spotted the shape of the
cutout using the template provided with the kit. The finished clamp
worked, but the buried screws and nuts gave me problems.
  1
October 2010: I redid my previous work. I countersunk the heads of the
screws on the bottom of the clamps. After that I let the screws protrude
through the top where the nut will not annoy me by rotating in a
countersunk hole.
  3
October 2010: I began to install the control horns. I first cleaned
the threaded fitting with a tap. The first photo shows duct tape wrapped
around the shaft of the horn. In order to fit the shim I have to remove
some powder coating. The tape shows me exactly how much to remove. The
second photo shows the shim in place.
 The
bearing halves trimmed to fit.
 The
first clecos. The post-it note is marked with the exact dimension
above the base. When that was established I gathered my courage and
drilled the first hole. When all the holes were clecoed I turned my
attention to the left control horn. For some unexplainable reason the shim
presented me with quite a lot of resistance that I didn't experience with
the right control horn. After a bit of struggling I decided to stop before
I do something rash. I'll resume my attack on this problem on the next
session. 6 October 2010: Done! By taking time
to think through my problem I was able to come up with a solution. I
colored the shim with a black marker and used a fine file to remove just
enough to take off the ink. This assured me that I'm removing a measured
and uniform amount. Two applications of this and I was able to make the
shim fit neither too tight nor too loose. I fit the left
control horn into position. Through all of this I forgot to take pictures.
Sorry! The instructions indicate that I should wait to finally rivet the
horns in place after painting. This is to avoid fouling the bearings with
paint. I may regret it, but, since I had such difficulty getting them in
place, I went ahead and drove the rivets. I'll have to do some careful
masking when I get to painting the flaperons.
    8
October 2010: Installation of Flaperon Reinforcement Brackets. I made
a cardboard template to spot the rivet holes. The drilling went quickly
and I was soon bonding and riveting the brackets in place.
  Continuing,
I bolted the Flaperon Brackets on the hinges. Tomorrow I'll attempt to
"hang" the flaperon on the wing.
   9
October 2010: Hanging the flaperon. I attached the flaperon to the
wing with spring clamps on the end brackets. I then spotted, drilled and
clecoed all the rivet holes. I will permanently attach the flaperon during
final assembly after the wing is covered and painted.
Preparing the Ring Wing
for Covering
  15 October 2010: Reinforcing the Trailing Edge. To allow the fabric
to be heat-shrunk to 350 degrees the trailing edge has to be stiffened by
bonding aluminum tubing in the gaps.
22 October 2010: Smoothing the edges. Every Fall the demand for my
services as a musician increases. I love being a musician and I love being
an airplane builder so I struggle to find time for both. Today I sanded
the top of the fuel tank and rounded edges that will come in contact with
the fabric.
 29
October 2010: Super-Fil, Varnish, and Paint: I continue preparing the
wing by filling the gaps with Super-Fil, varnishing the remaining
woodwork, and began priming the metal with White Poly-Fiber epoxy. A
primary concern with an airplane in Florida is corrosion, which is the
reason for the primer. It's not very adaptable for brush application but,
since I will not be applying a finish coat over it I do my best and accept
the brush marks. It will take several coats.
3 - 5 November 2010: Continued priming and varnishing.
14 - 17 November 2010: More priming. Despite the brush marks I try to
produce a "workmanlike" job. My schedule is starting to ease giving me
more time for airplane building. 25 - 28
November 2010: Continued priming! 30 November 2010:
Priming finished.
1 December 2010: Compliance with Service Bulletin 60. Recently
published SB 60 requires a more aggressive procedure when flushing the
fuel tank. Today I flushed the tank 3 times with acetone.
 5
December 2010: The right wing is ready for covering. I rounded the
last of the sharp edges and applied anti-chafe tape where needed. (Such as
over these rivets.) More on
Page Five |
