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The
outer spars and WAFS have been bolted together previously to provide
the proper dihedral and washout. They are now bolted to the
stub
wings in readiness for the next process. |
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The
wing spars have to be absolutely rigid before unbolting them and
placing in the building jig. The diagonal bracing stop the
spars
from moving parallel to each other and the struts between the spars
stop any twisting. |
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This
closeup shows how the diagonals are pre drilled and screwed and the
struts are floxed between the spars to prevent any movement what
soever. These will be cut out later. The innards of
the
wing will be built first and then the underside skin before the bracing
is gradually removed. |
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I
have drilled and ground the first 6061-T6 aileron bellcrank angle.
It is then bolted to another piece of ally which is drilled
and
ground to exactly match as the left and right bellcranks will need to
be identical. |
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A bellcrank
bearing (AN218-4) is riveted in place and two rod end bearings (MW-3)
bolted on.. |
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2"
x 1" 6061-T6 aluminum extrusions are shaped up and lightening holes
added in no time. These will be bolted to the back of the
main
spar. |
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Here
is the mobile jig. It is really simple. A long
length of
particle board is bolted to two skateboard like platforms.
The
hardwood in the center stops any flexing. The verticals are
screwed and bolted to the floor and some shelving angle added at the
base. |
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I have
bolted supporting timbers to the existing WAFs and then glued
and screwed the cross member. |
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Water
pipe passes through either end of the wing and into the vertical
supports. Now the wing can be freely flipped over for working
on
as well as rolled down one side of the aircraft for storage. |
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Now
the template at the tip of this wing is AS5045 airfoil with a chord of
30 11/16" and the one at the root is AS5048 with a chord of 44".
Any profile in between these two is going to be a combination
of
thereof. I have found a great software program called Profili
2, which even in the free demo version can quickly design and
print out any intermediate rib profile.
I set the number of rib templates in the program to 89 which is one for
every inch of the spar length. |
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The
two profiles I am interested in printing out are 36" & 48" from
the
root. So I go to #36 and #48 and print them out on a large
plotter. |
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My
split flaps are going to extend along this outer wing 36"
which
will give a total effective flap span of 5 feet when combined
with
the stub wing. The #48 profile is there to define the size
of
the aileron to the wingtip.
At the risk of sounding like a hair care commercial, all the
profiles line up perfectly from the root to the tip. |
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This
piece of carbon fiber covered foam is going to be the upper skin above
the split flap. It has been epoxied in place and the flap
will be
shaped to snuggly close against the underside. |
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Urethane
foam panels are cut and pushed into place. The ribs have been
scribed with a permanent marker to line up a 1/2"
skin thicknesss.
I then scratch the curvature of the ribs in to the end of the
foam panels. |
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I
then use a surform to carve out the profile and then a long sandpaper
straightedge. The micro, carbon fiber and peel ply come next.
The trick is to let it cure over night with some particle
board
weighted on top. This stops the edges from curving up. |
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It
is currently quite hot here in Australia and I have needed to string a
tarpaulin over my driveway to provide some shade. This
accounts
for the blue tinge the next couple of photos have. The bottom
skin panels are held in place with strips of carbon fiber. It
is
unbelievable how rigid each panel becomes when epoxied in place. |
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The
beauty of building the wing on a mobile jig is that I can just flip it
over to access the other side without any assistance.
This
is the wing upside down and the pre made flap has had a strip of CF
removed right where is starts to narrow down the the trailing edge.
It is hard to make out the color, but the inside of the upper
skin has gray duct tape to act as a release agent when I add the CF to
the aft part of the flap. |
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To
get a perfect fit, I clamp a timber straight edge beneath and place the
flap on top. The carbon fiber, resin and peel ply are now on
the
flap which is held against the duct tape area. |
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The
leading edge is made of two pieces of foam which are
internally
shaped. I no longer use expanding foam to stick it together
as it
is too hard to sand where it oozes though the join. All the
expanding foam does is hold the urethane together while the carbon
fiber cures. I came up with a better idea. Long
wood screws
with coarse threads. Their hold on urethane foam pieces has
to be
seen to be believed. |
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Here
is my placement of the screws along the leading edge and as anchors.
The inside of the leading edge has been microed and carbon
fiber
layed. |
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A surform
shapes the outside between the rib profiles and the sandpaper straight
edge eventually smooths it all out. |
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Here
I have dug out some hardened micro which came through the seam and
became a high spot which made sanding a difficult task. Stiff
micro is used as a filler just before I do the layup. |
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The clamps
hold each piece of the leading edge in place as it cures.
This stops any movement as they dry. |
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Here is the
split flap sanded and the last 3/4" of foam removed to then be
backfilled with flox. |
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Carbon
fiber now covers the flap which is held in place to cure over night.
The same goes for last section of leading edge. |
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Before
permanently fitting the leading edge to the main spar I run the landing
light wires out to between the 36" and 48" ribs. When the
time
comes to fit the lights I will know the wires are going to be there
waiting for me. |
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I
ensure the three leading edge panels are absolutely straight by lining
them up to the straight edge. A few icy pole sticks do the
job.
|
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I
set the top level first and add flox right at the leading edge joins.
Once this sets I can flex the the bottoms in or out as needed
and
know that the tops will stay put. |
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24
hours later I am reusing the blocks from the fuselage framing.
The straightedge defines how far I screw the blocks into the
spar
which then holds the bottom line of the leading edge in place.
The screws used are thin and can only enter the spar a
maximum
3/8". Dobs of flox at 6" intervals will hold the leading edge
to
the spar. |
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The
42" aileron is longer than my longest piece of 2" thick foam so I use
expanding foam to join a few together. The press stops the
blocks
being pushed apart and the holes allow the expanding foam to act like a
piece of reinforcing mesh. |
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The aileron
"block" is clamped in place while more expanding foam acts as a
temporary hold. |
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A surform
and some sanding brings out the beginnings of the aileron
.shape |
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A piece of
ally extrusion keeps the trailing edge straight while the carbon fiber
cures. |
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I use a
carving knife to break the expanding foam seal and then pop off the
aileron. |
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The
jigsaw cuts a line that measures 2" from the spar. This is
about
20% of the aileron chord which is the norm for hinge placement on a
frise aileron. |
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The
aileron is then placed back between the templates and supported from
below with timber and ally straightedges. It has been sanded
and
1/2" of the trailing edge removed in readiness for filling
with
flox. |
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The foam
has been removed to make room for the
timber. I have made a start on the first hinge which
protrudes
5/8" below the aileron. |
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This
is a shot of one of the hinge bolts going through the rear spar.
Foam had to be removed to get the bolt and washer through and
then a piece used as a plug later on. |
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A surform
shaped the foam to this stage in about 20 minutes. |
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My
long sanding board with sandpaper stapled to it (around the edges)
sands the last 1/8" of the foam down to the rib templates. I
sanded from side to side for most of it and then finished off with a
few up and down strokes to smooth any thin ridges. |
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I am
cutting the carbon fiber to start 45o
bias which is done to maximize surface strength.
Unfortunately it
leaves me with a heap of triangular offcuts which would be ok if I was
building a delta wing aircraft at the same time. |
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I now
know where the diagonal bolt will finish so I have cut 2 lots of
plastic and marked the spar placements too which makes aligning the wet
layup easier. |
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The
first of two layups for the bottom of the wing. It's too big
for
my table so I decide to wet it out on a huge piece of cardboard on the
ground. |
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It's
now drying under the peel ply. The layup goes past the point
of
the leading edge by 2". When this is mirrored from the other
side, the leading edge will be two layers thick from the spar and a 4"
band will be three layers thick along its ridge. The
slight dip in the carbon fiber along the front and rear spars
will
be filled with stiff micro as a feather fill. It is easier to
fill a tiny valley than to judge the foam to spar gap, get it slightly
wrong and end up trying to blend a small ridge. |
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In
an effort to lighten the aileron bellcrank, I substituted the 8 AN4
washers for 2 aluminum bushes made from 0.375" x 0.049" tubing which
saved 7.8 grams. I later cut four 1/2" lightening holes in
the
bases which reduced the weight by another 5.0 grams. It's not
a
lot in the whole scheme of things but it is almost 1/2oz less that this
KR has to lift. The MW3 rodend bearing in this pic has been
changed to an MM4 which will connect to the aileron pushrod. |
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With
the bellcrank roughly positioned on the back of the main spar,
I
need to drill some 7/8" holes in a straight line through the
templates and temporary supporting timbers. The 0.625" x
0.049"
pushrod will pass through these. I clamped the straight edge
4
1'2" out from the two end points and then just measured and marked the
4 1/2" points on the timbers followed by boring them out with a spade
bit. |
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Here
is the bellcrank with the first of four holes drilled through the spar
webbing. The pushrod to the aileron is 1/4" 4130N tube which
has
been heated and bent to avoid having to drill a hole through the aft
spar cap as opposed to the webbing. |
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This
is where I started to run into strife. I hadn't
finalized
the bellcrank position before adding the bottom skin panels which left
no room for the cordless drill to drill the holes through the webbing.
I bought one of these "snake" attachments which hooked up to
the
drill and worked a treat. |
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The
other problem was that the leading edge was fixed in place earlier but
I needed to insert the bellcrank bolts. I decided to cut a
"letterbox hole" through the underside of the leading edge. |
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After
a little difficulty trying to work blind and both hands in the
letterbox, the washers and bolts are eventually pushed through and
floxed in. |
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The rear
flap of carbon fiber is lowered back in place and a little flox added
underneath. |
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Some
micro is rubbed around on the inside and a shaped bar of foam is pushed
in and sanded just to below the surface. A smear of micro is
applied to the foam and the flap of carbon fiber. |
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It's a
little like surgery really. The duct tape "Band-aid" holds
the skin flap until it has healed. |
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I
have cut an inspection hole into the underside of the wing and lined it
with carbon fiber. All the nuts on the bellcrank face the
outside
to make for easy adjustments |
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The
inspection panel is made of foam and carbon fiber. 1/4"
plywood
pieces have been floxed into sides to support the plug which is pushed
into the hole while the carbon fiber cures. |
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The outside
skin is trimmed slightly larger than the hole so as to do away with any
gap and provide a flush fit. |
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Some
flox was added to the area beneath the countersunk machine screws.
Nylon locking nuts will be floxed to the backs of the ply. |
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Here is the
panel all finished |
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Duct
tape was used to keep the flox off the actual inspection panel and the
threads. Peel ply over the flox leaves a smooth finish when
cured. |
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Here is
what the underside of the wing looks like at the moment. |
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It
is now time to work on the upper surface of the wing. I have
unscrewed the diagonal brace and am cutting out the temporary strut
which is then finished off with a chisel and orbital sander. |
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The
skin has the carbon fiber strips and peel ply wetted out and put in
place before being pushed between the spars. The lightening
holes
in the templates are big enough for me to put an arm in and set the
strips against the spars. |
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A quick
trim with a razor blade removes the excess carbon fiber. |
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I
have used gold plated connector pins inside terminal blocks that will
allow an easy way to disconnect the wiring inside the wing. The proper
tool does a fantastic job of crimping the pins to the Tefzel AWG 16
wires. |
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Crimping
folds the two tabs over and into the wire in one action. The
final part is to crimp the back tabs around the insulation. |
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Six
pins are pushed into the 9 way "Mate-N-Lok" connector.
Another pair of AWG 14 wires for the landing light will be
added
soon. A blue seal plugs the back and helps keep each
connecting
pin clean. |
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Labeled
heat shrink (not yet shrunk) is going to remove any confusion when it
comes time to trace a mass of wires. I have also run a spare
pair
of wires the length of the wing in case I decide to add
something
else electrical later on. Maybe an aileron trim or deicing
boots.
Now that would be a first. |
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Here is the
receptacle block fixed in the stub wing and ready to be hooked up. |
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Some
over zealous sanding with the surform led to a 1/8" low point in the
middle of the upper outer panel. A bit hard to see in this
pic
but believe me, it is definitely there. |
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Airfoil
shape being critical meant I had to bring it up to level. The
easiest and quickest way was to break out the foam and and start again.
|
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To
avoid having the exposed carbon fiber sag I rebuilt the skin in 3
sections. The center mini panel in this pic was shaped and
then
expanding foam used to stick it to the CF beneath. The blue
packing straps are fantastic at holding down the panel to push the
expanding foam sideways. While this is drying I then break
out
the foam to the right in readiness for the next mini panel.
Twenty minutes is enough time to remove the packing straps
and
stick the next panel in. The center mini panel now holds the
curvature of the skin. |
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And
here is how it looked in the morning. In all it only took a
couple of hours to get the job done and rough sanded. That is
the
beauty of building with composites, almost any stuff up can be easily
repaired. |
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I
have not been 100% happy with the way my trailing edge floxing has gone
in the past. it seems that when getting the flox just right
and
then laying the wetted out carbon fiber over, the flox would become
ever so slightly runny from the added resin and be squeezed lower than
I wanted. This time I have floxed the trailing edge so it is
perfectly shaped all around and am letting it dry before going ahead
with the final layup. |
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The
leading edge of the aileron has had some foam stuck to it with
expanding foam and then roughly shaped to continue the current lines. |
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I
carved out channels where the hinges meet the aft spar and then bolted
the aileron in place. As the exposed foam was still square,
the
aileron was unable to move up and down so I slowly sanded away until I
was left with a rounded leading edge. |
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Now that I
was able to bolt the aileron in place, I was also able to shoot a
straight line along the trailing edge of the wing and jigsaw it off. |
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I
This is the beginning of the aileron fairing on the upper wing surface.
Expanding foam sticks down the urethane which has been
clamped
until cured. |
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The inside
is shaped and sanded until the aileron is able to move freely without
touching. |
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A single
layer of carbon fiber lines the inside of the fairing and dries
overnight. |
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Next
morning the top is sanded with a long straight board with sand paper
stapled to it. |
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The
last 1/4" trailing edge of the fairing has a small layer of flox then
the usual micro and carbon fiber covering. The aileron has
full
and free movement 20o up
and 10o down. |
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When
the aileron is up, the lower leading edge protrudes into the air stream
and creates a small amount of drag on that side which will help keep
the KR in balance when turning with little of no rudder input.
This is the benefit of a frise aileron. |
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After
a few months of building the wing on the mobile jig, the
crunch arrived when it was time to fit the outer wing to the
stub
wing. All is good as the WAFs still lined up perfectly.
Now
have a look at that for some serious flap action! |
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The photo
here clearly shows the washout when comparing the profiles between the
tip and root. |
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I just had
to hop in, belt up and gaze out at my left wing. A very
motivating moment. |
