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I designed
the forward template in AutoCAD then glued it to some particle board.
The 3 lines are marked on freehand and show the profile at
1/2", 1" and 1 1/2" in from the edge. The rear template was
drawn on particle board using a dinner plate as the initial profile.
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The first
piece of 2" thick
foam is cut and then placed on top of the two templates. I
then used a sawing action to cut through the foam down to the 1" line.
I have used a straight edge and some packing tape to stop
this first piece of foam from sagging. |
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Each
subsequent pieces of foam goes on exactly the same way and are shaped
into long wedges. |
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They are
all held snuggly together with tape and rope. I have a new
found respect for Eskimos building igloos. |
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The build
method I am using is very similar to the way I built the forward deck.
Apply two part expanding foam to the outer joints and allow
to dry. |
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Once cured
I gently lift the deck onto some timber and remove the particle board
templates. As i am working by myself, I gradually maneuver
the deck forward and over the firewall. |
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The deck is
now rigid enough to stand freely but I have placed the templates back
into position so it will hold its form when sanding and give me lines
to sand to. |
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The inside
is sanded down to the 1" line using a surform, wood rasp and sandpaper.
This actually took me hours and a massive amount of foam dust
to clean up. This fine dust gets everywhere and causes me to
come out in a rash where it rubs between my clothes and skin......the
price we pay. |
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A quick
outline is done on the plastic in readiness for the fiberglass layup.
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As
usual in any layup, the micro slurry is applied to the foam first.
I have used the slow hardener with the resin to slow the
curing
process down as this is the largest are I have had to fiberglass in one
shot and I don't want the slurry to cure before I apply the fiberglass. |
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The
KR2S is on the workbench which leaves me nowhere to cut and wet out the
fiberglass. My last 8' x 4' sheet of urethane foam came
sandwiched between two large sheets of cardboard which have come in
handy as this is now my ground level workbench. The big sheet
of
fiberglass is actually made up of two sheets which overlap about 2". |
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I
just love this plastic layup method. Once the fiberglass is
wet
out I fold it in half with the plastic on the inside. I then
line
it up along the center and pat down the right hand side in the shot.
It is easy to then fold over the second half and not have to
jostle the skin around until it fits. |
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Night
fell as I was patting out the peel ply. It's cool here at the
moment and dew forms at around this time so I clamped the spotlight to
the front of the large template. 500 watts of light gives off
a
good amount of heat. |
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The
next day the peel ply comes off and the deck goes back on the fuselage.
To stop the sides from bowing inwards when sanding, I have
clamped chocks at the cross member joints. |
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The
first pieces of foam removed are at the templates. I have
used
the surform to round the foam off. There is quite a bit to be
removed from front to back. Before going to far I cut out the
expanding foam originally used to hold the urethane together as it
leaves ridges which are hard to sand level with the urethane. |
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I
want to create a nice transition from the fuselage side to the turtle
deck. The deck is initially sanded at the same angle as the
fuselage and then a long straightedge is used to gradually remove the
foam down to the templates. |
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The rough
sand is done on this side first. To see the natural curve
begin to take shape is very rewarding. |
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Today
I had planned to take the KR off the bench and fiberglass the rear deck
out on the driveway where there is plenty of room to move around.
Unfortunately it has been raining on and off which means I
have
to set up and do my plastic layup on the bench and extension area in
front of the fuselage. |
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Duct
tape and plastic sheet is used to stop the layup from sticking to areas
I don't want it to stick to. The longerons, templates and the
side of the fuselage. Micro slurry is then applied to the
deck.
I have used the slow hardener even though the day is cold.
This will keep the slurry from going off before I get the big
layup done. |
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As
with the slurry, I have used the slow hardener on the layup as it takes
a bit of time to work the resin through the two fiberglass layers (200
grams and 85 grams). Like before, I folded the plastic layup
in
half and placed it length ways down the spine of the deck
before
unfolding the second half down the other side. Squeegee,
remove
the plastic sheet and then add the peel ply. This will be
allowed
to cure overnight before the peel ply is removed. I will
leave
the deck in place to fully go off over the week before lifting
it
free of the fuselage. |
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I
removed 1/4" of foam along the edges of the deck that abut the
longerons. A further 1/4" of foam is removed to
create
channels along both sides of fiberglass. The "plug holes" are
filled with flox and 5/8" x 5/8" hoop pine stumps. Piano
hinge
with removable pins will be used to secure the deck to the fuselage.
This will be screwed into the stumps. |
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The
channels are filled with flox too. A thin layer of flox
covers
the remaining foam and then a 3/16" strip of hoop pine is layed into
the gap while the flox is wet and it is all then allowed to cure.
The piano hinge has a strip of tape covering it but for the
exposed area underneath. T-88 epoxy is used to stick the
hinge to
the pine strip. Wood screws will be used through the hinge
and
into the underlaying stumps. All screw holes will be pre
drilled
to avoid splitting. |
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The
hinges are now epoxied to the aft deck so I am now setting them up to
be epoxied to the longerons. I have used loose icy pole
sticks as
spacers between the two hinge halves. Because of the shape of
the
hinge halves they are kept parallel to each other when closed which
means even pressure will be applied when epoxying to the longeron. |
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To work out
the angle to trim the aft deck, I have used a packing strap and
tightened it around the KR2S fuselage. |
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I then use
a marker which outlines where to jigsaw. |
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I
am going to make a 2"x2" carbon fiber roll bar which will be built into
the front edge of the deck. Just upend the deck onto some 2"
thick urethane foam and roughly mark around the outer edge. |
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Then I make
it match the exact contour of the deck with the sanding block. |
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Each
side of the roll bar will have four layers of carbon fiber.
These
two sides are done first and floxed to the aft deck. |
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I
have decided to add strength many fold with very little
additional
weight. The idea came to me when looking at some bamboo which
is
not hollow but has "internal walls". A quick search on the
Internet confirmed what I had thought. It is a concept that
is
used in all kinds of structures. Picture a big cardboard box
that
is open at both ends, laying on its side on the floor. It is
incredibly easy to collapse, even with one finger it will fold flat.
Now close both ends of the box and tape them shut.
You
would struggle to crush if with two hands. To apply the
bamboo
theory I have sliced pockets through the foam and inserted a multi
layer carbon fiber strip I made 12 months ago. |
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The
strip is marked and then cut level with a jigsaw. A
triangular
file is pushed through the foam either side of the strip and these
voids will be filled with flox. I have also used the file to
remove foam all the way around the top of the roll bar which now has
five of these "internal walls". |
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Flox is
used to fill the channels and a smear is applied on the rest
of the exposed foam. |
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Three
layers of carbon fiber cover the floxed area and then the forth goes
over this and 2" of the deck. |
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I
am using 1" screws through the hoop pine which will be floxed
into
place as per the above method. Foam channels and stump holes
will
be carved before adding flox. |
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Each side
of the aft deck has two separate piano hinges. A long one for
the longerons and a shorter one for where the parcel shelf steps up the
1/4". |
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Taping
plastic to the tail is going to stop foam dust and expanding foam
getting into the fuselage. |
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2" foam
wedges are pinned together using nails and then expanding foam is added
to the seams from behind. |
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It all sets
in about 20 minutes and is ready to be shaped. I use the
steel ruler to follow the line of the deck. |
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And
then it is just a matter of gradually removing more foam and blending
the curves together. Following the surform, I use rolled sand
paper to gently continue shaping. |
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I
want to fair the vertical stabilizer to the turtle deck so have cut a
puzzle like piece of foam to fill the gap between both sides. |
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And the
jigsaw piece is held with expanding foam from beneath. |
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A lot of
foam was removed and then sanded to a shape that I am happy with. |
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I
am going to make a mold from which I can create a fiberglass fairing.
The green urethane foam is no good for duct tape to stick to
so I
have decided to make the mold out of fiberglass. Thus the
micro
balloon slurry. |
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I
was not too fussy with building it out of one piece of fiberglass as it
is only going to be covered with duct tape anyway. So a lot
of
the left over scraps were used. The result is perfectly fine. |
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Duct tape
has no problems sticking to the mold now. |
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A
single piece of 200g/m and another 85g/m fiberglass top layer covers
the main body of the mold. A piece of the overhanging wet
layup
is trimmed off and then used to cover the vertical. |
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It dries
and pops away from the duct tape with very little effort. |
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And
here it how it looks when slipped into position without any trimming.
I anticipate sliding the forward edge under the
turtle deck
skin. |
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The fairing
is incredibly flexible when not supported. When trimmed and
taped as in this photo, it is quite rigid. |
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I
plan on using carbon fiber "seals" to hold the sides of the fairing in
a similar way to tucking a shirt into your trousers. The
edges of
the duct tape define the fairing edges and the dotted lines on the tape
mark how far up the fairing the seals will go. The pre-made
seal
is left over from earlier gap seal construction. Half of it
is
taped to stop it sticking when resin is applied to the exposed length
and flipped over. |
