The side view of the completed aileron hinge.
The bottom wing roof cuff and fairing. The wing’s top panel lines and
reinforcing plates were created with the conventional technique of
masking tape and spray primer.
automotive aluminum foil tape. I
burnished the tape to remove any
surface coatings, primed, then cut and
trimmed it to size with the help of the
CAD drawings. The hold-down screws
are #1 screws.
Wing Panel Lines
With the wing halves assembled and
wrapped in fiberglass, it was time to add
the details. Most of the wing panels on
the Beaver are overlapped, making a
ridge on the surface. The panel lines and
reinforcing plates were done with the
conventional technique of masking tape
and spray primer.
I used two layers of tape to get the
thickness right. They were sprayed with
three coats of automotive spot filler and
primer in a layer tapered toward the
tape, followed by a light sanding on the
edge of the tape before removing it.
There are a few butt joints in the
panels, mostly on the aileron and flaps.
These were simulated by painting over
a piece of 1/64-inch drafting tape and
then sanding down to the tape before
removing it. For the wing root cuff and
fairing, an extra thickness of primer was
used. It needed four layers of tape.
After the panel lines were in place,
simulated reinforcing plates were added
to the bottom of the wing. These were
scaled from the prototype photographs,
fabricated from 0.005 styrene sheeting,
and glued in place with vinyl canopy glue.
Control Surface Corrugations
The full-scale Beaver has corrugated
aluminum on both sides of the rudder,
both surfaces of the elevator, and on
the bottom of the flaps and ailerons.
They are all the same: corrugations at 3
inches center, roughly 3/8 inch high and
3/8 inch wide at the bottom, tapered to
approximately 1/8 inch at the top, and
rounded. On the model, this worked out
to a spacing of 0.54 inch and a height of
0.068 inch.
Trying to replicate these caused a
lot of head scratching. These would be
a fine feature, but they needed to be
approximately the right spacing to look
good, and, of course, parallel to each
other. Trying to glue on individual bits to
simulate the ridges seemed too daunting
and too prone to inaccuracy.
I tried manually
scribing ridges
into thin
aluminum, but
got inconsistent
results. A friend
suggested building
a machine to make
the crimps—it’s
probably the same
way that full-scale
ones are made—
but I had neither
the knowledge nor
the tools to make
such a device.
My solution
was to mold them. I obtained a piece of
1/4-inch aluminum plate and a machinist
friend cut shallow slots into it at the right
shape and spacing. He was able to shape
his cutting tool so that the slots had the
correct profile.
It was then a theoretically simple
matter to cast thin sheets of material
to replicate the aluminum sheeting on
the full-scale Beaver. I state theoretically
because it actually took a fair number
of rejects before I got the technique to
properly work.
In the end, I was casting the sheets
with polyurethane casting resin. I
embedded a sheet of 3/4-ounce fiberglass
into each one as it set to give the part
some strength. The finished sheets were
cut to shape and glued to the model
with 30-minute epoxy.
In the photos, you can see that the
mold is taped off to make an aileron
skin, and there is a sample piece of the
finished skin. The trim tab hinge is a
piece of styrene tube notched with a
hobby saw.
Aileron Mass Balance
The aileron mass balance is the last
step on the wing build before the rivets.
The support is a slightly flattened 5/32-
inch brass tube, and the weight was
carved from a piece of 5/16-inch dowel.
Pitot Tube
The pitot
is a 1/4-inch
diameter
brass tube
inset into a
9/32-inch tube
in the wing.
It is removable and held in place with
a rare earth magnet holding a steel rod
inset in the removable part.
The front tip was made from
aluminum tubes inset into the 1/4-inch
tube. The bracket on the wing was made
from styrene sheeting and a tube. Most
Beavers have a fin on the front of the
pitot, but not the C-FFHB.
Landing Light
The landing light was mounted on
an aluminum foil-covered bracket set
into the wing’s leading edge (LE). After
covering, the hole was cut out. The
cutout was covered with a piece of 0.01
50 Model Aviation APRIL 2017 www.ModelAviation.com
