Sparky
Rediscovered |
|
by Clint Brooks
(May 6, 2004)
|
|
Those of you who have been aeromodelers for some
time are quite familiar with the Comet Sparky. Then
again, it's likely some readers have never heard
of this classic model - or even Comet Models, Inc.,
the company that kitted the Sparky design probably
longer than any other model aircraft kit in history.
I don’t know the specifics, but I heard it
mentioned that production on this kit ran from some
time in the 1930's up through the 1960's, which
means the design and it’s delightful flying
characteristics touched many of us in the free flight
modeling world. My journey with the Sparky begins
only very recently, and with no knowledge of the
background of the design.
|
|
|
|
My good friend Lynn Ericksen and I were puttering
around his garage one afternoon, discussing my
attempts at building stick & tissue models
(something neither of us had done for many years).
He began pulling boxes of balsa down from the
rafters and came across bundles of old model airplane
plans - including the Sparky. He had built the
airplane long ago, and kept the plans all these
years. As we unrolled the drawing I was struck
by beauty of the classic lines, and knew I had
to build it.
|
|
|
|
I rushed to my local Kinko’s to make copies
of the plan sheet, and began to study what was involved.
Within a few weeks I was attempting to develop the
wing rib profiles myself, as there are no patterns
shown on the production kit layout. Then a bit of
luck came my way - a fellow employee who is also
a modeler found an old Sparky kit in his garage,
and let me use the print wood as patterns. Some
of the parts were missing, but those remaining certainly
made my job easier.
Now I typically cut my own stripwood from sheet
stock. I don’t want to ruin the balsa strip
sales industry, but I find it very cheap and quick
to cut all the stripwood myself. I probably don’t
always get the perfect dimensional results that
a milling operation provides, but it is certainly
close enough, and things generally get refined by
sanding and leveling in the building process anyway.
|
|
|
The fuselage
has no “flat” spots on top or bottom,
which makes it difficult to assemble the fuse halves
together over the plan top view. I ended up gauging
from one of the vertical members in the fuselage
side frame to level the fuselage over the plan view
and keep everything in rig. |
|
|
|
|
| I
spent quite a bit of time aligning the fuselage
side square to the building board, and then using
several cast iron tooling angle blocks to keep the
sides stabilized as I installed the cross members.
Indeed, the fuselage will take the most time to
complete on this project. Try and keep it as straight
and true as possible by not building "preloads"
into the structure. This requires accurate cutting
and fitting of the cross members to keep a uniform
tension in the fuselage longerons as they taper
forward and aft. |
My daughter Andrea posing with Sparky after it's
first flight |
|
I start at the constant cross section area of the
fuselage first, usually the cabin area, and work
in both directions from there, always mindful of
where the centerline of the airplane is relative
to the nose and tail, to avoid building in a bow
to the left or right. You have to jig this fuselage
as much as possible to keep it stabilized and true
during the assembly process, as it is long and slender.
|
|
Some
things I did different from what was shown on the
plan. The vertical fin assembly was constructed
using a laminated bow for the outline, from three
layers of 1/32 balsa laminated directly over the
plan. I push pins into the plan about 1/8"
to 3/16" apart, in such a way that the inside
outline is defined by a forest of pins that the
first strip of wood will be stretched around. This
is a quick and dirty method of laminating a bow,
and worked well on the Sparky shape with it’s
natural flowing elliptical outline. I also used
the Earl Stahl method of making the airfoil section
on the vertical fin-using caps glued over the basic
rib framework and sanding to an airfoil cross section.
|
|
|
I also elected to add the subrudder that is not
shown in the construction, but appears in all the
graphic images of the model that are shown on the
plan. I don’t know the history of why there
are two configurations - was this feature omitted
in error, or removed after some design modifications
were incorporated? Maybe some of the experts out
there will know the story here. Anyway, I built
this up using a laminated bow structure as well,
as I feel this feature adds a lot to the character
of the finished airplane.
|
| |
|
|
|
|
|
|
