April 1973 American Aircraft Modeler
[Table of Contents]
Aircraft modeling has undergone
significant changes over the decades - both in technology and preferences. Magazines like
American Aircraft Modeler,
American Modeler, and
Air Trails were the best venues for capturing snapshots of the
status quo of the day. Still, many things never change, so much of the old content is relevant to today's modeler.
Whether you are here to wax nostalgic, or are interested in learning history, hopefully you will find what you are seeking.
As time permits, I will be glad to scan articles for you. All copyrights (if any)
are hereby acknowledged.
is the article and plans for the Lockheed Sirius that I electronically scanned
from my purchased copy of the April 1973 American Aircraft Modeler magazine.
You might be able to scale up the image below if you cannot find suitable
plans for sale. Plans for this fine model were drawn by Mr. Maurice F. Philips.
All copyrights (if any) are hereby acknowledged.
There were actually
two separate articles, one that covered the history of the
, written by Patricia T. Groves, and the other this construction
article for a scale R/C version.
Lockheed Sirius Article & Plans
Well-detailed and perfect scale RC version of the Lindbergh inspired Lockheed
design uses foam wings and a glass fuselage. A docile flyer, too.
MAURICE F. PHILIPS
The search for a suitable model to scale
and to construct gets more difficult as modelers continually dig through
the files of civilian and military aircraft. It was surprising to find that
the Sirius hasn't recently been built. Many older modelers remember the
famous plane that Lindbergh used to map out some of Pan Am's early airways.
Admiration for the model of this grand old aircraft of the golden era was
expressed by many of the spectators at the '72 Chicago Nats. Several mentioned
that the model flew just like the full-sized plane they had seen fly in
the 30s. It was pleasantly surprising to find spectator appeal so high.
There were two friends that influenced my decision to build the Lockheed
Sirius - Monty Groves and Bob Palmer. Both, although separated geographically,
have a common interest in Lockheed aircraft.
The Sirius model results
from the combined unique talents of the three of us. Monty and his wife
Patty have researched Lockheed aircraft for years and has a large file of
photographs and technical data to support their documentation. Bob Palmer,
a professional modeler, has produced several fiberglass fuselage kits of
very high quality. This airplane was a natural for him due to his ability
to reproduce the scale details in epoxy. In making the decision to combine
our efforts, it was decided that fiberglass would more closely represent
the original plywood mold construction than conventional balsa planking
over formers. My contribution was to do the scaling, drawing, and inking
as well as to design the construction characteristic to fiberglass and polystyrene
Lockheed Sirius R/C Model
Fiberglass wheel pants come with the fuselages too and are quite durable.
Note plywood fill-in between inner landing gear struts.
Cowl alignment jig taped in place.
Fiberglass cowl has tabs epoxied inside for attachment to firewall.
The model can be flown in SuperScale or in Stand-off Scale contests. The
Sirius does not have either retractable landing gear or flaps, thus giving
other models a slight advantage in regular AMA or FAI contests. However'
its ability to perform contest stunt maneuvers does tend to be equalizing.
Almost every author attests to his model's ability to fly on a string. A
detailed description of the first few flights will follow later in the
In building the fuselage,
a Dremel tool IS used to cut out the cockpit openings and the openings for
the horizontal stabilizer of the fuselage. The tail cone should be cut off
using the minimum cerf. When fitting the stab, it will be necessary to file
the opening slightly. The fuselage tail cone will be epoxied back after
the stab is installed. Mount the radial engine mount using blind nuts. Note
that dimples indicate the centerline. Do not
tap the mount for
the engine until the engine is positioned at 0 degrees side thrust and 0
degrees down thrust. A propeller was used to assist in the measurement.
Measure the drawing to see how far the thrust washer protrudes past the
cowl. Don't forget the spinner back plate. Construct the plywood brackets
that hold the cowl to the fuselage. Use an extra strong ep'0xy such as 3-M
Structural Adhesive. With an alignment jig position the cowl while allowing
the epoxy to set.
After the brackets have been attached to the
cowl, fuel-proof them by coating with Hobbypoxy II glue. The battery and
fuel tank location worked out well on my model. Cut out two windshields
using the patterns. A strong material can be obtained by removing the copper
from a thin fiberglass circuit board .030 inches thick for the windshield
frames. Several jigsaw blades will be dulled cutting them out. Epoxy them
in place with the 3-M epoxy. A wet finger will form a fillet nicely. Set
the fuselage aside and return to it after completing the rudder, elevator
Shape the ribs of 'the horizontal stabilizer as shown.
When applying the sheeting, be cautious not to apply a warp. Fit the completed
stab into the fuselage by filing the fiberglass and sanding the wood.
Select soft balsa for the elevators and shape with a razor plane.
Install the horn and hinges matching them to the stab. Epoxy the stab in
place. Install the elevator Gold-N-Rod at this time. A music wire through
nylon tubing will possibly be less prone to change trim due to heat (if
you are worried .about that sort of thing).
Construct the rudder
using the same techniques as for the elevator. After hinging the rudder
to the fin and installing the Gold-N-Rod, epoxy the tail cone back on to
the fuselage. A good filler for the joint is common body-fender fiberglass
epoxy. It can be carved in the leather stage and sanded when hard.
Complete the basic construction of the fuselage including the tail skid,
servo tray, hardwood wing hold-down blocks, and servo installation. Use
Hobbypoxy II glue to secure parts to the epoxy fuselage. Micro balloons
or Cavasill may be added to the glue when a thicker consistency is required.
Cut the three sections of the wing using the airfoils that are shown
on the drawing. Deduct the skin thickness when making the templates for
the hot wire cutter. Wrap a two-in. wide piece of four oz. glass cloth around
the sheeted wing for a dihedral brace. Push the cloth against the wood with
a roll of toilet paper absorbing excess resin from the glass cloth. Feather
the edges with garnet paper.
Prior to the sheeting, install the
aileron horns and linkage system. The aileron movement should be not more
than 3/8" up and 3/8" down.
When making balsa wing skins use resin
to join together the skin sheets. A thin strip of silkspan doped over the
inner joint will prevent its raising after painting. Use a good contact
cement for joining the skin to the polystyrene foam. 3-M No. 77 is very
good, but be careful to allow the thinners to evaporate before attaching
the skin or foam will melt a bit. The hardwood landing gear blocks worked
very satisfactorily, but the plywood plate backing the shock absorber pivot
failed to support rough landings. A proposed modification will be to insert
a piece of No. G-Pad under the pivot to absorb the shock override. In general,
the wing is straightforward foam-balsa construction.
- The aluminum brackets can easily be cut from bar stock with a hack saw.
With a power drill and file, the bracket is completed in short time. Bend
the 3/16" and 5/32" dia. music wire landing gears to exactly match the drawing
(see front view for front strut).
The fiberglass wheel pants were
not available for the prototype, therefore the first set was formed from
balsa. Three pieces of wood were sandwiched and carved to shape. Plywood
bearings were used for the axles.
Epoxy Gel-Cote, unlike polyester,
does seem to have a few pinholes. After cleansing the fuselage with acetone,
spray the exterior with Dupont grey primer. Mix a small amount of epoxy
body filler and push through the holes from the inside of the fuselage with
your finger. After it hardens, sand with 280 wet and dry sandpaper. Small
holes may be filled from the exterior with thick primer available from the
auto parts stores. It may be necessary to reo peat this procedure until
all the holes are filled.
Surprising as it may seem, all the wooden
surfaces are covered with fiber-glass cloth and resin. This is an exceptionally
light finishing method if done properly. Purchase the following materials:
K&B 1/2 oz. glass cloth, Francis Products surfacing resin, single-edge
razor blades, a roll of toilet tissue. Cut a piece of the cloth slightly
larger than the surface to be covered. Using a stiff brush, apply the resin
over the cloth on the balsa surface. Roll out the toilet tissue over the
cloth absorbing the resin. Tear off the end and peel the saturated paper
away from the glass cloth. Be careful not to pull the cloth away from the
wood. Trim the cloth after the resin has hardened, sand slightly, and apply
another full coat of surfacing resin. After the resin has dried, scrape
the surface with a sinqle-edqe razor blade as far as possible without going
through the cloth. Slightly sand the surface with varying degrees of garnet
sandpaper. A coat of auto primer will show any defects to be filled.
The drawing shows the CG at 25%, although 32% is satisfactory. With
the short nose moment, the difference required approximately six more ounces
of lead in the nose. My model used about 14 oz. of lead mounted under the
engine mount and in the cowl. The Williams Bros. dummy engine was cut up
so badly that the weight was negligible.
Hobbypoxy was used to paint
the model, The wing, rudder, fin, stab, and elevators were orange while
the fuselage, cowl, wheel pants and fairings were black. Lindbergh's plane
had gold trim on the cowl and fuselage bordered with red pin striping. Gold
dope can be sprayed over the Hobbypoxy if the spray is mist-like. A heavy
coat will cause the Hobbypoxy to blister and peel. Be very careful in removing
the tape from the fuselage, as there is a tendency to peel the paint away
from the epoxy fuselage. This can turn a mild tempered modeler irate, raving
The first flying attempt was a disaster followed
by many successful, pleasing flights. Dr. Les Stephenson, Ralph Young and
I decided to give the Sirius its maiden flight at the Hollister airport.
A warm 102 degree day was chosen for the test. The Enya II engine and Perry
carburetor performed flawlessly, idling at 2700 rpm for as long as required.
The tail picked up with the first burst of power and the model made
a sudden turn. to the left. The correction with my left thumb must have
accidentally applied elevator and it cartwheeled. The nylon bolts sheared
from the cowl mounts and the wing tips were scuffed. Other than a few small
cracks, the damage was minor. Two adjustments were made. The elevator throw
was decreased and full right rudder trim was used for takeoff. Once airborne,
the trim was removed. This countered the torque, although there was a tendency
to steer to the right.
The next five flights were made at the '72
Chicago Nats. where it flew even better than I had expected. The roll is
slow and in loop it tracked perfectly. The landings were easy to control
which is probably due to the thick Clark Y airfoil. The Gold-N-Rods tended
to change trim in the black fuselage when the temperature rose. The next
model will probably have music wire running through the nylon tubing.
When the. engine was "honking," I found the nine-lb. wonder did not
perform at at all like a heavy model. It was an easy, fun to fly model.
The director of the airshow, at the '72 Nats, asked me to fly it for the
spectators. Many of the people showed their admiration by thanking me for
taking part in the exhibition. This was personally very rewarding.
After taking a dozen orders for the kit, I realized that this vintage
aircraft model left a little nostalgia with the spectators. My time has
been well spent.
The modeler wishing to purchase the fuselage may
send an inquiry to Bob Palmer, 9161 Morehart Ave., Arleta, Calif. 91331.
Lockheed Sirius Plans
<click for larger version>
Lockheed Sirius 3-View
<click for larger version>
AMA Plans Service offers a full-size version of
many of the plans show here at a very reasonable cost. They will scale the plans any size for you.
It is always best to buy printed plans because my scanner
versions often have distortions that can cause parts to fit poorly. Purchasing plans also help to
support the operation of the Academy of Model
Aeronautics - the #1 advocate for model aviation throughout the world. If the AMA no longer has this plan on file, I
will be glad to send you my higher resolution version.
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June 16, 2010