Park View: Multiplex Gemini-2007/12

This model’s impressive looks are possible
because of the molded-Elapor-foam
construction. The solid white material is
ready for paint or the supplied decals.
The Gemini is capable of sport and precision aerobatics with the recommended Himax
power system and Hitec radio equipment.
The airplane slows quickly for landing,
and the author recommends carrying a
little power until the wheels touch.
biplanes have held a special place in
aviation history. Many of their pilots and
designs come to mind, such as the Wright
brothers and the Red Baron, who is
commonly associated with flying the brightred
Fokker Dr.I triplane.
Then there are those seemingly fearless
pilots from the 1920s who made
barnstorming so widely popular with their
endless array of sometimes death-defying
stunts, some of which didn’t turn out as well
as planned. Have you seen one of those
black-and-white clips of a biplane crashing
through a barn?
Fast-forward a couple pages in history.
Those memories of biplanes from the past
are still alive and well, especially when you
look at all that aircraft designer Curtis Pitts
has done and all the full-scale EAA
(Experimental Aircraft Association)
homebuilt aircraft that are available. Many
people still hold the styling and grace of
those classic airplanes dear, including me.
Model-aviation enthusiasts worldwide
have been intrigued by the prospect of
building and/or flying a biplane but have yet
to “take the plunge” for one reason or
another. Could it be because of the
complexity of building such an aircraft or
the added cost that is usually associated with
such a build?
Well, no more excuses! Say hello to the
Multiplex Gemini from Hitec RCD USA.
It’s a sport aerobatic biplane made from
durable Elapor foam. Both cost and
complexity have taken a turn for the better.
Whether you choose the 200-watt power
set Hitec recommends or upgrade to a 250-
watt power system (such as the Himax
HC3510-1100), you’ll find the Gemini to be
a satisfying solution to scratching that
+•
Elapor-foam durability with great looks
• Great parts fit and hassle-free assembly
• Easy wing assembly and storage
• Motor mount accepts a wide variety of power systems and
can be fine-tuned to adjust thrust angles -•
The recommended power combination is nice for sport-flying
but requires full throttle for most aerobatics.
• Live hinges cause servos to work harder than necessary and
do not allow for full control-surface deflection.
The airfoil-shaped I-struts are glued to the
top and bottom wing. The wing assembly
is removable from the fuselage.
The builder can choose to paint the inside of the cockpit before
attaching the tinted canopy with cyanoacrylate glue.
The front hatch encloses the 3S 2500 mAh Multiplex Li-Poly
battery, which should be located as far forward as possible.
Hitec HS-55 servos complement the control surfaces. They fit
perfectly inside the molded pockets and are held in with hot glue.
The assembly process can be finished
more quickly because the hinges are
molded into the control surfaces.
Pluses and Minuses
biplane itch you might be having. For me
it’s time to start building.
Assembly Overview: After my initial
inventory and inspection of the parts
included in the kit, I found it hard to ignore
the quality and effort put into this model.
The section of the manual covering tools
included no mention of sandpaper, and for
good reason. The Elapor-foam parts were
nearly flawless. Besides, sanding makes the
foam fuzzy, which is okay for gluing areas
but bad for decoration plans.
As I made my way through the building
instructions, one tidbit of information that is
seldom associated with building foam
models grabbed my attention. The manual
recommends the use of medium- and highviscosity
cyanoacrylate—not foam-safe
cyanoacrylate. On the following page is an
important note concerning the use of proper
adhesives that you do not want to overlook.
Following the steps in building the
Gemini I had no trouble understanding the
explanations, which included bold part
numbers next to the parts referenced. Figure
illustrations located on following pages
completed the step-by-step assembly
description.
Someone with building experience could
Photos by Michael Ramsey
A profile view shows the built-in thrust and incidence angles. Fuselage decals hide the
elevator and rudder servos as well as the pushrods. Motor thrust is adjustable.
The Elapor construction is rugged. Even the spinner is made from the material, which was painted silver with Rust-Oleum spray.
Model type: RC sport
Pilot skill level: Intermediate to
advanced
Wingspan: 36.2 inches
Wing area: 527 square inches
Length: 36.2 inches
Weight: 32 ounces
Wing loading: 7.21 ounces/square foot
Motor: 200- to 250-watt outrunner
motor
Radio: Four channels (minimum), four
miniservos
Construction: Elapor foam
Price: $109.99
Specifications
Motor (Multiplex Power Pack
M993224): Himax HC2816-0890
motor, Multiplex BL-27 ESC, APC 10 x
5E propeller
Battery: 3S1P 2500 mAh Multiplex Li-
Batt
Motor current: 18 amps max
Motor output: 200 watts at 20,000 rpm
(gas equivalent: .15)
Radio system (Multiplex Flight
Pack M999224): Hitec Mini-6S
receiver, four Hitec HS-55 Feather
servos, two Hitec 6-inch aileron
extensions, Hitec Optic 6 transmitter
Flight duration: 10-15 minutes
Test-Model Details
almost put this project together by following
only the illustrations in sequence. It’s hard
to imagine anyone having an unsuccessful
building experience.
I could give you systematic instructions
for the build, but, as I just mentioned, you
have more than enough with the manual. I
will touch on the points of interest that arose
during the course of assembly.
The first step instructs you to assemble
the “control snakes,” also known as
pushrods. The following step is to glue the
servos into the fuselage halves.
Before gluing the servos in place, do not
forget to have them all centered and the
correct control horns installed. This makes
good sense, especially when installing the
servos in the bottom wing. The recessed
pockets for the aileron servos are snug and,
once in place, do not provide room for
removing the control horns without
damaging the wing.
When gluing the control snakes in place,
I dry-fit them and then exercised the servos
to ensure fluid movement of the control
rods. When I was confident of the
positioning I glued the outer sleeves in
place, being careful not to glue them to the
inner sleeves. I left enough of the sleeve end
loose at the tail end to permit the needed
range of movement.
The next step is to install the motor
mounts, with strong emphasis on using a
sufficient amount of glue—unless you want
to watch your motor eject in midflight. I
suggest roughing up the contact areas of all
the parts to give the cyanoacrylate
something more to “bite” into, making a
more secure bond between the joined parts.
Before gluing the canopy to the canopy
frame I detailed the cockpit to add a little
flair and then opted for the fully enclosed
version instead of the “open-top” option.
The box art shows an open cockpit; the
choice is up to you.
The horizontal tail has a nice, tight fit,
but it is hard to determine whether or not it
is level unless the wings are attached; that
building step is much further down the line.
The only way to get accurate alignment is to
Gemini’s 3-D Cousin: The AcroMaster
The AcroMaster has hollow wings and requires control-surface
hinge installation. It and the Gemini share a high level of quality.
Wingspan: 43 inches
Wing area: 557.27 square inches
Weight (as tested): 40.2 ounces
Wing loading: 10.4 ounces/square foot
Length: 45.25 inches
Power: 350-watt system
Battery: 2500-3200 mAh, 11.1 volts
Price: $119.99
Specifications
The AcroMaster uses a 350-watt Himax power system
while the smaller Gemini power system puts out 250 watts.
The AcroMaster hovers easily at half throttle. A 3200 mAh Multiplex
battery will provide at least 10 minutes of aerobatic performance.
THE GEMINI IS such a great-looking
product that Shawn and I decided to
build the Multiplex AcroMaster at the
same time. Comparison showed that
although the two models differ greatly
in looks, they share the same attention
to high quality and superb engineering.
The Elapor construction isn’t like
that of those “beer cooler” models made
from beaded Styrofoam. The airplanes’
finish is good enough for the
multicolored graphics to be applied
straight away, or with a quick wipe of
alcohol they can be covered with any
kind of paint.
The AcroMaster is purpose-built to
be a graduate model for the foamie
flying expert who is looking for an
aircraft to take outdoors to increase his
or her flying skills. The midwing design
is an excellent platform to show rolls
that are truly axial and to
do positive or negative
maneuvers harmoniously.
The thick, symmetrical airfoil and widebody
fuselage allow the airplane to maintain
a constant airspeed. The plug-in wings and
oversized canopy hatch make the model
“quick-flight” compatible.
Elapor foam is tightly molded, so it’s
rigid, but the material is flexible enough that
it can absorb the torcher a novice aerobatics
pilot might force it to endure. Even the
spinner is Elapor, and it can take a beating,
as will the wire landing gear and nylonreinforced
plastic parts.
We used the power kit Multiplex USA
recommended (item M993215). The Himax
3516-1130 motor has literally spoiled me; it
has so much power.
Advertising mentions that the
AcroMaster has the ability of a 30-size glow
model, but I have to disagree. It’s way better,
with low-speed torque that smoothly holds
the AcroMaster in a rock-steady torque roll.
The Castle Creations Phoenix-45 ESC
never skipped a beat. It was programmed
with the Castle Link and software to
correctly time the motor and set the voltage
cutoff so the Multiplex 3200 mAh Li-Batt
BX three-cell battery wasn’t drained
excessively.
Also recommended and used was the
Hitec Flight Pack (item M999215). We
complemented this precise radio
equipment with my Hitec Eclipse
transmitter, which makes programming
the model for RC Aerobatics and 3-D
aerobatics simple.
We use a flight condition instead of
the rate switches to change between the
two flying styles. Even though the
control-surface movements between the
two conditions are radically different,
the Hitec HS-85BB and HB-65HB
servos performs strongly and smoothly.
The Gemini biplane is an excellent
sport model with elegant lines a Top
Gun builder would cringe to replicate
from conventional materials and make as
light. The AcroMaster has all that going
for it and it excels at 3-D and can be a
great model for practicing Aerobatics. I
think Shawn and I will be trading
airplanes real soon. MA
—Michael Ramsey
temporarily mount only the bottom wing to
the fuselage and then sight down the
fuselage to assure that the horizontal tail
section mounts parallel to the wing.
After gluing the horizontal tail section in
place, the tail-wheel assembly needs to be
installed in the rudder. The tail-wheel wire
is spring steel and tough to bend. Putting it
upside down in a vise or clamp seemed to be
the easiest way to achieve the needed 90°
bend without causing undue stress to the
plastic control horn and bracket. Once
completed, the tail fin installs quickly.
You are to apply the decals before
starting the wing assembly, which makes
perfect sense. Once I started I finished all
the decals except those on the sides of the
fuselage, which cover the elevator and
rudder servos.
I waited to apply those until after all the
electronics were mounted—in case the servo
centering and operation needed to be
changed. The lightweight, three-color
graphics add a great deal of character to the
model; I did not want to take the chance of
damaging them.
Nothing was out of the ordinary with
installing the top and bottom wings.
However, do pay attention to the aileron link
horns; the holes in each end are different
sizes and are easily reversed.
Before the top and bottom wings are
joined, with the landing gear in place, the
receiver is installed inside the fuselage. I
found that the most convenient place for it
was through the bottom of the fuselage.
I placed the receiver just forward of the
opening on the right side to offset the weight
of the ESC, which would be mounted on the
left side in the front battery compartment.
That way the 6-inch aileron extensions
could easily exit the bottom wing opening.
This placement also helped to obtain the
proper CG.
With all the electronics installed, except
the motor, I joined the one-piece wings to
the fuselage. The easiest way to get the
fuselage between the wings was to lay it on
its side and roll it into place. Without
“rolling” the fuselage, a lot of prying was
necessary to fit the assembly and the
ailerons were difficult to connect.
Before installing the motor I had to
reverse the shaft to correctly install it on the
supplied mount and use the included colletstyle
propeller adapter. The motor bolted to
the center of a nylon-reinforced adjustable
mount with the adjustment screws turned to
the recommended offset (maximum right
thrust and no downthrust).
With the airplane assembly complete I
set up the controls with the recommend low
rates and full control throw on high rates.
After verifying proper operation I rechecked
the CG, applied the fuselage side decals, and
topped off the Multiplex Li-Poly battery.
Wow, what a great-looking biplane!
The Fun Part: The local soccer field
seemed like a perfect place for the inaugural
flight. The Gemini had to be at full throttle
to take off from short grass, but it was
smooth and predictable using the
recommended control settings. Putting the
airplane in a vertical climb made it apparent
that 3-D maneuvers would not be on the
manifest; it didn’t have the power.
The Gemini seemed comfortable in a
straight-ahead stall, whether upright or
inverted. Inverted flight indicated that I had
the CG a bit too far aft. The model seemed
to be fairly neutral after I moved the battery
forward approximately 1/4 inch.
Rolling right and left proved that aileron
differential would need to be programmed to
get the rolls to perform more axially, but it’s
not as unmanageable as it was. The Hitec
Optic 6 transmitter I was using employs
Channel 1 and Channel 5 for differential
mixing, so the Hitec Mini-6S receiver
wouldn’t have to be changed out for a
higher-channel-count version.
All I had to do was move the servo plug
from the Channel 6 position and exchange
the flaperon mix function for differential.
Only roughly a 20% mix was required to
help the rolls look straighter.
Pulling off a knife edge required an
intimate knowledge of coupling, not to
mention a good amount of altitude if a good
head of steam couldn’t be maintained. Most
aerobatic maneuvers required full throttle.
To extend the initial flight I backed off the
throttle to conserve power, and the Gemini
proved that it was comfortable flying at
slower speeds.
When landing the model my first
reaction was to drop the power and glide to
a nice touchdown. Quickly realizing the
additional wing drag a biplane has, I had to
carry approximately one-quarter power on
the approach to prevent an early stall. The
stalls were straight ahead in the air, so
dropping a wing wasn’t a concern.
At touchdown I throttled down before
the tail wheel touched, causing the airplane
to nose over. Call it a lesson learned on soft
grass fields. With nothing hurt but my ego,
the next flight was as good as the first and
finished without the ground loop.
Adding the Multiplex Gemini to my
aircraft collection has definitely been a good
building and flying experience. From start to
finish I had eight to 10 hours invested,
including the cockpit detail and spinner
paint job. I built it and flew it on the same
day. How many biplanes can be assembled
this quickly? MA
Shawn Rubush
[email protected]
Manufacturer/Distributor:
Multiplex Modelsport USA/Hitec RCD
USA
12115 Paine St.
Poway CA 92064
(858) 748-6948
www.multiplexusa.com
Products Used in Review:
Transmitter, servos, receiver:
Hitec RCD
(858) 748-6948
www.hitecrcd.com
Motor:
Maxx Products International
(800) 416-6299
www.maxxprod.com
Other Review Sources:
Backyard Flyer: November 2007

This model’s impressive looks are possible
because of the molded-Elapor-foam
construction. The solid white material is
ready for paint or the supplied decals.
The Gemini is capable of sport and precision aerobatics with the recommended Himax
power system and Hitec radio equipment.
The airplane slows quickly for landing,
and the author recommends carrying a
little power until the wheels touch.
biplanes have held a special place in
aviation history. Many of their pilots and
designs come to mind, such as the Wright
brothers and the Red Baron, who is
commonly associated with flying the brightred
Fokker Dr.I triplane.
Then there are those seemingly fearless
pilots from the 1920s who made
barnstorming so widely popular with their
endless array of sometimes death-defying
stunts, some of which didn’t turn out as well
as planned. Have you seen one of those
black-and-white clips of a biplane crashing
through a barn?
Fast-forward a couple pages in history.
Those memories of biplanes from the past
are still alive and well, especially when you
look at all that aircraft designer Curtis Pitts
has done and all the full-scale EAA
(Experimental Aircraft Association)
homebuilt aircraft that are available. Many
people still hold the styling and grace of
those classic airplanes dear, including me.
Model-aviation enthusiasts worldwide
have been intrigued by the prospect of
building and/or flying a biplane but have yet
to “take the plunge” for one reason or
another. Could it be because of the
complexity of building such an aircraft or
the added cost that is usually associated with
such a build?
Well, no more excuses! Say hello to the
Multiplex Gemini from Hitec RCD USA.
It’s a sport aerobatic biplane made from
durable Elapor foam. Both cost and
complexity have taken a turn for the better.
Whether you choose the 200-watt power
set Hitec recommends or upgrade to a 250-
watt power system (such as the Himax
HC3510-1100), you’ll find the Gemini to be
a satisfying solution to scratching that
+•
Elapor-foam durability with great looks
• Great parts fit and hassle-free assembly
• Easy wing assembly and storage
• Motor mount accepts a wide variety of power systems and
can be fine-tuned to adjust thrust angles -•
The recommended power combination is nice for sport-flying
but requires full throttle for most aerobatics.
• Live hinges cause servos to work harder than necessary and
do not allow for full control-surface deflection.
The airfoil-shaped I-struts are glued to the
top and bottom wing. The wing assembly
is removable from the fuselage.
The builder can choose to paint the inside of the cockpit before
attaching the tinted canopy with cyanoacrylate glue.
The front hatch encloses the 3S 2500 mAh Multiplex Li-Poly
battery, which should be located as far forward as possible.
Hitec HS-55 servos complement the control surfaces. They fit
perfectly inside the molded pockets and are held in with hot glue.
The assembly process can be finished
more quickly because the hinges are
molded into the control surfaces.
Pluses and Minuses
biplane itch you might be having. For me
it’s time to start building.
Assembly Overview: After my initial
inventory and inspection of the parts
included in the kit, I found it hard to ignore
the quality and effort put into this model.
The section of the manual covering tools
included no mention of sandpaper, and for
good reason. The Elapor-foam parts were
nearly flawless. Besides, sanding makes the
foam fuzzy, which is okay for gluing areas
but bad for decoration plans.
As I made my way through the building
instructions, one tidbit of information that is
seldom associated with building foam
models grabbed my attention. The manual
recommends the use of medium- and highviscosity
cyanoacrylate—not foam-safe
cyanoacrylate. On the following page is an
important note concerning the use of proper
adhesives that you do not want to overlook.
Following the steps in building the
Gemini I had no trouble understanding the
explanations, which included bold part
numbers next to the parts referenced. Figure
illustrations located on following pages
completed the step-by-step assembly
description.
Someone with building experience could
Photos by Michael Ramsey
A profile view shows the built-in thrust and incidence angles. Fuselage decals hide the
elevator and rudder servos as well as the pushrods. Motor thrust is adjustable.
The Elapor construction is rugged. Even the spinner is made from the material, which was painted silver with Rust-Oleum spray.
Model type: RC sport
Pilot skill level: Intermediate to
advanced
Wingspan: 36.2 inches
Wing area: 527 square inches
Length: 36.2 inches
Weight: 32 ounces
Wing loading: 7.21 ounces/square foot
Motor: 200- to 250-watt outrunner
motor
Radio: Four channels (minimum), four
miniservos
Construction: Elapor foam
Price: $109.99
Specifications
Motor (Multiplex Power Pack
M993224): Himax HC2816-0890
motor, Multiplex BL-27 ESC, APC 10 x
5E propeller
Battery: 3S1P 2500 mAh Multiplex Li-
Batt
Motor current: 18 amps max
Motor output: 200 watts at 20,000 rpm
(gas equivalent: .15)
Radio system (Multiplex Flight
Pack M999224): Hitec Mini-6S
receiver, four Hitec HS-55 Feather
servos, two Hitec 6-inch aileron
extensions, Hitec Optic 6 transmitter
Flight duration: 10-15 minutes
Test-Model Details
almost put this project together by following
only the illustrations in sequence. It’s hard
to imagine anyone having an unsuccessful
building experience.
I could give you systematic instructions
for the build, but, as I just mentioned, you
have more than enough with the manual. I
will touch on the points of interest that arose
during the course of assembly.
The first step instructs you to assemble
the “control snakes,” also known as
pushrods. The following step is to glue the
servos into the fuselage halves.
Before gluing the servos in place, do not
forget to have them all centered and the
correct control horns installed. This makes
good sense, especially when installing the
servos in the bottom wing. The recessed
pockets for the aileron servos are snug and,
once in place, do not provide room for
removing the control horns without
damaging the wing.
When gluing the control snakes in place,
I dry-fit them and then exercised the servos
to ensure fluid movement of the control
rods. When I was confident of the
positioning I glued the outer sleeves in
place, being careful not to glue them to the
inner sleeves. I left enough of the sleeve end
loose at the tail end to permit the needed
range of movement.
The next step is to install the motor
mounts, with strong emphasis on using a
sufficient amount of glue—unless you want
to watch your motor eject in midflight. I
suggest roughing up the contact areas of all
the parts to give the cyanoacrylate
something more to “bite” into, making a
more secure bond between the joined parts.
Before gluing the canopy to the canopy
frame I detailed the cockpit to add a little
flair and then opted for the fully enclosed
version instead of the “open-top” option.
The box art shows an open cockpit; the
choice is up to you.
The horizontal tail has a nice, tight fit,
but it is hard to determine whether or not it
is level unless the wings are attached; that
building step is much further down the line.
The only way to get accurate alignment is to
Gemini’s 3-D Cousin: The AcroMaster
The AcroMaster has hollow wings and requires control-surface
hinge installation. It and the Gemini share a high level of quality.
Wingspan: 43 inches
Wing area: 557.27 square inches
Weight (as tested): 40.2 ounces
Wing loading: 10.4 ounces/square foot
Length: 45.25 inches
Power: 350-watt system
Battery: 2500-3200 mAh, 11.1 volts
Price: $119.99
Specifications
The AcroMaster uses a 350-watt Himax power system
while the smaller Gemini power system puts out 250 watts.
The AcroMaster hovers easily at half throttle. A 3200 mAh Multiplex
battery will provide at least 10 minutes of aerobatic performance.
THE GEMINI IS such a great-looking
product that Shawn and I decided to
build the Multiplex AcroMaster at the
same time. Comparison showed that
although the two models differ greatly
in looks, they share the same attention
to high quality and superb engineering.
The Elapor construction isn’t like
that of those “beer cooler” models made
from beaded Styrofoam. The airplanes’
finish is good enough for the
multicolored graphics to be applied
straight away, or with a quick wipe of
alcohol they can be covered with any
kind of paint.
The AcroMaster is purpose-built to
be a graduate model for the foamie
flying expert who is looking for an
aircraft to take outdoors to increase his
or her flying skills. The midwing design
is an excellent platform to show rolls
that are truly axial and to
do positive or negative
maneuvers harmoniously.
The thick, symmetrical airfoil and widebody
fuselage allow the airplane to maintain
a constant airspeed. The plug-in wings and
oversized canopy hatch make the model
“quick-flight” compatible.
Elapor foam is tightly molded, so it’s
rigid, but the material is flexible enough that
it can absorb the torcher a novice aerobatics
pilot might force it to endure. Even the
spinner is Elapor, and it can take a beating,
as will the wire landing gear and nylonreinforced
plastic parts.
We used the power kit Multiplex USA
recommended (item M993215). The Himax
3516-1130 motor has literally spoiled me; it
has so much power.
Advertising mentions that the
AcroMaster has the ability of a 30-size glow
model, but I have to disagree. It’s way better,
with low-speed torque that smoothly holds
the AcroMaster in a rock-steady torque roll.
The Castle Creations Phoenix-45 ESC
never skipped a beat. It was programmed
with the Castle Link and software to
correctly time the motor and set the voltage
cutoff so the Multiplex 3200 mAh Li-Batt
BX three-cell battery wasn’t drained
excessively.
Also recommended and used was the
Hitec Flight Pack (item M999215). We
complemented this precise radio
equipment with my Hitec Eclipse
transmitter, which makes programming
the model for RC Aerobatics and 3-D
aerobatics simple.
We use a flight condition instead of
the rate switches to change between the
two flying styles. Even though the
control-surface movements between the
two conditions are radically different,
the Hitec HS-85BB and HB-65HB
servos performs strongly and smoothly.
The Gemini biplane is an excellent
sport model with elegant lines a Top
Gun builder would cringe to replicate
from conventional materials and make as
light. The AcroMaster has all that going
for it and it excels at 3-D and can be a
great model for practicing Aerobatics. I
think Shawn and I will be trading
airplanes real soon. MA
—Michael Ramsey
temporarily mount only the bottom wing to
the fuselage and then sight down the
fuselage to assure that the horizontal tail
section mounts parallel to the wing.
After gluing the horizontal tail section in
place, the tail-wheel assembly needs to be
installed in the rudder. The tail-wheel wire
is spring steel and tough to bend. Putting it
upside down in a vise or clamp seemed to be
the easiest way to achieve the needed 90°
bend without causing undue stress to the
plastic control horn and bracket. Once
completed, the tail fin installs quickly.
You are to apply the decals before
starting the wing assembly, which makes
perfect sense. Once I started I finished all
the decals except those on the sides of the
fuselage, which cover the elevator and
rudder servos.
I waited to apply those until after all the
electronics were mounted—in case the servo
centering and operation needed to be
changed. The lightweight, three-color
graphics add a great deal of character to the
model; I did not want to take the chance of
damaging them.
Nothing was out of the ordinary with
installing the top and bottom wings.
However, do pay attention to the aileron link
horns; the holes in each end are different
sizes and are easily reversed.
Before the top and bottom wings are
joined, with the landing gear in place, the
receiver is installed inside the fuselage. I
found that the most convenient place for it
was through the bottom of the fuselage.
I placed the receiver just forward of the
opening on the right side to offset the weight
of the ESC, which would be mounted on the
left side in the front battery compartment.
That way the 6-inch aileron extensions
could easily exit the bottom wing opening.
This placement also helped to obtain the
proper CG.
With all the electronics installed, except
the motor, I joined the one-piece wings to
the fuselage. The easiest way to get the
fuselage between the wings was to lay it on
its side and roll it into place. Without
“rolling” the fuselage, a lot of prying was
necessary to fit the assembly and the
ailerons were difficult to connect.
Before installing the motor I had to
reverse the shaft to correctly install it on the
supplied mount and use the included colletstyle
propeller adapter. The motor bolted to
the center of a nylon-reinforced adjustable
mount with the adjustment screws turned to
the recommended offset (maximum right
thrust and no downthrust).
With the airplane assembly complete I
set up the controls with the recommend low
rates and full control throw on high rates.
After verifying proper operation I rechecked
the CG, applied the fuselage side decals, and
topped off the Multiplex Li-Poly battery.
Wow, what a great-looking biplane!
The Fun Part: The local soccer field
seemed like a perfect place for the inaugural
flight. The Gemini had to be at full throttle
to take off from short grass, but it was
smooth and predictable using the
recommended control settings. Putting the
airplane in a vertical climb made it apparent
that 3-D maneuvers would not be on the
manifest; it didn’t have the power.
The Gemini seemed comfortable in a
straight-ahead stall, whether upright or
inverted. Inverted flight indicated that I had
the CG a bit too far aft. The model seemed
to be fairly neutral after I moved the battery
forward approximately 1/4 inch.
Rolling right and left proved that aileron
differential would need to be programmed to
get the rolls to perform more axially, but it’s
not as unmanageable as it was. The Hitec
Optic 6 transmitter I was using employs
Channel 1 and Channel 5 for differential
mixing, so the Hitec Mini-6S receiver
wouldn’t have to be changed out for a
higher-channel-count version.
All I had to do was move the servo plug
from the Channel 6 position and exchange
the flaperon mix function for differential.
Only roughly a 20% mix was required to
help the rolls look straighter.
Pulling off a knife edge required an
intimate knowledge of coupling, not to
mention a good amount of altitude if a good
head of steam couldn’t be maintained. Most
aerobatic maneuvers required full throttle.
To extend the initial flight I backed off the
throttle to conserve power, and the Gemini
proved that it was comfortable flying at
slower speeds.
When landing the model my first
reaction was to drop the power and glide to
a nice touchdown. Quickly realizing the
additional wing drag a biplane has, I had to
carry approximately one-quarter power on
the approach to prevent an early stall. The
stalls were straight ahead in the air, so
dropping a wing wasn’t a concern.
At touchdown I throttled down before
the tail wheel touched, causing the airplane
to nose over. Call it a lesson learned on soft
grass fields. With nothing hurt but my ego,
the next flight was as good as the first and
finished without the ground loop.
Adding the Multiplex Gemini to my
aircraft collection has definitely been a good
building and flying experience. From start to
finish I had eight to 10 hours invested,
including the cockpit detail and spinner
paint job. I built it and flew it on the same
day. How many biplanes can be assembled
this quickly? MA
Shawn Rubush
[email protected]
Manufacturer/Distributor:
Multiplex Modelsport USA/Hitec RCD
USA
12115 Paine St.
Poway CA 92064
(858) 748-6948
www.multiplexusa.com
Products Used in Review:
Transmitter, servos, receiver:
Hitec RCD
(858) 748-6948
www.hitecrcd.com
Motor:
Maxx Products International
(800) 416-6299
www.maxxprod.com
Other Review Sources:
Backyard Flyer: November 2007