BY DAVID ADAMS
Park View: Multiplex TwinStar II
An old favorite
is updated with
refreshed lines and
super-durable
Elapor foam
Although Elapor foam is flexible, there
is no reason to test its characteristics
on the airplane’s first flight!
The TwinStar II is smooth and predictable; an average
modeler should have no problems flying it. It would make a
good trainer with an instructor.
+
• The kit has well-thought-out, impressive
engineering with low parts count.
• Good molding of parts, which fit well.
• Built-in Elapor control hinges.
• Standard cyanoacrylate can be used for
construction.
• This good-size model is easy to hand
launch.
• Excellent flying characteristics—
forgiving and predictable while mildly
aerobatic.
-•
Multilanguage manual does not have the
photo illustrations next to the written
directions.
Pluses and Minuses
Multiplex designs its packaging to be multifunctional. A handle on the top of the box
makes the container useful for carrying and stowing the model.
THE TWINSTAR II is an updated version of the original TwinStar
design that has seen many years on the hobby market. Although the
TwinStar was a successful design, it was made from the more
conventional white expanded foam and was reinforced with wood
where strength was required. This made it a fine airplane, but the
foam’s inherent lack of flexibility caused it to break rather than
bend/bounce when firmly meeting the earth.
The TwinStar II is made from Elapor: a flexible foam. When I
looked at the TwinStar II’s parts, I initially noted that Elapor allowed
the molding to be done beautifully, with sharp edges where desired,
and that good detail was maintained. All parts fit together with no
adjustments. It is difficult to find fault with the material or its
implementation on the TwinStar.
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66 MODEL AVIATION
Photos by the author
The kit includes motors, motor mounts, propellers, and wingplug
adapter board, making it a good modeling buy.
Molded areas for servos and batteries fit the required parts perfectly.
The flashing on the wing’s motor nacelles will be trimmed off.
The provided connector block links the
servo and motor leads from the wing into
the ESC and receiver.
The two aileron plugs and two motor
power plugs are located at the root of the
wing.
The flight battery fits between the two
servos and makes the model balance
perfectly. The motors are easy to change.
The TwinStar II needs only a light hand launch to get airborne. Its
good flying qualities give the modeler a feeling of security, and the
twin-motor sound is great.
The canopy section snaps into place to retain the battery. The
cooling inlet at the nose allows the air to flow through the fuselage.
Type: RC sport electric ARF
Pilot skill level: Intermediate
Wingspan: 56 inches
Wing area: 677 square inches
Length: 43 inches
Weight: 53 ounces
Wing loading: 11.5 ounces/square foot
Recommended power: 6.0-volt brushed motors; eight-cell,
2400 mAh Ni-Cd; or three-cell, 3200 mAh 20C Li-Poly
Radio: Five-channel transmitter and receiver, four miniservos,
30-amp ESC
Construction: Molded Elapor foam, nylon reinforced,
miscellaneous plastic parts
Covering/finish: Decal sheet provided
Price: $89
Motors: Included Permax 400, 6-volt brushed
Battery: Eight-cell, 2400 mAh Ni-Cd and three-cell, 3200 mAh
20C Li-Poly
Propeller: Gunther 5.5 x 4.5
Radio system: Futaba 8U transmitter and receiver, Multiplex
Pico 400/20/12 BEC ESC for Ni-Cd batteries, Jeti Advance PLUS
40-amp ESC (item JESAP40) for Li-Poly batteries, four Hitec HS-
81 servos, two 12-inch extensions
Ready-to-fly weight: 33 ounces empty, 51 ounces with 20-
ounce battery
Flight duration: 10-15 minutes
Details and Recommendations
Test-Model Details
08sig3.QXD 6/22/07 10:21 AM Page 66
An instance of the Elapor’s flexibility is in
the stabilizer and its elevator control surface.
They are molded as one piece, with the
elevator attached to the stabilizer by a small
cross-section of Elapor foam, which allows
the control surfaces to be freed by cutting
with a knife along the extreme left and right
edges of the elevator.
The foam along the elevator LE then
becomes a nice control-surface hinge.
Bending the elevator back and forth shows
the Elapor to be flexible and strong. It is
perfect for this application.
The TwinStar II has no wood parts and a
minimal amount of small plastic parts. The
tubular glass-reinforced plastic (GRP) main
spar plugs into the two-piece wing, which
allows the separated wing pieces to be easily
transported in a small car (this is a fairly large
airplane) and makes for a strong assembly.
The wings showed minimal deflection in tight
loops.
The supplied plastic parts are the motor
mounts, snap-on canopy attachments, screw
hold-down wing attachments, and control
horns. All the servos press into place and are
secured with a bit of cyanoacrylate. The
receiver and ESC are held in place with selfadhesive
hook-and-loop material.
Assembly Overview: This is a well-designed
and -executed model and is enjoyable to
construct. The biggest problem is the
tendency to glance at the photos and build the
model without reading the instructions.
Read completely through the directions
before you start. It doesn’t take much time,
and if you don’t you might miss the
instructions to move the assembly drawings
out of the manual and that you can use
standard cyanoacrylate to assemble the
airplane.
I won’t go through constructing the
TwinStar II step by step. It is enjoyable to
experience the fit and finish of the various
parts as you build, and following the
directions exactly will result in a fine flier.
There are no parts in this airplane kit that
don’t fit, need adjustment, or won’t do the
job.
However, one thing needs clarification:
using cyanoacrylate and accelerator with
Elapor. For instance, the instructions call for
putting cyanoacrylate on one fuselage-half
mating surface and spraying the accelerator
lightly on the other fuselage-half mating
surface. Then you join the two surfaces, at
which time the cyanoacrylate is activated and
the fuselage is joined.
You must be careful to quickly align the
two sides before the cyanoacrylate sets. You
have just a few seconds, which is a bit of a
downer. However, the process does allow for
rapid building. Although I enjoyed putting the
airplane together and tried to stretch out the
assembly, the airplane was finished two
evenings later.
You do need to solder the “motor” leads
from the ESC to the connector board
assembly and the motors to their individual
leads. That is the only soldering that is
necessary; everything else is plugged in.
I didn’t paint my TwinStar II because
there are problems with paint adhering to the
Elapor. The very characteristics that make
Elapor nice also make the surface much too
slick for most paint to stick well to. If you
must paint the airplane, check the adhesion on
a small area in a hidden section of the model
before doing the whole thing.
The supplied decals are okay and they
stick well. Although the basic white is
scalelike and the airplane is visible in the air, I
plan on adding more color with decals and
adhesive colored paper in the future A
beginner might want to put a patch of Day-
Glo trim on the underside of the wings to aid
in orientation.
I balanced the completed TwinStar II at
the desired point by sliding the battery fore
and aft in the provided battery-compartment
slot. I glued a small bit of foam into the
bottom of the battery compartment to keep
the battery in the desired position.
The battery can be replaced with the
locating foam in place. The finished model’s
weight was within a few ounces of the value
recommended in the instructions.
Holding the TwinStar II over my head and
pretending to fly it (admit it, all of us do this
unless you have a 35-pound monster), I was
suddenly struck by the airplane’s size—it’s
big!
When I think of Speed 400 models, I tend
to imagine much smaller aircraft. It showed
promise to be an interesting flight-test
session.
Flying: A nice day finally arrived and I took
the TwinStar II to the local flying field. I slid
the wing halves together over the GRP spar,
and my wife held the wing steady while I
plugged in the motor and aileron cables. The
two wing hold-down bolts through the plastic
wing hold-down connectors keep the wing
together and in place.
I installed the battery through the canopy
hatch, and the canopy snapped into position. I
double-checked the control-surface travels
and directions. (Never skip this step—
especially with multimodel transmitters.
Don’t ask how I know to remember!) Then I
capabilities are limited because of the power
available from the twin Speed 400s. (It should
be obvious that this is not a 3-D/hovering/firebelching
airplane.) But as I was thinking about
the limited power, I was also thinking how
impressive it was that two small Speed 400
motors allowed the airplane to fly as well as it
did.
The airplane didn’t seem to have any bad
flying characteristics. It was controllable with
the application of full up-elevator, and it just
mushed around the sky in a nose-high attitude.
I immediately felt comfortable enough
with the TwinStar II to make low-level photo
passes, which dusted off the runway (which is
further proof that I was quickly at ease with
the model). The flight-control responses were
crisp and predictable, and they seemed just
right.
When the battery was getting low I entered
the flying field’s landing pattern. As I fed in
up-elevator the model slowed nicely and
settled onto the runway’s blacktop. Since a
full-stall landing was easy to achieve, the
resulting slide was extraordinarily short. Later
landings on the grass have been uneventful,
and they have the added advantage of not
resulting in black marks on the bottom of the
fuselage.
The propellers’ location on the wing has
protected them on landing. You can expect
them to remain on the airplane a long time if
you read the instructions.
It is time for an embarrassing confession.
The instructions direct you to use
cyanoacrylate on the motor shafts to help hold
the propellers in place. I had to push fairly
hard to press the propeller onto the motor
shaft. I decided to bypass using cyanoacrylate
because I thought I might want to use some
sort of propeller adapter to try different
propellers later.
During the second flight there was a loud
pop, and the airplane suddenly yawed and
rolled to the left. I input rudder and aileron
controls to level, although I had no clue what
had happened. I was able to get the airplane
under control and level, but it began a slow
descent.
I was able to make a nice, safe landing,
noting to myself that as I throttled back the
strange control inputs were no longer needed.
A look over the airplane revealed that it was
missing a propeller.
Although the model certainly needed
corrective control deflections, it flew
amazingly well on one motor. But I learned
the lesson: do follow the assembly
instructions.
Another thing I learned during the first few
flights was not to give into the temptation of
powering the model with a three-cell Li-Poly
battery. I did, and the motors lasted only two
flights.
The performance was amazing while the
motors ran; however, the 11.1 Li-Poly voltage
source is too high for the 6.0-volt motors,
which results in higher amperage flowing.
That results in far too much heat for the
motors to dissipate. However, it does result in
70 MODEL AVIATION
adequate heat to fry the motor quickly.
I replaced the 6.0-volt Speed 400 motors
with 7.2-volt Speed 400 motors. This allowed
me to use the three-cell Li-Poly batteries. The
motor system can deliver similar power to the
airplane, and I gain the performance boost of a
10-ounce weight loss.
I didn’t try the 6.0-volt Speed 400 motors
with the two-cell Li-Poly pack because I didn’t
have a large battery. My large packs are made
to use in bigger airplanes, and I wanted to be
able to use the same three-cell pack in many
different airplanes.
The TwinStar II is a heck of a lot of fun
with the 7.2-volt Speed 400 power source.
Speed is higher and maneuvering capability is
expanded. The low-level dust-off passes are
great because the twin motors’ sound adds to
the model’s impression. For the small cost of
higher-voltage motors, it is a good
performance enhancement if you have the
batteries available.
On my list of things to do because they
might be interesting is a possible upgrade to a
tricycle-landing-gear system to take advantage
of paved runways. I haven’t been able to make
a sliding takeoff from runway or grass
surfaces. The landing gear would be made
removable—plug-ins or something similar—
and could be extremely light. Not much is
required to allow propeller clearance.
Another upgrade to consider is using a
brushless-motor power system. The cost
involved will put this lower on the to-do list.
Multiplex should consider manufacturing
add-on fuselage parts to convert the TwinStar
II to a seaplane configuration. It would require
a minimal change in the lower fuselage mold
lines and could be made removable. This
would be useful for the summer float fly-ins.
The TwinStar II is a really nice airplane. It
builds quickly and flies well with the basic
power sources, and it has no bad habits.
Assembled as directed it will provide the
builder with a good modeling experience and
an airplane that will be around for a long time.
This model would make a good trainer when
used with dual training equipment but is
unsuitable for beginners on their own.
The TwinStar II is a Multiplex desig