42 MODEL AVIATION
ERIC HENDERSON
Plane Talk: Multiplex Mentor Electric ARF
The Mentor is happy flying inverted. This is one way to find out if
the battery is secure; of course it is. This model is fun for a trainer!
A versatile electric trainer
that can take a beating
The model is easy to put together at the field. The two-piece wing
attaches with two nylon bolts. The battery hatch snaps into place.
Multiplex’s Mentor has the appeal of a modern high-wing private aircraft. The absence of wing struts is a testament to the design’s
strength.
SELDOM DO YOU see an RC trainer that
comes in a box showing an aerotow as one
of the main features. But the Multiplex
Mentor is unusual in several ways.
A first look gives the impression of an
orthodox electric-powered RC trainer. Then
you realize that it is not one of those small
foamies with a little gear-driven motor, but
a full-blooded, 64-inch-wingspan airplane.
It is exciting to put together a new
airplane. It is even more thrilling when the
model is slated to have more than one
purpose. The Mentor is touted as a trainer
and a glider-towing tug.
(Editor’s note: Now it can even be made
to fly from water.)
As a trainer, the Mentor is aimed at the
beginner to intermediate modeler/pilot who
is 14 years of age and older. You should
probably also be an experienced RC pilot if
you are going to use this aircraft to aerotow
gliders.
The 40 trainer is one of the most popular
model sizes, and the Mentor uses a clean
and relatively quiet brushless-motor power
pack. In addition, little field-support
equipment is needed other than a battery
charger for the flight pack.
The Mentor is billed as having stable
flying characteristics and a low stall
(minimum airspeed) for easy landings.
Those things are desirable in a trainer.
When finished, the main wing is a twopart
structure with a removable carbon-fiber
spar joiner for easy transport. The canopy
hatch is removable with quick-release
10sig2.QXD 8/21/09 2:05 PM Page 42
October 2009 43
Five servos are used: two for the ailerons
and one each for the rudder and elevator.
The fifth servo, an HS-55, is for the aerotow
line release, to be used in the future.
The Multiplex brushless power pack
eliminates electric guesswork and consists
of a Himax HC3528-1000 motor, BL-55
ESC, propeller adapter, and APC 11 x 5.5E
propeller.
The Mentor carries a large Multiplex
three-cell Li-Poly 4800 mAh battery that
gives good flight times and plenty of
power.
Construction mainly consists of foam molded parts with an array
of tough plastic parts. The landing gear is made from pressed
aluminum plate.
Each wing half is molded in two pieces; they sandwich the
composite spar and servo leads. The interior includes ingenious
functionality.
Photos by the author
The tail-dragger configuration is mandatory for the Mentor. Extralong
aluminum gear is strong, and wheels are large enough for
rough-field maneuvering.
Multiplex models molded with Elapor foam are compatible with
regular CA adhesives. So are the plastic parts, which chemically
bond with the foam and adhesive.
catches, for an easy flight-battery swap.
Multiplex uses white molded foam
called “Elapor.” It is different from
expanded polystyrene foam, in that it does
not need special foam-friendly CA glue.
You are instructed to use only regular
medium CA.
The wings are also made from Elapor.
The ailerons are part of the mold and are
hinged with the same material. The wing
halves are stiffened by a carbon-fiber tube
that is also the removable wing joiner. The
wing halves are held together by the same
plate that the wing bolts use to hold the
wing in place.
The cowl and spinner are both made
from Elapor. I had never seen a foam
spinner, but it worked fine on the Himax
motor, which is available from Maxx
Products International. The motor mount
uses two rails that are glued into the foam.
The motor plate then screws into the mount
with four convenient-to-adjust machine
screws that are positioned around the motor
plate.
The landing gear is a prebent piece of
2.5mm-thick aluminum sheet. The two
70mm main wheels use lightweight foam.
Multiplex markets a set of component
10sig2.QXD 8/21/09 1:31 PM Page 43
All you have to do is open the throttle, and
this airplane will be airborne quickly. The
performance is surprising on only 11.1
volts; it handles the wind well
The decals add to this model’s look and help with in-flight orientation. Because the hinges
are molded in, the control surfaces’ effectiveness is greatly enhanced.
Floats are now available for the Mentor. Nothing is better for floating on water than foam, but as fun as this model is to fly, it will be
mostly airborne.
packs that meet several of its models’
needs. The Power Pack includes an
excellent Himax brushless motor, 55-amp
ESC, propeller, and hub assembly. The
company also sells Hitec and Multiplex
radio systems, but I used my JR8103 that
was converted to Spektrum with the 2.4
GHz module/receiver system.
Construction: The manual comprises a
series of high-quality drawings in four
languages. The builder should have some
RC model-building knowledge.
It was helpful to study the pictures and
then make construction lists. To make
assembly even easier, I cut the fourlanguage
instructions and sorted them into
their English components. Then I stapled
each narrative next to the pictures/diagrams
of the assembly.
Wing construction is made easier,
because it consists of two molded panels
that end up as halves. Assembly begins with
releasing the ailerons and flexing their
premolded foam hinge lines. I had to add
servo-extension leads to the aileron servos
so that they would reach the wing center
area.
Before gluing anything, you need to fit
the servo arms to the Hitec HS-81
microservos. This means that you must set
the neutral positions with your radio for
each arm on each servo. You can’t do this
once everything has been glued in place.
The foam cover forms a tube in the wing
panel for the carbon-fiber wing-joiner tube.
It also covers the servo lead/extension and
holds the servo in place.
Take care not to get CA in the tube area,
if you want to be able to easily slide in the
carbon-fiber wing joiner. Also, do not put
the carbon-fiber joiner in too soon, in case
any uncured CA decides to fix it there
permanently!
The fuselage comes in halves that
require a fair degree of preparation before
they can be glued together. Fit the Hitec
HS-322HD servos for the rudder and
elevator servos into recesses on the outside
of the molded fuselage halves and route
their leads inside. Adhere the pushrod outer
tubes into grooves in the outer skin of the
foam parts.
I deviated slightly from the instructions
with the wing bolts. I retapped the plates
out to a 1/4 x 20 thread and used two nylon
Allen-head bolts instead of the supplied
metric threaded bolts. This choice was
prompted by the better availability of
standard hardware.
I installed a Hitec HS-55 servo that
would operate a cable/towline release. This
assembly was buried in one fuselage side.
As did the ailerons, the servo arm needed to
be set with the radio before it was glued in
place. There would be no way to reach this
servo later.
When you are ready to glue the fuselage
halves together, lay everything out in
advance. It is a good idea to enlist a friend
to help with this task. I recruited my wife to
hold the rear section together while I
worked on the middle and front. I applied
the CA quickly and liberally onto one side
and gently squeezed the halves together.
The adhesive did not cure immediately,
especially where there was a lot of it.
Therefore, the halves needed to be held in
several places for roughly five minutes.
Some areas attached instantly, while others
kept coming apart.
Also, excess CA oozed out of the seams
and had to be wiped off quickly. The
process was a bit stressful, but we are still
married. Next time we’ll use more kicker.
To fit the stabilizer and fin, the wing
needs to be bolted in place. It sat square in
the wing seat and was a nice, tight fit. The
Multiplex molds’ accuracy was no more
evident than when the wings lined up
perfectly.
Gluing the tail feathers in place was
simple and quick. Connecting the controls
was easy because of the supplied adjustable
swivel connectors at the horn end. Z-bends
were used at all of the servo-arm ends.
A separate pushrod for the steerable tail
wheel lets you set the rudder trim
independent of the tail-wheel setting. The
tail-wheel assembly and the main landing
gear plate bolt together. The tail-wheel
assembly glues in place. The mains are
machine-screwed using additional landing
gear plates that sandwich and add support to
the preinstalled landing gear plate.
The motor was a good fit on the motor
plate. The plate then fitted perfectly onto the
previously installed motor mounts. You do
have to solder the connectors onto the battery
and the ESC.
A BEC in a large ESC is rarely used to
feed the receiver and servos, because too
much power can go to the motor and then not
enough is left for the onboard radio system. A
separate 1800 mAh NiMH receiver battery
was used for this task. Be sure to disable the
power feed to the receiver from the BEC.
The large 3S 4800 mAh needed to be
retained under the wing to get the correct CG.
The space was not a tight fit and there needed
to be room for cooling air to flow past the
battery pack.
me that used Velcro straps to hold the
pack in place. The Velcro allows the Li-
Poly pack to be removed for
charging/balancing.
Preparing the decals was tough; it took
quite awhile to cut them by hand. However,
they were easy to apply and could be lifted
for alignment purposes, as long as I had not
rubbed them down.
The result is worth the effort. The
graphics not only improved the Mentor’s
look and visibility, but they also covered
the servos on the outside of the fuselage.
Motor and Battery: When you configure
an electric model, it can be difficult to
choose the proper motor, ESC, and
battery. Multiplex has assembled a triedand-
proven optional package that takes
away all of the guesswork. It is optimized
to give you the most out of your airplane.
The configuration is designed to use a 3S
3200-4800 mAh Li-Poly battery pack.
The Mentor Power Pack includes a
Himax 3528-1000 brushless outrunner
motor with the following specifications:
Kv, 1,000; watts, 450; diameter, 35mm;
length, 54mm; and weight, 197 grams.
The pack also contains an APC 11 x 5.5E
propeller, hub, and driver to match the
motor’s shaft size.
Also included is a MULTIcont BL-55
brushless ESC, which has the following
specifications: max continuous current, 55
amps; voltage range, 6-15; maximum
battery, 3S Li-Poly; and a BEC that can
deliver 3 amps. The BEC was not used to
power the five servos.
The motor installation was tested and
measured. Initial results were that it drew
42 amps and 507 watts, showing 11.4
volts at full throttle. The motor turned the
APC propeller at 9,960 rpm. These figures
dropped off a bit after a few seconds.
Flight Report: An electric trainer this
size still tends to be a new thing at the
flying field. A few short taxi runs were all
it took to check the steering, and we were
ready.
I taxied the Mentor to the center of the
runway and aimed it into the wind. The
timer was set to go off after six minutes,
to give a good margin on the battery and
allow for several landing attempts, if
required.
The takeoff run was straight and rapid.
The big motor almost immediately
delivered maximum torque. The tail came
up quickly, and the aircraft was airborne
in approximately 15 feet.
The climb was a bit steep at first, and
then it got even steeper. I put in roughly
six clicks of down-elevator trim before
entering the first turn. No aileron or
rudder trim was required. The initial trim
setting was all that was needed to achieve
level and steady flight.
When I released the controls, the
model flew straight and level. When
entering a turn, some bottom rudder was
required to keep the fuselage nose level
with the horizon.
Varying the throttle settings showed
stable flight behavior down to a gentle
stall. The Mentor would then drop the
nose and regain airspeed in close to 4 feet
of altitude.
I selected half throttle and made a
landing circuit. Once the airplane was
over the runway landing threshold, nearly
two notches of throttle clicks kept the
propeller turning. The wings stayed level,
and the motor was brought back to 0 rpm
approximately a foot above the grass. The
model settled into a smooth landing 10
yards or so later.
The red, black, and silver decals had
orientation. The first flight was good and
was quickly followed by more adventurous
flights that included such exploits as loops,
rolls, and inverted flight. The airplane liked
to skim in on the main wheels rather than be
almost stalled down to a three-point landing.
The Mentor is a delight to fly and easy to
guide around the sky. It loops majestically
and gives a slight barrel roll with ailerons.
Making aileron turns at cruising or high
speed showed no adverse yaw. That is when
the higher wing has more drag than the
lower wing when a rolling action is created
with the ailerons.
Aileron turn entries at slow speed liked a
bit of bottom rudder to be added when
initially going into the turn. This rudder
input can be made manually or mixed in
using a computer radio.
The Multiplex Mentor has the feel of a
low-wing sport airplane—especially when
you send more electrons to the brushless
motor. Get some help putting one of these
models together if you are an inexperienced
builder, and it could appear early in your
RC chronicles.
Even though the Mentor appears
destined only to be a trainer, it can be so
much more. It flies as well as any 40- to 60-
sized sport aircraft and has no nasty habits.
It is a great airplane to fly for fun.
In addition, that aerotow release servo is
buried in the fuselage, just sitting there. You
could use it to pull a ribbon/streamer or tow
a banner, but it was designed to pull a
glider. Now where did I put that Multiplex
Cularis sailplane? (Editor’s note: See page
54 for that story.) MA
Eric Henderson
[email protected]
Manufacturer/Distributor:
Multiplex USA
12115 Paine St.
Poway CA 92064
(858) 748-6948
www.multiplexusa.com
Sources:
Maxx Products International
(847) 438-2233
www.maxxprod.com
Spektrum
(800) 338-4639
www.spektrumrc.com
JR
(800) 338-4639
www.jrradios.com
APC Propeller
(530) 661-0399
www.apcprop.com
Other Published Reviews:
RC Model World: October 2008
Model Airplane News: January 2009
Quiet and Electric Flight International:
January 2009
Edition: Model Aviation - 2009/10
Page Numbers: 42,43,44,46,48,51
Edition: Model Aviation - 2009/10
Page Numbers: 42,43,44,46,48,51
42 MODEL AVIATION
ERIC HENDERSON
Plane Talk: Multiplex Mentor Electric ARF
The Mentor is happy flying inverted. This is one way to find out if
the battery is secure; of course it is. This model is fun for a trainer!
A versatile electric trainer
that can take a beating
The model is easy to put together at the field. The two-piece wing
attaches with two nylon bolts. The battery hatch snaps into place.
Multiplex’s Mentor has the appeal of a modern high-wing private aircraft. The absence of wing struts is a testament to the design’s
strength.
SELDOM DO YOU see an RC trainer that
comes in a box showing an aerotow as one
of the main features. But the Multiplex
Mentor is unusual in several ways.
A first look gives the impression of an
orthodox electric-powered RC trainer. Then
you realize that it is not one of those small
foamies with a little gear-driven motor, but
a full-blooded, 64-inch-wingspan airplane.
It is exciting to put together a new
airplane. It is even more thrilling when the
model is slated to have more than one
purpose. The Mentor is touted as a trainer
and a glider-towing tug.
(Editor’s note: Now it can even be made
to fly from water.)
As a trainer, the Mentor is aimed at the
beginner to intermediate modeler/pilot who
is 14 years of age and older. You should
probably also be an experienced RC pilot if
you are going to use this aircraft to aerotow
gliders.
The 40 trainer is one of the most popular
model sizes, and the Mentor uses a clean
and relatively quiet brushless-motor power
pack. In addition, little field-support
equipment is needed other than a battery
charger for the flight pack.
The Mentor is billed as having stable
flying characteristics and a low stall
(minimum airspeed) for easy landings.
Those things are desirable in a trainer.
When finished, the main wing is a twopart
structure with a removable carbon-fiber
spar joiner for easy transport. The canopy
hatch is removable with quick-release
10sig2.QXD 8/21/09 2:05 PM Page 42
October 2009 43
Five servos are used: two for the ailerons
and one each for the rudder and elevator.
The fifth servo, an HS-55, is for the aerotow
line release, to be used in the future.
The Multiplex brushless power pack
eliminates electric guesswork and consists
of a Himax HC3528-1000 motor, BL-55
ESC, propeller adapter, and APC 11 x 5.5E
propeller.
The Mentor carries a large Multiplex
three-cell Li-Poly 4800 mAh battery that
gives good flight times and plenty of
power.
Construction mainly consists of foam molded parts with an array
of tough plastic parts. The landing gear is made from pressed
aluminum plate.
Each wing half is molded in two pieces; they sandwich the
composite spar and servo leads. The interior includes ingenious
functionality.
Photos by the author
The tail-dragger configuration is mandatory for the Mentor. Extralong
aluminum gear is strong, and wheels are large enough for
rough-field maneuvering.
Multiplex models molded with Elapor foam are compatible with
regular CA adhesives. So are the plastic parts, which chemically
bond with the foam and adhesive.
catches, for an easy flight-battery swap.
Multiplex uses white molded foam
called “Elapor.” It is different from
expanded polystyrene foam, in that it does
not need special foam-friendly CA glue.
You are instructed to use only regular
medium CA.
The wings are also made from Elapor.
The ailerons are part of the mold and are
hinged with the same material. The wing
halves are stiffened by a carbon-fiber tube
that is also the removable wing joiner. The
wing halves are held together by the same
plate that the wing bolts use to hold the
wing in place.
The cowl and spinner are both made
from Elapor. I had never seen a foam
spinner, but it worked fine on the Himax
motor, which is available from Maxx
Products International. The motor mount
uses two rails that are glued into the foam.
The motor plate then screws into the mount
with four convenient-to-adjust machine
screws that are positioned around the motor
plate.
The landing gear is a prebent piece of
2.5mm-thick aluminum sheet. The two
70mm main wheels use lightweight foam.
Multiplex markets a set of component
10sig2.QXD 8/21/09 1:31 PM Page 43
All you have to do is open the throttle, and
this airplane will be airborne quickly. The
performance is surprising on only 11.1
volts; it handles the wind well
The decals add to this model’s look and help with in-flight orientation. Because the hinges
are molded in, the control surfaces’ effectiveness is greatly enhanced.
Floats are now available for the Mentor. Nothing is better for floating on water than foam, but as fun as this model is to fly, it will be
mostly airborne.
packs that meet several of its models’
needs. The Power Pack includes an
excellent Himax brushless motor, 55-amp
ESC, propeller, and hub assembly. The
company also sells Hitec and Multiplex
radio systems, but I used my JR8103 that
was converted to Spektrum with the 2.4
GHz module/receiver system.
Construction: The manual comprises a
series of high-quality drawings in four
languages. The builder should have some
RC model-building knowledge.
It was helpful to study the pictures and
then make construction lists. To make
assembly even easier, I cut the fourlanguage
instructions and sorted them into
their English components. Then I stapled
each narrative next to the pictures/diagrams
of the assembly.
Wing construction is made easier,
because it consists of two molded panels
that end up as halves. Assembly begins with
releasing the ailerons and flexing their
premolded foam hinge lines. I had to add
servo-extension leads to the aileron servos
so that they would reach the wing center
area.
Before gluing anything, you need to fit
the servo arms to the Hitec HS-81
microservos. This means that you must set
the neutral positions with your radio for
each arm on each servo. You can’t do this
once everything has been glued in place.
The foam cover forms a tube in the wing
panel for the carbon-fiber wing-joiner tube.
It also covers the servo lead/extension and
holds the servo in place.
Take care not to get CA in the tube area,
if you want to be able to easily slide in the
carbon-fiber wing joiner. Also, do not put
the carbon-fiber joiner in too soon, in case
any uncured CA decides to fix it there
permanently!
The fuselage comes in halves that
require a fair degree of preparation before
they can be glued together. Fit the Hitec
HS-322HD servos for the rudder and
elevator servos into recesses on the outside
of the molded fuselage halves and route
their leads inside. Adhere the pushrod outer
tubes into grooves in the outer skin of the
foam parts.
I deviated slightly from the instructions
with the wing bolts. I retapped the plates
out to a 1/4 x 20 thread and used two nylon
Allen-head bolts instead of the supplied
metric threaded bolts. This choice was
prompted by the better availability of
standard hardware.
I installed a Hitec HS-55 servo that
would operate a cable/towline release. This
assembly was buried in one fuselage side.
As did the ailerons, the servo arm needed to
be set with the radio before it was glued in
place. There would be no way to reach this
servo later.
When you are ready to glue the fuselage
halves together, lay everything out in
advance. It is a good idea to enlist a friend
to help with this task. I recruited my wife to
hold the rear section together while I
worked on the middle and front. I applied
the CA quickly and liberally onto one side
and gently squeezed the halves together.
The adhesive did not cure immediately,
especially where there was a lot of it.
Therefore, the halves needed to be held in
several places for roughly five minutes.
Some areas attached instantly, while others
kept coming apart.
Also, excess CA oozed out of the seams
and had to be wiped off quickly. The
process was a bit stressful, but we are still
married. Next time we’ll use more kicker.
To fit the stabilizer and fin, the wing
needs to be bolted in place. It sat square in
the wing seat and was a nice, tight fit. The
Multiplex molds’ accuracy was no more
evident than when the wings lined up
perfectly.
Gluing the tail feathers in place was
simple and quick. Connecting the controls
was easy because of the supplied adjustable
swivel connectors at the horn end. Z-bends
were used at all of the servo-arm ends.
A separate pushrod for the steerable tail
wheel lets you set the rudder trim
independent of the tail-wheel setting. The
tail-wheel assembly and the main landing
gear plate bolt together. The tail-wheel
assembly glues in place. The mains are
machine-screwed using additional landing
gear plates that sandwich and add support to
the preinstalled landing gear plate.
The motor was a good fit on the motor
plate. The plate then fitted perfectly onto the
previously installed motor mounts. You do
have to solder the connectors onto the battery
and the ESC.
A BEC in a large ESC is rarely used to
feed the receiver and servos, because too
much power can go to the motor and then not
enough is left for the onboard radio system. A
separate 1800 mAh NiMH receiver battery
was used for this task. Be sure to disable the
power feed to the receiver from the BEC.
The large 3S 4800 mAh needed to be
retained under the wing to get the correct CG.
The space was not a tight fit and there needed
to be room for cooling air to flow past the
battery pack.
me that used Velcro straps to hold the
pack in place. The Velcro allows the Li-
Poly pack to be removed for
charging/balancing.
Preparing the decals was tough; it took
quite awhile to cut them by hand. However,
they were easy to apply and could be lifted
for alignment purposes, as long as I had not
rubbed them down.
The result is worth the effort. The
graphics not only improved the Mentor’s
look and visibility, but they also covered
the servos on the outside of the fuselage.
Motor and Battery: When you configure
an electric model, it can be difficult to
choose the proper motor, ESC, and
battery. Multiplex has assembled a triedand-
proven optional package that takes
away all of the guesswork. It is optimized
to give you the most out of your airplane.
The configuration is designed to use a 3S
3200-4800 mAh Li-Poly battery pack.
The Mentor Power Pack includes a
Himax 3528-1000 brushless outrunner
motor with the following specifications:
Kv, 1,000; watts, 450; diameter, 35mm;
length, 54mm; and weight, 197 grams.
The pack also contains an APC 11 x 5.5E
propeller, hub, and driver to match the
motor’s shaft size.
Also included is a MULTIcont BL-55
brushless ESC, which has the following
specifications: max continuous current, 55
amps; voltage range, 6-15; maximum
battery, 3S Li-Poly; and a BEC that can
deliver 3 amps. The BEC was not used to
power the five servos.
The motor installation was tested and
measured. Initial results were that it drew
42 amps and 507 watts, showing 11.4
volts at full throttle. The motor turned the
APC propeller at 9,960 rpm. These figures
dropped off a bit after a few seconds.
Flight Report: An electric trainer this
size still tends to be a new thing at the
flying field. A few short taxi runs were all
it took to check the steering, and we were
ready.
I taxied the Mentor to the center of the
runway and aimed it into the wind. The
timer was set to go off after six minutes,
to give a good margin on the battery and
allow for several landing attempts, if
required.
The takeoff run was straight and rapid.
The big motor almost immediately
delivered maximum torque. The tail came
up quickly, and the aircraft was airborne
in approximately 15 feet.
The climb was a bit steep at first, and
then it got even steeper. I put in roughly
six clicks of down-elevator trim before
entering the first turn. No aileron or
rudder trim was required. The initial trim
setting was all that was needed to achieve
level and steady flight.
When I released the controls, the
model flew straight and level. When
entering a turn, some bottom rudder was
required to keep the fuselage nose level
with the horizon.
Varying the throttle settings showed
stable flight behavior down to a gentle
stall. The Mentor would then drop the
nose and regain airspeed in close to 4 feet
of altitude.
I selected half throttle and made a
landing circuit. Once the airplane was
over the runway landing threshold, nearly
two notches of throttle clicks kept the
propeller turning. The wings stayed level,
and the motor was brought back to 0 rpm
approximately a foot above the grass. The
model settled into a smooth landing 10
yards or so later.
The red, black, and silver decals had
orientation. The first flight was good and
was quickly followed by more adventurous
flights that included such exploits as loops,
rolls, and inverted flight. The airplane liked
to skim in on the main wheels rather than be
almost stalled down to a three-point landing.
The Mentor is a delight to fly and easy to
guide around the sky. It loops majestically
and gives a slight barrel roll with ailerons.
Making aileron turns at cruising or high
speed showed no adverse yaw. That is when
the higher wing has more drag than the
lower wing when a rolling action is created
with the ailerons.
Aileron turn entries at slow speed liked a
bit of bottom rudder to be added when
initially going into the turn. This rudder
input can be made manually or mixed in
using a computer radio.
The Multiplex Mentor has the feel of a
low-wing sport airplane—especially when
you send more electrons to the brushless
motor. Get some help putting one of these
models together if you are an inexperienced
builder, and it could appear early in your
RC chronicles.
Even though the Mentor appears
destined only to be a trainer, it can be so
much more. It flies as well as any 40- to 60-
sized sport aircraft and has no nasty habits.
It is a great airplane to fly for fun.
In addition, that aerotow release servo is
buried in the fuselage, just sitting there. You
could use it to pull a ribbon/streamer or tow
a banner, but it was designed to pull a
glider. Now where did I put that Multiplex
Cularis sailplane? (Editor’s note: See page
54 for that story.) MA
Eric Henderson
[email protected]
Manufacturer/Distributor:
Multiplex USA
12115 Paine St.
Poway CA 92064
(858) 748-6948
www.multiplexusa.com
Sources:
Maxx Products International
(847) 438-2233
www.maxxprod.com
Spektrum
(800) 338-4639
www.spektrumrc.com
JR
(800) 338-4639
www.jrradios.com
APC Propeller
(530) 661-0399
www.apcprop.com
Other Published Reviews:
RC Model World: October 2008
Model Airplane News: January 2009
Quiet and Electric Flight International:
January 2009
Edition: Model Aviation - 2009/10
Page Numbers: 42,43,44,46,48,51
42 MODEL AVIATION
ERIC HENDERSON
Plane Talk: Multiplex Mentor Electric ARF
The Mentor is happy flying inverted. This is one way to find out if
the battery is secure; of course it is. This model is fun for a trainer!
A versatile electric trainer
that can take a beating
The model is easy to put together at the field. The two-piece wing
attaches with two nylon bolts. The battery hatch snaps into place.
Multiplex’s Mentor has the appeal of a modern high-wing private aircraft. The absence of wing struts is a testament to the design’s
strength.
SELDOM DO YOU see an RC trainer that
comes in a box showing an aerotow as one
of the main features. But the Multiplex
Mentor is unusual in several ways.
A first look gives the impression of an
orthodox electric-powered RC trainer. Then
you realize that it is not one of those small
foamies with a little gear-driven motor, but
a full-blooded, 64-inch-wingspan airplane.
It is exciting to put together a new
airplane. It is even more thrilling when the
model is slated to have more than one
purpose. The Mentor is touted as a trainer
and a glider-towing tug.
(Editor’s note: Now it can even be made
to fly from water.)
As a trainer, the Mentor is aimed at the
beginner to intermediate modeler/pilot who
is 14 years of age and older. You should
probably also be an experienced RC pilot if
you are going to use this aircraft to aerotow
gliders.
The 40 trainer is one of the most popular
model sizes, and the Mentor uses a clean
and relatively quiet brushless-motor power
pack. In addition, little field-support
equipment is needed other than a battery
charger for the flight pack.
The Mentor is billed as having stable
flying characteristics and a low stall
(minimum airspeed) for easy landings.
Those things are desirable in a trainer.
When finished, the main wing is a twopart
structure with a removable carbon-fiber
spar joiner for easy transport. The canopy
hatch is removable with quick-release
10sig2.QXD 8/21/09 2:05 PM Page 42
October 2009 43
Five servos are used: two for the ailerons
and one each for the rudder and elevator.
The fifth servo, an HS-55, is for the aerotow
line release, to be used in the future.
The Multiplex brushless power pack
eliminates electric guesswork and consists
of a Himax HC3528-1000 motor, BL-55
ESC, propeller adapter, and APC 11 x 5.5E
propeller.
The Mentor carries a large Multiplex
three-cell Li-Poly 4800 mAh battery that
gives good flight times and plenty of
power.
Construction mainly consists of foam molded parts with an array
of tough plastic parts. The landing gear is made from pressed
aluminum plate.
Each wing half is molded in two pieces; they sandwich the
composite spar and servo leads. The interior includes ingenious
functionality.
Photos by the author
The tail-dragger configuration is mandatory for the Mentor. Extralong
aluminum gear is strong, and wheels are large enough for
rough-field maneuvering.
Multiplex models molded with Elapor foam are compatible with
regular CA adhesives. So are the plastic parts, which chemically
bond with the foam and adhesive.
catches, for an easy flight-battery swap.
Multiplex uses white molded foam
called “Elapor.” It is different from
expanded polystyrene foam, in that it does
not need special foam-friendly CA glue.
You are instructed to use only regular
medium CA.
The wings are also made from Elapor.
The ailerons are part of the mold and are
hinged with the same material. The wing
halves are stiffened by a carbon-fiber tube
that is also the removable wing joiner. The
wing halves are held together by the same
plate that the wing bolts use to hold the
wing in place.
The cowl and spinner are both made
from Elapor. I had never seen a foam
spinner, but it worked fine on the Himax
motor, which is available from Maxx
Products International. The motor mount
uses two rails that are glued into the foam.
The motor plate then screws into the mount
with four convenient-to-adjust machine
screws that are positioned around the motor
plate.
The landing gear is a prebent piece of
2.5mm-thick aluminum sheet. The two
70mm main wheels use lightweight foam.
Multiplex markets a set of component
10sig2.QXD 8/21/09 1:31 PM Page 43
All you have to do is open the throttle, and
this airplane will be airborne quickly. The
performance is surprising on only 11.1
volts; it handles the wind well
The decals add to this model’s look and help with in-flight orientation. Because the hinges
are molded in, the control surfaces’ effectiveness is greatly enhanced.
Floats are now available for the Mentor. Nothing is better for floating on water than foam, but as fun as this model is to fly, it will be
mostly airborne.
packs that meet several of its models’
needs. The Power Pack includes an
excellent Himax brushless motor, 55-amp
ESC, propeller, and hub assembly. The
company also sells Hitec and Multiplex
radio systems, but I used my JR8103 that
was converted to Spektrum with the 2.4
GHz module/receiver system.
Construction: The manual comprises a
series of high-quality drawings in four
languages. The builder should have some
RC model-building knowledge.
It was helpful to study the pictures and
then make construction lists. To make
assembly even easier, I cut the fourlanguage
instructions and sorted them into
their English components. Then I stapled
each narrative next to the pictures/diagrams
of the assembly.
Wing construction is made easier,
because it consists of two molded panels
that end up as halves. Assembly begins with
releasing the ailerons and flexing their
premolded foam hinge lines. I had to add
servo-extension leads to the aileron servos
so that they would reach the wing center
area.
Before gluing anything, you need to fit
the servo arms to the Hitec HS-81
microservos. This means that you must set
the neutral positions with your radio for
each arm on each servo. You can’t do this
once everything has been glued in place.
The foam cover forms a tube in the wing
panel for the carbon-fiber wing-joiner tube.
It also covers the servo lead/extension and
holds the servo in place.
Take care not to get CA in the tube area,
if you want to be able to easily slide in the
carbon-fiber wing joiner. Also, do not put
the carbon-fiber joiner in too soon, in case
any uncured CA decides to fix it there
permanently!
The fuselage comes in halves that
require a fair degree of preparation before
they can be glued together. Fit the Hitec
HS-322HD servos for the rudder and
elevator servos into recesses on the outside
of the molded fuselage halves and route
their leads inside. Adhere the pushrod outer
tubes into grooves in the outer skin of the
foam parts.
I deviated slightly from the instructions
with the wing bolts. I retapped the plates
out to a 1/4 x 20 thread and used two nylon
Allen-head bolts instead of the supplied
metric threaded bolts. This choice was
prompted by the better availability of
standard hardware.
I installed a Hitec HS-55 servo that
would operate a cable/towline release. This
assembly was buried in one fuselage side.
As did the ailerons, the servo arm needed to
be set with the radio before it was glued in
place. There would be no way to reach this
servo later.
When you are ready to glue the fuselage
halves together, lay everything out in
advance. It is a good idea to enlist a friend
to help with this task. I recruited my wife to
hold the rear section together while I
worked on the middle and front. I applied
the CA quickly and liberally onto one side
and gently squeezed the halves together.
The adhesive did not cure immediately,
especially where there was a lot of it.
Therefore, the halves needed to be held in
several places for roughly five minutes.
Some areas attached instantly, while others
kept coming apart.
Also, excess CA oozed out of the seams
and had to be wiped off quickly. The
process was a bit stressful, but we are still
married. Next time we’ll use more kicker.
To fit the stabilizer and fin, the wing
needs to be bolted in place. It sat square in
the wing seat and was a nice, tight fit. The
Multiplex molds’ accuracy was no more
evident than when the wings lined up
perfectly.
Gluing the tail feathers in place was
simple and quick. Connecting the controls
was easy because of the supplied adjustable
swivel connectors at the horn end. Z-bends
were used at all of the servo-arm ends.
A separate pushrod for the steerable tail
wheel lets you set the rudder trim
independent of the tail-wheel setting. The
tail-wheel assembly and the main landing
gear plate bolt together. The tail-wheel
assembly glues in place. The mains are
machine-screwed using additional landing
gear plates that sandwich and add support to
the preinstalled landing gear plate.
The motor was a good fit on the motor
plate. The plate then fitted perfectly onto the
previously installed motor mounts. You do
have to solder the connectors onto the battery
and the ESC.
A BEC in a large ESC is rarely used to
feed the receiver and servos, because too
much power can go to the motor and then not
enough is left for the onboard radio system. A
separate 1800 mAh NiMH receiver battery
was used for this task. Be sure to disable the
power feed to the receiver from the BEC.
The large 3S 4800 mAh needed to be
retained under the wing to get the correct CG.
The space was not a tight fit and there needed
to be room for cooling air to flow past the
battery pack.
me that used Velcro straps to hold the
pack in place. The Velcro allows the Li-
Poly pack to be removed for
charging/balancing.
Preparing the decals was tough; it took
quite awhile to cut them by hand. However,
they were easy to apply and could be lifted
for alignment purposes, as long as I had not
rubbed them down.
The result is worth the effort. The
graphics not only improved the Mentor’s
look and visibility, but they also covered
the servos on the outside of the fuselage.
Motor and Battery: When you configure
an electric model, it can be difficult to
choose the proper motor, ESC, and
battery. Multiplex has assembled a triedand-
proven optional package that takes
away all of the guesswork. It is optimized
to give you the most out of your airplane.
The configuration is designed to use a 3S
3200-4800 mAh Li-Poly battery pack.
The Mentor Power Pack includes a
Himax 3528-1000 brushless outrunner
motor with the following specifications:
Kv, 1,000; watts, 450; diameter, 35mm;
length, 54mm; and weight, 197 grams.
The pack also contains an APC 11 x 5.5E
propeller, hub, and driver to match the
motor’s shaft size.
Also included is a MULTIcont BL-55
brushless ESC, which has the following
specifications: max continuous current, 55
amps; voltage range, 6-15; maximum
battery, 3S Li-Poly; and a BEC that can
deliver 3 amps. The BEC was not used to
power the five servos.
The motor installation was tested and
measured. Initial results were that it drew
42 amps and 507 watts, showing 11.4
volts at full throttle. The motor turned the
APC propeller at 9,960 rpm. These figures
dropped off a bit after a few seconds.
Flight Report: An electric trainer this
size still tends to be a new thing at the
flying field. A few short taxi runs were all
it took to check the steering, and we were
ready.
I taxied the Mentor to the center of the
runway and aimed it into the wind. The
timer was set to go off after six minutes,
to give a good margin on the battery and
allow for several landing attempts, if
required.
The takeoff run was straight and rapid.
The big motor almost immediately
delivered maximum torque. The tail came
up quickly, and the aircraft was airborne
in approximately 15 feet.
The climb was a bit steep at first, and
then it got even steeper. I put in roughly
six clicks of down-elevator trim before
entering the first turn. No aileron or
rudder trim was required. The initial trim
setting was all that was needed to achieve
level and steady flight.
When I released the controls, the
model flew straight and level. When
entering a turn, some bottom rudder was
required to keep the fuselage nose level
with the horizon.
Varying the throttle settings showed
stable flight behavior down to a gentle
stall. The Mentor would then drop the
nose and regain airspeed in close to 4 feet
of altitude.
I selected half throttle and made a
landing circuit. Once the airplane was
over the runway landing threshold, nearly
two notches of throttle clicks kept the
propeller turning. The wings stayed level,
and the motor was brought back to 0 rpm
approximately a foot above the grass. The
model settled into a smooth landing 10
yards or so later.
The red, black, and silver decals had
orientation. The first flight was good and
was quickly followed by more adventurous
flights that included such exploits as loops,
rolls, and inverted flight. The airplane liked
to skim in on the main wheels rather than be
almost stalled down to a three-point landing.
The Mentor is a delight to fly and easy to
guide around the sky. It loops majestically
and gives a slight barrel roll with ailerons.
Making aileron turns at cruising or high
speed showed no adverse yaw. That is when
the higher wing has more drag than the
lower wing when a rolling action is created
with the ailerons.
Aileron turn entries at slow speed liked a
bit of bottom rudder to be added when
initially going into the turn. This rudder
input can be made manually or mixed in
using a computer radio.
The Multiplex Mentor has the feel of a
low-wing sport airplane—especially when
you send more electrons to the brushless
motor. Get some help putting one of these
models together if you are an inexperienced
builder, and it could appear early in your
RC chronicles.
Even though the Mentor appears
destined only to be a trainer, it can be so
much more. It flies as well as any 40- to 60-
sized sport aircraft and has no nasty habits.
It is a great airplane to fly for fun.
In addition, that aerotow release servo is
buried in the fuselage, just sitting there. You
could use it to pull a ribbon/streamer or tow
a banner, but it was designed to pull a
glider. Now where did I put that Multiplex
Cularis sailplane? (Editor’s note: See page
54 for that story.) MA
Eric Henderson
[email protected]
Manufacturer/Distributor:
Multiplex USA
12115 Paine St.
Poway CA 92064
(858) 748-6948
www.multiplexusa.com
Sources:
Maxx Products International
(847) 438-2233
www.maxxprod.com
Spektrum
(800) 338-4639
www.spektrumrc.com
JR
(800) 338-4639
www.jrradios.com
APC Propeller
(530) 661-0399
www.apcprop.com
Other Published Reviews:
RC Model World: October 2008
Model Airplane News: January 2009
Quiet and Electric Flight International:
January 2009
Edition: Model Aviation - 2009/10
Page Numbers: 42,43,44,46,48,51
42 MODEL AVIATION
ERIC HENDERSON
Plane Talk: Multiplex Mentor Electric ARF
The Mentor is happy flying inverted. This is one way to find out if
the battery is secure; of course it is. This model is fun for a trainer!
A versatile electric trainer
that can take a beating
The model is easy to put together at the field. The two-piece wing
attaches with two nylon bolts. The battery hatch snaps into place.
Multiplex’s Mentor has the appeal of a modern high-wing private aircraft. The absence of wing struts is a testament to the design’s
strength.
SELDOM DO YOU see an RC trainer that
comes in a box showing an aerotow as one
of the main features. But the Multiplex
Mentor is unusual in several ways.
A first look gives the impression of an
orthodox electric-powered RC trainer. Then
you realize that it is not one of those small
foamies with a little gear-driven motor, but
a full-blooded, 64-inch-wingspan airplane.
It is exciting to put together a new
airplane. It is even more thrilling when the
model is slated to have more than one
purpose. The Mentor is touted as a trainer
and a glider-towing tug.
(Editor’s note: Now it can even be made
to fly from water.)
As a trainer, the Mentor is aimed at the
beginner to intermediate modeler/pilot who
is 14 years of age and older. You should
probably also be an experienced RC pilot if
you are going to use this aircraft to aerotow
gliders.
The 40 trainer is one of the most popular
model sizes, and the Mentor uses a clean
and relatively quiet brushless-motor power
pack. In addition, little field-support
equipment is needed other than a battery
charger for the flight pack.
The Mentor is billed as having stable
flying characteristics and a low stall
(minimum airspeed) for easy landings.
Those things are desirable in a trainer.
When finished, the main wing is a twopart
structure with a removable carbon-fiber
spar joiner for easy transport. The canopy
hatch is removable with quick-release
10sig2.QXD 8/21/09 2:05 PM Page 42
October 2009 43
Five servos are used: two for the ailerons
and one each for the rudder and elevator.
The fifth servo, an HS-55, is for the aerotow
line release, to be used in the future.
The Multiplex brushless power pack
eliminates electric guesswork and consists
of a Himax HC3528-1000 motor, BL-55
ESC, propeller adapter, and APC 11 x 5.5E
propeller.
The Mentor carries a large Multiplex
three-cell Li-Poly 4800 mAh battery that
gives good flight times and plenty of
power.
Construction mainly consists of foam molded parts with an array
of tough plastic parts. The landing gear is made from pressed
aluminum plate.
Each wing half is molded in two pieces; they sandwich the
composite spar and servo leads. The interior includes ingenious
functionality.
Photos by the author
The tail-dragger configuration is mandatory for the Mentor. Extralong
aluminum gear is strong, and wheels are large enough for
rough-field maneuvering.
Multiplex models molded with Elapor foam are compatible with
regular CA adhesives. So are the plastic parts, which chemically
bond with the foam and adhesive.
catches, for an easy flight-battery swap.
Multiplex uses white molded foam
called “Elapor.” It is different from
expanded polystyrene foam, in that it does
not need special foam-friendly CA glue.
You are instructed to use only regular
medium CA.
The wings are also made from Elapor.
The ailerons are part of the mold and are
hinged with the same material. The wing
halves are stiffened by a carbon-fiber tube
that is also the removable wing joiner. The
wing halves are held together by the same
plate that the wing bolts use to hold the
wing in place.
The cowl and spinner are both made
from Elapor. I had never seen a foam
spinner, but it worked fine on the Himax
motor, which is available from Maxx
Products International. The motor mount
uses two rails that are glued into the foam.
The motor plate then screws into the mount
with four convenient-to-adjust machine
screws that are positioned around the motor
plate.
The landing gear is a prebent piece of
2.5mm-thick aluminum sheet. The two
70mm main wheels use lightweight foam.
Multiplex markets a set of component
10sig2.QXD 8/21/09 1:31 PM Page 43
All you have to do is open the throttle, and
this airplane will be airborne quickly. The
performance is surprising on only 11.1
volts; it handles the wind well
The decals add to this model’s look and help with in-flight orientation. Because the hinges
are molded in, the control surfaces’ effectiveness is greatly enhanced.
Floats are now available for the Mentor. Nothing is better for floating on water than foam, but as fun as this model is to fly, it will be
mostly airborne.
packs that meet several of its models’
needs. The Power Pack includes an
excellent Himax brushless motor, 55-amp
ESC, propeller, and hub assembly. The
company also sells Hitec and Multiplex
radio systems, but I used my JR8103 that
was converted to Spektrum with the 2.4
GHz module/receiver system.
Construction: The manual comprises a
series of high-quality drawings in four
languages. The builder should have some
RC model-building knowledge.
It was helpful to study the pictures and
then make construction lists. To make
assembly even easier, I cut the fourlanguage
instructions and sorted them into
their English components. Then I stapled
each narrative next to the pictures/diagrams
of the assembly.
Wing construction is made easier,
because it consists of two molded panels
that end up as halves. Assembly begins with
releasing the ailerons and flexing their
premolded foam hinge lines. I had to add
servo-extension leads to the aileron servos
so that they would reach the wing center
area.
Before gluing anything, you need to fit
the servo arms to the Hitec HS-81
microservos. This means that you must set
the neutral positions with your radio for
each arm on each servo. You can’t do this
once everything has been glued in place.
The foam cover forms a tube in the wing
panel for the carbon-fiber wing-joiner tube.
It also covers the servo lead/extension and
holds the servo in place.
Take care not to get CA in the tube area,
if you want to be able to easily slide in the
carbon-fiber wing joiner. Also, do not put
the carbon-fiber joiner in too soon, in case
any uncured CA decides to fix it there
permanently!
The fuselage comes in halves that
require a fair degree of preparation before
they can be glued together. Fit the Hitec
HS-322HD servos for the rudder and
elevator servos into recesses on the outside
of the molded fuselage halves and route
their leads inside. Adhere the pushrod outer
tubes into grooves in the outer skin of the
foam parts.
I deviated slightly from the instructions
with the wing bolts. I retapped the plates
out to a 1/4 x 20 thread and used two nylon
Allen-head bolts instead of the supplied
metric threaded bolts. This choice was
prompted by the better availability of
standard hardware.
I installed a Hitec HS-55 servo that
would operate a cable/towline release. This
assembly was buried in one fuselage side.
As did the ailerons, the servo arm needed to
be set with the radio before it was glued in
place. There would be no way to reach this
servo later.
When you are ready to glue the fuselage
halves together, lay everything out in
advance. It is a good idea to enlist a friend
to help with this task. I recruited my wife to
hold the rear section together while I
worked on the middle and front. I applied
the CA quickly and liberally onto one side
and gently squeezed the halves together.
The adhesive did not cure immediately,
especially where there was a lot of it.
Therefore, the halves needed to be held in
several places for roughly five minutes.
Some areas attached instantly, while others
kept coming apart.
Also, excess CA oozed out of the seams
and had to be wiped off quickly. The
process was a bit stressful, but we are still
married. Next time we’ll use more kicker.
To fit the stabilizer and fin, the wing
needs to be bolted in place. It sat square in
the wing seat and was a nice, tight fit. The
Multiplex molds’ accuracy was no more
evident than when the wings lined up
perfectly.
Gluing the tail feathers in place was
simple and quick. Connecting the controls
was easy because of the supplied adjustable
swivel connectors at the horn end. Z-bends
were used at all of the servo-arm ends.
A separate pushrod for the steerable tail
wheel lets you set the rudder trim
independent of the tail-wheel setting. The
tail-wheel assembly and the main landing
gear plate bolt together. The tail-wheel
assembly glues in place. The mains are
machine-screwed using additional landing
gear plates that sandwich and add support to
the preinstalled landing gear plate.
The motor was a good fit on the motor
plate. The plate then fitted perfectly onto the
previously installed motor mounts. You do
have to solder the connectors onto the battery
and the ESC.
A BEC in a large ESC is rarely used to
feed the receiver and servos, because too
much power can go to the motor and then not
enough is left for the onboard radio system. A
separate 1800 mAh NiMH receiver battery
was used for this task. Be sure to disable the
power feed to the receiver from the BEC.
The large 3S 4800 mAh needed to be
retained under the wing to get the correct CG.
The space was not a tight fit and there needed
to be room for cooling air to flow past the
battery pack.
me that used Velcro straps to hold the
pack in place. The Velcro allows the Li-
Poly pack to be removed for
charging/balancing.
Preparing the decals was tough; it took
quite awhile to cut them by hand. However,
they were easy to apply and could be lifted
for alignment purposes, as long as I had not
rubbed them down.
The result is worth the effort. The
graphics not only improved the Mentor’s
look and visibility, but they also covered
the servos on the outside of the fuselage.
Motor and Battery: When you configure
an electric model, it can be difficult to
choose the proper motor, ESC, and
battery. Multiplex has assembled a triedand-
proven optional package that takes
away all of the guesswork. It is optimized
to give you the most out of your airplane.
The configuration is designed to use a 3S
3200-4800 mAh Li-Poly battery pack.
The Mentor Power Pack includes a
Himax 3528-1000 brushless outrunner
motor with the following specifications:
Kv, 1,000; watts, 450; diameter, 35mm;
length, 54mm; and weight, 197 grams.
The pack also contains an APC 11 x 5.5E
propeller, hub, and driver to match the
motor’s shaft size.
Also included is a MULTIcont BL-55
brushless ESC, which has the following
specifications: max continuous current, 55
amps; voltage range, 6-15; maximum
battery, 3S Li-Poly; and a BEC that can
deliver 3 amps. The BEC was not used to
power the five servos.
The motor installation was tested and
measured. Initial results were that it drew
42 amps and 507 watts, showing 11.4
volts at full throttle. The motor turned the
APC propeller at 9,960 rpm. These figures
dropped off a bit after a few seconds.
Flight Report: An electric trainer this
size still tends to be a new thing at the
flying field. A few short taxi runs were all
it took to check the steering, and we were
ready.
I taxied the Mentor to the center of the
runway and aimed it into the wind. The
timer was set to go off after six minutes,
to give a good margin on the battery and
allow for several landing attempts, if
required.
The takeoff run was straight and rapid.
The big motor almost immediately
delivered maximum torque. The tail came
up quickly, and the aircraft was airborne
in approximately 15 feet.
The climb was a bit steep at first, and
then it got even steeper. I put in roughly
six clicks of down-elevator trim before
entering the first turn. No aileron or
rudder trim was required. The initial trim
setting was all that was needed to achieve
level and steady flight.
When I released the controls, the
model flew straight and level. When
entering a turn, some bottom rudder was
required to keep the fuselage nose level
with the horizon.
Varying the throttle settings showed
stable flight behavior down to a gentle
stall. The Mentor would then drop the
nose and regain airspeed in close to 4 feet
of altitude.
I selected half throttle and made a
landing circuit. Once the airplane was
over the runway landing threshold, nearly
two notches of throttle clicks kept the
propeller turning. The wings stayed level,
and the motor was brought back to 0 rpm
approximately a foot above the grass. The
model settled into a smooth landing 10
yards or so later.
The red, black, and silver decals had
orientation. The first flight was good and
was quickly followed by more adventurous
flights that included such exploits as loops,
rolls, and inverted flight. The airplane liked
to skim in on the main wheels rather than be
almost stalled down to a three-point landing.
The Mentor is a delight to fly and easy to
guide around the sky. It loops majestically
and gives a slight barrel roll with ailerons.
Making aileron turns at cruising or high
speed showed no adverse yaw. That is when
the higher wing has more drag than the
lower wing when a rolling action is created
with the ailerons.
Aileron turn entries at slow speed liked a
bit of bottom rudder to be added when
initially going into the turn. This rudder
input can be made manually or mixed in
using a computer radio.
The Multiplex Mentor has the feel of a
low-wing sport airplane—especially when
you send more electrons to the brushless
motor. Get some help putting one of these
models together if you are an inexperienced
builder, and it could appear early in your
RC chronicles.
Even though the Mentor appears
destined only to be a trainer, it can be so
much more. It flies as well as any 40- to 60-
sized sport aircraft and has no nasty habits.
It is a great airplane to fly for fun.
In addition, that aerotow release servo is
buried in the fuselage, just sitting there. You
could use it to pull a ribbon/streamer or tow
a banner, but it was designed to pull a
glider. Now where did I put that Multiplex
Cularis sailplane? (Editor’s note: See page
54 for that story.) MA
Eric Henderson
[email protected]
Manufacturer/Distributor:
Multiplex USA
12115 Paine St.
Poway CA 92064
(858) 748-6948
www.multiplexusa.com
Sources:
Maxx Products International
(847) 438-2233
www.maxxprod.com
Spektrum
(800) 338-4639
www.spektrumrc.com
JR
(800) 338-4639
www.jrradios.com
APC Propeller
(530) 661-0399
www.apcprop.com
Other Published Reviews:
RC Model World: October 2008
Model Airplane News: January 2009
Quiet and Electric Flight International:
January 2009
Edition: Model Aviation - 2009/10
Page Numbers: 42,43,44,46,48,51
42 MODEL AVIATION
ERIC HENDERSON
Plane Talk: Multiplex Mentor Electric ARF
The Mentor is happy flying inverted. This is one way to find out if
the battery is secure; of course it is. This model is fun for a trainer!
A versatile electric trainer
that can take a beating
The model is easy to put together at the field. The two-piece wing
attaches with two nylon bolts. The battery hatch snaps into place.
Multiplex’s Mentor has the appeal of a modern high-wing private aircraft. The absence of wing struts is a testament to the design’s
strength.
SELDOM DO YOU see an RC trainer that
comes in a box showing an aerotow as one
of the main features. But the Multiplex
Mentor is unusual in several ways.
A first look gives the impression of an
orthodox electric-powered RC trainer. Then
you realize that it is not one of those small
foamies with a little gear-driven motor, but
a full-blooded, 64-inch-wingspan airplane.
It is exciting to put together a new
airplane. It is even more thrilling when the
model is slated to have more than one
purpose. The Mentor is touted as a trainer
and a glider-towing tug.
(Editor’s note: Now it can even be made
to fly from water.)
As a trainer, the Mentor is aimed at the
beginner to intermediate modeler/pilot who
is 14 years of age and older. You should
probably also be an experienced RC pilot if
you are going to use this aircraft to aerotow
gliders.
The 40 trainer is one of the most popular
model sizes, and the Mentor uses a clean
and relatively quiet brushless-motor power
pack. In addition, little field-support
equipment is needed other than a battery
charger for the flight pack.
The Mentor is billed as having stable
flying characteristics and a low stall
(minimum airspeed) for easy landings.
Those things are desirable in a trainer.
When finished, the main wing is a twopart
structure with a removable carbon-fiber
spar joiner for easy transport. The canopy
hatch is removable with quick-release
10sig2.QXD 8/21/09 2:05 PM Page 42
October 2009 43
Five servos are used: two for the ailerons
and one each for the rudder and elevator.
The fifth servo, an HS-55, is for the aerotow
line release, to be used in the future.
The Multiplex brushless power pack
eliminates electric guesswork and consists
of a Himax HC3528-1000 motor, BL-55
ESC, propeller adapter, and APC 11 x 5.5E
propeller.
The Mentor carries a large Multiplex
three-cell Li-Poly 4800 mAh battery that
gives good flight times and plenty of
power.
Construction mainly consists of foam molded parts with an array
of tough plastic parts. The landing gear is made from pressed
aluminum plate.
Each wing half is molded in two pieces; they sandwich the
composite spar and servo leads. The interior includes ingenious
functionality.
Photos by the author
The tail-dragger configuration is mandatory for the Mentor. Extralong
aluminum gear is strong, and wheels are large enough for
rough-field maneuvering.
Multiplex models molded with Elapor foam are compatible with
regular CA adhesives. So are the plastic parts, which chemically
bond with the foam and adhesive.
catches, for an easy flight-battery swap.
Multiplex uses white molded foam
called “Elapor.” It is different from
expanded polystyrene foam, in that it does
not need special foam-friendly CA glue.
You are instructed to use only regular
medium CA.
The wings are also made from Elapor.
The ailerons are part of the mold and are
hinged with the same material. The wing
halves are stiffened by a carbon-fiber tube
that is also the removable wing joiner. The
wing halves are held together by the same
plate that the wing bolts use to hold the
wing in place.
The cowl and spinner are both made
from Elapor. I had never seen a foam
spinner, but it worked fine on the Himax
motor, which is available from Maxx
Products International. The motor mount
uses two rails that are glued into the foam.
The motor plate then screws into the mount
with four convenient-to-adjust machine
screws that are positioned around the motor
plate.
The landing gear is a prebent piece of
2.5mm-thick aluminum sheet. The two
70mm main wheels use lightweight foam.
Multiplex markets a set of component
10sig2.QXD 8/21/09 1:31 PM Page 43
All you have to do is open the throttle, and
this airplane will be airborne quickly. The
performance is surprising on only 11.1
volts; it handles the wind well
The decals add to this model’s look and help with in-flight orientation. Because the hinges
are molded in, the control surfaces’ effectiveness is greatly enhanced.
Floats are now available for the Mentor. Nothing is better for floating on water than foam, but as fun as this model is to fly, it will be
mostly airborne.
packs that meet several of its models’
needs. The Power Pack includes an
excellent Himax brushless motor, 55-amp
ESC, propeller, and hub assembly. The
company also sells Hitec and Multiplex
radio systems, but I used my JR8103 that
was converted to Spektrum with the 2.4
GHz module/receiver system.
Construction: The manual comprises a
series of high-quality drawings in four
languages. The builder should have some
RC model-building knowledge.
It was helpful to study the pictures and
then make construction lists. To make
assembly even easier, I cut the fourlanguage
instructions and sorted them into
their English components. Then I stapled
each narrative next to the pictures/diagrams
of the assembly.
Wing construction is made easier,
because it consists of two molded panels
that end up as halves. Assembly begins with
releasing the ailerons and flexing their
premolded foam hinge lines. I had to add
servo-extension leads to the aileron servos
so that they would reach the wing center
area.
Before gluing anything, you need to fit
the servo arms to the Hitec HS-81
microservos. This means that you must set
the neutral positions with your radio for
each arm on each servo. You can’t do this
once everything has been glued in place.
The foam cover forms a tube in the wing
panel for the carbon-fiber wing-joiner tube.
It also covers the servo lead/extension and
holds the servo in place.
Take care not to get CA in the tube area,
if you want to be able to easily slide in the
carbon-fiber wing joiner. Also, do not put
the carbon-fiber joiner in too soon, in case
any uncured CA decides to fix it there
permanently!
The fuselage comes in halves that
require a fair degree of preparation before
they can be glued together. Fit the Hitec
HS-322HD servos for the rudder and
elevator servos into recesses on the outside
of the molded fuselage halves and route
their leads inside. Adhere the pushrod outer
tubes into grooves in the outer skin of the
foam parts.
I deviated slightly from the instructions
with the wing bolts. I retapped the plates
out to a 1/4 x 20 thread and used two nylon
Allen-head bolts instead of the supplied
metric threaded bolts. This choice was
prompted by the better availability of
standard hardware.
I installed a Hitec HS-55 servo that
would operate a cable/towline release. This
assembly was buried in one fuselage side.
As did the ailerons, the servo arm needed to
be set with the radio before it was glued in
place. There would be no way to reach this
servo later.
When you are ready to glue the fuselage
halves together, lay everything out in
advance. It is a good idea to enlist a friend
to help with this task. I recruited my wife to
hold the rear section together while I
worked on the middle and front. I applied
the CA quickly and liberally onto one side
and gently squeezed the halves together.
The adhesive did not cure immediately,
especially where there was a lot of it.
Therefore, the halves needed to be held in
several places for roughly five minutes.
Some areas attached instantly, while others
kept coming apart.
Also, excess CA oozed out of the seams
and had to be wiped off quickly. The
process was a bit stressful, but we are still
married. Next time we’ll use more kicker.
To fit the stabilizer and fin, the wing
needs to be bolted in place. It sat square in
the wing seat and was a nice, tight fit. The
Multiplex molds’ accuracy was no more
evident than when the wings lined up
perfectly.
Gluing the tail feathers in place was
simple and quick. Connecting the controls
was easy because of the supplied adjustable
swivel connectors at the horn end. Z-bends
were used at all of the servo-arm ends.
A separate pushrod for the steerable tail
wheel lets you set the rudder trim
independent of the tail-wheel setting. The
tail-wheel assembly and the main landing
gear plate bolt together. The tail-wheel
assembly glues in place. The mains are
machine-screwed using additional landing
gear plates that sandwich and add support to
the preinstalled landing gear plate.
The motor was a good fit on the motor
plate. The plate then fitted perfectly onto the
previously installed motor mounts. You do
have to solder the connectors onto the battery
and the ESC.
A BEC in a large ESC is rarely used to
feed the receiver and servos, because too
much power can go to the motor and then not
enough is left for the onboard radio system. A
separate 1800 mAh NiMH receiver battery
was used for this task. Be sure to disable the
power feed to the receiver from the BEC.
The large 3S 4800 mAh needed to be
retained under the wing to get the correct CG.
The space was not a tight fit and there needed
to be room for cooling air to flow past the
battery pack.
me that used Velcro straps to hold the
pack in place. The Velcro allows the Li-
Poly pack to be removed for
charging/balancing.
Preparing the decals was tough; it took
quite awhile to cut them by hand. However,
they were easy to apply and could be lifted
for alignment purposes, as long as I had not
rubbed them down.
The result is worth the effort. The
graphics not only improved the Mentor’s
look and visibility, but they also covered
the servos on the outside of the fuselage.
Motor and Battery: When you configure
an electric model, it can be difficult to
choose the proper motor, ESC, and
battery. Multiplex has assembled a triedand-
proven optional package that takes
away all of the guesswork. It is optimized
to give you the most out of your airplane.
The configuration is designed to use a 3S
3200-4800 mAh Li-Poly battery pack.
The Mentor Power Pack includes a
Himax 3528-1000 brushless outrunner
motor with the following specifications:
Kv, 1,000; watts, 450; diameter, 35mm;
length, 54mm; and weight, 197 grams.
The pack also contains an APC 11 x 5.5E
propeller, hub, and driver to match the
motor’s shaft size.
Also included is a MULTIcont BL-55
brushless ESC, which has the following
specifications: max continuous current, 55
amps; voltage range, 6-15; maximum
battery, 3S Li-Poly; and a BEC that can
deliver 3 amps. The BEC was not used to
power the five servos.
The motor installation was tested and
measured. Initial results were that it drew
42 amps and 507 watts, showing 11.4
volts at full throttle. The motor turned the
APC propeller at 9,960 rpm. These figures
dropped off a bit after a few seconds.
Flight Report: An electric trainer this
size still tends to be a new thing at the
flying field. A few short taxi runs were all
it took to check the steering, and we were
ready.
I taxied the Mentor to the center of the
runway and aimed it into the wind. The
timer was set to go off after six minutes,
to give a good margin on the battery and
allow for several landing attempts, if
required.
The takeoff run was straight and rapid.
The big motor almost immediately
delivered maximum torque. The tail came
up quickly, and the aircraft was airborne
in approximately 15 feet.
The climb was a bit steep at first, and
then it got even steeper. I put in roughly
six clicks of down-elevator trim before
entering the first turn. No aileron or
rudder trim was required. The initial trim
setting was all that was needed to achieve
level and steady flight.
When I released the controls, the
model flew straight and level. When
entering a turn, some bottom rudder was
required to keep the fuselage nose level
with the horizon.
Varying the throttle settings showed
stable flight behavior down to a gentle
stall. The Mentor would then drop the
nose and regain airspeed in close to 4 feet
of altitude.
I selected half throttle and made a
landing circuit. Once the airplane was
over the runway landing threshold, nearly
two notches of throttle clicks kept the
propeller turning. The wings stayed level,
and the motor was brought back to 0 rpm
approximately a foot above the grass. The
model settled into a smooth landing 10
yards or so later.
The red, black, and silver decals had
orientation. The first flight was good and
was quickly followed by more adventurous
flights that included such exploits as loops,
rolls, and inverted flight. The airplane liked
to skim in on the main wheels rather than be
almost stalled down to a three-point landing.
The Mentor is a delight to fly and easy to
guide around the sky. It loops majestically
and gives a slight barrel roll with ailerons.
Making aileron turns at cruising or high
speed showed no adverse yaw. That is when
the higher wing has more drag than the
lower wing when a rolling action is created
with the ailerons.
Aileron turn entries at slow speed liked a
bit of bottom rudder to be added when
initially going into the turn. This rudder
input can be made manually or mixed in
using a computer radio.
The Multiplex Mentor has the feel of a
low-wing sport airplane—especially when
you send more electrons to the brushless
motor. Get some help putting one of these
models together if you are an inexperienced
builder, and it could appear early in your
RC chronicles.
Even though the Mentor appears
destined only to be a trainer, it can be so
much more. It flies as well as any 40- to 60-
sized sport aircraft and has no nasty habits.
It is a great airplane to fly for fun.
In addition, that aerotow release servo is
buried in the fuselage, just sitting there. You
could use it to pull a ribbon/streamer or tow
a banner, but it was designed to pull a
glider. Now where did I put that Multiplex
Cularis sailplane? (Editor’s note: See page
54 for that story.) MA
Eric Henderson
[email protected]
Manufacturer/Distributor:
Multiplex USA
12115 Paine St.
Poway CA 92064
(858) 748-6948
www.multiplexusa.com
Sources:
Maxx Products International
(847) 438-2233
www.maxxprod.com
Spektrum
(800) 338-4639
www.spektrumrc.com
JR
(800) 338-4639
www.jrradios.com
APC Propeller
(530) 661-0399
www.apcprop.com
Other Published Reviews:
RC Model World: October 2008
Model Airplane News: January 2009
Quiet and Electric Flight International:
January 2009
Edition: Model Aviation - 2009/10
Page Numbers: 42,43,44,46,48,51
42 MODEL AVIATION
ERIC HENDERSON
Plane Talk: Multiplex Mentor Electric ARF
The Mentor is happy flying inverted. This is one way to find out if
the battery is secure; of course it is. This model is fun for a trainer!
A versatile electric trainer
that can take a beating
The model is easy to put together at the field. The two-piece wing
attaches with two nylon bolts. The battery hatch snaps into place.
Multiplex’s Mentor has the appeal of a modern high-wing private aircraft. The absence of wing struts is a testament to the design’s
strength.
SELDOM DO YOU see an RC trainer that
comes in a box showing an aerotow as one
of the main features. But the Multiplex
Mentor is unusual in several ways.
A first look gives the impression of an
orthodox electric-powered RC trainer. Then
you realize that it is not one of those small
foamies with a little gear-driven motor, but
a full-blooded, 64-inch-wingspan airplane.
It is exciting to put together a new
airplane. It is even more thrilling when the
model is slated to have more than one
purpose. The Mentor is touted as a trainer
and a glider-towing tug.
(Editor’s note: Now it can even be made
to fly from water.)
As a trainer, the Mentor is aimed at the
beginner to intermediate modeler/pilot who
is 14 years of age and older. You should
probably also be an experienced RC pilot if
you are going to use this aircraft to aerotow
gliders.
The 40 trainer is one of the most popular
model sizes, and the Mentor uses a clean
and relatively quiet brushless-motor power
pack. In addition, little field-support
equipment is needed other than a battery
charger for the flight pack.
The Mentor is billed as having stable
flying characteristics and a low stall
(minimum airspeed) for easy landings.
Those things are desirable in a trainer.
When finished, the main wing is a twopart
structure with a removable carbon-fiber
spar joiner for easy transport. The canopy
hatch is removable with quick-release
10sig2.QXD 8/21/09 2:05 PM Page 42
October 2009 43
Five servos are used: two for the ailerons
and one each for the rudder and elevator.
The fifth servo, an HS-55, is for the aerotow
line release, to be used in the future.
The Multiplex brushless power pack
eliminates electric guesswork and consists
of a Himax HC3528-1000 motor, BL-55
ESC, propeller adapter, and APC 11 x 5.5E
propeller.
The Mentor carries a large Multiplex
three-cell Li-Poly 4800 mAh battery that
gives good flight times and plenty of
power.
Construction mainly consists of foam molded parts with an array
of tough plastic parts. The landing gear is made from pressed
aluminum plate.
Each wing half is molded in two pieces; they sandwich the
composite spar and servo leads. The interior includes ingenious
functionality.
Photos by the author
The tail-dragger configuration is mandatory for the Mentor. Extralong
aluminum gear is strong, and wheels are large enough for
rough-field maneuvering.
Multiplex models molded with Elapor foam are compatible with
regular CA adhesives. So are the plastic parts, which chemically
bond with the foam and adhesive.
catches, for an easy flight-battery swap.
Multiplex uses white molded foam
called “Elapor.” It is different from
expanded polystyrene foam, in that it does
not need special foam-friendly CA glue.
You are instructed to use only regular
medium CA.
The wings are also made from Elapor.
The ailerons are part of the mold and are
hinged with the same material. The wing
halves are stiffened by a carbon-fiber tube
that is also the removable wing joiner. The
wing halves are held together by the same
plate that the wing bolts use to hold the
wing in place.
The cowl and spinner are both made
from Elapor. I had never seen a foam
spinner, but it worked fine on the Himax
motor, which is available from Maxx
Products International. The motor mount
uses two rails that are glued into the foam.
The motor plate then screws into the mount
with four convenient-to-adjust machine
screws that are positioned around the motor
plate.
The landing gear is a prebent piece of
2.5mm-thick aluminum sheet. The two
70mm main wheels use lightweight foam.
Multiplex markets a set of component
10sig2.QXD 8/21/09 1:31 PM Page 43
All you have to do is open the throttle, and
this airplane will be airborne quickly. The
performance is surprising on only 11.1
volts; it handles the wind well
The decals add to this model’s look and help with in-flight orientation. Because the hinges
are molded in, the control surfaces’ effectiveness is greatly enhanced.
Floats are now available for the Mentor. Nothing is better for floating on water than foam, but as fun as this model is to fly, it will be
mostly airborne.
packs that meet several of its models’
needs. The Power Pack includes an
excellent Himax brushless motor, 55-amp
ESC, propeller, and hub assembly. The
company also sells Hitec and Multiplex
radio systems, but I used my JR8103 that
was converted to Spektrum with the 2.4
GHz module/receiver system.
Construction: The manual comprises a
series of high-quality drawings in four
languages. The builder should have some
RC model-building knowledge.
It was helpful to study the pictures and
then make construction lists. To make
assembly even easier, I cut the fourlanguage
instructions and sorted them into
their English components. Then I stapled
each narrative next to the pictures/diagrams
of the assembly.
Wing construction is made easier,
because it consists of two molded panels
that end up as halves. Assembly begins with
releasing the ailerons and flexing their
premolded foam hinge lines. I had to add
servo-extension leads to the aileron servos
so that they would reach the wing center
area.
Before gluing anything, you need to fit
the servo arms to the Hitec HS-81
microservos. This means that you must set
the neutral positions with your radio for
each arm on each servo. You can’t do this
once everything has been glued in place.
The foam cover forms a tube in the wing
panel for the carbon-fiber wing-joiner tube.
It also covers the servo lead/extension and
holds the servo in place.
Take care not to get CA in the tube area,
if you want to be able to easily slide in the
carbon-fiber wing joiner. Also, do not put
the carbon-fiber joiner in too soon, in case
any uncured CA decides to fix it there
permanently!
The fuselage comes in halves that
require a fair degree of preparation before
they can be glued together. Fit the Hitec
HS-322HD servos for the rudder and
elevator servos into recesses on the outside
of the molded fuselage halves and route
their leads inside. Adhere the pushrod outer
tubes into grooves in the outer skin of the
foam parts.
I deviated slightly from the instructions
with the wing bolts. I retapped the plates
out to a 1/4 x 20 thread and used two nylon
Allen-head bolts instead of the supplied
metric threaded bolts. This choice was
prompted by the better availability of
standard hardware.
I installed a Hitec HS-55 servo that
would operate a cable/towline release. This
assembly was buried in one fuselage side.
As did the ailerons, the servo arm needed to
be set with the radio before it was glued in
place. There would be no way to reach this
servo later.
When you are ready to glue the fuselage
halves together, lay everything out in
advance. It is a good idea to enlist a friend
to help with this task. I recruited my wife to
hold the rear section together while I
worked on the middle and front. I applied
the CA quickly and liberally onto one side
and gently squeezed the halves together.
The adhesive did not cure immediately,
especially where there was a lot of it.
Therefore, the halves needed to be held in
several places for roughly five minutes.
Some areas attached instantly, while others
kept coming apart.
Also, excess CA oozed out of the seams
and had to be wiped off quickly. The
process was a bit stressful, but we are still
married. Next time we’ll use more kicker.
To fit the stabilizer and fin, the wing
needs to be bolted in place. It sat square in
the wing seat and was a nice, tight fit. The
Multiplex molds’ accuracy was no more
evident than when the wings lined up
perfectly.
Gluing the tail feathers in place was
simple and quick. Connecting the controls
was easy because of the supplied adjustable
swivel connectors at the horn end. Z-bends
were used at all of the servo-arm ends.
A separate pushrod for the steerable tail
wheel lets you set the rudder trim
independent of the tail-wheel setting. The
tail-wheel assembly and the main landing
gear plate bolt together. The tail-wheel
assembly glues in place. The mains are
machine-screwed using additional landing
gear plates that sandwich and add support to
the preinstalled landing gear plate.
The motor was a good fit on the motor
plate. The plate then fitted perfectly onto the
previously installed motor mounts. You do
have to solder the connectors onto the battery
and the ESC.
A BEC in a large ESC is rarely used to
feed the receiver and servos, because too
much power can go to the motor and then not
enough is left for the onboard radio system. A
separate 1800 mAh NiMH receiver battery
was used for this task. Be sure to disable the
power feed to the receiver from the BEC.
The large 3S 4800 mAh needed to be
retained under the wing to get the correct CG.
The space was not a tight fit and there needed
to be room for cooling air to flow past the
battery pack.
me that used Velcro straps to hold the
pack in place. The Velcro allows the Li-
Poly pack to be removed for
charging/balancing.
Preparing the decals was tough; it took
quite awhile to cut them by hand. However,
they were easy to apply and could be lifted
for alignment purposes, as long as I had not
rubbed them down.
The result is worth the effort. The
graphics not only improved the Mentor’s
look and visibility, but they also covered
the servos on the outside of the fuselage.
Motor and Battery: When you configure
an electric model, it can be difficult to
choose the proper motor, ESC, and
battery. Multiplex has assembled a triedand-
proven optional package that takes
away all of the guesswork. It is optimized
to give you the most out of your airplane.
The configuration is designed to use a 3S
3200-4800 mAh Li-Poly battery pack.
The Mentor Power Pack includes a
Himax 3528-1000 brushless outrunner
motor with the following specifications:
Kv, 1,000; watts, 450; diameter, 35mm;
length, 54mm; and weight, 197 grams.
The pack also contains an APC 11 x 5.5E
propeller, hub, and driver to match the
motor’s shaft size.
Also included is a MULTIcont BL-55
brushless ESC, which has the following
specifications: max continuous current, 55
amps; voltage range, 6-15; maximum
battery, 3S Li-Poly; and a BEC that can
deliver 3 amps. The BEC was not used to
power the five servos.
The motor installation was tested and
measured. Initial results were that it drew
42 amps and 507 watts, showing 11.4
volts at full throttle. The motor turned the
APC propeller at 9,960 rpm. These figures
dropped off a bit after a few seconds.
Flight Report: An electric trainer this
size still tends to be a new thing at the
flying field. A few short taxi runs were all
it took to check the steering, and we were
ready.
I taxied the Mentor to the center of the
runway and aimed it into the wind. The
timer was set to go off after six minutes,
to give a good margin on the battery and
allow for several landing attempts, if
required.
The takeoff run was straight and rapid.
The big motor almost immediately
delivered maximum torque. The tail came
up quickly, and the aircraft was airborne
in approximately 15 feet.
The climb was a bit steep at first, and
then it got even steeper. I put in roughly
six clicks of down-elevator trim before
entering the first turn. No aileron or
rudder trim was required. The initial trim
setting was all that was needed to achieve
level and steady flight.
When I released the controls, the
model flew straight and level. When
entering a turn, some bottom rudder was
required to keep the fuselage nose level
with the horizon.
Varying the throttle settings showed
stable flight behavior down to a gentle
stall. The Mentor would then drop the
nose and regain airspeed in close to 4 feet
of altitude.
I selected half throttle and made a
landing circuit. Once the airplane was
over the runway landing threshold, nearly
two notches of throttle clicks kept the
propeller turning. The wings stayed level,
and the motor was brought back to 0 rpm
approximately a foot above the grass. The
model settled into a smooth landing 10
yards or so later.
The red, black, and silver decals had
orientation. The first flight was good and
was quickly followed by more adventurous
flights that included such exploits as loops,
rolls, and inverted flight. The airplane liked
to skim in on the main wheels rather than be
almost stalled down to a three-point landing.
The Mentor is a delight to fly and easy to
guide around the sky. It loops majestically
and gives a slight barrel roll with ailerons.
Making aileron turns at cruising or high
speed showed no adverse yaw. That is when
the higher wing has more drag than the
lower wing when a rolling action is created
with the ailerons.
Aileron turn entries at slow speed liked a
bit of bottom rudder to be added when
initially going into the turn. This rudder
input can be made manually or mixed in
using a computer radio.
The Multiplex Mentor has the feel of a
low-wing sport airplane—especially when
you send more electrons to the brushless
motor. Get some help putting one of these
models together if you are an inexperienced
builder, and it could appear early in your
RC chronicles.
Even though the Mentor appears
destined only to be a trainer, it can be so
much more. It flies as well as any 40- to 60-
sized sport aircraft and has no nasty habits.
It is a great airplane to fly for fun.
In addition, that aerotow release servo is
buried in the fuselage, just sitting there. You
could use it to pull a ribbon/streamer or tow
a banner, but it was designed to pull a
glider. Now where did I put that Multiplex
Cularis sailplane? (Editor’s note: See page
54 for that story.) MA
Eric Henderson
[email protected]
Manufacturer/Distributor:
Multiplex USA
12115 Paine St.
Poway CA 92064
(858) 748-6948
www.multiplexusa.com
Sources:
Maxx Products International
(847) 438-2233
www.maxxprod.com
Spektrum
(800) 338-4639
www.spektrumrc.com
JR
(800) 338-4639
www.jrradios.com
APC Propeller
(530) 661-0399
www.apcprop.com
Other Published Reviews:
RC Model World: October 2008
Model Airplane News: January 2009
Quiet and Electric Flight International:
January 2009