RCU Review: Multiplex Mentor

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    Contributed by: Greg Covey | Published: December 2008 | Views: 96702 | email icon Email this Article | PDFpdf icon
    Multiplex Mentor

    Review by: Greg Covey
    Assembly Photos: Greg Covey
    Flying Photos: "Papa Jeff" Ring
    Video 1 Pilot: Greg Covey
    Video 2 Pilot:
    Lynn Bowerman


    Dealer Info

    Multiplex USA Inc.
    Distributed in the U.S.A. by:

    PO Box 9078

    Champaign, IL 61826-9078
    Ph: (800) 637-6050

    Complete Kit with hardware
    Easy to build and repair
    Superb Flying Performance
    Durable Elapor Foam
    Removeable Wings
    Matched Power Set

    Some Soldering Required
    Brittle Canopy Latches
    Multiplex Mentor

    The Multiplex Mentor is a replacement for the Magister and is a robust trainer and tug (tow plane) made of ELAPOR (pronounced el-a-pore) foam. Medium CA glue used with an activator (or kicker) as the only method of gluing recommended by the manufacturer. This radio controlled model is electric powered and Almost-Ready-to-Fly (ARF). It is meant for beginners to intermediate fliers.

    Trainers have been around since the very beginning of model flying. The so-called .40-size trainer was offered in a multitude of variations all over the world. The beginner is expected to cope from the outset with an easily damaged all-wood model and a motor which is not properly set up or even broken in. It was no surprise that this type of "first model" was often the modeler's last.

    The Multiplex Mentor was designed with the beginner in mind. The ELAPOR foam provides a robust, high-strength structure that is easily and quickly assembled using CA glue. The aircraft's flying characteristics are simply outstanding! When using the mating Multiplex Brushless Motor Power Pack (M993228), which contains a motor, ESC, Prop, and hardware, the trainer provides reliable, maintenance-free power flight after flight.


    • Wingspan: 64.2" (1630mm)
    • Length: 46.1" (1170mm)
    • Wing Loading: 14.58 oz/sq ft (44.5g/sq dm)
    • Flying Weight with 3 LiPo Cells: 4.3lbs (1950g)
    • Airfoil: Flat bottom high-wing placement
    • Center of Gravity: 3.3" (85mm) Back from the wing's leading edge at the fuselage
    • Elevator Throw: Up 0.59" (15mm), Down 0.47" (12mm)
    • Rudder Throw: Right to Left 0.59" (15mm)
    • Aileron Throw: Up 0.59" (15mm), Down 0.27" (7mm)

    Key Features:

    • Wings are removable for easy transport
    • Radio Compartment: Accessible under wing
    • Landing Gear: Pre-bent aluminum 0.098" (2.5mm) thick
    • Steerable 1" (26mm) tailwheel
    • Two foam 2-3/4" (70mm) Wheels included
    • Landing Gear: Pre-bent aluminum 0.098" (2.5mm) thick
    • Aileron Control: Dual servo
    • Elapor foam, 2.5" (63mm) spinner
    • Peel and stick decals

    Kit Contents :

    The Mentor parts fit into a custom foam base that protects them during shipment. The well-designed packaging eliminates damage during shipment. The kit includes a large decal sheet, a detailed manual in five languages, and all the hardware needed for completion.

    The mating Multiplex Brushless Motor Power Pack (M993228), contains a Himax HC3528-1000 motor, Castle Creations Phoenix 45-amp ESC, APC 11x5.5 e-prop, adapter, and mounting hardware sets.



    The assembly begins by gluing in the motor mount pieces. I was impressed at how the plastic pieces fit perfectly into the foam mold fuselage halves. A little medium CA on the fuselage inside and spray kicker on the plastic pieces was all that I needed for a quick strong bond.

    For the elevator and rudder, I'm using Hitec HS-475HB servos. These are standard size servos with ball bearings and Karbonite gears. Each servo weighs 1.41oz and has 61oz/in torque on a 4.8v supply. They press into place on the fuselage and are held by a few drops of glue. I cut away the outer holes in the servo arm so it would fit in the servo compartment of the fuselage.

    The ailerons will use smaller Hitec HS-85BB "Mighty Micro" servos. The servos weigh only 0.67oz each and deliver 42oz/in torque on a 4.8v supply. The HS-85BB servo is meant to fit in the smaller aileron compartments in the wing.


    The elevator and rudder control snakes are made from a thin metal rod and an inner and outer set of tubes. The Z-bend of the rod connects to the servo arm and the outer tubes press into the fuselage after lining the channel with medium CA. I used Pacer Zap CA+ (PT-02) and Zip Kicker spray accelerator.

    Note that the thicker control rod for the steerable tailwheel (which does not use an inner tube) is crossed over the rudder control rod at the servo arm. The cross-over is just another example of the elegant German engineering that went into the Mentor. It is simple and requires no fancy linkage hardware. There is no binding because the Z-bends are a different size so the tailwheel control rod rides over the other one.

    The wing screw supports snap together and then get CA'ed into the fuselage.


    I installed the aero-tow mechanism. It was well designed and easy to install. I used an older Expert SL300 Micro BB servo I had on hand. Just about any micro-sized servo will work for this feature. I decided cut the control rod later when I activate my receiver.

    The next step is to join the fuselage halves. I have found from assembling previous Multiplex Elapor models that using medium CA and a spray accelerator like the Pacer (PT-15) Zip Kicker makes this assembly procedure quite easy. After first test fitting the two halves, I applied CA to one side and sprayed kicker onto the other side. You can then press the two halves together being careful not to warp the fuselage tail in the process. It is helpful to do this on the floor with towels under the fuselage so it can be compressed with multiple hands. I finished this procedure by checking all the seams and re-applying CA where needed.

    Landing Gear:

    The tailwheel unit and main undercarriage are installed next. I assembled them from the matching diagrams in the manual without issue. A 1.5mm hex wrench is needed to tighten the wheel collars. Be sure that all wheels spin properly when finished and use Pacer Z-42 Thread Locker on all the nuts and hex head "grub" screws.

    The main undercarriage is installed with four M4x68mm flat head screws into three of the thick plastic plates. The plates sandwich the fuselage and provide a solid foundation for the gear mains. Everything fit well and Pacer Z-42 Thread Locker was applied to the four nuts that sit inside the fuselage.

    Mentor Servo Pack:

    My Mentor Servo Pack arrived from Tower Hobbies. The pack consists of two HS-322HD servos (for elevator and rudder) and two HS-81 servos for the ailerons. It also contains the two 6" and two 12" servo extensions needed to complete the Mentor.

    Tail Assembly:

    After first cutting the control surfaces free, the swivel pushrod connectors are mounted to the control horns. The elevator and rudder connectors use the outermost hole in the horn and the aileron connectors use the second hole from the outside of the horn. As with everything else on this model, the pushrod connectors fit perfectly onto the control horns and the control horns fit perfectly into their custom slots of the control surfaces. I used a small dab of Zap Z-42 thread locker on the nuts of the pushrod connectors to keep them in place.

    The stabilizers glued easily in place onto the fuselage. After first testing the fit, I spread medium CA onto the fuselage area and sprayed the stabilizer area with PT-15 Zip Kicker accelerator. This made for a quick assembly as the stabilizers are easy to center in position. The same technique was used to mount the tailwheel assembly.

    All the pushrods were inserted into the swivel connectors and lightly tightened for now. When the receiver is made active, I will center the servos, adjust the pushrods, and tighten the grub screws with a dab of Locktite.

    Wing Assembly:

    The aileron servo openings in the wing are perfectly designed for Tiny S, HS-85, or HS-81 servos. They snugly press into place with a small amount of CA to hold them. Since the servo arm was not easy to unscrew after mounting the servo, I decided to first center them with my live receiver and Rx. battery pack.

    I used Hitec (57345S) 12" Aileron Extensions to route the servo wire to the center of each wing half. A small piece of foam was cut in the wire channel to accept the joining cable connectors. I used a small amount of CA to hold it in place and then clear cellophane tape along the entire channel.

    The spar covers were installed with my usual CA and spray kicker technique. The key here is not to get any CA inside the channel where the carbon tube must slide.

    Mentor Power System:

    The motor assembly begins by soldering the connectors on both ends of the Castle Creations Phoenix 45 ESC. I did not find any shrink tubing for the ESC motor wires so I used my own. My battery connector preference is Dean's Ultra connectors. The Himax HC3528-1000 motor came with the connectors already on the wires.

    The Mentor motor bulkhead has an innovative adjustment for thrust angle. I used the recommended starting points for right and down thrust.


    My Mentor Power Set came with many parts that are not needed. I wasn't sure if I had received a prototype kit or if the Power Set was meant for multiple models.

    A complete bulkhead motor mount kit was included but not needed. I only used the 4 motor mount screws in the X-mount kit. The APC 11x5.5 prop, Multiplex prop adapter, and spinner adapter are all used.

    After mounting the motor with the 4 screws from the X-mount kit, the whole assembly is screwed into place from the front of the fuselage nose. Note how easy it is to change the thrust angle by adjusting the screws.

    Component Placement:

    I placed my Hitec Electron 6 receiver and Multiplex ESC (CC Phoenix 45) in the recommended locations. When the battery is in the back of the fuselage chamber (as suggested) the plane balances perfectly! Note the gap in the fuselage at the center of the wing leading edge. This is where the aileron control wires are routed from the wing to the inside of the fuselage.

    The 72MHz antenna wire is routed along the bottom of the fuse toward the tail. I used clear cellophane tape to hold it in place.

    Air Cooling:

    The Mentor was designed with exceptional air flow through the inside of the fuselage to cool the motor, ESC, and battery pack.


    Battery Options:

    I measured the following static power setups. You can see that for a little more money, you get 10% more power from the 30C FlightPower pack.

    • 315w, 30amps, 81w/lb w/ElectriFly 20C 3s 3200mAh pack
    • 350w, 34amps, 90w/lb w/FlightPower 30C 3s 3200mAh pack

    Multiplex also has their own cost-effective 20C 3s 3200mAh pack.


    My Multiplex Mentor was Ready-To-Fly at 63oz (3.9lbs) including the 10-oz flight battery pack and extra tow servo.

    Test Flying

    I tested the Mentor at a local schoolyard just down the street. As expected, it flew very predictable and offered no surprises. Take-offs required some rudder correction in the cross breeze but it had plenty of power for basic aerobatics and could slow down to a docile crawl around the field. I only needed only a few clicks of elevator and aileron trim to keep it flying straight. Landings were as simple as turning off power to the motor and gently flaring the elevator as you watch it glide onto the grass. My flights lasted for at least 10 minutes while performing aerobatics. Using the 30C Flightpower 3s 3200mAh pack provided a noticeable increase in power over my 20C pack.

    The maiden flight video of the Multiplex Mentor shows that it can safely take-off and land in a smaller field like a school yard. A young boy saw it fly and ran across the field to see where the Mentor landed. He was mesmerized by the model that was as big as he was, so, after unplugging the battery, we gave him a transmitter to play with. His Dad told me that his father used to have tissue and dope planes and he never knew this type of foam plane and electric power existed. Perhaps the Mentor has attracted a new pilot to our hobby.

    Multiplex Mentor Maiden Flight Video (12meg)


    Aerobatic Flying

    Mentor Aerobatic Flight Video
    CLICK HERE (12meg)

    The maiden flight video was intended to be more realisitic of what most people may do with a Mentor. It was flown safely because I was in a school yard at the time, not a club flying field. This second video shows more of the Mentor's capability at the club flying field.

    Our final good weekend of the flying season to make a trip to the club field came on November 2nd. My pilot, Lynn Bowerman, had a chance to test out the Mentor while I worked the video camera. As expected, he enjoyed it as much as I did and gave it a good workout. All the take-offs and landings were using the same FlightPower 30C battery pack so we had at least 10 minutes of flying while performing many aerobatics.



    The Mentor kit is more work to assemble than a Ready-To-Fly model but can be built in just a few evenings. Although it does require more than a beginner's knowledge to create a successful experience, the result is a better choice for the intermediate or more serious modeler. The brushless power system has plenty of power to fly off grass and the forward landing gear virtually eliminates nose-overs on rough terrain. Best of all, the Mentor can be quickly repaired with CA and kicker right at the field!

    Since the Mentor is extremely stable in flight, it can provide a relaxing experience or perform all the basic aerobatic maneuvers including inverted flight. The extensive flight envelope ranges from a very slow pass to a fast knife-edge. As a successor to the popular Multiplex Magister, the Mentor is similar in size but weighs 10oz less. The steerable tail-dragger was designed from the ground up for today's brushless motor and Lithium Polymer technology. A great addition for all pilots!


    Dealer/Distributor Information

    Multiplex USA Inc.
    12115 Paine St.
    Poway CA, 92064

    Distributed in the U.S.A. by:

    PO Box 9078
    Champaign, IL 61826-9078
    Ph: (800) 637-6050

    Hitec RCD USA
    12115 Paine St.
    Poway, CA 92064
    Phone: (858) 748-6948
    Fax: (858) 748-1767
    Email: service@hitecrcd.com

    ZAP Glues On-line at Frank Tiano Enterprises

    Pacer Z-42 Thread Locker
    5-minute Z-poxy
    Pacer POLY ZAP(tm)

    Comments on RCU Review: Multiplex Mentor

    Posted by: ekotil on 12/09/2008
    Great review!
    Posted by: jackbell on 11/20/2009

    Posted by: jackbell on 11/20/2009
    Great review and a lot of helpful ideas on assembling. But I have a problem installing the battery and securing it.
    Posted by: foldingprop on 01/30/2012

    Posted by: foldingprop on 01/30/2012
    Greg, Just starting the mentor RR. Does it require a receiver battery and a flight Battery? I did not see one in your build pic but one is mentioned in the directions. Nice review! Jimclousing@hotmail.com
    Page: 1
    The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.

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