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Multiplex Fox RC Conversion

Gallery

Some photos of the conversion and the power system components used. Click an image to see a larger version or a slideshow.
      

Summary

The following is a short guide on how to convert a Multiplex Fox into a powered RC plane. In short, the following steps are required: -

• Hollow out the nose of the plane and canopy
• Cut and hinge the control surfaces
• Cut recesses for servos
• Connect pushrods between servos and control surfaces
• Fit the motor
• Mount the folding propeller
• General tips

Assumptions

Before we start, we are assuming the following: -

• Suitable radio gear is available (receiver and servos)
• Our suggested power system for the Multiplex Fox is being used (the procedure will be very similar for other outrunners)

Hollow out the nose of the plane and canopy

Remove the metal ballast from the canopy.
Takes your best guess based on the size of your receiver. We used a light-weight Jeti Duplex 4-channel Receiver. A pair of long-nosed pliers comes in very handy here. Simply cut a rectangle into the nose area (not all the way through!) and then use the long-nosed pliers to pull and twist out the Elapor foam. Later on, we will be cutting off the aeroplanes nose, so do not remove any foam forward of the end of the canopy.

Check that the ESC, your receiver and battery fit snugly into the canopy area. It may help to remove some foam from inside the canopy itself, to provide more depth within the cockpit area to mount your particular components.

Cut and hinge the control surfaces

Our Fox uses rudder and elevator only. If you’re feeling adventurous, omit the rudder and go for Ailerons. We simply cut a rudder out of the fin, approximately 12mm deep, from top to bottom and bevelled the edge. Tape can be used as a hinge (We used some parcel tape, because we have a lot of it!)

Similar for the elevator. Bevelled and then the two halves joined with a strip of balsa.

Cut recesses for servos

We used two 3.7g servos which were donated to us. A recess was cut, just behind the wing area, to accommodate the servos lay on their side with the servo arms to the outside, pointing upwards. The servos were glued in place (it is safe to use Cyano on the Elapor foam of the Multiplex Fox but take care not to allow glue into the servo case (Do not use thin cyano and wrap some tape around the servos!)

Connect pushrods between servos and control surfaces

We simply used some light-weight wire for the control rods, with a z-bend in each end. Complete the linkages to your preference and ensure all surfaces are hinged securely.

Fit the motor

Now take a hacksaw or similar and cut the front of the Fox off as square as possible. Ours was cut directly in front of the end of the canopy. It is best to cut approximately 2mm back from this point as it allows more room for securing the AXi 2203/52 to the front of the model.
The nose of the model could be recessed to allow a more aesthetically pleasing job, if time is available!

Secure the motor to the front of the model using suitable screws through the 3 motor lugs. A very small dab of glue may be used if desired, to secure the screws in the foam (Take care not to allow glue to come into contact with the motor!)

Mount the folding propeller

Because the AXi 2203/52 has a built-in prop saver, the folding-propeller hub of the prop assembly must be re-drilled to ~8mm to fit onto the motor. We did this by hand with a drill-bit. Use the collar provided with the motor, over the top of its nose and secure the hub using the rubber o-ring provided with the motor. A larger prop can be used but we find the 6" folder is very efficient.

General tips

• Use 2mm gold connectors between the motor and speed controller to save weight.
• 10g of lead will be required on the tail (as far rearward as possible) to attain the correct CoG
• On a perfectly still day, the Multiplex Fox is a lovely flier and will happily cruise below half-throttle for at least 8 minutes on a 350mAh pack. Please take care to keep muck and grit out of the motor, being mounted the way it is.
• The weight and wing-loading of the Mutliplex Fox with this setup does not allow any kind of wind tolerance! Retain the metal ball weight supplied in the canopy to experiment with some ballast!

Thanks

Thanks for reading our short guide. Why not check out our other power systems or some of our aeroplane kits.