Multiplex Fox RC conversion, page 2
Continuing on from page 1 of the Multiplex Fox rc conversion, we pick up still at the hole-making stage!
Make hole for battery lead
I used 5mm aluminum tube and sharpened one end with a fine metal file. Twisting and gently pushing it through the foam cuts a neat hole from the nose to the battery compartment, but make sure you line it up well so it comes through in the right place! Below left is starting the hole at the servo slots, below right is the tube appearing in the battery compartment...
Insert the battery pack
Once the hole is made you can insert the pack. Feed the lead through the hole to the nose, and then push the pack into its compartment. Hopefully you've made it a snug fit and so won't need anything to hold it in place. Incidentally, I removed the plastic JR connector to feed the lead though, otherwise you'll need to make a larger diameter hole. If you do the same, be careful - make sure you insulate the exposed terminals so that positive and negative don't touch and short the battery. A momentary lapse of concentration led to that happening with my fully charged pack, hence the heat shrink repair around the melted insulation...
Cut the control rod slots
I used masking tape to mark the slots and a very sharp knife to make the cuts. My choice of control rod was thin gauge piano wire (0.32" I think) placed inside clear plastic tubing glued into the slot, one in each side of the fuselage for rudder and elevator...
Below you see the finished slot, ready for the plastic tubing to be glued in place...
Make the elevators
I made the elevators 6.5cm long by 2cm deep*, this gave roughly a 20% elevator surface of the tailplane surface area. Chamfer the leading edge of each elevator to give the necessary clearance for up and down movement. Also cut 2mm off the length of each elevator to avoid binding at each end...
* NB - with hindsight I'd make the elevators larger, although this size does work fine.
Find a way to join both elevators
I bent some wire to make a connecting rod, and carefully inserted each end into each elevator leading edge. Make sure both elevators are laying flat when you do this, cyno should hold the wire in place nicely...
Fix the elevators
Make small hinges from mylar strip, or use your preferred choice of hinge material. Another practical option is to just use tape along the upper surface. If using hinges, line everything up and cut the slots carefully, ensuring all upper surfaces are flush. Carefully horizontally slice the piece of tailplane that separates the elevators and push the wire joiner into the cut. Take your time getting everything lined up well, and do a dry test before gluing the hinges in place...
Cut the rudder
My rudder measures 3cm x 8cm. As for the elevators, chamfer the leading edge and cut 2mm or so off the height to avoid binding....
Insert a carbon spar in the wing
I don't know if this is absolutely necessary but the EPP wing does flex a lot, so I think it's worth taking the time. I used 2mm round carbon fiber rod and cut it into the wing on the CG line. Again, a very sharp knife is needed here, and there's no easy way to obtain a square-based trench. As an extra precaution, once the spar was glued in place I covered it with 3M cross-weave reinforced tape.
For ease of photo size, just one wing is shown...
Cut the ailerons
My ailerons are 15cm long by 2.5cm at the root, 2cm at the tip, with the root starting 1.5cm off the fuselage. I made 4 mylar hinges for each aileron, I think 3 would suffice. As with the elevators, chamfer the leading edge and cut 2mm or so off the length. To stiffen things up, I put a strip of the 3M cross weave tape on the underside of each aileron...
Start adding the hardware
With all the cutting done and control surfaces made, it's time to start adding the hardware! This stage is no different to setting up a standard rc plane - install the servos and take your time making the control rods.
For control horns, I used Multiplex 11mm mini-horns, #70 3026. These were the perfect size and ideal for pushing through the foam. Cyno holds them in place well.
I used brass 'Quick links' on the servo horns, and the only other additional thing needed was a few JR/Futaba to JST adaptors for the servos and battery to plug into the Spektrum AR6300 receiver. These didn't prove easy to find, those in need should look for Spektrum part number SPMAJST1UL.
One final thing you'll need to do is cut away the inside of the canopy so that it fits over all the components. This didn't work out so well for me, I ended up chopping away the back 1/3 of the canopy to clear the aileron servo - d'oh! And don't use a soldering iron to melt away the inside, the whole canopy warps out of shape and shrinks in width - how did I find that out??...
Multiplex Fox RC conversion detail photos on next page...
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Related pages
RC gliders - an overview of the proper ones.
Slope flying - tips on using the wind.
Donuts Models Valentino - my other glider.
