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Saturday, March 24, 2012

Z8RC Hypelesstaxi - Build and Flight Review

I've always enjoyed flying the Great Planes Electrifly VFO in the sim.  So when E-Flite ripped the VFO off wholesale and marketed as their own UMX Hypertaxi with AS3X, I thought it was time to do a scratch build of my own.
Z8RC Hypelesstaxi before attaching the four servos with mounting tape.
In their marketing videos, E-Flite insists the Hypertaxi would've been absolutely impossible to fly without AS3X (which is odd since the VFO is marketed as a super stable hovering trainer); the boisterous remark naturally piqued my interest.  So I decided to lean more towards E-Flite's copycat craft in size, shape (and color scheme) rather than mimic the original VFO.  A VFO would have been easier to assemble and no doubt would have flown better, but no one ever said life was going to be easy, just that it would be fun.

I spent almost 10 seconds designing the Hyplesstaxi.  I spent most of that time agonizing over the proper wingspan.  I wound up going one step smaller than the Hypertaxi, so the wing planform could fit inside two sheets of 11.5" square Midwest Cellfoam 88.  That kept the airframe cost under $4.
Time - 
  • Shameless theft of concept from Electrifly VFO, 10 seconds
  • Design and Advanced Aerodynamic Calculations, 9 secs
  • Build - About 2 hours from scratch, plus optional paint dry time
Total Time = About  2 hours and 19 seconds

Materials -
  • 3/16th" Foam board, 2 x $1.90
  • OrangeRx DSM2 reciever  $5.99
  • Turnigy 4.4g servos, 4 x $3.39
  • ESC, 10A $6.11 
  • Motor, Extreme Performance $7.99
  • Optional Motor,  Outrageous Performance $18.25
  • Carbon Fiber, $5
  • Misc, $7                                                         
Total BNF Cost = $49.46 + Shipping if not tacked to another order
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 The Boda antenna of the Hitec 6 Lite adds a cute touch.  Although easily doable with OrangeRx as priced above, it's important to have built-in telemetry on a VTOL aircraft so I used a spare Hitec receiver at least for the time being.
Radio Setup:

One of the things that makes a VFO-type model interesting is how the radio is set up.  There are a number of ways to do it, but only one way that gets the most out of the model. The optimum way looks like this:
  • Ailerons move all four control surfaces in the direction of stick movement
  • Elevator moves the ailerons up and down as Elevons
  • Rudder moves the top and bottom rudder in the direction of stick movement
Here is one possible Hitec Setup.  Since Hitec allows you to assign functions to channels, it doesn't matter how you do it but my servo Channels are plugged-in and assigned like this:
  • The left aileron servo is plugged into receiver Ch1 
  • The right aileron servo is plugged into receiver Ch 2
  • The top rudder servo is plugged into receiver Ch  3
  • The bottom rudder servo is plugged into receiver Ch 4
  • Nothing is plugged into receiver Ch 5 
  • The throttle ESC is plugged into receiver Ch 6 
The control sticks are assigned like this:
  • Right stick, left/right (J1) is assigned to Ch 1 and Ch 2
  • Right stick, up/down (J2) is assigned to empty Ch 5 (for mixing later)
  • Left stick, left/right (J4) is assigned to Ch 3 and Ch 4
  • Left stick, up/down (J3) is assigned to Ch 6

There is a built-in Elevon wing/tail type but then I'd have to plug the servos into the receiver correctly and I didn't feel like figuring out the proper configuration.  By doing all the mixes manually, I can plug each servo into a random channel on the receiver and work it out with the channel map shown above.  I mapped the ELEV function to Channel 5 and stick J2 (up/down movement of the right joystick) even though the receiver's Channel 5 plug is empty .  That is so I can mix ELEV with AILE and AIL2 to make Elevons.  I assigned AUX1 to the rudder stick (J4)  for the bottom rudder surface because of the way I mounted my servos, the bottom rudder servo required reversing while the top rudder servo did not.  A second reason to distinguish the bottom rudder as AUX1 is to allow the top and bottom rudder to move in opposite directions when acting as ailerons (Ailerudder).
No wing or tail type is selected so there are four logical mixes.  Mixes 1 & 2 create Elevons.  Mixes 3 & 4 make the rudder deflect as ailerons (Ailerudder)
Left Elevon
Right Elevon

Top Ailerudder

Bottom Ailerudder
It couldn't be much easier, really. Even though I only used a 6 Channel receiver, I considered mapping to Ch 7 FLAP:LS (Left slider) so I would have Spoilerons/Flapperons on a slider, but in an Elevon configuration Spoileron/Flaperon isn't a whole lot different than elevator trim. I might experiment with it later.

...more to come...
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