X-UAV Mini Talon Build Number 2

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© Mark Qvale - August, 2016

Maiden Day.jpg
  Ready for Maiden!

Introduction - Mini Talon Number 2

On this, my second MT build, I have designed and printed a "Kit" of 3D parts that will make assembly easier and more organized as well as helping with aerodynamic drag. On the Power side I am going to try a Cobra 2221/16-1250kv motor, a 4S/6600/10C Multistar and an Aeronaut 8x7 Cam Carbon folder. AUW should be close to 1750g which should make for an easy, medium range flyer.

For radio gear on this one I will first try a FrSky L9R long range 2.4G RX with my Taranis TX before going to the standard DragonLink 433 LRS. Video will initially be a 400mW RMRC VTx on 1280mHz to see if I can get the range I want on less power.

General Specifications

Distributor - BangGood USA
Aircraft - X-UAV Mini Talon
Build Date - August, 2016

Airframe Type -  Top Wing V-Tail FPV Specialist All-Up Weight -  57oz (1625g) w/ 4S/5200 Pack
Wingspan -  51 inches (1300mm)   61oz (1730g) w/ 4S/6600 Pack
Length -  33 inches (830mm)   65oz (1836g) w/ 4S/8000 Pack
Wing Area -  3.23 ft^2 (30dm^2) *Wing Load -  18.9 oz/ft^2 (58g/dm^2)
Motor -  Cobra 2221/12-1250kv Max Continuous Power (4S) -  474 watts continuous
Propeller -  8 x 7 Aeronaut Cam Carbon Folder Max Prop Power -  448 watts @ 2550ft ASL
Static Thrust -  45oz (1268g) @ 2550ft ASL *Static Thrust/Weight -  0.73
Battery Type -  4S1P Lipo Battery Capacity -  6600mah/10C
In flight efficiency -  <130mAh/mile (<81mAh/km) Typ. Flight Time -  Up to 80 minutes
COG -  53mm @ Wing root (Stock) *With the  6600mAh pack 

Flight Gear

The following are some of my selected components with links to some of my favorite vendors.

Power Set-up

For power on this build I originally chose the Cobra 2221/12-1250kv motor which I have now changed back to the Cobra 2221/16-940kv. I'm a huge Cobra fan because of the quality of the product, the design elements spec'd by Inov8tive Designs and the awesome customer service I have received from RCDude.com over the years. I have also changed from the Cobra 33A ESC to a YEP 40A ESC because I want to see if the Active Freewheeling feature in the YEP units actually reduces heat generation and improves efficiency.

For more informaion on setting up a pusher folding prop - How To - Set-Up a Pusher Style Folding Prop
2221MTR .jpg

With respect to the Aeronaut folding prop and in addition to the other 3D parts found here, I designed a prop-stop insert based on an idea I got from another RCG poster (Noircogi). It is a one piece unit which stops over-fold and over-extension. The part files can be found on Thingiverse here:

Aeronaut Folding Prop Stop Insert


Test Conditions

I always test the chosen power components with a selection of props I plan on using. For these tests I generally do a set of test runs using a regulated power supply to compare to published results and a set of runs using the flight battery to get a reality check. Because I am at 2550ft ASL and generally operating in less than 15% relative humidity, my results will be a bit different from most others.

  • Altitude (ASL): 2550ft
  • Power: Multistar 4S/8000mAh, 10C Pack
  • Test run time - 10 seconds @ 100% throttle

Test Results

Each prop run is ten seconds at wide open throttle with a battery starting voltage of 4.1v per cell (16.4v). This test is repeated three times and the results are then averaged to mean values for direct comparison.

MT PropTest.jpg

Flight Control

For flight control I have chosen a mini version clone of an APM 2.6 from Ready to Fly Quads. It is very small at 35mm square but still has all the functionality of a standard APM. There are a couple of challenges with this unit the first being you need to build a servo buss to carry the motor current of the servos as the FC is really designed for multicopters (no servos). The second challenge was getting the latest version of the Arduplane software loaded. To do this I had to use APM planner and a downloaded stable version of the firmware.

w/Arduplane 3.4


RC Control

For radio gear I am initially going to use a FrSky L9R long range 2.4G RX. Some folks have posted very good range with this unit so I will give it a try. I will likely then change to my LRS standard, a DragonLink Micro RX with their 433 dipole antenna as this set-up is incredibly reliable and provides much longer range than the MT is capable of flying.


For an OSD I am using the Micro MinimOSD which is reliable and easy to set-up with the APM. A big advantage is the size as I am able to servo-tape a 4 pin servo connector on top of the APM case and simply plug the OSD into the connector. I am using the MinimOSD Extra firmware version r800 because it has been ultra stable for me and has the display features I like.

w/Firmware r800


Video Downlink

(Slightly larger version of the HS1177 camera)

Pan Servo

  • GWS S125 1t - 360 degree winch servo (ebay)

Airframe Build and Assembly

For this build I developed a kit of 3D printed parts to make component installation easier and to help with aerodynamics. The kit includes the following components:

  • Mount bracket for the GWS pan servo, FPV cam and Aero cover
  • Turret mount for the Mobius camera
  • Aerodynamic nose cover
  • VTx mount and cover
  • Gear deck for the center structure
  • Front and rear landing skids

I have uploaded the kit files to Thingiverse here:

X-UAV Mini Talon Parts Kit

Some components may be updated

Fuse Prep & Glue

For gluing EPO foam, I use Beacon Foam-Tac which works very well and it sets fairly quickly. To prepare the pieces, I always wash all surfaces of all parts in hot water with a small amount of dish soap to get rid of any mold release agents. Next I do a wipe down with denatured alcohol and finally a light sand on the glue surfaces with #100 grit sandpaper.

Before gluing the fuse halfs, I set up the motor mount plate with APC prop bushings and 3mm blind nuts to get the motor off the wood for better cooling.

Motor mount prep

3mm Blind Nuts

Mount glued in

After gluing in the motor mount I glued in the center structure, added three cable guides to each side and some Dual lock to hold the ESC.

Fuse prep

With the fuse glued up, I mounted the front and rear ABS skids. I printed them in ABS this time to see if it is more durable than the PLA material I have used in the past.

ABS Front skid

ABS Tail skid

Nose Kit pieces

After making the cut-outs, the front kit pieces are mounted and the FPV cam, pan servo and bearing plate are installed.

Mounted front kit components

I drilled slots for wire ties and added silicone tubing to hold and cushion the camera switch assembly

Cam switch and v/regulator mount prep

The camera switch assembly is a DPCAV.com camera switch with an add-on 5v regulator for the Mobius all mounted up front under the cover.

Front ready to be closed up

Nose assembly complete

Front view

Gear Deck

The printed gear deck has threaded deck clips to mount it with four M3 x 10mm nylon stand-offs and four M3 x 6mm screws. The stand-offs are used so there is room underneath to mount a step-down buck regulator and an LC filter.

Gear deck test fit before fuse glue

On the top of the deck I mounted the Mini APM 2.6 flight controller, FrSky L9R reciever and a made-up servo buss which is required when running this flight controller on a fixed wing aircraft. The servo buss gets its power from the ESC and is wired into channels 1,2,3,4 & 6 with channel one having two pin sets for the ailerons. There is also a pair of pins to power the Micro MinimOSD which makes it easy to reset on start-up.

Additionally there is a USB extension plug which, through a small cut-out in the fuse, makes it very easy to plug the flight controller into my laptop without having to open up the plane or move wires around, etc.

Top side components

On the bottom I mounted an RMRC LC filter and a step-down Buck regulator to feed clean 12v power to the cameras and VTx. There is also a FrSky SBUS/CPPM converter mounted on the bottom (not shown).

Bottom side components

General Component layout

Battery Hold Down

To hold the battery down I printed a battery strap well which is in-layed on the bottom, outside of the fuse. The fuse floor is 14mm thick in this area and the well is 4mm deep. I do it this way because it is easier than building a heavy plywood or plastic battery tray inside the fuse and it also makes it very easy to change strap sizes. Inside the fuse I glue down strips of velcro to help stabilize the pack.

Battery strap well, under the fuselage


Nothing too special here. I did add a 3D printed NACA style duct to the top rear to force a little more air at the ESC and Motor. The rear of the hatch has a CF tab which engages a slot in the fuse rather than using a screw and the front still has a screw (for the moment).

Hatch treatment


On the tail linkage I used a similar set-up as on MT#1. That is I used spherical rod ends to deal with the high miss-alignment caused by the stock geometry which puts the linkage at an angle to the control surface.

TowerPro or "Lofty Ambition"? :)


If you are planning on using the Dubro brass threaded couplers shown above, you must make your own wire rods out of steel as the kit comes with stainless steel which is near impossible to solder.
Also DO NOT use loctite thread locker (blue or red) on any part of your control linkage as Loctite attacks the black plastic used in the stock horns and they will fail. Better to either double nut or use thin CA glue on the threads.


I added 1" (25mm) of 3 mil laminate to the leading edge. Linkage is stock and servos are TowerPro MG90S.

Maiden Video!

Finally got to maiden Mini Talon #2 and it went great! It was a beautiful 78 degree morning at Eldorado drylake and wind was near zero. Everything worked as I'd hoped including the new GWS winch servo I am using for Pan. Next will be some longer range shake-down flights.

This video was post processed in Mercalli V4 for taking out minor shakes and roll jitters. There is what appears to be jello but this is actually from the Mercalli software which I am still learning to use.


Maiden Day - 24 September, 2016


  • Changed (back) to a Cobra 2221/16-940kv motor with a 9x7 Aeronaut folder
  • Changed the ESC to a YEP 40A with Active Freewheeling
  • Added the tilt deck from my Heavy Duty Pan and Tilt project
  • New Airspeed sensor mount

Now with Pan AND Tilt! :)

Hook it up!

  • Added a new mini-mount for my airspeed sensor

Pitot Tube mount assembly

Pitot Tube front view

Pitot Tube side view

Future Changes

  • Swap the Mini APM out for a Pixracer flight controller
  • ...

See Also

Mini-Talon on RC Groups
Mini Talon Noses
X-UAV Mini Talon Build Number 1
X-UAV Mini Talon Build Number 3
X-UAV Mini Talon Build Number 4

Project 3D Print Files

The following are the 3D print ZIP files used in this build. For more versions and information, please see my Thingiverse postings here:
Mark_q Thingiverse Designs

Some of the Vendors I used for this project

R/C Dude Hobbies
Ready To Fly Quads
Aloft Hobbies
Ready Made RC

Comments? Questions?

email me!