FreePilot Pre-Maiden Status


Hi Guys,

Its been some time since I gave any public updates to you people (contributors have got weeklies) on the status of the FreePilot project. Now as the project nears completion, I am posting photos and the current status for you people to comment on , advise, criticize , etc. I have run into some issues, most of which have been solved, but still need some help on the others.


  • All body work finished except canopy.
  • Everything bench tested.
  • Some ESC issues (summarized below)
  • XBee joystick control perfected.
  • Latest ArduPlane 2.5 (with modifications) loaded.
  • Battery and voltage sensor connected to APM on-bench.
  • Airelons tested to breaking point (still works perfectly)
  • Custom control rods attached (flexible plastic)
  • On the inside, spruce spars in original design replaced with fiberglass.
  • Everything else to get it flying.

To Do and Issues:

  • Make the canopy (almost finished)
  • Fix ESC heating issues: The 20A JDrones ESC is overheating on bench, without the motor running and just APM drawing from the BEC. My battery is a 11.1v 25C 2200mAh Turnigy pack, which should be suited for the ESC, but it still heats up, even after adding a beefy heat-sink on top. The MOSFETs on the bottom cannot be touched after a minute. I think I need a beefier ESC.



Heat-sinked ESC (which still gets too hot)



Just-arrived Turnigy LiPo recessed in the body


APM, GPS and Xbee recessed in the body


Servo connected to right aileron using my 'specialized' push rods


Top View without Canopy

Let me know what you guys think, whether it will it fly or not, etc. 

If you want a photo-log of the entire project, its down below :

Parts Arrived (courtesy of Martin)

Electronics Assembled

Airframe 1

Airframe 2

Battery and Charger (courtesy of Sandesh)


If anyone is interested in contributing towards the advancement of FreePilot please PM me!

This project would not have been possible without the generous contribution of :

  • Sandesh (for batteries and charger)
  • Martin (for APM, servos, Xbees, Motor, ESC and more)
  • Crasher (ESC and motors pledged)
  • Jaron (for airframe design which I have modified to suit my needs)
E-mail me when people leave their comments –

You need to be a member of diydrones to add comments!

Join diydrones


  • I've made teh same plane but i used 3mm and 6mm depron sheet to do it!

    The average weight of my plane is around 750grs for 135cm of wingspan.


  • That wing looks WAY too thick.  I build one of these Intermezzo's a while back and the wing was only 3/4" thick.  How thick is it?  If you divide the wing chord by the thickness, it should be less than 15% max.  I'd suggest building another one EXACTLY according to the plans, with a much smaller battery and without your precious apm, and getting some flying time in it first... then add in the APM... then go up to bigger batteries.  Then you can think about changing the design and seeing how differently it flies.

  • Developer

    Weight is around 900 grams , as far as I can guess.For the ESC heating issues, I have planned a duct system in my canopy to temporarily air-cool the ESC until I get one with a UBEC/SBEC.

    I'll check the current draw and let you know. I'll be chafing/cutting the trailing edges soon and will tell you then.

  • Moderator

    Also for the first flight you should have about 1-2mm up elevator (reflex) and the elevon up/down movement about 15mm/15mm. Do some glide tests first using a hard throw, fix a scrap piece of balsa or foam underneath just behind the CG to be able to grip when you throw.

    Paint some colour on, dark (Black/blue/red) underneath and light (white/yellow/neon) on top, likewise for the vertical fins, dark on the inside, light on the outside. All these will help to ensure success.

    You never said the weight and current draw?

  • Moderator

    Yup, the trialing edge should be as thin as is practical, 2-4mm is about right and the leading edge as round as possible. As mentioned too the pushrods must be as stiff as possible with no slop, the hinges likewise must have as little slop as possible. Are you still having ESC heating issues?

  • Developer

    Ok checked, I think the CG is now perfect, as calculated by

    Flying wing CG calculator
  • Developer

    So I should just reduce the thickness, thats it?

  • Moderator

    CG should be around 18% for that type (use this to calculate: For a thinner trailing edge just cut the foam using a straight edge, although I like to line my edges with balsa if possible.

    Flying wing CG calculator
  • Developer

    @ Graham and Melih the design is a KFm Airfoil. How can I reduce the thickness of the trailing edge?

  • Developer

    @ Graham I have since fixed the CG,I moved the battery up front and now the CG is where in the middle wing layer starts.

    @Petrus I did what you said and the epoxy dries as I write.

    @Melih Lets see ... It glides OK , when I had tested it without electronics. 

This reply was deleted.