On 2013-01-26, late in the evening, I got my first monocopter to do more than just rotate: it actually lifted. It was a tethered flight, in the sense that the copter was secured to a vertical rope to keep it from going astray.

It could only climb about a meter or so before it reached the upper end of the rope, but the rotation was pretty stable at about 3.3 Hz, and by working the throttle, it could be made to climb and descend repeatedly. Let's call it v1.0.

Since it was night, there's no video, and I also forgot to take pictures.

The next day, I rebuilt the center section to improve weight and to get the COG in front of the wing (as the Charybdis should have), but rotation was unstable, which finally led to the wing folding right at the end of the dowel, I suspect because the whole thing flapped wildly. That was v1.1.

Now I have a new wing waiting for the glue to dry, and I'll continue with that next weekend.

Things to improve/next steps:

  • Try (slowly!) which position of COG/center of rotation is stable.

  • Get it to climb again.

  • Document that status!

  • Play with the AoA to find an optimum. See whether lift can be quantified, record RPM, see if there's stability impact

  • Measure power and thrust with various props (waiting for Giantshark to return the wattmeter - as delivered, it showed 0.6A of current with no load connected) and select the best one.

  • Brave enough for untethered flight?

A bit of description of the various iterations:


The copter is inspired by the age-old Charybdis model, that is, it had a 60x10cm² depron wing, a 35cm 7mm round dowel glued 5cm into the wing (the rest of the wing had a depron spar), and the wing consisted of two 30cm sections - I had started with a 30x10 wing that didn't produce enough lift, and taped a second section onto the end.

The center section (plywood) had machine screws and a second piece of plywood clamping the dowels (wing and balance shaft), so the angle of attack could be adjusted easily. The motor was mounted with a similiar construction. The LiPo was velcroed to that center plate, and there was a hole to put the starting stick or rope through, at the COG.

The power plant is a M2222/31 from Giantshark, 50W, 2280kv, a rather small brushless outrunner - but the original Charybdis ran a motor rated at 10 or 15 watts. It is driven by a Hobbywing 10A ESC, a 800mAh 2S LiPo, and a Spectrum receiver.

COG was next to the wing, at about 10-20% chord. AoA was about 30%, mass ca. 175g.


The only change was the center section; I went from 2mm to 3mm plywood, because the 2mm flexed to much when clamping the rods. The balance rod is now glued on (6x8mm Pine), the hole at the COG is about 1cm in front of (and next to) the wing, and the battery is further out to adjust the COG.