Belated Updates

I have not posted any updates in a long time, even though quite a lot has happened. I’ll keep this brief and hopefully not take so long before I post up something new again.

  • I built a Zebro 38 flying wing that is working great
  • Team Basement RC held an awesome meet up with lot of flying wings
  • I stopped flying my Spirit even though it is a great model because I was focused on the new wing
  • My tricopter is nice but gets bad jello in its current design and needs another update
  • I finally got an OpenPilot Revolution flight controller that I can try out and help with
  • I have gimbal parts and motors for a brushless gimbal, but I did not get a controller yet
  • I switched from my DX6i transmitter to the 9XR and am pretty happy

Related Links:


Spirit FPV – Small island through an HD keychain

I made two flights with my Freewing Spirit and got a lot more confidence. Unfortunately the broadcast recording did not work, but for the second flight, I taped a keychain camera on top of the plane. That appears in is the second part of the video. The first part is ground video from my tripod.

More discussion on the OP site.

My new Turnigy 9XR

I got a new Turnigy 9XR RC transmitter from Hobby King in the hope that it can replace my Spektrum DX6i and provide some more functionality.

Getting out of the way my first comment — there is no printed material with the transmitter or anything on the box that credits the authors of the firmware or gives a location to see source for HK’s modifications. So it’s a plain and clear violation of the firmware’s distribution license. They should have had time to slip a sheet of paper into each box before shipping, and they are going to have to fix this eventually. Really no excuse. Moving on….

I basically concur with the favorable reviews you are reading out there. It’s a 9X that already has the popular mods done to it. The gimbal quality felt perfectly fine. The switches and trim tabs too. Mine has the hairline marks you read about, but it looks only cosmetic and I might not have noticed myself. It feels fine in the hands and is a bit thinner than my DX6i. The worst controls are the 4-position cross and up/down buttons around the LCD used to navigate the menu — they stand out as cheap and having poor feel compared to the rest.

It took some fiddling to get working with my EZUHF, and the solution is not ideal. The transmitter has both JR and Futaba connector ports. Plugging into the JR port turns on the transmitter, but it cannot supply power to the tx module that way. Plugging into the Futaba port on the other hand does not turn on the transmitter, but this port will supply power from the transmitter to the tx module. Without a trick, the EZUHF just squeals like a bad PPM signal in the Futaba port. In the JR port it seems to work, but the action is very flaky, clearly something wrong — I didn’t resolve this yet.

The trick for the Futaba port is to insert a 3.5 mm plug into the JR port to begin using it. This turns on the transmitter and makes the PPM work. This video shows the procedure.

Here is the earlier video from before I got my EZUHF to work at all.

Along with the transmitter, I got the ugly DSM2 2.4GHz tx module with an external antenna. It seems OK, but the antenna is in an inconvenient location. I have not tried to use it at all.

I also got the metal case they offered for the transmitter, thinking I might use it regularly. Actually, I think it is a little too thick and bulky and I don’t think I will really ever use it, so a bit of a waste. The venom case for DX6i is far better.

The firmware is very configurable and it is a nice step up from a DX6i to have so much more functionality in the form of switches, including one 3-way one and also 3 knobs. The stick calibration and transmitter customization features look really good. Of course that is the ER9X firmware.

Hopefully I can get the EZUHF working entirely smoothly, and then I will be very happy to use it in place of my DX6i.

Finally a smooth landing

I realized my last few flights were quite nose heavy. I was adjusting the elevator to center quite far up, and it hardly had any range to pitch up further. Still it wasn’t enough, and I came down hard a few days ago. A wing and video antenna broke.

Only then did I finally look up the suggested center of gravity in the manual — 40-50 mm behind the leading edge of the wing. After some fixes and adjustments to match the recommendation, I got much better results. I also changed to a 3-blade propeller that can put out more thrust than the APC 5×5, at least in my static testing.

This is a pretty successful flight, if only for 40 seconds. The landing at the end was actually quite nice. I think it is still a little nose heavy. I had not realized how sensitive this is for planes.

The roll rate Kp has been adjusted here down to 28. The problem is this still looks too high for the higher speed cruising here — clear oscillations. On the other hand it is too low to keep the attitude steady shortly after launch. This seems like a tough problem to solve in general — how do you tune a plane to fly crisply without oscillation at a full range of speeds?

Spirit First FPV Flights

I converted the Spirit to FPV and made a few flights with it.

The flight controller is clearly overtuned in roll here. I had thought the sudden dip at the end was a stall, but now I think it was a FC feature that kicked in when I zeroed the throttle.

At least I am learning a lot. Hopefully more and better flights coming up. At some point I’ll want to figure out how to put a better camera on this plane.

spirit-fpv-gear spirit-fpv-gear-front

Spirit Flight Practice

Here are some flights I made with the Spirit by LOS.  They are all brief and I didn’t feel like I could turn it sharply enough — I was using ailerons only here, no rudder.

Changing the Spirit to Pusher

The Freewing Spirit model that I got from Hobby King came in a tractor configuration with a 2621 1100kv motor and an 8×5 folding propeller.  I have only played with it on 2S batteries, and it has enough power to fly around smoothly that way.  You might need 3S batteries to get really strong performance.  But I broke my propeller and have not been able to fly for a while.

I have been getting parts to convert the model to a pusher configuration.  To fit inside the motor nacelle, the pusher motor should be 22mm in diameter or perhaps a tad more.  The recommended motor is a “2226-2200kv” motor, and I found it available at  And here is the bundled 5×4.5 pusher propeller too.

Unfortunately, I could not find stats for the recommended motor!  I actually ordered a different motor for this purpose from RC Timer, the BC1712-13 2000kv, weighing 32g.  It fits into the nacelle just right and looks like it should work well.  But it is slightly lower kv than the recommended 2200.  It also has a 1/8″ (3.17mm) smooth shaft instead of 3mm threaded one, like the recommended motor.  This means you need a prop adapter and the bundled pusher propellers cannot be used.

Propeller choice can matter a lot, and I don’t have much knowledge here.  I have bench tested the motor with a Master Airscrew 5×3 3-blade propeller and an APC 5×5 2-blade propeller.  Both are nice quality, and I really like the look of the MA.  But the pitch on the MA is low, it even looks like a flat airfoil at the extremeties, and it’s hard to see how this will have a lot of bite in forward flight.  The 5×5 on the other hand may have too much bite — I read some reviews that this propeller shines for high speed pylon racers and the blades stall at low speed.

I bench tested wide open throttle for both with these approximate results.

Propeller Battery Thrust
MA 5x3x3 2S 100g
3S 200g
APC 5x5x2 2S 150g
3S 240g

So I decided on the APC 5×5.  I will probably get a few more props to test.

I weighed the old motor pulled out of the nose at 40g, and another 20g for the full prop assembly.  The replacement cone is weighed at 20g.  And the nacelle with pusher motor and prop weighs 74g.

It is very hard to get the center of gravity in a good spot in the pusher configuration.  I had to put all gear in the nose, rather than the battery bay under the wing, and also use a heavier battery than I wanted.  All together the plane weighs 335g without a battery as a pusher, and 390g with battery — this is getting bloated for a small 850mm plane.

I had to flip my CC flight control board back right-side-up to make room in the bay underneath.

Enjoy the pictures of the procedure and results.

Now I need to find a chance to practice flying it some more!

spirt-new-motor spirt-new-motor-nacelle spirt-converted-overall spirt-converted-nose spirt-converted-motor