XR-61: Completed and Maiden Flight

I did the maiden flight yesterday. The plane flies beautifully, but I had some radio issues so I had to cut the flying session short.

 

Precision Aerobatics XR-61 - Unboxing and Build Pictures

I have a new plane that I've been working on finishing up for flight. It's called the XR-61 from Precision Aerobatics, who is known for building extremely lightweight airframes which excel at 3D maneuvers.

I have two of their other planes, the Electric Shock, and the Katana MD, both of which got a ton of use and fly very well. The XR-61 is a bit bigger than either of those, with a 61" wingspan. It's supposed to be a fantastic plane to be able to mix 3D and precision/pattern type flying. I'm really looking forward to it, as it's been a few years since I've done any real aerobatics. I'm going to try using low rates and possible mid rates with this plane to more properly fly different types of aerobatics. In the past, I only ever used high rates, and I have a feeling that my precision flying suffered some from that.

I bought the ARF with the iPAs power package, which includes the servos, motor, ESC, and prop. I also bought the "bling package" which includes a carbon fiber spinner, carbon fiber wheel pants, carbon fiber vortex generator kit, carbon fiber servo arm extensions, and wing bags. I also added a prop protection sleeve because the Vox prop is wood and is prone to damage.

Here are some pictures from the build process:

Wing Bags

Unboxing

Carbon Fiber Spinner

All the Goodies!

Control Horn Work

Carbon Fiber Wheel Pants

Fiberglassing the Motor Mount

Motor Box Installed with ESC and Motor

Tape holding the Horizontal Stabilizer Parallel with the
Wing Tube while the Epoxy Sets

Finished Landing Gear and Landing Gear Cuffs

Control Repeater Upgrades (Again)

After using the upgraded control repeater a few times, it became apparent that having a power switch would be really useful, especially when doing the short flights with the Mojo.

I added a switch next to the model select switch, so instead of opening the lid and unplugging the battery, I can just quickly switch it off.

In addition, I added a voltage monitor/alarm which is easily visible through the top of the case. This is a good way to ensure the battery that's powering the ground station has plenty of life left, without having to use the telemetry cable from the repeater receivers.

Control Repeater Upgrades

Now that I have two models being flown with Dragon Link (the Sabre and the Mojo), I realized that there is a complication with the control system. The reason for the complication is that the repeater receiver must be bound to selected model in the DX20, and it must have failsafe programmed correctly.

For the Sabre, this means that the repeater receiver must be programmed to engage return to home, which means the equivalent of the top two right switches on the DX20 are "down."

For the Vortex, since it does not have a return to home, the desired failsafe is to simply cut the throttle. In this case, that means the top two right switches must be "up" (opposite the failsafe position for the Sabre).

The switch positions that cut the throttle in the Mojo and that engage return to home in the Sabre are arbitrary, but that's how I have them set up and how I am used to them.

I had three options to remedy the failsafe issue for two models:

1) Rebind, reprogram failsafe, and re-test failsafe (turn off DX20 and see what happens) every time I switch models.

2) Reprogram the switch positions on one of the two model programs in the DX20, to ensure that the desired failsafe behavior results are trigger the same for each model (Would require overriding Model Match in the DX20).

3) Use two repeater receivers, one for each model, and switch receivers when switching models.

I didn't choose number one because it's hugely inconvenient and prone to messing up the failsafe programming, resulting in potentially unsafe conditions during the necessary failsafe test. I didn't want to do two either because it is also hugely inconvenient, but I also am very used to the way the two switches are used in each model. Changing the switch positions would slow down my reaction in the event of an emergency and could cause problems.

I chose number 3. It may seem more clumsy than necessary, but I think I made it pretty convenient with my setup. I also chose to "package" all the gear in the repeater ground station in a much nicer and more durable way than the previous foam board version. (I used some foam board, but more for convenience than for structure.)

I used a DPDT (double-pole, double-throw) switch and completely rewired the whole ground station. Now, when choosing a model, I simply plug the battery in to the BEC, which powers the Dragon Link transmitter, and then use the switch to pick which model I am flying. The switch directs power from the BEC to the correct receiver, and directs the SBUS control signal from the correct receiver to the input of the Dragon Link transmitter.

The case I found at Target is the perfect size for this application because I was able to get all the electronics in one side, and leave the perfect space on the other side for the battery that powers the whole ground station. On top of that, the whole thing fits perfectly in my DX20 case.

Here are some pictures from the build:

Completed with the Lid in Place, 2S, 5000mAh Lipo Installed

The Lid Removed, Power Cable (Deans), Telemetry Cables

The Foam Board Cover Removed, Revealing a Bit of Wiring,
the DPDT Switch, the Two Receivers, and the BEC

Model Select Switch

New Repeater Station in the DX20 Case

Bench Testing the New Wiring (1 of 2)

Bench Testing the New Wiring (2 of 2)

Mojo, Kenney Field

I flew another 5 (only 4 videos because I forgot to start recording once) flights in the Mojo yesterday. It was a cool and breezy day, but it was really fun, thanks to being able to fly from the car with the control repeater setup. For the last flight, I decided to take off from the moon roof of my car, just for something interesting.

Vortex 230 Mojo, Westwood Park

More onboard videos with the Mojo and the GoPro. I changed the GoPro from 30 frames per second to 60, and the videos came out noticeably better, including seemingly less jello. There are only a few places where I notice it, and it's not enough to detract from the video. I'm pretty happy with the camera so far. I'm getting more confident with flying the Mojo as well. I had a couple close calls with trees, but for medium speed cruising, I've gotten much smoother at coordinating the yaw and roll together. This is most noticeable in video 2 of 3.

Vortex 230 Mojo, GoPro

I did some more flights today with the Mojo. For the first time, I put my GoPro on board and flew with that. There is some jello in the video at certain throttles. I'm not sure what's causing that, but it isn't terrible. The picture is noticeable better than the Mobius, but I think I will use 60 frames per second from now on. It will result in much larger file sizes, but the video will be much smoother and more enjoyable to watch.

I'm glad I have Dragon Link installed in the Mojo, because I was able to set up my control repeater on the hood of my car, and fly from the driver's seat. Otherwise, I wouldn't have even flown, as it's still only about 35 degrees and breezy, which is just way too cold for comfort.

Here are the two videos: