Build highlights

This build is an exploration of the idea of a lightweight ReelSteady Go capable Cinewhoop built around 1306 motors. The result? It definitely works, here is what I managed to film with a Hero 5 Session:

Weight breakdown

It is important to keep the weight low with smaller motors. My thrust stand tests show they start losing efficiency rather quickly after you cross 100-110 grams of static thrust per motor, so I tried to keep it as light as possible when choosing the components.

Quad, dry: 164 grams
Quad + Hero 5 Session + hardened glass lens protector: 237 grams
Quad + Session + 450 mAh 4S pack: 292 grams
Quad + Session + 650 mAh 4S pack: 309 grams

Potential for additional weight savings:

1. The Micro Eagle camera is rather heavy. I like the picture it produces combined with OLED goggles, but it would be possible to save about 5 grams if replaced with a Nano format camera. Personally, I am willing to sacrifice those 5 grams for extra clarity and definition of my FPV feed.
2. Toothpick class flight stack. They weigh about 6 grams compared to 11 grams for Mamba mk2 and require shorter screws, but there are two problems. The frame does not have the holes for a whoop style board, and mounting the VTX becomes tricky. Still, going this route would probably save some 5-10 grams extra.

Flight time

Surprisingly, it came out to be an efficient flier. 650 mAh 4S gets me about 5:30 cruising time. A cute tiny 450 mAh 4S pack is good for about 4 minutes of cruising, and I actually like it more that way. Four minutes are enough to film one long or two shorter takes, and 17 grams of weight difference make a significant change in the flight characteristics.

3D printed parts

I published all the custom parts for this build on Thingiverse:

• Propeller guards
• GoPro mount
• RX antenna tube mounts, you need the low profile 30 degrees version.

The guards require rigid but impact resistant material. My choice is NinjaTek Armadillo, which is very hard kind of TPU (Shore hardness 75D). The Session and antenna tube mounts should be printed with a regular soft TPU, like the omnipresent SainSmart 95A.

Ducts VS prop guards

I tell you this, ducts are really not your friends. Even though they generate extra thrust, they make the quad fly weird and suffer from typical whoop class issues like washouts and unpredictable "on/off" throttle feel. That's why instead of using stock ducts that came with the frame I designed my own super skinny prop guards. They interfere less with the thrust columns coming out of the rotors, and surprisingly enough still increase the efficiency by about 10%.

Becoming a smooth Cinewhoop operator

You need to be very gentle and flowy at the controls when you film for ReelSteady. Two things help a lot in my experience: slow rates and a throttle cut.

I set my rates at 260-300 degrees per second. You might think that is way too slow, but trust me, it really helps bringing that smoothness to the flying. Betaflight 4.1 rates are as follows. Roll and pitch: RC rate 0.80, Super rate 0.40, RC Expo 0.35. Yaw rate: RC rate 0.90, Super rate 0.40, RC Expo 0.35. I like having it a bit faster on yaw to be able to do 180 degree turns comfortably.

Throttle cut allows you to tame the quad and increase the throttle stick resolution. I absolutely love having my throttle cut on the radio potentiometer. You just keep bringing it down until you feel the quad is under control in the given environment and that really helps when you film in tight spaces. I made a full how-to video on the throttle cut on the radio. I talk about racing there, but it is 100% applicable to Cinewhoops. Setup instructions are at 4:32, check it out https://youtu.be/a7PInDtsFGc?t=272

Build log

The build itself is rather simple. You start with putting the bottom plate and the arms together, mounting the motors (only 3 screws per each to save weight!) and soldering the motor wires to the ESC. Emax 1306 have the wires of just the right length to be soldered in the front-and-back fashion. Don't forget to put some heatshrink over the arms to hold the wires.

I always recommend mounting the flight stack with metal screws. For this one you need to remove the threaded parts of the 5mm nylon standoffs and drill the holes all the way through so they fit on the 20 mm M2 screws that come with the Mamba stack. Put silicone grommets underneath the second row of standoffs.

For better wire management I recommend soldering the battery leads to the bottom side of the ESC. Keep enough length so they stick out at the back a bit and also put a piece of heatshrink over them to reinforce the area that is zip-tied to the frame for stress relief.

The stack can be made shorter, but since the quad is intended for slow flying, the electronics needs better cooling. 5 mm standoffs provide enough spacing.

Here you can see the stress relief zip tie. I always recommend tying power leads to the structural component so ESC pads do not get ripped off in case of battery ejection. The relief point is marked by an arrow.

Flight controller wiring is pretty straight forward. Solder camera and VTX wires as shown in the Mamba stack manual. Solder the S.Port wire of the receiver to the PPM pad to get the FrSky telemetry working. Having the ability to change camera settings is very handy, so solder a 2-pin pigtail to RX6 and TX6. Those are used for the RunCam device interface.

The VTX needs to be soldered into the Nano-Nano board. Connection to the flight controller is as shown on the picture. You can also see my favourite way to reinforce u.Fl connectors – a dab of liquid electrical tape. The board has seen several builds, so please pardon the burned flux.

To mount the flight controller take a 3 mm antenna tube and cut small portions to fit into the blue silicone grommets. This way the FC does not wiggle in place and is still isolated from mechanical noise. The tube piece at the very front on the picture is ready to be inserted into the grommet.

The flight controller goes on top of the ESC, and there is just enough screw length left to install the next row of nylon standoffs.

By the way, MG Chemicals makes silicone conformal coating that dries quickly enough to work with the parts in about 10 minutes after the application. I recommend coating all your quads, always. Even the cheapest black light torch from Amazon makes coating process a piece of cake.

Next step is to mount the VTX. Use 5 mm nylon standoffs and nylon nuts.

The stack looks neat! If you have an ESC cable kit, you can make a longer harness to mount the flight controller straight. You can also put it sideways and use the harness that comes with the stack. A longer one allows easier access to the USB port.

Next step is the control link. Conformal coat the receiver, wrap it into a hearshrink and stick a piece of copper tape over the bottom part. The receiver is mounted on top of motor wires and since R-XSR is known to cause interference with telemetry signal, extra shielding seems to be a good idea.

Mount the receiver at the back of the frame with a small zip tie. Just place it over motor wires and tighten it up.

Next, put the propeller guards on and install the antenna tubes with the mounts. Slide the antennas in as shown in the picture, leaving some space for the power leads that will be coming out at the back.

The camera goes at the front. Don't forget to put the guard spacers on top.

Fix the guards to the arm ends with 20 mm steel M2 screws and M2 nuts.

Time to finish it up with the top plate! Stick some pieces of silicone anti-slip stuff to it, mount the video antenna with a zip tie and screw the GoPro mount on. I recommend mounting the video antenna a bit away from the receiver antennas to avoid video interference due to telemetry transmission.

Secure the propellers and add a battery strap. Et voilà!