My Cinewhoop is lighter than yours

By ErgoFPV on Dec 01, 2019

15  401  8

This build is an exploration of the idea of a lightweight ReelSteady Go capable Cinewhoop built around 1306 motors. I would say it definitely works with a Session 5, check out the video at the end.

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 keep it light at all costs!

Weight breakdown:
The quad, dry (with the 3D printed loop-style Session mount): 165 grams
With Session 5 and 450 mAh 4S: 287 grams
With Session 5 and 650 mAh 4S: 306 grams

Those skinny 3D printed prop ducts weigh 5 grams less than the stock ones. I will publish them soon on my account on Thingiverse, you can follow me there to get notified.

Flight time:
Surprisingly, it came out to be an efficient flier. 650 mAh 4S gets me about 5:30 cruising time. That cute tiny 450 mAh 4S pack gets 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 19 grams of weight difference make a drastic change in the flight characteristics.

Ducts VS prop guards:
I tell you this, ducts suck. Even if 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 throttle cut.

I set my rates at 260-300 degrees per second at maximum stick deflection. You might think that is way too slow, but trust me, it really helps to bring 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 to have a bit faster rate on yaw to be able to do 180 degree turns easier.

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. It 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

Here is a video I shot with this quad carrying a Session 5:

More photos and build details later!

Photos

Part List

Frame

Donut" 3 Inch 140mm H-type Frame Kit 3D Printed + Carbon Fiber for RC Drone FPV Racing 75.5g (4 builds)
Banggood.com
$29.99

Flight Controller

MAMBA F405 Mini MK2 Betaflight Flight Controller & F25 20A 3-4S DSHOT600 FPV Racing Brushless ESC (14 builds)
Banggood.com
$39.99

Motors

4 x EMAX 1306 RS1306 Version 2 RS1306B 2700KV 4000KV Brushless Motor 3-4S For RC Drone Multi Rotor (11 builds)
Banggood.com
$43.96

Propellers

6 Pairs Emax AVAN Mini 3 Inch 3X2.4X3 3-blade RC Drone FPV Racing Propeller CW CCW (38 builds)
Banggood.com
$5.49

FPV Camera

RunCam Micro Eagle 1/1.8" CMOS 800TVL Global WDR 16:9/4:3 Switchable FPV Camera for RC Drone (266 builds)
Banggood.com
$44.99

FPV Transmitter

TBS UNIFY PRO32 NANO 5G8 (82 builds)
Pyrodrone.com
$29.95

Antenna

Lumenier Micro AXII U.FL 5.8GHz 1.6dBi Gain FPV Antenna RHCP / LHCP For RC Drone (3 builds)
Banggood.com
$19.99

Receiver

Original FrSky New Version R-XSR Receiver Antenna 95mm 2400~2480MHz 1 PC (3 builds)
Banggood.com
$1.93

Batteries

TATTU 650mAh 4S1P 75C 14.8V Lipo Battery Pack with XT30 plug (33 builds)
Getfpv.com
$14.99

Batteries

Tattu 14.8V 4S 450mAh 75C LiPo Micro Battery Battery - XT30 (13 builds)
Racedayquads.com
$10.11

HD Camera

GoPro HERO5 Session (197 builds)
Amazon.com
$299.00

Misc Parts

MINI Pyro-Drone Battery Strap 4 Pcs. / Pack (12.5mm x 160mm)
Pyrodrone.com
$4.99

Misc Parts

Unify Pro Nano Mounting Board (Nano-Nano) (20 x 20) (4 builds)
Whitenoisefpv.com
$3.95

Misc Parts

GoPro Session mount for Reelsteady Go (Donut 3 inch cinewhoop frame) by ErgoFPV
Thingiverse.com
See Site
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Discussion

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1Smug_Bastard   13 hours ago  

That FC look really nice for 1-2A Builds. https://emaxmodel.com/emax-tinyhawk-s-indoor-drone-part-aio-flight-controller-vtx-receiver.html

Whats it weight, cause this spec isnt listed...

Apeian   19 hours ago  

Hey Ergo - You did a great job on the video and the flight. Did you try the flight before getting rid of the larger ducts? Did the sacrifice of a few grams effect your flight much?

ErgoFPV   19 hours ago 

Thank you! I tried the original ducts and also went full circle designing my own full ducts trying to get higher efficiency based on this article https://capolight.wordpress.com/2015/01/14/quadcopter-rotor-duct/ I was able to make the ducts improve the efficiency by 27% while original ones provide about 19% improvement.

What I found though is ducts make the flight performance worse not because of the weight, but because they do something to the motor thrust output. The quad did not really react to fine throttle adjustments, I experienced washouts similart to those typical for tiny whoops, yaw response was somewhat delayed, and overall it felt weird in the air. I thought it was the weight, but then remembered that theory of prop unloading always mentioned by KababFPV and decided to try designing guards instead of ducts. The guards weighed just a bit less, but the quad flew much much better. It felt just like a regular quad, overwheight for sure but nothing weird in reactions to the inputs. Surprisingly enough, guards also provided efficiency improvement, I measured about 10% increase.

1Smug_Bastard   7 days ago  

The BetaFPV F4 20A AIO FC is aprox 6 grams or about half the weight of your current AIO.
https://betafpv.com/collections/brushless-flight-controller/products/toothpick-f4-20a-aio-brushless-flight-controller

ErgoFPV   7 days ago 

Very interesting, thanks for sharing! I chose the Mamba stack because of reliability and low price. Since this craft is intended for smooth flight I would be a bit careful with a toothpick board which has everything on one PCB. There's more potential for the voltage spikes to affect the gyro readings, and maybe a capacitor would be required. My current setup has no cap and flies beautifully smooth. Whoop stack screw pattern is not compatible with the Donut frame, so a custom solution would be needed, and same for the VTX. At the moment everything except the RX is in one stack at the middle of the frame, nice and clean. But yeah, there might be a potential to shave off some 5-10 grams.

1Smug_Bastard   7 days ago 

I've a 4S nano-tricopter that flies really well using that card: https://rotorbuilds.com/build/20766

Now as for a custom solution, all you need is a 2mm thick PLA board. Using 3M holes supporting both 30mm and the 26.5 mm FC spacing. Maybe rotate one set of holes 90 degress from the others to help prevent the screws over-lapping.

joshielevy   7 days ago  

Smooth as butter! Out of curiosity - how'd you get the mall to yourself?

ErgoFPV   7 days ago 
1

Thanks! The administration were interested to see if it is possible to do something different for their commercials, and I happened to know the person who worked with them.

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