KISS of calm --- Update: BF 4.3 / 6S whisperer / 128 kHz / Druckbär Ultralight 4 / FETtec 2104 /

By MamaJOE on Sep 10, 2021

23  903  8

The story behind the build

The starting point of this build was a repetitive situation that I assume most of you know:
Angry people coming towards you and yelling at you to get out of here with that bothersome "thing"...
I don't like this experience - and that's the reason, why I wanted to build a quad that's as silent as possible, but without limiting flight performance.

Choice of components

It was clear to me, that a 5- or 6-blade prop should be quieter, so I searched for a suitable prop.
The only one I found was the HQProp 4x4x6, what defined the build to be 4".
Furthermore I want as high PWM as possible, why I chose the FETtec ESC with 128 kHz.
After that I had to look for suitable motors. And on my search I found this Quadmovr video.
So the choice for the motors was clear an I changed my mind, to make it 6S instead of 4S :)
Of course the weight got a big influence on the noise level. So I watched out for a lightweight but durable frame.
I found the Ultralight 4 frame which seemed to be a good choice.


The build was pretty straightforward without bigger problems.
I really like the look of the motors, so I tried to match the color scheme of the raw aluminum for the entire build.
But the stack and Vista didn't fit in the frame, so I put the ESC under the base plate, as I did with my toothpick build.
I had to make my own mount for the video antenna, where I chose aluminum of course.
This is the first time I have mounted the Immortal T on the front. The reason is that I can (mis)use it here as a bumper for the ESC deck.
But since it's easy and cheap to replace, that seems like a good idea.
The video system is detachable, for easy access to the FC.

Flight quality

This thing is really silent - completely comparable to the video above.
And it's damn fast... Not as fast as in the video (because of the higher weight), but it's really amazing!
The tuning was pretty difficult - on stock PIDs it's more or less unflyable.
I found a good tuning, but here I have to spend more work to get the last 10 %.


I didn't manage to get this build fly properly on KISS (vibration issues), so I gave up my tuning efforts and changed to Betaflight. I want to keep the Fettec ESC, because it works great, but unfortunately this means no RPM-filters. On 4.2.11 I had to do a lot of work to find the right filter settings, but I found a good tune and everything was fine. Now I tried 4.3 RC2 and it is a really big improvement for this build. It works almost perfect on stock settings - good work BF devs!
The fine tuning is still in progress but I'm confident to make it fly like I visualize...


Weight with props: 199 g
AUW with 6S 650 mAh: 312 g
Flight time (650 mAh): approx. 3:30 to 5:30


Part List


Ultralight 4
See Site


Conversion Kit (25,5x25,5mm / 30,5 x 30,5mm)
See Site

Flight Controller

FETtec KISS FC (4 builds)

Flight Controller

MAMBA F722 MINI MK2 FLIGHT CONTROLLER - 20x20mm (6 builds)

Flight Controller

JHEMCU Betaflight F4-Openlager High-speed Serial Port BlackBox Module - World's No.1 Most Loved Hobby Store


FETtec 4in1 ESC 35A V1.1


4 x FETtec Motor FM2104M - 1800KV (3 builds)


HQProp Duct-4X4X6 for Cinewhoop Grey (2CW+2CCW)-Poly Carbonate (2 builds)

FPV Camera

Caddx Nebula Pro Vista Kit (10 builds)
See Site


TBS Crossfire Immortal T V2 Antenna (149 builds)


Polar Antenna For Vista (21 builds)
See Site


TBS Crossfire Nano Rx - FPV LONG RANGE DRONE RECEIVER (1491 builds)


Tattu R-Line 650mAh 22.2V 95C 6S1P Lipo Battery Pack with XT30 Plug (9 builds)

Power Distribution

FETtec Spike-Absorber (15 builds)


Boxer EdgeTX Rotor Riot Edition Radio Controller - ELRS (4 builds)


21700 5000mAh Battery for TX16S
See Site


DJI Goggles 2 - Ultra Low Latency 1080p/100FPS 4K/60FPS Digital HD FPV (22 builds)


CopterFarm Super Sticky Cow Tongue Pad Batterie LiPo (7 builds)
See Site


2 x Taste Kopf M2 Titan schrauben M2x3 M2x4 M2x5 M2x6 M2x7 M2x8 M2x10 M2x12 M2x14 M2x16 M2x18 M2x20 Hex Fahrer Ti GR2 QCTI Schraube (5 builds)

Misc Parts

Matek Lost Model Beeper & FPV FC 5V Loud Buzzer (34 builds)

Misc Parts

Plasti Dip Liquid Electrical Tape schwarz 118ml 4oz black (9 builds)

Battery Charger

2 x Power Genius SAFE Parallel board XT30 and XT60 2S to 6S with Fuse Protection (3 builds)

Battery Charger

3 x BAT-Safe LiPo Tresor sicheres Laden und Aufbewahren der Akkus
See Site

Battery Charger

ISDT PC-4860 Lipo Ladegerät Parallel Ladestation Unterstützung 4 Packs von 1-8S XT60 RC LiPo Akku
See Site

Battery Charger

HGLRC Thor Lipo Battery Balance Charger Board Pro 40A XT60 XT30 Plug 2-6S Integrated with Lipo Discharger for IMAX B6 ISDT Q6 Na (2 builds)

Battery Charger

Q6 Nano Lipo Ladegerät, DC 200W Smart tragbares digitales Ladegerät fü

Battery Charger

2 x Amacoam 2 Stück Lipo Batterie Sicherer Beutel Feuerfeste Explosionsschutz Lipo Battery Guard Tasche Sack Gebühren Schutz Tasch
See Site

Battery Charger

K2 Air Bluetooth Fernbedienung LIPO Ladegerät, AC/DC 200W/500WX2 20A S

Soldering Iron

Tilswall Soldering Station, 65W Solder Station Welding Iron with Smart Temperature Control (392°F-896°F), Extra 5pcs Sol (2 builds)
See Site


Tarion Pro PB-01 Professional Camera Backpack


ETHIX Heated Deluxe Lipo Bag V2


Kesser® Campingstuhl faltbar klappbar tragbar Angel Stuhl Camping Stuhl Faltstuhl bis 120 kg Strandstuhl Angelstuhl Klapphocker
See Site


LINGHUANG Avata Tragbar Aufbewahrungstasche für DJI Avata für DJI Goggles 2 für Motion Controller, Tragetasche Schutzhülle f
See Site


Onseuk Kompatibel mit DJI AVATA Goggles 2 Foam Pad Sponge Comfortable Eye Mask Drone Goggles Zubehör (Grau+Schutzhülle)
See Site

Misc Supplies

Bier – Wikipedia
See Site
Show stores (18)


Sign in to comment

Lukasyus   Feb 01, 2022  

Hey, love the build! What's your source for saying that more blades = quieter?

MamaJOE   Feb 01, 2022 

Thanks! There's not really a source, it's more empirically. I don't know if more blades are quieter in general, but in this case they are! It sounds more like a turbine, than the famous screaming.

juliett.papa   Sep 13, 2021  

Wow. Very nice and clean build! Did you use the conversion kit as an additional bottom plate?

MamaJOE   Dec 14, 2021 

see my comment from Sep. 13th.
The additional bottom plate is the "normal" one.

techguy1623   Oct 01, 2021  

Very clean -Very Very Clean! Thanks for posting.

MamaJOE   Oct 01, 2021 

Thanks for your comment! Yes, I have tried to build it as clean as I can. And I'm also almost happy with the result...

schroedermckenzie951176@g   Sep 20, 2021  

It's great!! happy wheels unblocked

MamaJOE   Sep 13, 2021  

Almost... I have used the original top-plate as an additional bottom-plate (rotated by 180). The plate from the conversion kit is mounted on top, as intended 😉

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