y3 Tri-Copter - with Tail Yaw Mechanism - |Build Log|


Y3 Tri-Copter - with Tail Yaw Mechanism - |Build Log|

Carbon TriCopter with Novel Yaw Mechanism
|Scratch Build Log|

Hey Guys,
i'm new here, and starting to plan my first build with a tricopter design. love the flite test videos, very good to get to grips with everything!
i will document my steps along the way, maybe it'll be helpful to somebody.

my plan is: i want it to be relatively cheap (around 250EUR/270$), but still be accurate and have the capacity to race or start to learn aerobatics once i know how to fly.
i already did a lot of research, got confused, then less confused, then more confused(mainly about motor, prop and battery sizes)
i'm just wondering if my plans and parts will cooperate and fit together. but im looking forward to building, fiddling and figuring it all out as i go.

thinking ahead:

Tail Yaw Mechanism
the 10x10mm tail arm is inserted into two 10mmØ ball bearings, rotating the whole back arm assembly, instead of just the motor. fastening the arm and ball bearings into the stiffened tail end of the main frame, hopefully making it really robust, but also freely tilt-able with next to no resistance.

and not only that, but with this configuration i can put the yaw servo right in the middle of the copter, behind the arm inside the main frame, thus keeping all the parts in the middle and the center of gravity focused.

Center of Gravity
i will also try and mount the motors on the ends of the arms as well as 'bend' the arms down if i manage to get that done. all that to keep the center of gravity (height wise) right in the middle.
(instead of the main frame 'dangling' under the motors like a shallow pendulum... but.. i guess moving the arms and motors down like this will actually bring the CG below the main frame because the force is transmitted at the bottom of the motor where it is fastened to the arm, right?.. hmm not so good. although with the battery pack its probably spot on )

i also thought, maybe i can even mount the ESC's around the tail-ball bearing mechanism(white boxes, red cables - as pictured) and feed the motor wires through the hollow arms. keepin' it tidy :p
there's also a slot in the top plate under the KK1.2.5 board to feed cables through.

Planned Parts/Specs:
KK2.1.5 + 19S firmware
EMAX CF2822 1200Kv
ESC Simonk 30A
EMAX ES08MD 12g/ 2.4kg/ .08 sec
3000MAh Fleureon 30C, 11,1v
9x5 or 10x4.5 Props
Flysky FS-T6-RB6 FS 2.4GHz
maybe fpv; SKY2 800TVL (flat spot on the main frame front for camera)

Updated Parts:
Carbon Plate 40cm x 20cm
Carbon hollow Tube ø12mm x 1m
2x Ball Bearring ø12mm x 24mm x 6mm
MWC Multiwii SE 3.0
FlySky FS-T6 V2 + RB6
Sunnysky x2212-10, 1250Kv
Corona DS-319MG Servo
ESC Simonk 30A
Turnigy Nano-Tech 3200mAh 25-50C
Turnigy Nano-Tech 2500mAh 5-10C (Tx Battery)
9x4.7“ SlowFlyer Prop

carbon arms, carbon frame plates, plastic frame fillers

Sketches: (made with blender)

Y6 - Race Edition 1b.png

Y6 - Race Edition 1a.png
tail yaw mechanism and ESC to Motor cables

Screen Shot 2015-01-16 at 01.23.11 Kopie.jpg
folded arms

Screen Shot 2015-01-16 at 01.37.21.jpg
inside main frame without servo - ball bearing yaw mechanism, ESC to motor cables
__________________________________________________ _______

Screen Shot 2015-01-15 at 23.46.52.jpg
Screen Shot 2015-01-15 at 23.47.13.jpg

Planned Dimensions:

Maße A.jpg
everything is not fixed yet, don't know if 3D dimensions correspond to the real world...
all the bought parts(esc's, KK2.1.5, motors etc.) have the correct proportions in these sketches though

thats about it, i'll keep updating this if i can as i go along.
if you have suggestions, critique, ideas, words, unicorns feel free to share.
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Senior Member
Hey there, welcome!

Wow great renderings, I am no expert in tri-copters as have only recently built one.
I'm intrigued by the tilt machanism, do you think the servo will need mjore torque to rotate the whole arm?



Senior Member
Welcome to the forums. Your model looks great and I can't wait to see this build. I really like the design of tricopters where the whole rear boom tilts instead of just a mechanism on the end.

I see you're going with carbon arms, but the arms in your model are bent in two places. Do you plan on keeping these bends? I've only seen straight carbon arms so I'd be interested to hear how you plan on getting the bend.


thanks guys!
@nilsen yeah it probably has a higher load also cause of wind and the back arm assembly being heavier, but since i'm mounting my servo inside the main frame, i tought i'd use a slightly bigger/stronger one
although i've not seen one tricopter video/post where people were complaining about their servos being too weak so, gonna have to test it..

yeah im really thinking about those bends... they're supposed to keep the center of gravity down height wise and also the rotation point of the back arm+motor in the center. but i think i would be sacrificing boom strength, because i'd cut up the carbon and fix it/bolt it back together precisely angled somehow. so its probably not worth it to keep the bends.. but they look so cool! like them alot actually
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Senior Member
Very cool!
I'm quite keen to see how it works out as the idea of "decluttering" always apeals to me.

Good luck!


Quick Update:part II (22.1.15)

hey guys,
here a quick update, i changed my plans a little, got my MultiWii SE 3.0 board and got some good input from commenters also on my other thread, thanks for that, thats helping a ton!

so first up; new design.
long story short, i will make the arms straight (and round for that matter) just because its easier to assemble, and has more strenght. especially thinking about putting square tubes in round ball bearings :s
nope. simpler = better.

Y3 - v4 round arms c.jpg
experimental stuff added, cover and tail fan thingy to direct the prop pressure?.. cause the fans will move with the arm.

Y3 - v4 round arms a.jpg
new board on top. the reciever is actually mounted upside down directly under the MWC,
metal plate inbetween to add weight/reducing vibrations. and shielding against interference.

Y3 - v4 round arms b.jpg
gopro Hero3 dimensions in front for scale.

2015-01-22 05.24.00.jpg
i kind of impulse bought this MultiWii SE 3.0 without research, but two nights of good old surfing before it arrived did the trick(still almost no documentation on this board, if someone needs infos, ask me ;) )
its basically already set up for flying, took 15 mins!

my main concern now is, if i am judging the sizes correctly, i guess ill figure that out when the parts arrive.
sorry i dont have inches on there. so 60cm Motor to Motor or 57cm... or 65cm? kinda limited by the carbon fiber booms that only come by the meter. that means i have 33.3cm for each arm. or buy two, and pay for two...

and i also did some calculations:
Screen Shot 2015-01-18 at 03.10.07.jpg

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Part III: update

Part III
main frame plates done.

slowly but surely my parts are arriving;
so i cut out my main top and bottom plates with hand and jigsaw and filed them down. not recommended to use standard fine wood/metal jigsaw blades!! they wear out really fast.
there probably are blades for carbon available but i wanted to get it done quickly.
filing down carbon is perfect, but wear breathing protection! (as i didn't..)

cutting and filing carbon is very messy...

2015-02-08 20.20.44.jpg
top and bottom plates are done!

and after filing it down a hair, the ball bearings fit perfectly on the back arm!

next up on the list is:
the arms and the 'spacer' material piece that goes in between the frame plates. i think i'll try making it out of wood at first, because its an intricate part (probably too complicated).
this is the piece. but i'll probably try to simplify it, leave it out completely or have it laser cut/cnc machined (a friend showed me a cheap shop to do that). there are also two more spacers for the back assembly, we will see..

read you next time,
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Part IV

Part IV:

Hey guys,

i finally ordered all my remaining parts, so now i just have to wait.
in the meantime i did some more work on the main frame.

2015-03-10 13.47.47.jpg
spacer plates for the arms to rotate on.


filing out the holes for the bearrings.
Please use gloves and breathing protection for carbon! (not as i did)

2015-04-01 01.17.27.jpg
servo, tail mechanism dry assembly. still got to do the wooden back spacer. and drill all the screw holes.
and figure out a way to lock down the servo...

Once my ESC's, motors and Rx/Tx arrive (FrSky T6, RB-6),
i can start testing the electronics and my tail yaw mechanism!
Y3 - v5 electronics.jpg
read you next time,
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Winter is coming
Very nice work! Looks like it's coming along well. Just a small concern... It looked like you weren't wearing protective gloves with the carbon cutting and sanding. I'm not very familiar with working with carbon fiber, but I personally would use some personal protective gear... minimally, gloves, eye protection and breathing mask/filter. I believe that some people work with the carbon cutting and sanding under water to mitigate the dust...


hey thanks man:) it is coming along...
and you are so right about the protection! especially breathing protection should be worn. i didn't do it while filing the holes, because i just had a tiny bit to go.



Update: (Part IV ½)

Main frame assembled


tail yaw mechanism is working like a charm!

the CG of the frame is exactly where i designed it!
2015-04-25 21.29.13 HDR.jpg
also finished the flight controller shock mount. lots of sanding, but its pretty sturdy and absorbs shocks nicely.
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Part V

Part V

Hey guys,

this will be the last update before the Maiden! :)


(soldering battery+esc's, shot from inside my lamp)
2015-05-18 18.34.24.jpg
My motors and ESC's finally arrived, i had to get them from the german customs (Zoll) because they wanted to get some more taxes from me..

so i installed all the electronics and tested them. my tail mechanism still showing no weakness. not even a deadband.(its not centered in this gif, i know)
everything worked quite well until i fried my first ESC
2015-05-19 23.34.44.jpg
the FC was programmed wrong, min. throttle was at 900 instead of 1000 so the inputs freaked out and overloaded one ESC
but in great foresight (and great advice from Bruce/RCModelReviews) i purchased 4 ESC's! phew..
plus i always wondered what the magic blue smoke looked like, now i know!
2015-05-11 22.42.06.jpg
also made the battery holder
2015-05-19 22.28.26.jpg
so this is what it looks like right now, still need to manage the cable mess and do some little things like extend the FC LED over the top plate, because i want to see when its armed. but im loving the Black/Red design i chose.

Next time i will post a video of the maiden flight and maybe even a 'tour around' the tricopter if someone is interested. or anything in particular i should highlight
I'll also include some nice HD beauty shots.

also, if i would ever start a multicopter building company, youtube channel or anything i have a name and idea for a logo.

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Senior Member
congrats, ill probably forget what blue smoke looks like in time.. but one will never forget
what it smells like. the smell of burning electronics nothing quite smells like that.


little bit of a setback, i burned the second ESC..
what seemed to have happened was:

first the FC freaked out a little. motors made noises and didnt start, the servo jerked around, didnt react. so i thought its the fc, so i changed some settings (back to 50Hz for the servo i.e.) but it still had the same problems.
But when i plugged in only the USB, the fc was perfectly fine(checking via the GUI program) problems started when plugging in the battery again. so i thought its the esc calibration, so i recalibrated them via the reciever. thats when i noticed the motors still had difficulties spinning up and making noises except for the left one strangely..
while trying to spin up a motor, the back arm ESC smoked, so i stopped. Also the ESC's got pretty hot before, especially the back arm esc, that was powering the fc.

so now i'm wondering, is it just the bad quality of the ESC's, the flight controller, or maybe -my biggest 'fear'- the length of wire between the ESC and the motors? or is a 35cm-40cm, 18AWG wire fine between motors and esc's. i'm suspecting the resistance is too high, but would that have this effect on the esc's? and if thats the case, how could i solve this without putting the esc's right next to the motors..?
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