Monotwirl Electric Autogyro - Page 7 - RC Groups
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Jul 15, 2011, 04:17 PM
Thanks for the suggestion about fitting the rudder,I will do that tomorrow.I am not using rotor tilt on this one,instead I am using taileron as leadfeather did on his Mr Twister.I don,t know if it will work or not but that's the fun with these foamies.

Thanks once again for your help Al.

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Jul 16, 2011, 04:46 AM
This is the balance at the centre of the rotor.Will that be OK for starters

Aug 01, 2011, 05:12 PM
Keep it simple
alfoot's Avatar
I dug the prototype Monotwirl out from under the dust and gave it a go tonight. I had a small problem (well a big one actually) when it threw a blade not long after launch.

Check out the movie to see what happened next......


Monotwirl Prototype Autogyro 1 August 2011 (1 min 23 sec)
Aug 02, 2011, 05:59 PM
Keep it simple
alfoot's Avatar
Here's a better movie of the prototype, with the glue joints checked over a little better.

There are two flights, the second starting with a ROG take-off.



Monotwirl Autogyro 2 August 2011 (4 min 56 sec)
Aug 02, 2011, 06:15 PM
It's all in the Blades!
SafeLandings's Avatar
I cant believe that it flew so well when it threw a rotor!, not much vibration either.

Thanks for posting that, it was interesting.


Aug 03, 2011, 02:32 AM
My 125% Monotwirl has had its maiden flight but I was not very happy with the performance compared to the twin rotor version.I think it ended up a bit on the heavy side so I will build another exactly to the plans.
Al, your one is flying well,not bad for an oldie.

Aug 07, 2011, 05:31 PM
Registered User

I've built a Monotwirl to Al's plans, everything to the original design with the exception of building a ballraced rotor hub and aluminium rotor tilt mechanism. I made the rotor using parts from a spare cheap brushless motor (as shown in photos). Total weight is 228g (8.05 oz) including 500mAh 3S Lipo. UHU Por used for joining the Depron blades to the 3mm ply rotor discs.

Motor = EMAX CF2805 1600kV brushless

ESC = 10A Hobbywing

Prop = GWS 8x4 DD (on propsaver)

Battery = 500mAh 20C 3S Lipo

Servos = 9g for rotor tilt and 5g for elevator and rudder

Rotor = made using EMAX CF2805 brushless motor parts.

This comboination pulls about 10A 11V 110W max (2S about 50W felt underpowered and did not have enough power to climb - was using full throttle just to stay level.) I dont need to use full throttle with the current 3S setup and use about 75% throttle on launch.

Flies very well straight from the first flight. Has had about 8 flights now. Now that it is trimmed the rotor is tilted down by approx 10 degrees to the right; elevator is slightly up (1-2mm); rudder is straight.

Photos attached from before final decoration.


Last edited by dominic_baker; Aug 07, 2011 at 05:37 PM.
Aug 09, 2011, 09:46 AM
jodini's Avatar
WOW Dominic, I love the hardware!

Al, good to see you still playing around out here! Great design!
I still fly my Twirl whenever I get the chance!
Jan 09, 2012, 04:03 PM
Registered User
thechannelmast's Avatar

hi i need help

it funny i see al fly his mono on one broke off blade i have all four and mine will not fly.if i hold it and point it toward the wind and walk fast it spins up but the rotor does not make any lift and i built the rotor to off the plans. so i need some help mine thinking is if the blade are spining fast they should make at least little lift but there no lift at all. the blades are not stiff but not loose
Jan 10, 2012, 07:39 AM
Registered User

Good to hear you have built a Monotwirl too. Mine has probably had about 40flights now.

Have you actually tried flying yet, or just tilting it and walking into the wind ?

With mine if I tilt the rotors 90 from the horizontal and then jog into the wind the rotors spin up and you can feel some resistance in your hand (more than if the rotors were stationary). The resistance is not that high though, it dosent need to be as this autogyro is not that heavy. Maybe there is a little resistance from yours ?

I have an improved bearing for my rotor (described in my post a few before this one) - this reduces friction on the rotor which should allow a higher rotor speed if all else is equal.

It may be tht you just have to give it a try flying.


Nov 14, 2012, 04:45 PM
Mike's Ma Maaaaaaaaan
PaulB's Avatar
Hi, finished mine last night, maiden today :-))

Flight lasted around 2 - 3 seconds and ended with my Baby in her rotor head :-((((

Too much wind and blowing straight out of the sun, span the blades up, ran a few paces, leveled the nose and let go. Could not see what happened (blinded) but saw her hit the ground upside down, ouch!! I have modded the head spindle with ball races and a thrust race (pictures to follow) but after the crash the actuating arm was loose, could have vibrated loose when I was spinning the blades up (spent a couple of minutes doing this) or it could have been the wind/ lack of head speed. Building a new rotor and the story will continue ;-))
Nov 18, 2012, 12:28 AM
Registered User
Hello PaulB,

It's great to hear you have built a Monotwirl too. The ballraced rotor is a very good idea to help increase rotor speed, my method is shown several posts above (using parts from a brushless motor).

Also as shown in my post my rotor's default position for straight flying is ~10 degrees tipped to the right, otherwise my monotwirl will turn over fairly quickly - maybe this is what happened to yours ?

Also when launching I don't launch level, probably at about 20 degrees up from horizontal.

Hopefully you will get yours working OK as it is great to watch flying and people are always amazed that it works !

Nov 18, 2012, 02:58 PM
Mike's Ma Maaaaaaaaan
PaulB's Avatar
Sadly no, new rotor built and the actuating arm locked down solid. Slight breeze so I ran with the model at 45% and got the blades spinning real good, dropped the nose to just above the horizon and launched. The model just flipped over to the right and crashed. As only one blade was cracked I tried again, ran even faster and tried to push the model upwards and forwards to launch, model flipped over to the right and crashed inverted (total distance about 2 meters away, i.e. straight over and nose dived). Built a new (3rd) rotor head and increased the length of the blades by 1/2” back to the field to try again. This time I trimmed both the rudder and the ‘head’ to the left slightly before running like hell and launching using just over half throttle (I could feel the model pulling gently), launched to an instant half roll right to crash inverted!! All 3 times the model rolled violently to the right and creamed in after just a metre or so, didn’t even look like she tried to fly!!

Here are a couple of pics of my ‘head solution’.

PS:- The first picture shows the bottom of the rotor, the blades do spin anti-clockwise as they should.
Last edited by PaulB; Nov 18, 2012 at 03:01 PM. Reason: Clarification
Nov 18, 2012, 07:49 PM
Sky's not the limit, ground is
skydanz's Avatar
Paul, which way is your rotor spinning, looking down from the top? Something doesn't look right in the pics. If the rotor is spinning ccw or anti clockwise, then the wood leading edge is backwards.

Last edited by skydanz; Nov 18, 2012 at 08:47 PM.
Nov 19, 2012, 10:24 AM
Mike's Ma Maaaaaaaaan
PaulB's Avatar
Hi Don, thanks for he interest and help. Well spotted, the head is on upside down but I had just slid it back on for the photos. When I tried to fly the blades span CCW (or anti-clockwise for us Europeans) with the hardwood leading edge forwards and lower than the trailing edge (negative pitch).

Been through the thread again and looked up loads of stuff, checked the negative angle of the blades (spot on – 10 degrees using my helicopter pitch gauge, mast is raked back by 10 degrees, the C of G is 2 – 4 mm in front of the mast and there is no side thrust on the motor. This thing should fly!!!! The only thing that I can now think of is the weight. I just put all of the bits onto the scales and came out at 155 Grams (5,5 Oz) which I think is quite light and if I am honest the tail feathers are slightly flexible (stiff enough for a Shocky but more force is at work here).

Could I just have too low a disk loading for:-

a) The conditions at the time, i.e., a breeze and
b) The speed which I got the blades spinning at??

The model defiantly shot up out of my hand but flicked straight over, maybe too much lift for the weight making her instable??

So, new undercarriage (I modded Al’s design to produce a very light useless wobby mess  which will not support the weight of the model), a new rotor and I am going to try a ROG take off from concrete with a lager battery (800 mAh 2 Cell to replace the current 350 mAh 2 Cell). This should allow me to get the blades up to the correct speed (like when she lifts off on her own) and if she is then un-flyable in the air it must either be a too stiff rotor head, flappy tail feathers or the C of G, right??

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