Think Tank! Vario NOTAR how would you Electric convert it? - RC Groups
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Jan 13, 2007, 06:33 AM
Ghia's Avatar

Think Tank! Vario NOTAR how would you Electric convert it?

Just a general plan. Everyone jump in here as to how ya would do a Eletric scale heli with no tail rotor.

I have this:

now it comes with a 5 bladed head and a webra 90 eng wich spins a 5" dia alu fan for eng cooling/tail velocity cfm. a fast tail servo opens/closes a vent in the end of the boom for tail control

My thoughts are to lose the heavy alu fan and use maybe a 32-3 for the rotor and a smaller inrunner like a B50-13L ducted fan setup for the tail. Not sure though how Id get them to work together, if at all.

What would ya'll do mild to wild??
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Jan 13, 2007, 06:43 AM
Registered User
cgbole's Avatar
hey that would be one bad project. can you post some pics of the "innards"?
Jan 13, 2007, 10:24 AM
Das Universus Elektrikus
Albig's Avatar
Hey Garland,

I've been thinking about doing some kind of a ducted fan NOTAR tail but I'm not sure how effective it would be.

First off it states clearly on the Vario site that this NOTAR setup is "very demanding to fly". This I'm sure this is due to very low tail authority.

I've seen Vario mechanics fly that had that 5" fan just for cooling and it doesn't put out that much thrust.

Even if you attached a big EDF to bottom of a 32-3 by the time you ducted it to the tail through even a LARGE boom, 30mms in diameter, you have lost most of your thrust due to all the restriction.

Unfortunately 17,000 RPMs is not nearly enough to produce much thrust a with a fan small enough to comfortably fit in the frames.

I haven't yet, but intend to do some static testing of a typical tail rotor to find out what kind of watts it actually produces.

A 600mm heli with 95MM TR blades constitutes approx a 10" prop turning about 9000 RPMs and in some cases capable of 16* or more of pitch.

I'm guessing here but it would not surprise me to find that it's capable of producing 500Ws or more at the extremes.

A decent brushless CF 55 to 60MM EDF will produce about 2 to 2.5 pounds of thrust and maybe 250Ws at 40,000 to 45,000 RPM.

One thing about EDFs is they perform at these levels only if they have a very clean airflow from intake to exhaust. They also depend on the forcing of air inflight for these maximum ratings. Something they won't see in a helicopter's tail rotor.

I've thought about doing a "Pod" that attached to the boom using a brushless EDF and I'm sure it would work but how well is definitely a question that only doing it would answer.

Once again though you would have the lost efficiency of vectoring the thrust through whatever nozzle design you used and how efficient it is.

The other nagging problem I see with this approach is that without some kind of integrated system that mixed the NOTAR's motor to the Gyro/ESC/RX so that it's ESC could raise and lower the motor's speed according to demand, you'll have a TR that draws max amps continuously even when they aren't in demand. This is true with a main motor driven fan as well.

This isn't a problem on the MD 520s because they have to divert the turbine exhaust regardless so why not take advantage of this and vector it at the end of the boom.

That is one of the great advantages of the oh so complicated TR system, the blades can feather when anti torque response is in low demand.

I still feel that there is a possibility here but I'm not sure a true NOTAR can be very effective or advantageous. I am sure you could come up with a more effective system than what they're using for that Vario by going E power, but it will suffer from the same issues the glow version does.

I may try the Pod approach for a special purpose drag racer just because I'm sure it would be more aerodynamically slippery than a standard TR. The demand on a TR isn't that great in this situation, and could add a few MPH to the FFF speed.

And also the idea of getting rid of the mechanical inefficiency of the TR drive system is very appealing to me as well. I'm toying with the idea of mounting small brushless motor at the end of the boom perpendicular to it and just mounting the existing TR system on a 5mm shaft extension that would serve as the TR shaft. No belts, drive shafts or the required mechanics in the frame to drive them any more. This should make up for any weight or cost of the small ESC required to run the tail rotor. And with variable pitch you would retain the ability to draw only as much power as necessary to keep the tail locked.
Jan 13, 2007, 03:37 PM
Registered User
You can use a gyro to run a seperate ESC to a tail edf to control it. Leave the opening fixed. That's how a lot of guys do the bl tail motors on the blade cp's. Other option would be to run a tail servero and gyro with a variable opening, and then use a 2nd esc mixed to the main throttle for EDF speed.
Jan 13, 2007, 03:38 PM
Registered User
GGoodrum's Avatar
You can hook an ESC directly to the gyro, in place of a tail servo. That's basically what the micros, like the Picolos do, I think. I remember a Hornet I had, where I put a small Astro motor on the tail, with a small 10A ESC, which I plugged into a GY240. This, of course, didn' thave variable pitch on the tail blades. I'm thinking maybe you keep the variable pitch tail blades, as you are thinking about, and "Y" the tail motor ESC in with the main controller throttle channel. Or maybe a separate AUX chanel with a program mix into the main throttle.

Anyway, interesting stuff.

-- Gary
Jan 13, 2007, 04:23 PM
Suspended Account
Or maybe a separate AUX chanel with a program mix into the main throttle.
That would be better cause then you would have seperate control of the tail. i do this with a motrised variable pitch tail, to start the tail i use a switch, this way i can alter the tail speed on the tx to suit the mains(no gears ,pinions, ratios etc to change).With this set up you will have more authority as you can set the tail to suit rather than be restricted by the main rotor speed in the conventional way.
I have a feeling(inner) that the notar on rc helis will not be able to provide the power to weight that we require unless it is coming from a turbined force(make more power than what we have now for free with out gaining extra weight).
I am one with my experiments so have felt first hand the power of the tail and it takes a lot to counteract it.
Last edited by Snott; Jan 13, 2007 at 04:34 PM.
Jan 13, 2007, 04:30 PM
Registered User
glucoseboy's Avatar
Great find. I've been thinking that the NOtar would be a great r/c heli project. you've brought it to the next level, r/c electric heli project.
Jan 13, 2007, 05:09 PM
Renewed interest
ozace's Avatar
I want to see it fly. I am sure a DF could provide all the mumbo the tail needs, the extra weight of motor and packs may be an issue though.
Jan 13, 2007, 05:13 PM
Ghia's Avatar
I'll post pics tonite. thanks for any tips guys!

They make variable pitch EDF? Is that what ya trying to say Al/Gary?
The tail boom looks every bit 3" dia across.

Ozace, do ya think 15s1p would swing 2 BL motors?

Alot more thought is needed as Whatyagointodo said, weight will be a big enemy here. I just need scale like flight.
Last edited by Ghia; Jan 13, 2007 at 05:21 PM.
Jan 13, 2007, 08:57 PM
rroback's Avatar
What's the intended flying weight? It can be done, just might not be easy, and definetly won't be cheap.

Jan 13, 2007, 11:41 PM
more kW, more problems
trashmanf's Avatar
Darth had a thread going on this in the micro forum. so cool!!!

I do not know of any variable pitch DF systems.
Jan 14, 2007, 12:46 AM
Registered User
I think you're missing the point of NOTAR... it's not about creating thrust as per a fenestron tail, which is basically a ducted fan. It's about using some aerodynamic trickery to make the rotor wash produce the torque. So it probably doesn't need near that much power going into the tail... possibly even less than a tail rotor.

So, if the nitro NOTAR suffers from lack of tail authority, the simple solution would appear to be to keep the fan, and find a motor that can be geared differently so the fan does 50% more RPM while keeping the headspeed where it should be. That would be about 25000. That seems eminently doable. Yes, it will use quite a bit more power than you'd expect for a 90 conversion, but then you're improving the performance.

One point here: NOTARs are going to work better with a slower headspeed and more pitch for a given amount of lift, so it's probably not a good idea to go increasing the headspeed.
Jan 14, 2007, 01:24 AM
Ghia's Avatar
I email Joe about the AUW of a nitro Vario notar. but I think around 15lbs would be right.

Im charging my cam so pics in a bit!
Tail boom is 3.75" diameter

What about a variable pitch prop like those 4D planes use?
Jan 14, 2007, 09:55 AM
Das Universus Elektrikus
Albig's Avatar

I can't believe you actually bought that thing already

Very cool!!

Now give me your credit card before you raise the national debt any further

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