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Old May 02, 2012, 12:48 AM
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MassiveOverkill's Avatar
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Small ducted fan for NOTAR micro heli

You think it's possible to make a micro EDF work as NOTAR for my V911 micro heli? The existing tail rotor weighs about 2 grams. The ducted fan system would probably have to weigh at most 4 grams, and be around 20mm. 30mm would be too big. Thanks.
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Old May 02, 2012, 03:42 AM
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notar, or ducted tail?
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Old May 02, 2012, 05:12 AM
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NOTAR without the need to have a variable nozel, with the idea that the EDF would be mounted close to the frame and a small lightweight tube would channel the thrust to the tail, increasing center-of-gravity.

I suppose a ducted tail would be an option if it didn't weigh a whole lot more, but I think it would, and the extra efficiency wouldn't offset the extra weight.
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Old May 02, 2012, 02:34 PM
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I have seen others trying similar things on I believe a 325 heli size. I didn't see if he ever got it to fly though. But it had a 40mm ducted fan with a depron thrust tube with an elbow at the tail. One thing you'll need to figure out is what the max thrust the stock tail can make. Then you need a fan that puts out likely 25-30% more than that to account for tube and bend losses.
are you going for a scale body to go with it?
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Old May 02, 2012, 05:38 PM
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Originally Posted by derk View Post
I have seen others trying similar things on I believe a 325 heli size. I didn't see if he ever got it to fly though. But it had a 40mm ducted fan with a depron thrust tube with an elbow at the tail. One thing you'll need to figure out is what the max thrust the stock tail can make. Then you need a fan that puts out likely 25-30% more than that to account for tube and bend losses.
are you going for a scale body to go with it?
Thanks, not looking for scale acuracy, but don't want a tube that was so big that it affects aerodynamics.
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Old May 03, 2012, 10:27 AM
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Intriguing idea. But the one I've seen a few years back (ona Mini sized Heli though).
was problematic as in the EDF couldn't really spool up 'n down fast enough to keep up with sprited flying.
Might be ok if one avoided 3d?
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Old May 03, 2012, 01:03 PM
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If I can make the tube light enough (multple drinking straws as tubes?) and find the best length to power-loss ratio to place the end as far out as possible to increase torque. I'm really hoping the ducted fan for something so small will have more than enough thrust as it's just for correction and not trying to help produce lift via acceleration.
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Last edited by MassiveOverkill; May 04, 2012 at 04:48 AM.
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Old May 03, 2012, 10:57 PM
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erm you missunderstood? EDF (on one i was a small part of) was ineffective at holding the tail, even in the right general direction, let alone 'steady'.
Tough to beat a simple stupid propeller for pure tail holding power.
Then there's the extra weight problem :-)
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Old May 04, 2012, 04:59 AM
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Originally Posted by Bare View Post
erm you missunderstood? EDF (on one i was a small part of) was ineffective at holding the tail, even in the right general direction, let alone 'steady'.
Tough to beat a simple stupid propeller for pure tail holding power.
Then there's the extra weight problem :-)
I guess I'll have to measure the thrust of the current setup at some point. I'm hoping power of micro motors has improved in 3 years.
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Old May 04, 2012, 06:22 AM
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The thrust may not be the problem, but the reaction time is. An edf needs to spin a lot faster to provide more thrust, which takes time. Where a prop can produce more thrust almost the moment you give a control input edfs can take up to 1-2 seconds to gain their speed. Turbines have the same problem, they have to get to speed before you will notice their effect, which means it might not be the best choise to use as a replacement for a tail rotor since those need to react fast and accurate.
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Old May 04, 2012, 06:51 AM
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Thanks for the clarification. The V911 more than enough tail authority......so much that many of us are installing resistors in our stock TX's to smooth out 0-50% throw.
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Old May 05, 2012, 09:31 AM
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Real NOTAR works with nearly constant thrust and most of the torque reaction comes from the slots in the tailboom and the Coanda effect, with only steering control comes from the tip.

This would be incredibly hard to model on a small scale, because the aerodynamic forces don't really scale down too well.
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Old May 06, 2012, 09:38 PM
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It's NOT a real notar just a naive notion of using a wee EDF instead of the simple stoopid propellor.. which works "perfectly' by the way. Just a "bling' attempt imo.
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Old May 13, 2012, 10:24 AM
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I put a small edf under my Blade CP once. Foward speed was crazy and flight time dropped. Very weird flights, while it lasted.
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Old Jun 11, 2012, 06:19 PM
Brosol
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Quote:
Originally Posted by MassiveOverkill View Post
You think it's possible to make a micro EDF work as NOTAR for my V911 micro heli? The existing tail rotor weighs about 2 grams. The ducted fan system would probably have to weigh at most 4 grams, and be around 20mm. 30mm would be too big. Thanks.
Some NOTAR related threads:

helli newbie: http://www.rcgroups.com/forums/showthread.php?t=827630

Honeybee FP - MD520N (notar)
darthdrk: http://www.rcgroups.com/forums/showthread.php?t=604655

Ishikawa's notar system
K2-tokyo: http://www.rcgroups.com/forums/showthread.php?t=1204538



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