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Old Feb 14, 2011, 01:11 PM
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The Spies

Hello guys,

Usually i am not speaking anymore on forums but after so many questions about my plane all along the last week-end I am ready to use my keyboard ;-)

So, The Spies is my new design for 2011, the shape look like a conventional plane but I use on it some tricks and tips which i have found along last year and I bring all of them into a same plane like a concept car!!! I am using the third prototype (I made the first one last week of decembre)!!!! and I am already working on the forth! I am leading all of my tests in collaboration with my sponsor Donuts Models of course.

The weight of my plane ready to take off is about 150g! I use on it 4 servos JR 188 with, 6channels RX futaba, 2 controllers 06EPpower and a 360mah 7.4v battery.

About the airframe it made with a 6mm depron covered by mylar film, which is the lightest airframe which I ever built! By the way i reduce the weight at about 60% of a 3mm airframe without milling and for the same rigidity!!!

As you can see I use a contra-rotating system made by myself in collaboration with Donuts models (www.donuts-models.com) and some very good friends. The motor should be available on the market, I am working on it with Donuts Models and will say you asap it will be available.... the weight is 30g without props and controllers. It look like heavy but you will forgot it in flight...

In some words the biggest advantage of this system in flight is the annulment of the torque effect during up line and of course during torque roll, It become a good airbrake during down line, both right and left knife-edge flights are exactly similar....

As you can find attached two videos one is a short presentation and the other one my last flight yesterday in Paris where I used it and finished in 3rd position behind Gernot Bruckmann and Donatas Pauzuolis!!!!

See you

Fabien
www.fabien-turpaud.com

http://www.rcpilot-online.com/The-Sp...aud_a1597.html

The Spies, new F3P model from Fabien Turpaud (3 min 50 sec)


IITOP 2011 - Fabien TURPAUD (FRA) - F3P-A Final - Flight 7 (2 min 25 sec)
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Old Feb 14, 2011, 02:22 PM
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Johns Creek, GA
Joined Jan 2005
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Wow!! Just Wow! Great stuff!


-Curtis
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Old Feb 14, 2011, 03:20 PM
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Ireland, Kildare, Leixlip
Joined May 2002
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Very nice approach. I like it!

Are you using any mixing with the speed controllers for torque trim and/or control?
I'm guessing the answer is no for torque control as it would add back in some of the asymmetry you're trying to eliminate but just checking.

Aidan
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Old Feb 15, 2011, 01:30 AM
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53859 Niederkassel, Germany
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Quote:
Originally Posted by Aio_1 View Post
...
Are you using any mixing with the speed controllers for torque trim and/or control?
...
Hello Aidan,

may I answer for Fabien, as I was asking the same question:

No, he does not use differential power to support the rotation, because it would be harder to stop precisely.

Jürgen
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Old Feb 15, 2011, 04:33 AM
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Quote:
Originally Posted by Jurgen Heilig View Post
....he does not use differential power to support the rotation, because it would be harder to stop precisely.
Good point.

Thanks Jurgen
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Old Feb 15, 2011, 07:47 AM
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Kimmo Kaukoranta's Avatar
Tampere, Finland
Joined Apr 2004
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Nice work on the coaxial and great flying Fabien! The coaxial arrangement ideed offers many benefits for F3P. I've also done a bit of experimenting with a bit different coaxial power system, I posted something on a separate thread:
http://www.rcgroups.com/forums/showthread.php?t=1390240
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Old Feb 15, 2011, 09:31 AM
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Hello Kimmo,

Really nice work from you....i am also coming in the lithuanian championship, hope to share some experiences with you in LT!!!
Your solution is ligther than mine but what a noise! We tested an other solution which was used only one motor and it made about the same noise! This is why we have switched to the current solution which make less noise!
I am working on carbon prop too, but they weren't perfect be used at the IITOP....i plan to bring it with me for the Lithuanian Championship!
One question; do you fell some airbrake effect in down line with your system?
If i think right i can't work...

Wait to meet you ;-)

Fabien
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Old Feb 15, 2011, 10:44 AM
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Tampere, Finland
Joined Apr 2004
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Fabien, there is significant braking action from the props. I do not have much fixed brakes on the plane, only those little fences on the elevators are tilted a bit. The props are the main brake.

One of the reasons for going to geared motors was the ability to swing much bigger props than possible with light enough direct drive outrunners, to achieve better braking. Since the torque is cancelled with the coaxial, there is nothing keeping one from slapping a pair of 20" props to a 85cm plane, should be a pretty good brake The ground clearance could be a problem though...

In general I feel the braking action with a geared motor is more than with an direct drive outrunner. The outrunner will pick up more RPM in a dive, where as the geared motor will better hold the same RPM.

There is a bit of noise, but I think it is not as bad in real life as it may appear on the video. But certainly it could be a bit quieter. Maybe I should bring ear plugs for the judges in Lithuania Looking forward to meeting You there and exchanging ideas!
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Old Feb 15, 2011, 11:17 AM
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Of course I didn't notice that you use 10" prop...of course with two 10" props it should brake!
I was more thinking about the motor brake, In fact, in my set up I am trying to use the motor brake setting up by the controler to keep the rpm at a constant low level....which mean the air flow can't increase the RPM! like in a full scale plane.
But you use the surface of the prop like an usual airbrake, and the motor brake has no effect compare to the force of air flow which is increasing by the gear box....
I hope you understand my english????

I will try with a 10" prop to fell the different...my motor should turn it!

See you

Fabien
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Old Feb 16, 2011, 01:01 PM
Team JR
Medford, NJ
Joined Jan 2004
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Fabien,

Very nice work and flying!

From F3A flying (most of my experience) -

Geared motors provide more braking than outrunner (direct drive) motors when all other items are the same. For F3A, the brake settings of the ESC are often used, and with proper setup, the braking difference between the geared motor and outrunner is very small.

For the braking action of the prop, the amount of surface area in the circle of the prop is related to the braking action. Wider blades or adding additional blades will increase the braking action.

Regards,

Dave Lockhart
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Old Feb 17, 2011, 01:49 AM
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Kimmo Kaukoranta's Avatar
Tampere, Finland
Joined Apr 2004
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I think another good comparison two stroke vs four stroke in F3A. With the two stroke like OS140 no matter how low You set the idle, it will pick a lot of RPM and speed on the downline. A four stoke like the YS170 will pretty much hold the RPM and keep the speed more constant. Same goes for direct drive outrunner vs a geared motor, when not using an ESC brake (I'm not saying just "outrunner" since my geared motors are also outrunners)

I have done some playing around with brake in the CC Phoenix 10 and indoor planes, but I think it does not really help indoors with the "normal" 8-9" props. You get more braking from a small idle or just letting it freewheel. Outdoors it's of course a different matter, there the ESC brake really helps.

Slapping a 10-11" prop to an Axi or something like that will help with the braking, but really harms the efficiency and makes the throttle response a bit sluggish.

On my geared coaxial, the props are carbon copies of APC 10x3.8 SF, which are available as a contra rotating pair.

Here's a video of one of my other planes with a geared outrunner (not a coaxial) using a DIY 11x3.8" carbon extremely wide blade prop, like twice the chord compared to an GWS or APC SF. No fixed airbrakes at all, only the prop. The motor+gearbox is around 15g, plane 135g.
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Old Feb 17, 2011, 03:29 AM
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Hello dave and kimmo...

I think we are thinking the same things....It should be easier to understand what we mean with a Lithuanian beer in three week!!!

Of course, I understand the point which is "bigger the prop is better the brake effectis", and of course most of the time with a geared motor we can use bigger props....

But my first question was to know if kimmo use the ESC brake....because at the same size of prop, I suspect that the ESC brake on a geared motor has less effect than on outrunner, because the gearbox increase the torque from the prop to the motor which the esc should oppose.
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Old Feb 17, 2011, 04:43 AM
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Tampere, Finland
Joined Apr 2004
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No, I do not use the ESC brake. Not with the coaxial, and not with that other geared system with the 11" prop. Instead I set the throttle trim to a low idle.

Interestingly, with this system the best braking does not happen at the lowest idle speed the YGE ESC allows, but a few trim clicks higher. Using the ESC brake would slow the RPM too much, and the downline speed would be higher.

In the downline the prop is not braking just because the frontal area it has. Instead it's more like a helicopter or an autogyro in autorotation. The propeller blades are creating lift, in addition to the drag.
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Old Feb 17, 2011, 05:01 AM
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Quote:
Originally Posted by Kimmo Kaukoranta View Post
Interestingly, with this system the best braking does not happen at the lowest idle speed the YGE ESC allows, but a few trim clicks higher. Using the ESC brake would slow the RPM too much, and the downline speed would be higher.

In the downline the prop is not braking just because the frontal area it has. Instead it's more like a helicopter or an autogyro in autorotation. The propeller blades are creating lift, in addition to the drag.
Of course I can understand that the best RPM is not the lowest for creating brake...but i don't understand how system can products lift without variable pitch?
I am thinking more about the over pressure in the front of props combine with blades who aren't product lift at low RPM(blades are over stall at low RPM)...isn't it?
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Old Feb 17, 2011, 05:10 AM
Janne Lappi, F3A Team Finland
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Helsinki, Finland
Joined Sep 2008
129 Posts
I think you mean 10" Kimmo

Fabien, are you going to fly The Spies in Lithuania, too? Nice plane, there seem to be almost no other materials than big holes


Janne
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