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Old Dec 16, 2005, 04:57 PM
Micro Jet Pilot
Chris T's Avatar
Joined Jul 2005
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Build Log
8'' Micro Jet (L-39 Albatros, MiniDisc, 30mm EDF)

Here we go...
Chris
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Last edited by Chris T; Dec 21, 2005 at 09:50 AM.
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Old Dec 16, 2005, 05:50 PM
Micro Flyer, Big Poster
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AUW??? Breakdown?? Wonderful Job!!!
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Old Dec 16, 2005, 06:21 PM
Micro Jet Pilot
Chris T's Avatar
Joined Jul 2005
2,091 Posts
Wingspan: 8''
AUW: 30-33g
Minidisc motor: 3g, brushless, 6 stator poles, 4 magnet poles
300mAh E-3D single cell, 4.5 amp max.
30mm ducted fan (clipped gws edf50)
tailerons, actuator driven

Hope it works...

Chris
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Last edited by Chris T; Dec 19, 2005 at 04:16 PM.
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Old Dec 17, 2005, 01:10 AM
Team30 Micro EDF
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Adelaide, Australia
Joined Apr 2004
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fingers crossed this end Chris!
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Old Dec 17, 2005, 01:47 AM
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Very cool looking. Who can I get to make me a Jet? lol
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Old Dec 17, 2005, 08:18 PM
Micro Jet Pilot
Chris T's Avatar
Joined Jul 2005
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Perfect Couple! A MiniDisc motor and a clipped gws edf50 with 30mm diameter. 4 pole magnet configuration, 3x3x0.5mm N50's, NNN SSS NNN SSS...

Chris
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Last edited by Chris T; Dec 19, 2005 at 04:14 AM.
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Old Dec 17, 2005, 08:48 PM
Team30 Micro EDF
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Adelaide, Australia
Joined Apr 2004
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Sweet!

I am still trying to get my hands on a MD motor
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Old Dec 19, 2005, 04:29 AM
Micro Jet Pilot
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Joined Jul 2005
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The plan will by updated when I am finished building. This version contains most of the required information already. A detailed report of the building process can be found at http://www.rcgroups.com/forums/showthread.php?t=437883

Regards,
Chris
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Old Dec 20, 2005, 04:17 PM
Micro Jet Pilot
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The cabin is made from heat shrink tube. Looks pretty clear...

Chris
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Old Dec 22, 2005, 03:43 PM
Micro Jet Pilot
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Joined Jul 2005
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I have exchanged the fan with a clipped 5 blade edf50. Motor is mounted inside the fuse. There are a bit of vibrations. I will see if I can balance the unit a little better, but it is running quite well. Now I am waiting for a new bl controller since my first one fried...

Regards,
Chris
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Old Dec 22, 2005, 09:36 PM
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Neat !!!! ....gotta get my self a minidisk motor
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Old Dec 23, 2005, 04:12 AM
Micro Jet Pilot
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Joined Jul 2005
2,091 Posts
Thanks guys. I am wondering if I should add lights in the tip tanks? The weight of a 5mm LED is about 0.2g. The wiring would be alomst nothing. The only trouble is that the wing is a sheet of balsa sanded to shape. No way to run a wire inside. I could tape thin magnet wire on the bottom side, but I don't know if it looks too silly. Lights on the other side are very neat! I have the brightest white leds in my 16'' L-39 and I have been flying in the dusk until it was so dark that all you could see was two bright spots. Helps flying bigtime. Next problem is that this model is setup for a single cell. White leds require 3.6Volts but under load voltage drops down to 3V (with 3amps motor current). That won't be enough to power these leds. I could use a different color. I think I saw some "gold" color and yellow led running down to 3.3 / 2.9 Volts. They are not that bright though. A different approach would be to put 10 or 20mAh Lipos in each tank which would then only be used for the lights. I think at 20mA led current, they could stay above 3.6Volts for a while. On the other side, I probably should worry about different things than the lights at that point.

Do you guys think, the actuators will be fine? I have heard about flapping control surfaces at higher speed. Also, I will have to adjust the fan stator correctly. At the moment (without stator), it feels like the motor produces more roll momentum than the tailerons could compensate. Well, that's what the stator is there for. It just has to be setup correctly....

Regards,
Chris
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Old Dec 23, 2005, 06:52 AM
did it flied?
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London, UK
Joined Apr 2005
760 Posts
Just like gravy goes with sausages and mashed potatoes, so does blinking LED's go with a fine plane like yours. I can't give you a good enough suggestion how to do this on your plane, but I had success with hooking them up to a the 4th channel on my receivers and running the wires to any part on the plane.
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Old Dec 23, 2005, 07:46 AM
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Buffalo, New York
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Chris,
I don't recall if your using the RX-101 but if you are don't forget that you can operate the lights with a switch if you run it through the receiver and the seventh channel can be configured so a red LED wired to that channel would give you a rotating beacon effect. Also if your going to wire up LEDs why not make it really scale and use a proper navigational light configuration. Contact Ruth or Kipp at DU as I think we had some white LEDs that operated on a single cell just fine and I'm sure they would be willing to share the part number or throw a couple in a package if you plan on ordering anything in the near future.

Dan
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Old Dec 23, 2005, 02:13 PM
Micro Jet Pilot
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Joined Jul 2005
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Hey Electronick, guess what, you inspired me to go get some suitable LEDs. In our local electronic store I even got a presentation that some damn bright white LEDs are still operating well at 3Volts. Great! I think, apperance is as essential as good performance. If LEDs cost me 1g, which is about 3% of total weight, so what. I will try to put it in.

About EDF performance, from my experience this is something completely different, than what is targeted for let's say shock flyers with "vertical performance". The major difference is, that power is transferred into an air beam with much smaller diameter, but much larger efflux velocity. The consequence is, that static thrust is smaller, but cruise and top speed are considerably higher. Thus, "vertical performance" of a jet is very hard to achieve, since it requires more static thrust than weight. This ultimately happens at an incredible efflux velocity and requires a lot of power. For conventional sized model jets, this can be achieved, but it is not necessary for great performance. Great performance of a jet is ballistic flying, which basically means that height is transferred into speed and vice versa. Once you have stored sufficient energy in the jet, you can do long vertical climbs without having more thrust than weight, simply because you have reached a high speed. Requirements for ballistic flying are good aerodynamics (especially in the duct), high efflux velocity (which comes for free) and decent power. To be honest, I will be happy, if this plane is flying nicely at all. I am going too close to some limits to expect the performance typical for large edfs. However, also typical for edfs is a high wing load. The difference to slow flyers can be so severe, that you find wing loads in different orders of magnitude. This also means, if an edf jet has enough power to fly at all, it will have a decent speed and it will be fun and a challenge to fly. At least it will be visible with some scale tip tank spot lights!

BTW this is a build log, but I am happy to have a discussion going here too...

Merry Christmas!

Chris


P.S.: I attached some pics of my 16'' L-39 with the lights on, so you know what I am talking about...
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Last edited by Chris T; Dec 23, 2005 at 02:23 PM.
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