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Old Nov 06, 2005, 01:05 PM
Micro Jet Pilot
Chris T's Avatar
Joined Jul 2005
2,091 Posts
Build Log
8'' Micro EDF (L-39 Albatros)

Hi guys,

This is going to be my new L-39. The bird will not be designed for indoor, but is definitely small enough for the micro forum. 8'' (20cm) wingspan, 3 gram minidisc motor 30mm fan, actuators... Can't wait to get started. What do you think?? I will also discuss this project in the micro forum, but more (the only) knowledge about edf is clearly found here. I will need input from all sides, thats for sure

Cheers,
Chris
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Old Nov 06, 2005, 01:16 PM
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Gordon's Avatar
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Quote:
Originally Posted by Chris T
3 gram minidisc motor 30mm fan, actuators <snip> I will need input from all sides, thats for sure
Hi Chris

I'd expect that more than a few of us who've never visited the micro forum would need some input from you on the characteristics of the motors and the actuators (magnetic?) you plan to use

Does the 30mm fan exist commercially, or will you have to make it from scratch?

Cheers

Gordon
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Old Nov 06, 2005, 01:43 PM
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Chris,

did you decide to make your 30" L39 plans available??? 8" is too much, my eyesight can't take it!!! lol.. looking forward to this build!
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Old Nov 06, 2005, 02:49 PM
Micro Jet Pilot
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Joined Jul 2005
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Gearup, my L-39 (see avatar) is 16'' span, not 30'' and I think it is quite big Unfortunately, there were no plans used, just the 3view. The rest happened in my head. This time I will try to make templates! I hope, somebody will build along so it is worth it.

About your eyesight, here is my theory. If you half dimensions of any plane and reduce weight enough so speed is halved as well, visibility will reain the same, since you fly within half the distance at equivalent relative speed. I am not afraid of scaling down. The good thing is, the smaller you build the more stable the stuff gets (I think).

Gordon, the 30mm fan is a cutdown GWS edf 50, so a modified commercial product. Easy to do... It might be harder to find a mini disc motor

Check http://www.rcgroups.com/forums/showt...4&page=5&pp=15

Chris
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Old Nov 06, 2005, 03:31 PM
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Hi Chris t

Just discovered this post on the off chance doing a search - I have quite the opposite L-39 model , one of my favourite jet shapes. I am building th Savex EDF version as I do not the courage for the turbine version . I was searching for suitable retracts

The reason for my post here is that I am a distributor of a range of jet planes ( see www.robotbirds.com) and on my last trip to Czech we were designing a EPP L-29 and have yet to decide on the size - The pusher version is already made and is 22" span - I would like to get a 14-16" EDF version made but there are many production difficulties in keeping to scale proportions. I will return to your posts with great interest.

Andy

[IMG]www.robotbirds.com/catalog/images/l-39.jpg L-39 pusher[/IMG]
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Old Nov 06, 2005, 04:18 PM
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sorry this one

http://www.robotbirds.com/catalog/images/l-39.jpg
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Old Nov 07, 2005, 06:23 PM
Micro Jet Pilot
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First Facts

Weight of wing: about 3g


Chris
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Last edited by Chris T; Nov 08, 2005 at 09:25 AM.
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Old Nov 08, 2005, 06:51 AM
Micro Jet Pilot
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Joined Jul 2005
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Want Templates??

Anybody got the courage to go real micro along with me?
Sign up now, if you want to build a micro L-39 as well!!!
At least, the raw material is cheap since you need almost nothing

A perfect area ruled duct will be modeled into the fuselage. Inlet area 100% FSA (slightly off scale but worth it). BTW, I am using balsa carbon and glass, no foam at all! Wing: 3mm balsa sheet, sanded to shape, elevator 2mm balsa. I selected the lightest balsa I could get with a precision scale.

Chris
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Old Nov 09, 2005, 05:28 AM
Micro Jet Pilot
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Motor and Fan

This is the minidisc bl motor and 30mm fan. Total weight of motor + fan without fan-stator and shroud: 4.4g

Current winding scheme: 18 x .3mm wire, star connection, 8 pole stock magnet, N50 3 x 3 x 0.5mm magnets are on the way...

Chris
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Old Nov 09, 2005, 07:31 AM
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Chris. Although I was very interested in your last L-39, I'm ecstatic about this one! I really am not the only one who's fascinated by miniaturising things!

It's just occurred to me just how tiny this model is going to be. 8" wingspan! Wow!

I'm following with very close interest...
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Old Nov 09, 2005, 08:31 AM
Beware of the cabbage
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I'm sure you must have seen this?

http://www.rcgroups.com/forums/showthread.php?t=266333
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Old Nov 10, 2005, 09:53 AM
Micro Jet Pilot
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Joined Jul 2005
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Thanks MeGrimm,

yes I have seen this one. Very nice indeed. That is kind of what I am aiming for, just with ductwork, bl motor and a little more power. I like that tiny little fan. Incredible! I would like to have one too.

I am still working on the plan for the micro. Will be done soon. I have a clue now how to do the actuator mount. Targeted weight is now 1 ounce...

Regards,
Chris
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Old Nov 16, 2005, 09:00 AM
Micro Jet Pilot
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Joined Jul 2005
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Duct Design

Hi guys,

I just wanted to have this confirmed:

I am designing the inlets as Winmodel suggests: 100%FSA highlight area (measuring from the center of the intake lip, see air flow with diffusion). This means, the throat area will be below 100% (about 80%). This is due to a 3mm thick lip. For the 30mm fan with 15mm hub, this is 26mm highlight diameter and 23mm throat diameter. For the outlet I was thinking of 90%FSA.

You should consider, that this model will have plenty of power for its size and is designed to be a fast flyer. These usually have rather small inlets to reduce drag. At speed, sufficient air is still provided.

Does this sound ok?
I don't want to have too small inlets this time, but these numbers are already way larger than scale on this model...

Thanks for your feedback

Chris
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Old Nov 16, 2005, 02:19 PM
Micro Jet Pilot
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2,091 Posts
... where are you experts?
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Old Nov 17, 2005, 06:30 PM
Micro Jet Pilot
Chris T's Avatar
Joined Jul 2005
2,091 Posts
Status of the drawings

...I will start building very soon. I still wonder if the inlet lip is not too thick. I could trade it for some more "throat" area...

Chris
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