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Old Oct 04, 2012, 05:19 AM
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twin edf- micro DC9 project

I started this project late 2009. The idea was to build the fiddlersgreen model (see pictures i found on Internet) with an EDF set up.

Wing span is 54 cm.

I began the building with 2mm wall foam covered with the fantastic water slide decals from Crafty computer. This is my favourite way of making planes.

I made the fuse, the nose and the tail and used some durobatics and polystyrene for the wings and the elevator + rudder.

I was not satisfied by the result: it looked great, but the foam was too flexible.
So i stopped the project for a while and destroyed my building...

Late 2011, i decided to make a new try with 4mm wall foam. The same i've used for my Gee Bee Z.

The big challenge is the weight. I want to fly the plane indoor, and i'm using 2 Airhogs edf30.

Of course, the size of the fan will not be scale, but i think that i can't use smaller units unless i use bigger motors etc...

The thrust is 11g per unit, which makes 22g for both. The AUW limit of the plane should be 1.5 x 22 = 33g as i consider that the thrust should be at least equal to 2/3 of the AUW.

It is not possible to make such a light airplane especially with 2 EDF units.

In 2010, i read on the micro edf forum that the 7mm walkera motors were stronger. I tried them at 5V with the Airhogs unit, and i found that the thrust was around 15.5 - 16g with a 1.2 A current. The motor seems to stand this power.

i made a micro edf jet using a dc/dc converter (to get 5V) and the edf equipped with the walkera motor, and the plane, weighing 27g, flew well.

http://www.rcgroups.com/forums/showthread.php?t=1346020

So the first solution is to use 2 dc converters (1.2g-90% efficiency).

If the output current is equal to 2 x 1.25 =2.5A, the input current is equal to 2.5 x (5/3.5 x 0.9) = 3.75A. That means that i would need a 300 mA.h battery: 10g.

10+ 2x1.2 =12,4g

The other solution is to use a 2S battery with a 2S ESC and limlit the throttle on the radio in order to keep the current just at 2.5A max.

I need smaller batteries (180 mA.h-5g) and the esc weighs 1.5g only:

1.5 + 2 x 5 = 11.5g

I choose this option.
My target AUW is less than 50g.

I will show you what i have done so far, but i will need your advices as i am still wondering about the wings and other things.
Please, do not hesitate to share your knowledge and your experience.
Thanks in advance.
Frank.
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Old Oct 04, 2012, 09:21 AM
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Quote:
Originally Posted by indoor_fr View Post
I started this project late 2009.
Looking forward to how you progress. Are the pictures of the Fiddler's Green paper model?

Quote:
2mm wall foam covered with the fantastic water slide decals from Crafty computer.
What is "Crafty computer"?

Gene K
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Old Oct 04, 2012, 10:29 AM
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Hi Gene.

Yes, these are the pictures of the Fiddler's green model.

Crafty computer is an English company:

http://www.craftycomputerpaper.co.uk/default.aspx

Frank.
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Old Oct 04, 2012, 10:55 AM
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Crafty computer is an English company....
Thanks, Frank.

Since you're printing onto decal paper, have you also considered printing onto tissue and applying that to the foam?

Gene K
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Old Oct 04, 2012, 12:22 PM
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id second that. tissue and foam make a strong composite. and you might be able to get away with less foam. (cutouts)
tho id play it safe and add 25% to you weight estimates. either way youll be happier. (IMHO)
wiill be looking at this. no one has done a brushed EDF in awhile.

WERE DID YOU FIND THOSE AND WERE CAN I BUY SOME?

ive got a 3d printed order on order that im working on the duplicate the 7mm airhogs brushed EDF, but i am working on this mostly cuz i can find any to buy!
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Old Oct 04, 2012, 12:46 PM
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ive got a 3d printed order on order
To go briefly off topic, could you provide a link to that printer?

Gene K
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Old Oct 04, 2012, 12:54 PM
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Originally Posted by nemoskull View Post
id second that. tissue and foam make a strong composite. and you might be able to get away with less foam. (cutouts)
tho id play it safe and add 25% to you weight estimates. either way youll be happier. (IMHO)
wiill be looking at this. no one has done a brushed EDF in awhile.

WERE DID YOU FIND THOSE AND WERE CAN I BUY SOME?

ive got a 3d printed order on order that im working on the duplicate the 7mm airhogs brushed EDF, but i am working on this mostly cuz i can find any to buy!
Kevin (BiM) is working on small EDF's in the micro EDF forum.

I'm ordering some 20mm's for Albatros 7mm motors to try out. I'm thinking of a 20" A380. I figure each will make an easy 10g of thrust on 1S... more if I throttle 2S.


For larger EDF's the 30mm GWS rotor fits onto the 8.4mm motors. You can buy housings from BiM
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Old Oct 04, 2012, 01:13 PM
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Originally Posted by UNGN View Post
Kevin (BiM) is working on small EDF's in the micro EDF forum.

I'm ordering some 20mm's for Albatros 7mm motors to try out. I'm thinking of a 20" A380. I figure each will make an easy 10g of thrust on 1S... more if I throttle 2S.


For larger EDF's the 30mm GWS rotor fits onto the 8.4mm motors. You can buy housings from BiM
I would be surprised if you'd get 10g of thrust on 1S with a 20mm EDF and with the albatros motor. I tested the albatros motor last year and it didn't give a good thrust with an EDF30.
I also doubt that you'll be able to run it on 2S without frying it (it is hotter than the walkera motor). Anyway, it worth a try.

I'm waiting for your test results.
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Old Oct 04, 2012, 01:17 PM
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Originally Posted by nemoskull View Post
id second that. tissue and foam make a strong composite. and you might be able to get away with less foam. (cutouts)
tho id play it safe and add 25% to you weight estimates. either way youll be happier. (IMHO)
wiill be looking at this. no one has done a brushed EDF in awhile.

WERE DID YOU FIND THOSE AND WERE CAN I BUY SOME?

ive got a 3d printed order on order that im working on the duplicate the 7mm airhogs brushed EDF, but i am working on this mostly cuz i can find any to buy!
Thanks for the input. I have noticed that a lot of people make very nice planes with printed tissue. I've tried once in the past, but i didn't like the result (for my plane).
I will make an other try with printed tissue for a future project, but the DC9 is already begun, so i can't go backward.

The decals i buy are not the very fragile decals used for decorating static models. In fact, It's a kind of an "elastic skin" that gives a very glossy aspect and make the foam very strong as well. The additionnal weight is not very high.

About the edf30 fan for 7mm motors, these are fans from Airhogs JetScream. You'll have to buy one and dismantle it:

I don't know if they are still available...
Here is one on EBAY:
http://www.ebay.com/itm/Airhogs-Jets...item1c2bd738ab

What is the price of your 3d maker?
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Old Oct 04, 2012, 09:29 PM
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Originally Posted by indoor_fr View Post
Thanks for the input. I have noticed that a lot of people make very nice planes with printed tissue. I've tried once in the past, but i didn't like the result (for my plane).
I will make an other try with printed tissue for a future project, but the DC9 is already begun, so i can't go backward.

The decals i buy are not the very fragile decals used for decorating static models. In fact, It's a kind of an "elastic skin" that gives a very glossy aspect and make the foam very strong as well. The additionnal weight is not very high.

About the edf30 fan for 7mm motors, these are fans from Airhogs JetScream. You'll have to buy one and dismantle it:

I don't know if they are still available...
Here is one on EBAY:
http://www.ebay.com/itm/Airhogs-Jets...item1c2bd738ab

What is the price of your 3d maker?
Isn't it shapeways?
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Old Oct 04, 2012, 10:01 PM
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Originally Posted by indoor_fr View Post
I would be surprised if you'd get 10g of thrust on 1S with a 20mm EDF and with the albatros motor. I tested the albatros motor last year and it didn't give a good thrust with an EDF30.
I also doubt that you'll be able to run it on 2S without frying it (it is hotter than the walkera motor). Anyway, it worth a try.

I'm waiting for your test results.
I was able to get just under 10g with a jury rigged 7mm setup using a cut down GWS fan, a first gen 22mm housing without a bellmouth, using a "just OK" Nanotech 160.

I'm ordering fwd and reverse rotation fans and 22mm and 20mm housings from Kevon.

In a few weeks, when I get the parts, I'll post the thrust results.

For 2S, i have 7A brushed Pixie ESC's and I can throttle the ESC with the travel extents in the TX and a Voltmeter. Just want to see what kind of thrust happens @ 5.0 or 5.5 volts.
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Old Oct 04, 2012, 10:12 PM
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Putting them together right now actually.
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Old Oct 04, 2012, 10:55 PM
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Quote:
Originally Posted by UNGN View Post
I was able to get just under 10g with a jury rigged 7mm setup using a cut down GWS fan, a first gen 22mm housing without a bellmouth, using a "just OK" Nanotech 160.

I'm ordering fwd and reverse rotation fans and 22mm and 20mm housings from Kevon.

In a few weeks, when I get the parts, I'll post the thrust results.

For 2S, i have 7A brushed Pixie ESC's and I can throttle the ESC with the travel extents in the TX and a Voltmeter. Just want to see what kind of thrust happens @ 5.0 or 5.5 volts.
with the albatross motor?
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Old Oct 04, 2012, 11:14 PM
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Originally Posted by minimicrorc View Post
with the albatross motor?
Flyzone Albatros 7mm. $2.99 @ Tower hobbies.

Will easily fly a 40g plane @ about 1amp current draw through a gearbox... probably about 25-30g of thrust depending on the battery/prop.

EDF's of course aren't as efficient, but infinitely cooler.
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Old Oct 05, 2012, 07:33 AM
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The wing

Ok, let's talk about the wing.

The wing is made of a sheet of polystyrene. It is flat. I have glued it to the fuselage but i think it is possible to remove it (with care...).

I'm aware that a flat wing will bring drag.
I'm wondering if i shouldn't make a pair of under camber wings that could be attached to the sides of the fuselage with magnets:
Not only this will add lift, but i will be able to store the plane in a much smaller box!

Should i stay with the flat wing or should i change?

If i had to make new wings, how could i do? Both wings should weigh 5g max...
I have some 2mm depron and 2mm wall foam...

I could make ribs and cover with 2mm wall foam (coverd with decals of course).
Or maybe, i could use 2mm depron and give an under camber shape with hot water?

What do you think? If you have already made something like that, please tell me.
Thanks!
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