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Electric Ducted Fan Jets Discuss electric ducted fan jets here including setup tips, power systems, flying techniques, etc.

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Old 12-28-2010, 09:42 PM   #26
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Dang! Looks like it's producing plenty of thrust.

If you've kept the weight down, I think this will fly fine.


I can't wait for the flight reports.

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Old 12-29-2010, 03:07 AM   #27
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Very nice! Is it just me, or is your fan producing a different sound to the typical one of an EDF? Perhaps it's just because it's running slower, or maybe it has to do with the lack of stators, but yours seems to be comparitively quiet.

A crashed airplane is like a jigsaw puzzle...
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Old 12-29-2010, 03:59 AM   #28
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Lower RPM, larger blades...?

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Old 12-29-2010, 11:06 AM   #29
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The fan sounds like it's very well balanced, better than a lot of 'off the shelf' EDF's I've got to say!.. Perhaps the relatively low RPM helps?

Looking forward to flight report and hopefully video...

Good luck

Steve
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Old 12-29-2010, 11:48 AM   #30
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Hi quorneng, nice video.
By the way, have you try to experiment some fix stator fin at the exhaust.
The fix fin or stator is very important integral component of a EDF. Without the stator fin, the air that rushes out, will exit the exhaust in a swirl resulting is a lost of kinetic energy. The fix fin stator straightened the air swirl and reduce the lost in kinetic energy resulting in a significant improvement to the static thrust.

Cheers
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Old 12-29-2010, 05:00 PM   #31
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It does indeed make a different noise because:
a) It is only turning at about normal prop speed (12000 rpm).
b) The shroud almost eliminates the tip noise you get from a normal prop. It should be pretty quiet.
On a shrouded fan such as this I am not sure the benefit of stators will outweigh their drag.
It will be painted in my "house" colours of black and yellow.
Click image for larger version

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ID:	141088
It is just under the expected 12oz AUW.


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Old 12-30-2010, 02:28 AM   #32
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Originally Posted by quorneng View Post
It does indeed make a different noise because:
a) It is only turning at about normal prop speed (12000 rpm).
b) The shroud almost eliminates the tip noise you get from a normal prop. It should be pretty quiet.
On a shrouded fan such as this I am not sure the benefit of stators will outweigh their drag.
It will be painted in my "house" colours of black and yellow.
Attachment 141088
It is just under the expected 12oz AUW.
Hi quornen, some key factors that will help you to improve the EDF efficiencies.

1) Number of blade. More blades more static thrust but to a certain limit before diminishing returns sets in. Some people thought that if I increase say up to 12 blades from 6 blades the fan would be more efficient. Unfortunate more blades actually load the motor and hence the electrical efficiencies decreases. Loading the motor with the right number of blade improve efficiencies. 5blade looks like a good number.
2) Fix stator Blade. As mentioned, this fin straightened the air flow as the air leave the ducted fan.
3) Intake or the mouth. Unobstructed intake is the most ideal case. Some ducted intake has a lip or intake ring curve up to increase the surface area of the EDF mouth. This also increases the static thrust.
4) Thrust tube (not talking about the funnel cone cut out from McDonal’drinking cup) shape like a cigar located at the centre of the exhaust end , will further straightened and improve lamina airflow as the air exit the duct. This tube aerodynamically shaped properly can improve the static thrust by as much as 25% without consuming additional electrical power. See attachment

Further reading on EDF and its history see...
http://massflow.archivale.com/ductbook.htm

Cheers and all the best.


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Old 12-30-2010, 06:53 AM   #33
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I think it's gonna fly!

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Old 12-30-2010, 09:53 AM   #34
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Originally Posted by mclarkson View Post
I think it's gonna fly!
I'm pretty sure it will fly.. But just not like you would expect from a plane with nearly 200 watts per pound. With that sort of power and a halfway efficient propulsion system you would expect to just about pull the wings off, unlimited vertical, the works.

time will tell.........

Steve
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Old 12-30-2010, 11:24 AM   #35
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It probably won't perform that well, but damnit, it's using a CPU fan as a fan unit! That's...

*Puts on sunglasses*

...cool...

Yeaaah!

A crashed airplane is like a jigsaw puzzle...
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Old 01-01-2011, 06:30 PM   #36
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It does indeed fly.
Just like.............a park flyer!

CofG a bit too far back. It needed full forward trim so I dared not explore the flight characteristics too far.
Climbs strongly and only need just over 1/2 power to maintain height.
Pronounced left wing drop on the stall but it glides well enough to do a complete circuit and landing stopping in its own length on the wet grass.
So battery forward a bit and the Key Chain cam on next time.
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Old 01-01-2011, 08:17 PM   #37
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NICE! Do you have any video of it?

"I didn't crash... I just did an inverted nose landing!"
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Old 01-01-2011, 09:47 PM   #38
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Congratulations!

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Old 01-02-2011, 12:22 AM   #39
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Thanks but as I fly alone I can only video with a cam 'on board'.
Finish painted and the nose modified to move the battery forward 4mm.
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The Key Chain cam will be mounted on the battery hatch.


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Old 01-02-2011, 12:31 AM   #40
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Not true... You can tape the keychain camera to the bill of a baseball cap. Then it's filming wherever you look.

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Old 01-02-2011, 12:32 AM   #41
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Originally Posted by quorneng View Post
It does indeed fly.
Just like.............a park flyer!
Great news. I can't wait to see V2...

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Old 01-02-2011, 04:03 PM   #42
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A video of only its second flight.
CofG still a bit too far aft and the cam mounting could be improved but it certainly flies.
YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.

After I removed the cam (I did not want to risk loosing the record!) It flew on for another 5 minutes. Rolls much faster to the left (with the motor torque) than the right. Loops are very tight and it tends to fall off to the left (motor torque again) but fast it is not!
A few more adjustments required.
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Old 01-02-2011, 06:04 PM   #43
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It flies great, but not I think you might agree; not like you might expect from a plane with a power/weight of 200W/pound.
Anyway, efficiency aside, performance certainly looks perfectly acceptable. Regarding the left torque. as well as producing extra thrust stators also cancel out much, if not all, of the torque produced by the motor.

What makes you think the CG needs to go forward?.. it appears stable enough in the video.

Steve
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Old 01-02-2011, 06:30 PM   #44
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I think it has got to be plenty efficient for an 8 minute edf flight time!

"I didn't crash... I just did an inverted nose landing!"
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Old 01-02-2011, 07:02 PM   #45
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Nice design. For more thrust and minimal weight, try extending the thrust tube 3" and have the exit opening be 15% smaller than the inlet.

"It takes a big man to cry after crashing his plane and it takes a bigger man to laugh at the man crying". Can I get you a garbage bag?
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Old 01-02-2011, 07:38 PM   #46
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Steve.
This is the "as flown" elevator position.
Click image for larger version

Name:	Elevtrim.JPG
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ID:	141305
With this much effective under-camber on the tailplane it is not particularly pleasant to fly with marginal stability.
The nose will be extended to move the battery forward another 1/4".

After listening to the video sound track a couple of times it is noticeable that the fan slows down slightly just after the launch. I did not touch the throttle.
This suggests to me that when stationary the fan is restricted in some way either the inlet or that the fan blades are partially stalled. At about 9" pitch it is after all pretty coarse for 3" diameter.

Is it normal for a fan to slow down slightly with initial forward air speed?


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Old 01-02-2011, 07:41 PM   #47
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Originally Posted by skyman View Post
I think it has got to be plenty efficient for an 8 minute edf flight time!
or a big battery?
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Old 01-02-2011, 09:03 PM   #48
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Originally Posted by quorneng View Post
Steve.
This is the "as flown" elevator position.
Attachment 141305
With this much effective under-camber on the tailplane it is not particularly pleasant to fly with marginal stability.
The nose will be extended to move the battery forward another 1/4".
You could adjust the mounting angle of the tail, drop the TE 1/8" or so.. Alternatively adjust the wing LE down a bit. That would get rid of the downtrim.

If the CG is too far back you would usually experience 'twitchiness' in pitch control.

Steve

PS.. fan slowing down with forward speed is not something I've come across. if the blades were stalled then that would slow them down (stalled blades/wings produce more drag than non-stalled ones).
It's possible I guess, but could it be that it just 'sounds like' it's slowing down, perhaps the acoustics change when the model leaves your hand?
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Old 01-02-2011, 10:43 PM   #49
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Congratulations on your successful experiment, quorneng!

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Old 01-03-2011, 06:22 AM   #50
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Congratulation. looks like you have fun. Maybe get us a video of the plane in flight will be great. We like to see how the plane flies from the pilot perspective.

Cheers
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