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Old Apr 09, 2012, 02:46 AM
It should fly at least once
clive45's Avatar
Australia, NSW, Grenfell
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Unless you are using twin EDF's bifuricated outlet ducting is a power waster, even turbine guys make a single outlet between the twin outlets to not loose power..
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Old Apr 09, 2012, 03:36 AM
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MagnusEl's Avatar
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Joined Jan 2004
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Peter, please take some measurings of inlet and outlets. Since it is a 64mm plane and you get lower current draw I am almost sure the fan is starving, not geting enugh air.
Bifurcated outlet for this fan should be around 40mm each to be @ 80-85% FSA.
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Old Apr 09, 2012, 06:06 AM
Kamikaze Ace
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USA, FL, Lakeland
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Peter thanks for the info on the fan lips and ducting.

And yep I have to agree with everyone else, it's starving for air.
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Old Apr 09, 2012, 06:31 AM
It should fly at least once
clive45's Avatar
Australia, NSW, Grenfell
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Or is it constipated...............It won't go in the front unless it can get out the back.
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Old Apr 09, 2012, 09:32 AM
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Madison, MS
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Quote:
Originally Posted by clive45 View Post
or is it constipated...............it won't go in the front unless it can get out the back.
lmao!!!
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Old Apr 09, 2012, 09:48 AM
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Australia, VIC, Melbourne
Joined Nov 2006
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Err, seemed conflicting decision on the cause(?).
Exhaust side?
I had sat and thought about the idea of conjoining the rear ducts, via opening a central channel 'bridge'. I think the "makeshift cheater hole" (via fan cover off) showed it is not the inlet side - though that might show up to be another issue later if the rear end is opened to more throughput!

But apart from looking and thinking about the read end stuff, I then put it back in the workshop corner in disgust !! LOL. The rear end 'opening' project doesn't look like it will be easy, or best looking. But maybe if I try hard, I can get it to look good... and HOPEFULLY it will actually help!
It will be a good learning curve too!

I have a Dynam Meteor with a 5S CS10 that is losing just over 100g of thrust compared to the bench testing. So that is another one I want to "find" the cause of loss. And will be another good learning source!

With the common used "80% FSA" for exhaust nozzle size..... wouldn't that really alter according to fan volume/thrust? If outputs are within a commonly seen range, then it might be a fair enough general rule. But when we have high speed fans, lower speed 'torque' fans, and even quite dramatically different power systems to drive fan types at wide ranges of thrust outputs, wouldn't that alter what size the flow path restrictions can be efficiently?
Plus the front end's flow ability must match off (in some ratio) to the rear end's flow ability too. (??)
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Old Apr 09, 2012, 10:21 AM
3DHOG
jcdfrd's Avatar
USA, CA, Aromas
Joined Sep 2010
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the intake and exhaust exits are commonly way too big on most foamy jets.
Peter
measure you fan I.D of the housing and O.D. of the motor tube and then measure you exhaust exits for me and I can run the numbers and post them for you
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Old Apr 09, 2012, 12:56 PM
I make bad look so good.
SteveC68's Avatar
League City, Texas
Joined Sep 2006
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Quote:
Originally Posted by clive45 View Post
Unless you are using twin EDF's bifuricated outlet ducting is a power waster, even turbine guys make a single outlet between the twin outlets to not loose power..
No it isn't a power waster. It just takes time to design correctly so most people take the short cut of a single outlet.

http://www.rcgroups.com/forums/showthread.php?t=879830
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Old Apr 09, 2012, 03:44 PM
3DHOG
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Quote:
Originally Posted by SteveC68 View Post
No it isn't a power waster. It just takes time to design correctly so most people take the short cut of a single outlet.

http://www.rcgroups.com/forums/showthread.php?t=879830
+1 Steve
I also dont believe the fan is starving for air, instead the exits are almost certainly way too big. anyway this is my guess and we wont know until measurements are taken
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Old Apr 09, 2012, 05:49 PM
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beavercreek,ohio
Joined Jan 2007
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Hi all, I'm about to pull the trigger on a pair of these: http://www.hobbypartz.com/96m32-car-2848-2618.html The data looks pretty good on 4S but does anyone have any data on 3S, I want to use these fort the windrider 737 and my target weight for the plane is about 4-5 pounds. Would this motor be a suitable fit?
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Old Apr 09, 2012, 05:55 PM
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Australia, VIC, Melbourne
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I will measure it up and post that when I get home tonight!! Thanks.
The airflow/thrust FEELS nice... LOL. (When using the scientific 'hand behind it' method).
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Old Apr 10, 2012, 05:57 AM
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F-15 measurements:

Inlet ducts have a "vertical" area of 70mm (height) by 33mm (width) X 2 of course.
The pic distorts the view a bit, they are perfect rectangles - just with sloped side profiles.

Exhausts are 37mm Inner Diameter. And are larger before that final tapered exit.
And X 2 again of course.

It is of course a CS10, with a 28mm inrunner, so I guess the real "inner radius" item is the fan's motor shroud anyway. Which pretty well means that all CS10's would have the same FSA.

The fan housing is a pefect fit into the rearwards ducting, so it is mounted right up against that and goes marginally into that opening - like 0.1mm. It is a good seal just like that.
The forward area is also a pretty good match to the fan housing, and the fan cover closes down the open area and forms a taper to that forward area. But it is not quite perfect and I will be modifying it to be a perfect match and taper.
.
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Old Apr 10, 2012, 06:15 AM
Extreme CNC Alloy EDF
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Australia
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39mm = 80% FSA for a bifuricated setup, so its not far off. The small square sharp edged intakes wont help with static figures, I would fly it and see what happens.
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Old Apr 10, 2012, 06:22 AM
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At 0.56Kg static thrust, I would assume that means pathetic acceleration.... that gains more and more thrust as it gains speed. But in time to take-off? Or a very very long roll out !!? LOL (eg building up to speed and thus thrust increase.)
That would not make for a very good hand launcher either! hehe
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Old Apr 10, 2012, 06:25 AM
EDF rules... :)
AirX's Avatar
Joined Nov 1999
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Mark, from my numbers on my spreadsheet the outlet area is pretty tight for this fan, the FSA = 2933mm^2 and the outlet area figures to 2148mm which is 73% of FSA.
The fan is definitely being choked and this is where the losses are coming from.

Eric B.
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