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Old Aug 02, 2009, 02:35 AM
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Sydney, Australia
Joined Mar 2008
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Small EDF rough power guide

Hi All,

I'm looking to design and build a small EDF jet but am new to the EDF world. I've done a lot of trawling on past posts on the power output of the smaller fan units but with motors and fans in this size becoming better and better and more common, I was wondering if anyone could give a rough guide on the power output of current generation 30/40/50 and 55mm units. Preferably using 3-cell lipos as it seems to get decent flight times from 4 cells will mean heavy batteries.

Thanks
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Old Aug 02, 2009, 04:56 AM
James L
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Beck Row Mildenhall
Joined Mar 2009
811 Posts
This is a really hard question to answer because you can put almost anything together.

So for example we have Derek Knight's 32mm fan with a Feigao 7.8 KV 12mm weighing 26 grammes and puting out 130 grammes of thrust. 86 Watts

GWS EDF40 with a Feigao 5800 KV puting out 120-160grammes weighing 20grammes About 60Watts

GWSEDF50 or similar with a Feigao 5300-5800KV puting out 140-180grammes weighing about 29 grammes. About 65-70 watts

Wemotech Microfan 50mm with outputs from 300 grammes to 440 grammes at 50 to 70 grammes in weight and 150 watts to 350 watts

Ele Model GWS EDF55 combo puting out 420 grammes weighing 55 grammes. At 200 watts.

Xflights 55mm puting out about 500 grammes weighing 97 grammes. At 219 watts

and there are some putting out more or less 700 grammes at about 500watts.

GWS actually got 444grammes out of their EDF40 by squeezing a 20mm motor in it and 365 watts I don't think they offered a warranty on this one! http://www.rcgroups.com/forums/showthread.php?t=847976
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Old Aug 02, 2009, 05:59 AM
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Sydney, Australia
Joined Mar 2008
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Thanks TANGOSIERRAROM - sorry, yes, definitely a bit of an open question, but your answer is exactly the sort of thing I'm after. I'm not really interested in particularly exotic motor/fan combos, more just run of the mill stuff.

It's interesting to note that most of the figures about show about 2 grams of thrust per watt of power. Wonder if this is the norm for EDF units?
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Old Aug 02, 2009, 11:19 AM
James L
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Beck Row Mildenhall
Joined Mar 2009
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Don't actually know somebody else might do, but most fans have a sweet spot in terms of rpm. If you go beyond that you start to use a lot of power to generate thrust. However it does seem to be your 2 grams thrust per watt for most applications. Good spot.

What were you hoping to put this unit in? Were you looking for a hand launch or a bungee launch. The reason being that these sort of things can make a difference in terms of whether a particular EDF will work in our models as we want it to.

Mostly it is down to whether the edf is moving a large mass of air relatively slowly hand launch or ROG is in but top speed is lower

Or a small mass very quickly, bungee launch may be necessary but high potential top speed.
Thrust works out the same but the way the model behaves is different.
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Old Aug 05, 2009, 05:00 PM
Team30 Micro EDF
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Stellenbosch, South Africa
Joined Apr 2004
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Quote:
Originally Posted by mikerogers74
Hi All,

I'm looking to design and build a small EDF jet but am new to the EDF world.
If you want to go EDF30 size do a search in the Micro and Indoor forum.
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Old Aug 05, 2009, 06:49 PM
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Skunk Water, Rhode Island
Joined Jul 2002
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Mike, don't always think that static thrust is the end all, for EDF's. Fans like the WeMoTec Microfan give their power with high efflux. This can be seen in the blade area. Large hub/smaller blade area. Some fans have lots of blade area, as compared to the hub. These are slower turning static thrust producers.

You can have thrust that is more than the weight of the airframe. But, if high speed is the goal, static thrust is not always the answer. The type of airframe, gives indication as to what type of system is needed.

A draggy early scale type will favor more thrust over high efflux. A sleek airframe will only go as fast as the efflux speed at the outlet. It is best to start with the airframe type you desire. And tailor the power system to compliment.

And don't think that a 3s system is lighter than a 4s. 3s systems are usually higher amp draw. Requireing larger batt to avoid V drop. A higher V lower A draw sys will give the same watts, lower amp draw, with a smaller Mah cells. This with a lower Kv mtr that is more efficient. HigherV/lowerA = higher efficiency and less wasted heat.

The variables are broad, in power systems. Chose your airframe type. Approx AUW, and then decide on the fan, mtr, cells, etc. to meet your requirements.

Fuzz
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