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Old Nov 13, 2012, 03:33 AM
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Originally Posted by Ron101 View Post
From the pics it looks like 2 128mm would fit in the CARF T-45....

Prolly should have no issues with the Tomahawk..
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Old Nov 13, 2012, 03:39 AM
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Sec....

is the weight of the plane 44 pounds empty or is that the flight weight with turbine?

I've found there's a notable weight loss when going to EDF depending on the fans
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Old Nov 13, 2012, 05:18 AM
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Originally Posted by Ron101 View Post
I would think as big as that plane is you could do a twin 128mm Tam Jets Dynamax conversion... giving you a total of a 256 mm fan
When i read the first post i was thinking the exact same thing. Two dynamax fans, and if those dont fit then two stumax 110 fans should do it. This is by far the most cost effective option also because as soon as you go to a large single fan like the new larger scheubeler or aeronaut fans, the cost goes up astronomically. But installing one fan is easier as you wont need to fabricate dual intakes and dual fan mounts ect..

However the area of a single dynamax fan is around 9800mm, x2 fans is around 19600mm the area of a 256mm fan would be around 47600mm. a 256mm fan would have 4x the area of a single dynamax fan..

Terry, you need to get the measurements of the intakes on that L-39 and the exhaust size. you are also going to need quite a large outlet.. once you have that then you can figure out what is the largest size fan/fans you can use, then see if that size fan/fans will even fit inside the plane.


here is a video of two jets flying with single scheubeler fans..

Composite ARF Hawk mit Schübeler DS-94 DIA HST (2 min 19 sec)


ALBATROS L39; C&C Models, Schübeler HST Impeller, 1.Teil (6 min 9 sec)
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Old Nov 13, 2012, 06:11 AM
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Originally Posted by Christian W. View Post
Hi Terry,

I have problems sending you emails. They are always coming back. Hopefully you received my PM I sent you a few minutes ago.

Christian
Christian,
Got your PM via RC Groups. I don't understand why you can send me an mail? Strange as you have in the past when we communicated?

Terry
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Old Nov 13, 2012, 06:13 AM
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I have a simillar problem

I been currently working on an EDF design to produce 40 lbs of thrust, to be used in an RPV, military application. The fan is 6" in diameter, using Dynamax rotor blades, and stator vanes. Of course the rotor blades are modified to handle the addtional blades mounted on the hub assembly. The issue I have run into is the current draw at 14S is over 800 Amps. Thats just to high to live with. I talked to Steve Neu about rewiring the motor, from the standard 3 phase to a 6 phase, that way the current in each phase is basically cut in 1/2. The Batteries aren't a problem, but the ESC is. At this time there are no ESC's that can handle 6 phases, in the model industries. Castle wasn't to interested in getting involed, mainly because of the time required, and a big concern of going to 30S batteries. They consider that a safety issue. At present, I'm looking to design a modulized ESC that can handle from 6, up to 9 phases. and 30S LiPo's. But I now need optical feedback from the motor to commutate the phase switching. Thats how this all started 15yr's ago.

My 2 cents worth.

Larry E.
SouthEast Model Products Inc.
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Old Nov 13, 2012, 07:15 AM
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Quote:
Originally Posted by Chuchuf View Post
Alright guys, I'm looking to the braintrust of this forum to see how you think the Tomahawk L39 2.7m could be set up as an EDF model.
http://tomahawk-design.com/produkte/...ros-l39-270cm/

I have some ideas of my own and am trying to get some answers from Schubeler of the upcoming DS-215-HST.

I'm open to any and all ideas no matter how radical.

The goals are to keep it light and have reasonable flying speeds like the turbines do.
http://www.youtube.com/watch?v=lBvccb_uigI
Thanks,

Terry
I was at Ejets and talked with Daniel himself about suitable planes for the DS-215 fan unit, and he named this L-39 as a perfect plane for it. So I would say that sounds like the way to go. The fan will be making over 50 lbs of thrust on 14S so it has the power to push a plane of this size.
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Old Nov 13, 2012, 08:06 AM
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Thanks for the thoughtful insight guys on how this can be done.

I have been in discussion briefly with Schuebler and they are recommending the new DS-215-HST on an open duct system (their inlet ring), MGM Compo ESC and 14S 2P 8000 in batteries for a total capacity of 16000 mAh on 4 batteries.
I have begun to build a spread sheet of the (2) DS-78, (2) DS-94 and DS-215 to analyze the thrust, current draw, total weight and cost of each setup. This assumes 14S on all the setups and 6500mA, 8000mA and 16000mA for each of the respective fans.
If I did go with the twin, I would like to do something similar to what Tam did on the T45 setup that's posted earlier in the thread.

Another requirement is 4 min flight time with reserves for a go around in the event of a missed approach for landing.

At the moment this plane is in storage and I can't easily measure the inlets and outlet but will try and get in touch with Tomahawk to see if they can give me some numbers to analyze the twin closed ducting setup.

Double E, The plane I referenced that Ali was flying at Jet Power was and had to comply with a Germany's strict sub 25 KG ( With fuel) regulation and had an IG Hammer 180+ in it. Since then Ali replaced he turbine with a P200 and has added some weight to the nose as he stated it felt a bit tail heavy to him. As you can see the plane looks to fly very light at 25 Kg (55lbs) and with 180N power (around 41lbs) thrust had pretty good vertical pull. That's about 0.75 thrust to weight.
I have doubts looking at the battery requirements of being able to get this plane to come in at 25Kg EDF but would like to strive for that.
That means that 40 lbs thrust would be the minimum I would strive for with 50 lbs better.

Terry
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Old Nov 13, 2012, 09:31 AM
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Terry,

The 90mm setup that Tam used was flying an 18.5lbs BVM F-86 on 12s 6500mah packs. I would bet you could get close to the numbers you are looking for on two 100mm Tam fans and use a closed ducted system. I can only imaging some of the issues you would run into trying to run an open system with the 215. I figure it would only be a matter of time before the fan sucked something up or collapsed part of the airframe. You would also be giving up quite a bit of performance/efficiency with an open system. It would be interesting to know where you get the most thrust per dollar spent.
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Old Nov 13, 2012, 09:41 AM
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Originally Posted by EDF Crazy View Post
Terry, you need to get the measurements of the intakes on that L-39 and the exhaust size. you are also going to need quite a large outlet.. once you have that then you can figure out what is the largest size fan/fans you can use, then see if that size fan/fans will even fit inside the plane.
Yup, direct from Thomas at Tomahawk (thanks Thomas for the quick reply)

1 inlet has a size of round about 120 cm2
So both round about 240 cm2

The outlet has round about 150 cm2 but when you leave away the scale cone you can also make a maximum of 200 cm2

Have to get my slide rule out and do some calculations.


Terry
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Old Nov 13, 2012, 09:57 AM
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Originally Posted by Double E View Post
Terry,

The 90mm setup that Tam used was flying an 18.5lbs BVM F-86 on 12s 6500mah packs. I would bet you could get close to the numbers you are looking for on two 100mm Tam fans and use a closed ducted system. I can only imaging some of the issues you would run into trying to run an open system with the 215. I figure it would only be a matter of time before the fan sucked something up or collapsed part of the airframe. You would also be giving up quite a bit of performance/efficiency with an open system. It would be interesting to know where you get the most thrust per dollar spent.
I think that 100mm fans (Tams, Stu, etc) will be way to small for this setup considering I'd like to achieve 0.85 or so T/W ratio.So I'll need to put out about 45lbs thrust, minimum.
I would also argue that the open system while it _may_ give up a bit of top end speed, is really ther best of both worlds. It allows the EDF to produce maximum thrust using the inlet ring so doing immelmans, loops, cubans the fan can produce max static thrust when you start to run out of momentum. As you know I ran this open system in planes up to 25 lbs and honestly don't think I was suffering in top speed. Would I use an open system if I were building some for absolute top speed, no certainly not. But then I also wouldn't choose a fan designed for max. static thrust. You have certainly convinced me of that with your wemo. FOD on an open system can be a problem if you aren't careful.

Most thrust per dollar, I believe of the three choices I've laid out so far (DS-215, DS-94 and DS-78) the winner will be the DS-215. But that's just an early look at the figures. I believe it will also be the lightest setup but I have to get some more accurate figures on the weight of the batteries and I haven't accounted for wire which will be larger and heavier on the DS-215 setup.

Terry
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Old Nov 13, 2012, 10:02 AM
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Cool project Terry. Keep us posted.
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Old Nov 13, 2012, 10:18 AM
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?

Quote:
Originally Posted by Double E View Post
Maybe aluminum is the way to go. Check out this 120mm fan from Easy Tiger that they claim can handle 100k RPM. I'm pretty sure this fan is just a private label of something that is already available on the market.

http://easytigermodels.com/index.php...2vutv5e8m7boh5
I have a question. How do you get a 120mm EDF to turn 100k rpm, and produce the thrust they claim, when the tip stall speed is aprox 53K ? Some of these claims I see here just don't meet the laws of physics. Bottom line is an EDF is an air pump, not a turbine. If the tip speed exceeds the speed of sound, the blades are going to stall.

If you get 18lbs of thrust on 14s at 6KW, 50lbs would be 2.8 times that, or over 320 A, and that doesn't include any efficency losses. Thats over 100A RMS per phase, with #12 wire. You can break any law humans can make, but you will NEVER break the laws of physics.

My 2 cents worth
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Old Nov 13, 2012, 12:19 PM
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Originally Posted by LJE4357 View Post
If the tip speed exceeds the speed of sound, the blades are going to stall.
Why would this have to be true? Wouldn't every fighter jet fall out of the sky then because the wing would stall at supersonic speeds?

A prop or fan can be made to run supersonic as long as the airfoils and angle of attack are under control. This was tested by NACA with a 6,000 hp prop dyno/windtunnel and the XF-88B and XF-84H

It is however unlikely that the ET fan was designed for this or that they ever ran one near 100k rpm.
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Old Nov 13, 2012, 12:20 PM
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Quote:
Originally Posted by LJE4357 View Post
I have a question. How do you get a 120mm EDF to turn 100k rpm, and produce the thrust they claim, when the tip stall speed is aprox 53K ? Some of these claims I see here just don't meet the laws of physics. Bottom line is an EDF is an air pump, not a turbine. If the tip speed exceeds the speed of sound, the blades are going to stall.

If you get 18lbs of thrust on 14s at 6KW, 50lbs would be 2.8 times that, or over 320 A, and that doesn't include any efficency losses. Thats over 100A RMS per phase, with #12 wire. You can break any law humans can make, but you will NEVER break the laws of physics.

My 2 cents worth
A good 2 cents indeed. Plus I wouldn't use their fan.

Fans I would consider are Schubeler HST line, VESA 120mm 14 blade (unproven but looks interesting), Dynamax because of it's proven history but built with maybe a Neu motor and 14S setup, Stu if he has anything big enough, EJets once again if the get a larger fan, possibly Tams 120 or Dynamax setups.

I think there are some of you here that have run twin setups on a single engine plane (or is Tam the only one?). Is there anything special I would need to know about the thrust tube?

Terry
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Old Nov 13, 2012, 02:01 PM
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A pioneer (10 years ago) use a dual-motor/esc set up to get more power using technology available at the time. I am sure that this is till applicable using todya's off-the-shelf technology to manage more power!

http://www.rcgroups.com/forums/showthread.php?t=32881
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