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Old Oct 15, 2012, 03:09 AM
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BAE Hawk EDF converted to C/L

This project is just something different. I'm starting with an R/C kit from Hobby King and converting it to control line. The kit is the BAE Hawk for a 70mm Electric Ducted Fan. I will be replacing their stock EDF with a Change Sun 70mm 10 blade fan. The Change Sun fan has a great "turbine like" sound instead of the typical screeching EDF. It will have throttle control via a 3rd line and will be launched by a bungee.

My Dad is already successfully flying a Hobby King F9F Panther he converted to control line with throttle and bungee launch.

More to come.....

Derek

[Edit] I forgot to list the specs. The only thing stock is the airplane shell.

BAE Hawk from Hobby King
Wing Span: 39 in
Length: 43.3 in
EDF: Change Sun 10 blade 70mm
Motor: Turnigy L2855 2800 kv
Battery: 4S 2500 to 3000 mAh at least 35C good quality (TBD)
ESC: Hobby King BlueSeries 85 Amp
Flying Weight: 2.2 lbs

Conversion to Control Line:
Bellcrank: "Perfect" brand aluminum bellcrank, 2-5/16 x 1-1/16
Throttle: U/Tronics single channel for 3rd line control, modified with 50k ohm rotary potentiometer
Handle: Custom made 3 line handle
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Old Oct 15, 2012, 07:38 PM
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Mounting the ESC

The normal location for the ESC is up under the removable cockpit, next to the battery pack. However, this airplane is nose heavy, so I decided to move the ESC as far back as possible. I found a nice place in front of the ducted fan, and the cooling fins are exposed to the intake airflow.

More to come...

Derek
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Old Oct 15, 2012, 08:56 PM
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Testing the EDF

Up to this point, there was no difference in setup for Radio Control or Control Line. It was all about getting the EDF and ESC installed.

Even this step - motor testing - is still pure R/C style. I promise, the conversion to Control Line will be coming next !

The best way I know to test an electric setup is simply use an R/C receiver and transmitter. This is a good way for me to know the motor / ESC / battery are working properly, drawing the correct amps, and producing the correct thrust level. I'm doing all this before hooking up the U/Tronics throttle control. This way I have a benchmark. This particular ducted fan and motor combination in this exact airplane are well tested on the R/C side, so I know how it should perform.

If you are purely control line and don't have any R/C stuff, you can get a 2.4 GHz transmitter and receiver for about $23 here. For example, the receiver I'm using was $8.

For testing EDF's, I found it's a good idea to use a much larger mAh and C rating than you know the fan needs. That way, you can see the true amp draw and know it's not being limited by a battery that can't deliver. Of course you have to stick with the correct cell count, 4S in my case, for the motor / fan system. Also, an in-line amp meter is critical for testing. Use an ESC that's rated for 20% more than the max amp draw. And finally, the airplane must be "buttoned up" the way it will be flying. Propellers are out in the clear air, whereas EDF's are in the middle of an intake and exhaust tube system. You can't have stray sources of "extra" air, say from a hatch that's open or something, that will ultimately be closed when flying.

The number one first step is to calibrate the ESC to the receiver (follow the instructions that come with the ESC). This must be done to assure getting full throttle range. Later, when the U/Tronics throttle control is swapped in, I will need to re-calibrate the ESC for that throttle range.

After a few false starts and fiddling, I got the results I expected. The EDF draws 70 amps initially on a fresh LiPo charge and settles at 65 amps, producing 2.2 lbs of thrust.

My All Up Weight will be right around 2.2 lbs, so that's 1:1 thrust to weight. This is good for an EDF flying free on R/C. We shall see what happens with the extra drag of the control lines and going in a circle .

Derek
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Old Oct 15, 2012, 09:56 PM
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A little background....

I'm building this BAE Hawk control line EDF for my Dad. I only fly R/C and live in Florida, while he only flies control line and lives in Pennsylvania. He flies mostly glow powered, like a Smoothie, a Brodak Corsair, and others I can't remember.

Rewind a few years: Dad has always been fascinated by ducted fans, going way back to the 1970's when we built and I flew one on a 40 size glow engine for R/C. That was a one time deal and no more since then. Recently, I started dabbling with electric ducted fans on R/C, and from us talking on the phone, Dad got interested in trying an EDF on control line. He really wanted to do a scratch built balsa and silkspan model. We could not find any EDF control line plans, so he bought a set of plans for the Strike, designed by Joe Beshar, and converted it to control line.

We muddled through (vie telephone) all the electric components, both being newbies to EDF, it was like the blind leading the blind. Anyway, Dad proceeded to build it, fly it, crash it, re-build it, fly, crash, re-design, fly, crash, and re-design, etc. etc. The result was 4 very different variations of the Strike, each one getting better and more convinced that it actually works. All the while, we were on the hunt for another EDF airplane design.

Each version of the Strike used the U/Tronics single channel throttle control and a 3 line handle.

After much deliberation, I managed to convince Dad to try an ARF foamie (gast !!). He bought an F9F Panther from Hobby King (double gast - foamies from China !). Well, it turned out to be quite a nice flying EDF airplane on control line. The only problem was, after the conversion to control line, it turned out a bit on the heavy side at 3.5 lbs.

I could not figure out how someone (not naming any names here ) can take an ARF kit from R/C that's supposed to have an flying weight of 2.4 lbs and turn it into 3.5 lbs while converting to control line.

That's when I decided to buy the BAE Hawk (similar size to the Panther) and do the conversion myself, come in at 2.2 lbs all up, then ship it to Dad when's it's all done.

Actually, I plan to ship the Hawk to him, then follow afterwards on a real airplane to visit and fly the control line EDF Hawk together.

More to come...
Derek
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Old Oct 15, 2012, 11:20 PM
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That is a pretty cheap radio. Almost a gift, I remember paying $200 for radios similar to that when minimum wage was $1.80 an hour. I thought I should mention there are a few companies making timers for control line, Eflight is one that I can remember the name of. It is about $12 and has a preadjustment of throttle and one minute increments of time. It would save the drag of another line although no touch and goes as with a throttle. Nice project. Remember a bit of tipweight and control line is usually better slightly more noseheavy.
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Old Oct 16, 2012, 01:33 AM
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Originally Posted by aspeed View Post
That is a pretty cheap radio. Almost a gift, I remember paying $200 for radios similar to that when minimum wage was $1.80 an hour. I thought I should mention there are a few companies making timers for control line, Eflight is one that I can remember the name of. It is about $12 and has a preadjustment of throttle and one minute increments of time. It would save the drag of another line although no touch and goes as with a throttle. Nice project. Remember a bit of tipweight and control line is usually better slightly more noseheavy.
Thanks for the ideas. I happen to have the Eflite timer. It works well, but like you say, no touch and goes - you only get one throttle setting. With the few EDF's I have right now on RC, they tend to really need full throttle to get going, but then you can back off. And since the amp draw is so high, I don't like to leave them at full throttle. Throttle management on an EDF is a good thing to have. Whereas prop planes can be more happy with say 3/4 throttle from takeoff and through the whole flight. So I feel like a throttle control on this EDF is the way to go, despite the extra drag from a 3rd line. It's all an experiment anyway.

I already have the U/Tronics throttle control on hand, so I'll give it a go.

Derek
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Old Oct 16, 2012, 10:21 AM
Mike A.
Des Moines, IA
Joined Oct 2005
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Since AMA has approved the use of 2.4 ghz radios for control line functions (other than elevator) many are in the process of converting their three line systems to 2 line systems. I have spent the last couple of nights mounting the necessary parts of a HobbyKing pistol-grip radio to the top of a control handle (can't post a pic as I'm at work right now, so I'll post a couple of pix of other guy's conversions). I got the radio transmitter and receiver for under $30 including delivery as Hobbyking has them in stock in their US warehouse. If you are using it to control only throttle in an electric, you don't even need a servo or a separate airborne battery - just plug the ESC into the throttle channel.

The two pictured conversions are for Carrier event, so the handles are really beefy, since the pull tests can be up to 100 lbs. For sport flying, a lot less handle would be needed, and some guys are just going to hold the pistol-grip radio in their left hand and a normal 2-line handle in their right. For glow engines, that would allow you to have the transmitter near the plane while starting, and you would just carry it to the center of the circle once the engine(s) are running.

No 3rd line, no insulated lines.
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Old Oct 16, 2012, 05:42 PM
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Several built up EDF plans here, some likely suitable for C/L conversion. There are a variety of interesting and unusual subjects, some seldom seen:

http://shop.traplet.com/browse.aspx?c=51
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Old Oct 17, 2012, 02:53 AM
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Originally Posted by mikeainia View Post
Since AMA has approved the use of 2.4 ghz radios for control line functions (other than elevator) many are in the process of converting their three line systems to 2 line systems. I have spent the last couple of nights mounting the necessary parts of a HobbyKing pistol-grip radio to the top of a control handle (can't post a pic as I'm at work right now, so I'll post a couple of pix of other guy's conversions). I got the radio transmitter and receiver for under $30 including delivery as Hobbyking has them in stock in their US warehouse. If you are using it to control only throttle in an electric, you don't even need a servo or a separate airborne battery - just plug the ESC into the throttle channel.

The two pictured conversions are for Carrier event, so the handles are really beefy, since the pull tests can be up to 100 lbs. For sport flying, a lot less handle would be needed, and some guys are just going to hold the pistol-grip radio in their left hand and a normal 2-line handle in their right. For glow engines, that would allow you to have the transmitter near the plane while starting, and you would just carry it to the center of the circle once the engine(s) are running.

No 3rd line, no insulated lines.
Wow! Thanks for all the great information. That's looks like a nice system. I presume, since it's not a free flying airplane, then a "ground" transmitter is allowed? And of course, the car radios have the pistol grip design, which is perfect. My dilemma is I'm not in the control line circle (pun intended ) so I really appreciate this kind of information. I only had one R/C electric car, long since gone, but I remember the transmitter is just throttle and steering, which is fine. But I wonder, are there any car radios that have additional channels / switches that could be used for, say, flaps or retracts?

I know that a pull test is a requirement, but I don't know what those rules are. My flying weight will be 2.2 lbs and just sport flying. I don't know if it will be capable of a loop or not. My only choice is to test fly it in a BIG vacant lot near my house (like 4 acres, cleared and dead level) before shipping it off to Dad. There is no control line circle within many many miles. But once Dad has the plane, he goes to various C/L clubs and Brodak's, etc., so I want to make it "pull test legal". What should the test be for an all foam electric?

Derek
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Old Oct 17, 2012, 03:00 AM
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Originally Posted by JKinTX View Post
Several built up EDF plans here, some likely suitable for C/L conversion. There are a variety of interesting and unusual subjects, some seldom seen:

http://shop.traplet.com/browse.aspx?c=51
Thanks a lot for that link! Just looking at the first few pages, they indeed have a lot of unusual airplanes, many I've never seen. That's the problem with this hobby - too many choices .

Derek
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Old Oct 17, 2012, 09:11 AM
Mike A.
Des Moines, IA
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Originally Posted by DerekB View Post
Wow! Thanks for all the great information. That's looks like a nice system. I presume, since it's not a free flying airplane, then a "ground" transmitter is allowed? And of course, the car radios have the pistol grip design, which is perfect. My dilemma is I'm not in the control line circle (pun intended ) so I really appreciate this kind of information. I only had one R/C electric car, long since gone, but I remember the transmitter is just throttle and steering, which is fine. But I wonder, are there any car radios that have additional channels / switches that could be used for, say, flaps or retracts?

I know that a pull test is a requirement, but I don't know what those rules are. My flying weight will be 2.2 lbs and just sport flying. I don't know if it will be capable of a loop or not. My only choice is to test fly it in a BIG vacant lot near my house (like 4 acres, cleared and dead level) before shipping it off to Dad. There is no control line circle within many many miles. But once Dad has the plane, he goes to various C/L clubs and Brodak's, etc., so I want to make it "pull test legal". What should the test be for an all foam electric?

I got my conversion pretty well finished up last night -- it is a little more compact than the two I showed above. I am going to power it with a 3-cell 1000 mah LiPo, rather than the 8 pen-cells that it originally used. It has a steel frame rather than the aluminum ones shown in the above pictures, and the HK $20 transmitter is a little more compact than those also. Hope to fly it before winter shuts us in (here in Iowa).

Derek
It must be 2.4 gHz. - I don't think there are 'Ground' & 'Aircraft' frequencies under that umbrella. My main interest is in the Navy Carrier event. We are using the pistol grip radios because they lend themselves to converting as the pictures show, they are cheap, and we don't need any more channels than that. I know several Scale flyers who already use multi-channel 'down the lines' control who will are converting their models to use 2 stick transmitters - hanging from the belt or a neckstrap.

Since this is primarily a sport model, my recommendation would be to just build a normal, 2-line bellcrank which controls elevator and install the receiver in the normal RC fashion. Use whatever transmitter you've got.

A word about pull tests -- I don't know what your bellcrank install looks like (or will look like) but in order for the AMA insurance to be in effect, even sport flying requires a pull test 'before flight'. It's kind of up in the air whether that means before every flight, before the first flight of the day, or before the first flight of the plane's life -- and many have asked that question directly of the AMA Safety Committee and the AMA Insurance department and gotten no answer, so here is how we handle it at our club. If the plane was successfully pull tested at any time prior and the lines, handle and controls have not been changed or modified, we feel comfortable that we are safe and in compliance. If we change any part of the control system or find a swirl or feel any other reason to (eg: first flight of the model for the year, etc.), we go ahead and pull test it -- even if it's just a good healthy pull while someone holds the other end. It only takes a second, and it really does help one's peace of mind and impresses the spectators with how safety-minded and conscientious you are . (By the way, you can get digital scales that can be made into pull test scales very inexpensively any more - Hobbyking even has one).

The Safety Code rules for sport flying state that if the model doesn't fit one of the rulebook events, then use the 'Precision Aerobatics' (Stunt) pull test chart. Stunt uses a 10G (10 x model weight) pull test and specifies minimum of .012 lines for model less than 2.5 lbs - so set it up for a 25 lb pull test on .012 diameter lines. That (25 lbs) is a really wimpy pull test, and you should have no trouble with it. There was a thread on here about a guy who flew small electrics on control line, but using the throttle of a pistol grip radio -- he just modified the whole transmitter into a handle - even those cheap-o pistol grip would be able to take a 25 lb. pull test if you were to go THAT route.

(edit: Check this thread: http://www.rcgroups.com/forums/showthread.php?t=974579, especially starting at post #25 and on)
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Old Oct 17, 2012, 08:37 PM
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Hmm actually you could use monoline with a radio for up and down with some fiddling, and a throttle to cut off or throttle. Just an ARF or RTF with nose and tipweight and a bit less dihedral would be the easiest. Even a post in the ground, and fly from outside the circle. I have all kinds of crazy ideas that may not work.
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Old Oct 17, 2012, 09:02 PM
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Hmm actually you could use monoline with a radio for up and down with some fiddling, and a throttle to cut off or throttle. Just an ARF or RTF with nose and tipweight and a bit less dihedral would be the easiest. Even a post in the ground, and fly from outside the circle. I have all kinds of crazy ideas that may not work.
They might. I have thought of similar. The only thing about RTP is maintaining line tension in the event of a wind gust or the like, as if you are on the outside of the circle, you can't step (or run!) back to recover. Auto rudder/aileron kick in perhaps???
The dihedral will affect nothing- many of the old C/l designs used it back in the dawn. It was easier to build a flat wing, so it went away.
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Old Oct 18, 2012, 02:59 AM
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Installing the bellcrank and linkage

Installing the bellcrank and linkage turned out to be a little challenging. First of all, I had a few objectives: 1) Make the wing removable, 2) Minimal weight gain, 3) have minimum blockage of airflow to the fan. Also, it's a split elevator so it needs dual pushrods and the pushrods have to go in the hollow space in the turtle deck above the intake duct and emerge on top of the elevators.

No problemo !!

Well, I'll let the pictures tell the story.

I am quite happy with the end result. It moves freely with no binding. Next step is to install the pushrods and the leadouts. But that should be a walk in the park . I should note, for the ailerons (which could become flaps for control line), I am going to install dummy pushrods and clamp them off for now.

Derek
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