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Author Topic: Attempting my first ever Electric Ducted Fan Jet  (Read 2322 times)
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crashcaley
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« on: November 09, 2008, 04:39:27 PM »

Although what I have here is what they call an (B)ARF, meaning that it is supposedly almost ready to fly, it was nothing of the sort. I am attempting to enter the realm of radio controlled electric ducted fan jets. This is something I've wanted to do for many years, but just didn't have the flying skills.

This jet is produced, as most are, in China by Starmax and distributed by Hobby Lobby. Do wish Hobby Lobby would just sell the airframe and allow the builders to add their own components, as a quick look reveals that they are lower end quality, just good enough to allow the model to fly. Hopefully the components won't fail in flight.

Another problem is that this airplane comes with retracts. You have no choice. And the retracts are of super poor quality, collapsing easily if landed even slightly hard. It doesn't like bumpy runways or grass, which collapse the gear easily. Hope my flying field will be kind to this landing gear.

The other bad thing about this kit and many others from China is the total lack of good instructions to put the kit together, or in this case no instructions. If it hadn't been for a thread over at RCGroups, I would never have been able to get it together properly.

But it has one positive quality. It is a great looking airframe, and apparently, once built and proper CG attained, flys pretty much like a trainer, though with semi synmetrical wings and tail feathers, it does go where you point it. It does need a pilots constant attention. But it does slow down very nicely and lands easily, based on the few videos I've seen of it in action.

I am still working on the airplane. The missile rails on the wingtips were only made of very soft foam, and got broken almost immediately. I have fabricated hard balsa ones with an piano wire backing to make it stronger. The photo is of the airframe without the missile rails. I am also fabricating two Sidewinder AIM-9 missiles. The body of the missiles are Burger King soda straws. Nose is balsa, and fins will also be balsa. I will try to remember to post a pic of the missile twins when done.

Ah, you ask what is it I am talking about. It is an F5-E. I thought I would fly it this morning, but as fate would be, the winds were here in abundance.

More to come as I make modifications and hopefully am successful at flying it.

Caley
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Attempting my first ever Electric Ducted Fan Jet
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Mike Taylor
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« Reply #1 on: November 10, 2008, 10:11:54 PM »

Good luck on it, Caley.

My first EDF was a Kyosho F-80 - heavy, under-powered, and with a very nasty stall at low speed (like trying to slow down an approach to landing - ouch!). My only advice is to keep the power up, get it up high, and test what happens as you slow down. Unlike prop planes, there is no air flow being forced over the controls, and you have to keep it moving if you want to keep control.
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crashcaley
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« Reply #2 on: November 10, 2008, 10:37:20 PM »

Mike, Thanks. I've seen videos of this model. It can fly very very slowly due to the large flat body bottom acting much like a wing. I've been practicing a lot on my landings making sure I use the motor/prop to keep the speed up just enough to maintain stability and try slicking the airplane in every time. I am getting fairly good at doing that and flairing just as the mains are about to touch down. I rarely have a hard landing anymore. The model may have little wings and small wing area, but the body probably nearly doubles it. It's weight is only 36 ounces AUW and it is powered by a 70mm fan unit on 4-cell lipo. So it will fly, but not fast. It probably can cruise around at 40mph and maybe reach 60mph flat out with the power setup it has. Most guys are putting in a better fan unit, motor, speed control and 5-cell battery to push the speeds up to 80+mph. Of course they have to reinforce the airframe with fiberglass and carbon fiber to take the loads that kind of speed puts on it. I'm flying it stock just to learn how to fly something this fast and slippery. Thought I might get a chance this morning, but the winds were here as usual, so all I could fly was my trusty Liberty prop plane. Maybe will get lucky this coming sunday and get one of the expert flyers to take it up on its maiden flight, and then tell me what I need to do to make it fly better.

Caley
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crashcaley
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« Reply #3 on: November 12, 2008, 02:32:04 PM »

I am almost finished with my first ever rendition of AIM-9 Sidewinder missiles for my jet. They are pretty light at 5 grams each. They are made of Burger King drinking straws for the fuse and 3/32 balsa sanded to shape for the fins, and glued on with canopy glue, then a bead of white glue along the bases of each fin for extra strength. I still have two black stripes that band the fuse in the center.

I had difficulty placing the fins, so I think that a jig to hold the fins agains the fuse would make things easier for the next set I make, if I do make another set. Don't know how well drinking straws hold up to 40mph. Smiley

Caley
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Re: Attempting my first ever Electric Ducted Fan Jet
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« Reply #4 on: November 12, 2008, 04:26:43 PM »

Hi Caley,
Stuff the straws with toilet paper, and then they will hold their shape and not have a tendency to get kinked, that way they should hold up to 40 mph with not too much trouble.

Just a thought.

Sundance12
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crashcaley
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« Reply #5 on: November 13, 2008, 07:50:54 PM »

Sundance, Thanks for the suggestion. But I realised that if I just glued them to the missile pylons that are now on the wingtips, they will do fine. About two thirds of their length is attached. I finally finished this airplane and hopefully will get it in the air this sunday, wind permitting. Always like a calm day when maidening an airplane so trimming it out with the computer radio isn't an adventure. Pic is attached.

Caley
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Re: Attempting my first ever Electric Ducted Fan Jet
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Mike Taylor
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« Reply #6 on: November 15, 2008, 01:53:25 PM »

You could put your eye out with that thing! Handle with care! Grin
I always wind up with an EPP nose to take the brunt of landings. It saves me a lot of repairs. Good luck on the test flights.
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crashcaley
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« Reply #7 on: November 15, 2008, 04:15:15 PM »

Mike, Thanks a lot. Tomorrow is looking good with the winds. I won't fly this the first time. An expert pilot will take it up and see what still needs to be done with the trim and any improvements that will allow an intermediate pilot like myself to fly it.

Caley
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Don McLellan
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« Reply #8 on: November 15, 2008, 06:17:29 PM »

Hi Caley,

Very interested in hearing how your jet performs.
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crashcaley
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« Reply #9 on: November 15, 2008, 07:01:30 PM »

Don, I will post the results once back from my outing. Have flying and then over to visit a friend. I am very questioning of the retract mechanisms that came with the airplane. If I'd had my druthers, I would have wanted fixed landing gear. My runway is very bumpy and may collapse at least the nose gear if it hits anything. If I can remember, and it does get into the air, I'll try my best for a picture of it as it passes.

Caley
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crashcaley
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« Reply #10 on: November 16, 2008, 01:06:46 PM »

I'm back from the flying field. Unfortunately the jet never got into the air. The stock fan that comes with the airplane is terribly out of balance or is just totally useless. I won't know until I cut into the foam and remove the unit to find out what is wrong. It runs at low rpm's, but when higher power is supplied, the fan unit quit rotating. Think I will have to purchase a quality fan, motor, speed control and battery, if this airplane is ever to fly.

My thoughts are that if the airplane had managed to lift off and the fan had frozen just after that, there would be no more airplane. Guess I should feel quite lucky with this initial test. The odd thing is that the fan and motor ran perfectly on the bench. Proves that bench testing and actual flight are two different things.

Caley
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« Reply #11 on: November 16, 2008, 01:34:33 PM »

Sorry to read that, Caley - disappointing for you. But .. you will overcome.
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albackstrom
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« Reply #12 on: November 16, 2008, 05:56:01 PM »

Applehoney expressed my sentiments exactly. I hope you can get it sorted out without too much trouble and expense.
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crashcaley
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« Reply #13 on: November 16, 2008, 06:24:08 PM »

Jim and Al, I really should have known that things wouldn't go well. Problems like this are indemic to the (B)ARF's that are coming out these days. Everything is mass produced and components aren't QC'd usually. This is another Chinese built airplane. Very nice looking. But sentiments over at RCGroups concerning the compenents have not been kind. Seems that the servos are all plastic and can't handle the stress of high speed flying without stripping. Of course, if a servo strips out in the air, the average pilot has just lost his or her investment. The fan units are also plastic and not dynamically balanced which can result in anything from working right to fan blades rubbing to blades seperating from the hubs and destroying that area of the airframe. This model also has the absolute minimum speed control in it which won't allow you to run it at high speed more than a few seconds without smoking it. The battery is also not rated at the amp draw, though it is labeled as being able to, but failing often enough to question that labeling.

Hobby Lobby has the exclusive rights to sales in the US from the manufacturer, and comes only in the plug and play version that includes the servos and drive train. Elsewhere in the world, you can apparently order just the airframe without the electronics, so you can install your own high quality components and know they will function. Just another of my mistakes trying to get an EDF in the air. My third try and third failure.

Guess I should do like Mike does and build my own out of foam, carbon fiber, fiberglass and balsa. My plan was and now might be to build a Chris Golds design, an A-10 Warthog. My problem is that I am not good working with foam, carbon fiber or fiber glass. I guess we all have to eventually try to learn something new, if we wish to do something.

I am awaiting help over at RCGroups on how to open up the airplane at the fan unit location, so I can remove the drive train and put it on a test stand to see what is happening. I will probably set it up so that I do it remotely, just in case the fan, speed control or battery does decide to fail with an explosion or fire.

Will report back on my progress, once I find out what is happening.

Caley
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NRoshier
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« Reply #14 on: November 16, 2008, 10:47:58 PM »

Pffft!...I've seen your prop carving, you will find foam no trouble at all. Fibreglass and carbon are nothing to be afraid of either...well you can be afraid of the expense of carbon, that is rational!
If you were here we could whip up an A10 frame to your desired size in an afternoon. Foam is also cheap! Why not try a profile foam ducted fan model from foamboard?
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crashcaley
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« Reply #15 on: November 16, 2008, 11:11:55 PM »

NRoshier, I think it is that I am just so used to balsa and tissue. Changing to new materials is difficult with me because I anticipate, like my adventures in prop carving, to take half a dozen trys and failures before I get something that comes out halfway decent. Lots of money and time each time I venture into something new when it comes to materials. I'm going to try this week to create my own liteply by using 3/4 ounce fiberglass cloth and 1/32 inch thick balsa and gluing it with Gorilla Glue. I've already been told how to do it, so I will just need that 1/2 dozen tries to get one right and understand how it is done. These liteply sheets will be for the bulkheads and formers for that A-10. I am also going to try to learn how to do what is called lost foam shaping of fiberglass things like tubes and cowlings and canopies, anything requiring a curved surface. I will probably just make a block of foam the first time, and cover it with fiberglass, then melt the foam away once it is hardened. Of course, I need to discover what is needed to melt that foam. Will have to Google the internet on how to do that. This is how I learn along with asking questions of those on our forums.

I guess you could say that I am not a very adventurous type when trying something new. Takes me time to learn and adjust. Tis probably a problem I need to overcome. I'm old fashioned, which I think is called being a Luddite, resistent to change. LOL!!!! Grin

Anyway, I am much more happy doing that learning and finding out how to do things and then building my own airplanes, than having to put up with these cheap Chinese things that I occasionally purchase, thinking it will be a quick fix and get me in the air sooner.

By the way, I opened up the fan unit area and looked closely at things, and couldn't find a thing wrong with anything. I even did a high powered runup of the fan unit, and it performed perfectly. So I put things back together and will give it another try at the flying field. It is possible that I am getting radio interference between the components when the airplane gets out to a certain distance from the transmitter. if that is so, I need to figure out how to route the receiver antenna in such a way that I don't get that motor cutoff.

Guess one way to do such a test is to have someone hold the model down and for me to walk out a hundred feet or so to see if the same thing happens. If so, I will have to make those changes I mentioned.

Caley
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NRoshier
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« Reply #16 on: November 17, 2008, 12:49:27 AM »

Not sure what gorilla glue is. I would recommend you get familiar with 3m 77 spray adhesive, it is very very good.
Also, do you know anyone wrecking an old fridge?...if yes ask for the refrigeration pump out of it, it will come in handy.
Do you have any place that sells styrofoam near you?
Lost foam FG has always seemed a bit pointless to me, but acetone or petrol will do the job. You MUST use epoxy resin as you probably know.
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« Reply #17 on: November 19, 2008, 11:35:18 AM »

Caley,
a buddy of mine in my club has the A-4 EDF from that same company. The first thing he changed after its first 'appearance' at the field, was to replace the lipo. It was supposedly rated at 20C, but pooped out after 15 SECONDS just trying to taxi out to the runway.

During the taxi to the runway, the gear collapsed and the strut was bent (grass field). Out again the next day with new Lipo (HACKER EVO) - GOBS of power with the stock fan system. Taxied 15 feet, gear collapsed - tried about 15 times with same results and finally tried a gear-up slingshot takeoff (a short high-start). The plane flys great but stripped a servo on landing! How, was anyone's guess (cheap, CR** servos).

Came out again the next day with the gear locked in the down position (epoxied the buggars) and HITEC 55's all around plus a decent ESC and was able to make 5 takeoffs from the grass before losing that pretty plane to a tree - he failed to heed the following:

THE ONE MAJOR THING TO REMEMBER WHEN FLYING A DUCTED-FAN MODEL: They take nearly 5 seconds to react to an increase to throttle!! This is called throttle-lag - the time that it takes the fan unit to move the amount of air to cause a reaction. You should be able to fly that 3-5 seconds "ahead" of the aircraft.

Pete
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crashcaley
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« Reply #18 on: November 19, 2008, 01:00:54 PM »

Hi Pete, I will keep that advice in mind when I get the airplane functioning properly. I wrote Hobby Lobby, the United States distributor, and told them about several things. They are sending me a new speed control and motor, since they think one or the other is defective. They are also sending me three new retract servos. They think mine may have limited throw, and that is why they can only lock the landing gear either in the up position or down position, but not both. So, this puppy probably won't get in the air until next year.

Servos are on back order. Right now I cannot afford a new battery of proper C rating, so whenever I do get to the field with it, I will just fly it slowly. No fast stuff for a while. It apparently can fly at less than 20mph due to the huge flat fuse body acting like more wing area.

At the moment I am in another model airplane building stutter. Things are just sitting there, almost finished.

I am diverting my time to building a manually operated mini drywasher for gold mining. This is a first for me, but it isn't any more difficult than building an airplane.

Gosh, I should go to the painting area and at least put another coat of dope on my little SortaSenator. Smiley

Caley
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« Reply #19 on: November 19, 2008, 02:10:08 PM »

HL is pretty good at customer service, but they have enough ACTIVE modelers on the staff with enough experience to catch faulty or 'not enough' engineering - actually, screwups in making parts from the drawings. The problem that Reinhard and I found with his A-4 retracts was the locking cam - it just wasn't engaging as it should. We even tried a longer servo arm (more throw) - nada.

The noises coming from the fan/motor unit could very well be from centrifugal expansion of the fan blades /hub. The clearance between the blades and the shroud is probably a bit too close. The stress from a short, full power burst in the pit area is WAAAY lower than on a takeoff attempt, which is a much longer full power run.

I wouldn't try to fly the F-5 with a suspect batt. OR ESC. You NEED full power to get the thing in the air (start phase) and acceleration for a go-around or getting out of trouble. These are just two areas where near maximum current draw is taken. You'll probably NEED at least a 18C battery - 20-25 is even better if the thing fits in the batt. pocket.

Be aware that EDF's do not react proportionally to increasing throttle. The MOTOR reacts NOW but until the thrust builds up, the plane is just along for the ride.

Pete
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« Reply #20 on: November 19, 2008, 03:01:24 PM »

Pete, Do wish I could afford a better battery pack. But the darn things cost around $125 for the absolute minimum mAh to do just three minutes. A larger one that will take the airplane through the air for six minutes will cost me around $200. I will just have to baby it. Apparently it can be done, as I've seen the video of someone flying in a really small area just above where it would fall out of the sky. The model was dragging its tail, as slow as it was going. As I said before, HL is sending me a new motor and speed control. That will hopefully solve the drive system problem, though not give me the ability to fly faster than say 30mph, which MotoCalc says is optimum cruising speed for this airframe.

Maybe next year I can afford to go out and purchase a Wemotec MiniFan Pro with a HET motor and bigger speed control and battery pack. Of course, with increased speed and stress on the flying surfaces, that usually calls for reinforcement, since this model is all foam.

Caley
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« Reply #21 on: November 19, 2008, 03:39:09 PM »

That is a lot of $ for pack! Over here, I've gotten used to paying about 60 EUROS (approx $90) for a 4 cell 25C 2300 mAh pack. Reinhard was using the same pack in his A-4 and was getting at least 10 - 12 minutes with aerobatics.

We also have at least 1001 different places to obtain Lipos and some of my crowd are even buying bulk pre-assembled packs direct from China, so far with good results and the price can't be beat. 'Course, the matched/tested packs from the likes of THUNDERPOWER, SAEHAN, HACKER, or KOKAM (There are others) are probably more consistant in output, but are EX_PEN_SIVE! You might do well to check with HOBBY PEOPLE. They've got a chain of shops in Cal. Nev. and I think Arizona and good pricing.

http://www.hobbypeople.net

Pete
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tonyaqp20
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« Reply #22 on: November 28, 2012, 10:19:26 PM »

nice jet i hope u can help me to build 1 like this
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« Reply #23 on: December 12, 2012, 01:58:46 PM »

Dear crashcaley,
I read your experience with the chinese hardware, very similar to mine, which I posted today. I hope your plane is of EPO foam which makes things easisier after a crash. I bought my jet also at Hobby-Lobby and think they should have a better quality control, specially with electronics. Take care with your plane before you fly it, control all suspicious items 1000 times!
Your plane looks too nice to become an oil drill, too.
Greetings,
Kurt
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