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ducted fan alternative for twin jets appearance.

Old 11-22-2014, 05:36 AM
  #1  
gadgeter
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Default ducted fan alternative for twin jets appearance.

I am building what will be a kit for beginners to put together starting from a foam glider. The kit will include the radio receiver servos and linkages to put together a four channel (or three) airplane. The parts will be included along with a prefab glider and instructions to do it yourself!
The plane has a about a 34 inch wingspan but is very light and I'm looking to put twin ducted fans under each wing for power that will mimic a jet engine look.

Any suggestions on where to start looking for ducted fans and how to assess their power ratings? I have never dealt with ducted fans before and I am not familiar with thrust to weight ratio they provide.
Any suggestions would be great I am just getting started on this project.
Thanks!
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Old 11-22-2014, 08:11 AM
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hmm I wish I could help answer your question. I have to ask are you putting together a kit for beginners into building but no how to fly or are you thinking this plane kit will be good as a beginner plane? EDFs can be a challenge for the new pilot. Just curious, but as far as you question goes I think you need to provide a bit more info as to what size 64mm or smaller?
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Old 11-22-2014, 09:02 AM
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EDF have some tendencies that make them generally poor choices for beginners.

The shroud adds weight.

The high RPM is relatively inefficient requiring you to use appx 150% the watts you would need if using a conventional 2 blade prop. This means even more weight for batteries or significantly reduced flying time (usually both)

The nature of the fan working best with high speed "ram" air intake means that they are best suited for higher speed models which are not appropriate for beginners.

High speed, overweight and short flights... Good for impressing people but not for learning how to fly.
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Old 11-22-2014, 11:12 AM
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Originally Posted by gadgeter View Post
I am building what will be a kit for beginners to put together starting from a foam glider. The kit will include the radio receiver servos and linkages to put together a four channel (or three) airplane. The parts will be included along with a prefab glider and instructions to do it yourself!
The plane has a about a 34 inch wingspan but is very light.
I understand what you are trying to do, but the information you have givin is a little vague. It sounds like a pair of 30mm fans might work however....
Do you have any details on the "kit" and "foam glider" you will be getting? Maybe who makes the kit, what is their reccomendation for a motor prop and ESC? You mention none of these. Just remember for dual fans you will need 2 ESC's not to mention the extra wiring.
Any details on the glider? Gliders generally have longer thicker wings for high lift/ slow flying characteristics. Just about the opposite of what you want for an EDF airplane.
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Old 11-22-2014, 11:24 AM
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Picking up on the points already made... It would be a very bad idea to use EDF on trainer, particularly a trainer that small and especially twin EDF. Small EDF fans are incredibly inefficient, they will make the model overweight and relatively underpowered compared to using a conventional single prop. Overweight is the very last thing you want in a trainer.

If this is your first RC plane just keep it simple and build it as per original design. You will have plenty of time to experiment with your own ideas one you have learned the basics.
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Old 11-22-2014, 12:47 PM
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Originally Posted by gadgeter View Post
I am building what will be a kit for beginners to put together starting from a foam glider. The kit will include the radio receiver servos and linkages to put together a four channel (or three) airplane. The parts will be included along with a prefab glider and instructions to do it yourself!
The plane has a about a 34 inch wingspan but is very light and I'm looking to put twin ducted fans under each wing for power that will mimic a jet engine look.

Any suggestions on where to start looking for ducted fans and how to assess their power ratings? I have never dealt with ducted fans before and I am not familiar with thrust to weight ratio they provide.
Any suggestions would be great I am just getting started on this project.
Thanks!
Hi, A 34" wing span IMHO wont carry the weight of 2 Ducted fan, their esc and lipos, it will turn out very heavy, and might not even get off the ground with 2 - 30mm EDFs, 30mm edf are very under powered, find a plane that has a larger wing span,40 + inches and use 50 or 55mm EDFs , if this is your first rc plane, build it, but put it on the shelf, untill you have a few rc planes under your belt that you have flown.
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Old 11-22-2014, 04:05 PM
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You guys are mostly missing the details. He (she?) Isn't building this himself to fly, he's "building what will be a kit for beginners to put together". Although I hope gadgeter will put this together and see how easy it is to assemble and how it flies before mass marketing it, if it really is intended for beginners. Also, if you read closely, this will be a 4 engine plane: "... I'm looking to put twin ducted fans under each wing..." That's 2 per wing.

The whole thing, including the title, is rather vaguely worded and tough to follow, honestly leading me to wonder if we're trying to help someone with an honest interest who may have English as their 2nd language or is very young or something(since we can't see who we're 'talking' to), or we're the victims of trolling. One thing I hate about the internet.

Gadgeter, if you want our help, we'll really need to know your experience level in the hobby. From what you've written, it sounds like you've never experienced a hobby grade rc plane before, yet you want to put together a kit for beginners to build. That's a tough hill to climb. Even then you may not get the answers you wanted to hear. As has already been explained, a multi-engined edf is not a beginners rc plane. At least as far as many of us know.
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Old 11-23-2014, 03:21 AM
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thank you all for your replies. And especially you xmech as you cleared up some misleads and I got a kick out of your assessment.
This project is still in very early stages and is why my question was so vague. I myself don't know all the details yet, it's just something I thought would be a good idea once I get all the bugs worked out.
To clear the plane up, it is a Styrofoam throw glider made by a company called just for kids. it is the only one I have found with characteristics suitable for doing what I'm trying to do. It is extremely well built and puts together easily, it has a a lot of lift for its weight I think this ratio will remain high after placement of receiver ,ESC, batteries and motors. it has outlines for control surfaces that I have cut out and applied horns and rods to for servo connectivity.

I was going for the twin jet engine look but was not sure just how inefficient a ducted fan is. In my mind the appearance was the driving factor for EDFs not functionality. This needs to be corrected, obviously.

As far as my experience goes, I am no expert by any means but I am ambitious about little projects like this. I have six different airplanes ranging from ultra-micro to 6 foot calypso and Radian Pro. I enjoy the larger slower flying planes and was looking to make something out of this glider that I absolutely fell in love with at a hobby lobby. Sounds funny I know but you have to see the plane to understand my faith in it. "we have the technology,..."

However, I realize the ducted fan motors I had pictured simply are not available and would not be efficient enough if they were. I guess I will go back to the single engine two bladed folding prop configuration.
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Old 11-23-2014, 03:28 AM
  #9  
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remember the kits you used to be able to buy to turn a Volkswagen Beetle into a sports car that nobody has ever seen before and everybody goes WOW!!!!!

That's the idea behind this
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Old 11-23-2014, 03:39 AM
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Oh, my bad the plane is 46"
This may help clear some things upClick image for larger version

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Old 11-23-2014, 03:51 AM
  #11  
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some more early prototype pics[ATTACH]Click image for larger version

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Attached Thumbnails Click image for larger version

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Old 11-23-2014, 04:09 AM
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Ah! Ok. Thanks for the clarification. Cool idea. Looking at that glider, it sure has a long nose and looks short coupled between the wing and h-stab. Careful with the cg! And are those linear servos in the fuselage?

Oh, and I apologize about questioning your post. It's just we see so many things like this you begin to wonder. Like how many times people who've never flown rc show up and want to know how to build a solar powered plane. Maybe not on this forum but on another, but that's an example.
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Old 11-23-2014, 05:12 AM
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Yeah, sorry, I went the wrong direction with this one. Thanks for the clarification. In my own defence however, Join date: NOV 2014 Number of posts: 1, had me a little biased.

This is an intresting project. I would love to be able to buy all the components out of an eflight umx *whatever* as a kit, instead of looking for crashed planes on the internet or buying the components individually at the same cost as buying the entire BNF.

I will watch this with intrest.
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Old 11-23-2014, 05:12 AM
  #14  
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Looks a lot like the linear servos typical of Parkzone micros. Hard to tell size by the photos though. If they are the PZ ultramicro servos they'd be marginal for that size aircraft as a glider.
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Old 11-23-2014, 06:08 AM
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your right on the nose but whats great about that is I have room to cut off and to help balance the weight of gear and keep cg where it is now. This plane/glider flies so well as is....smooth ans slow. I hope to keep design elements close to orig. like cg, etc.
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Old 11-23-2014, 04:05 PM
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Gadget,

I've tried something similar to what you are attempting
I used the " chuck gliders" you can buy at Wally World for 10 bucks. Of course.", these are made from styrofoam.

I made an airliner to resemble a B-737 using 2 eflight 68mm edfs. Also included retracts.
The problem I had was wing loading. Came close, but ... Too heavy. Might try using a pair of 50mm and mount them on the rear fuse ( Cessna Citation). The nacelles are easy to make from 3mm Depron and drink cups

A few threads here and on RCG. It's called "bashing". Where you're morphing the base glider into something else. A lot of fun. Did make a couple of prop jobs that actually flew well.

Chillie, this would be a great contest. We all start off with the same $10.00 wal-mart glider and transform it into a rc plane. Pusher, puller, edf, etc

Don't give up and have fun !

Hawk
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Old 11-23-2014, 08:01 PM
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Back 30 years ago the Midwest Jetster is/was exactly what you propose. It followed a slightly different
composition in that it had a single recip/elf for power. They were very fast for a traditional plane form
sail plane.

Hobby King introduced its high performance Durafly Zephyr V-70 plane for about as inexpensive as one
can imagine capable of walking pace flight all the way to 90 mph passes! By the way...$99 to $149. It
will be difficult to justify a scratch with this a proven design.

Last edited by Flite-Metal; 11-24-2014 at 01:00 AM.
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Old 11-23-2014, 10:21 PM
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Yep did not mean to question your post. I just did not understand what kind of kit you wanted to design therefore did not know how to answer your original question. Good luck looks like you are off to a good start.
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Old 11-24-2014, 01:09 AM
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THANKS Y'ALL FOR THE RE-RE-REPLIES. I have a habit of assuming people think the way I do and therefore my comments come out very vague.

Fuselage mounted EDF seems the way to go if I am going to stick to EDF's. The one thing this plane has over all the other gliders I have found is that it is exceptionally light and strong. They do not say what type of foam it is using but I don't see it used often on inexpensive aircraft or other hobby use. Again it is sold at Hobby lobby if anyone is in there and wants to take a look at it, 10 bucks.
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Old 11-24-2014, 01:12 AM
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what actually gave me this idea was the plane is very similar to the flyZone Calypso. if all the parts came together and were available in a kit for cheap this plane would be a good match for those parts. The wings are thick enough for servos to be mounted inside and channels dug out leading to the fuselage and then taped over
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Old 11-24-2014, 01:16 AM
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Default Keep CG Where It Is/Was... ?

Originally Posted by gadgeter View Post
your right on the nose but whats great about that is I have room to cut off and
to help balance the weight of gear and keep cg where it is now. This plane/glider flies so well as is....
smooth and slow. I hope to keep design elements close to orig. like cg, etc.
Do you currently fly? I ask because you were going to try to keep CG at the location it is at now. As long as
the wing and its angle do not change the CG point will not change. However, this was a simple beaded white
foam glider with little to no weight bearing capability.

Do you have access to the internal cavity of the glider? If its the typical yard dart it is solid expanded foam.
Hot wiring the cavity could create a CG issue given the way the wings are attached as that area will be the
sacrafical lamb.

If you are still interested in using EDF for power I seriously suggest you go to take a look at the performance
of the Hobby King Zephyr 70 as it uses carbon fiber rod and other crutch mechanics to achieve superior strength
without accumulative weight issues.

This is one of the two or three packagings of the Zephyr so all you need buy is the EDF battery, an ESC, and
of course place a receiver to plug the servos into. The least expensive packaging is $99.00. They are here in
the U.S. and can ship by USPS Priority on the cheap.

Last edited by Flite-Metal; 11-24-2014 at 02:02 AM.
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Old 11-24-2014, 05:41 AM
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Originally Posted by dahawk View Post
Chillie, this would be a great contest. We all start off with the same $10.00 wal-mart glider and transform it into a rc plane. Pusher, puller, edf, etc.
Seconeded!
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Old 03-23-2015, 12:15 AM
  #23  
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Default Back on this project....I think

With the help of photo shop here is a better idea of what I'm thinking
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Old 03-23-2015, 01:13 AM
  #24  
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Its possible to power that with EDFs either slung under the wings or with them on each side of the fuselage between wing ant tail.

The whole airplane will need stiffening. added weight means added stress so you'll want to insert main wing spars and do something for the fuselage. Something as simple as covering the fuselage with clear packing tape might stiffen it enough.

Keeping as light as practical I'd look at 50 mm EDF units intended for the relatively lower speed DEF models. GWS used to have some decent units. I haven't kept up with the small EDFs.

Use battery placement for CG and you should be able to put the fans toward the tail. that would protect them better in landings than having them slung under the wings.

Nacelles made using styro cups to get the rear taper will help. You want final inner dia about 80% of inlet diameter. (80% of "fan swept area" or FSA) "Close enough" will work OK, then you can try slightly larger and smaller outlets to try and improve performance.

FSA = (fan radius ^2 * Pi) - (hub radius ^2 * Pi)

I've stuck a motor on the nose and made one of these type chuck gliders into an RC model before. Tape hinged control surfaces made of coroplast for elevator-aileron-throttle.
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Old 03-23-2015, 01:24 AM
  #25  
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Epoxy and tape covering some of that plastic banding they use for securing pallets or "skids" along the length of the wings can add a bit of strength.
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