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General control line discussion => Open Forum => Topic started by: RC Storick on February 16, 2013, 08:43:47 AM
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I would just like to know has anyone ever thought of ducted turbo fan propulsion. This would lend it self easy to electric power and might have some advantages. All the concentrated weight would be in the center of the plane. Not only that it would look cool .Your thoughts?
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As I sit here and think about it ,it probably wouldn't work as we are using the prop as a brake. Oh well just a thought.
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You also don't get the benefit of prop blast over the control surfaces, so you would probably have control authority issues.
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I think one of the Moon brothers tried this with a Midwest kit. Can't remember the name of it though.
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People have mentioned it before (someone mentioned a semi-scale A-10). You'd probably need significant active control on the throttle to keep the speed decently constant.
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Are you talking about something like this?
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I'll try to find the post, I remember Al Rabe concluding it wouldn't work for stunt use.
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Well Sparky,
A few years ago Bill G-Man Gruby was building a twin ducted fan control line model. As far as I know he never finished it although I seem to remember some posts on the construction over in the Brotherhood of the Ring Forum. They had their own melt down and lost everything (similar to what you experienced) and those posts are gone. The Brotherhood forum did not heed what happened here on SH and history repeated itself for them too! n1 y1
Here is a link to something he posted about the project, here on Stunt Hanger, after you had your crash and burn losing your past posts:
http://stunthanger.com/smf/index.php?topic=11165.0 (http://stunthanger.com/smf/index.php?topic=11165.0)
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I've seen a c/l ducted fan Mig 15 scale ship fly and for that it was OK but I think there would be many problems. The big one in my mind is no acceleration out of a corner-turn and die so to speak. That scale ship wasn't all that heavy but came up to speed very slowly.
Dave
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I've seen a c/l ducted fan Mig 15 scale ship fly and for that it was OK but I think there would be many problems. The big one in my mind is no acceleration out of a corner-turn and die so to speak. That scale ship wasn't all that heavy but came up to speed very slowly.
Given what I've read about the subject of propeller size on constant-speed shafts (electric or piped IC), I think you'd be disappointed. A ducted fan is getting you a lot closer to the ideal "zero prop size" than it is the "big prop" that folks advocate. You might be able to get a ducted fan with enough grunt to accelerate you out of the corners -- but then you'd need to do something to keep from going 90 miles an hour on the flats (or more). Hence my comments about active control (although drag plates might do it, if you could stand the resulting turbulence).
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Bill Darkow of WA State recently built a stand-off scale CL model of an experimental German plane. Picture of this plane is seen at <flyinglines.org> under the "favorite Plane section for 2012. for some reason I don't seem to be able to downlaod this picture, but I have added it to my NW Column of Control line Wlorld magazine for the next issue. Bill indicates that the 44" wingspan ship flys at about 75mph with an impressive turbine sound.
Joe
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I would just like to know has anyone ever thought of ducted turbo fan propulsion. This would lend it self easy to electric power and might have some advantages. All the concentrated weight would be in the center of the plane. Not only that it would look cool .Your thoughts?
Robert,
Let them laugh! LL~ LL~ LL~ LL~ LL~
I've been working, on and off, mostly off, with this model for sometime. I may even have a build someplace?
Electric DF.
And it will stunt. Probably not do the pattern as described in Nats compitition, But I don't care. At any field it'll still be the center of attention.
I'll get it done one day.
Charles
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The Moons flew a rocket-propelled ME-262 CL stunt model. Maybe Doug or Steve will post their findings....
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Here's Darkow's Jet.
Joe
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And it will stunt. Probably not do the pattern as described in Nats compitition,
But I don't care. At any field it'll still be the center of attention.
I'll get it done one day.
OK, guys, next time you accuse me and everyone else of picking on people, remember that no one responded directly to this post.
Brett
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Steve built a twister and mounted a ducted fan on top of the fuse. It was either a .15 or a .21. It was so funny!!!! First off the whole setup is heavy. The prop, duct, motor, everything. But that didnt stop him! HELL NO! Onward we must go! It was name the Twistojet.
It takes a heck of a starter to get it running. But once it kicks in the motor really starts to sing. At launch it just kinds of drives away real slow. It took over a lap to get to get in the air. It did get in the air and was flyable but that motor was designed for pretty even steady thrust. It really cant accelerate out of a corner like you need in stunt.
It was a fun project and at the same time very funny.
The rocket powered 262 was cool. I built a profile 262 with an FP 40 complete with dummy jet engine nacelles. At the rear of the nacells I put in small A sized rocket engine tubes. I used A sized with no ejection charge. At the launch signal the holder would look at the rocket engines and the other helper would press the button and as soon as they hit the holder would let go. Jet Assisted Take Off, JATO! Made for a cool looking quick launch leaving a massive cloud of smoke. There is a pic of it somewhere in a district VIII column. I may need to revisit that one day.
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The Twist-O-Jet! What a hoot that thing was. With help from my buddy John
Grigsby we modified a Twister by cutting off the cockpit and building a mount;
kind of like a tray, to mount a K&B 21 motor and ducted fan unit to. We then cut
the rudder and added twin rudders, like a Heinkel 162 Salamander. We also
changed the landing gear to tricycle gear.
Overall, it was pretty heavy and we had to add quite a bit of nose weight. I also
replace the throttle with a venturi with a long intake. As Doug said, the plane took
a long time to get into the air and then didn't have enough power to effectively
stunt. The lap times were just fine and I could fly level and climb and dive fine.
I was also able to do round loops. After awhile I decided to come out of the loops
and try some inverted flight. When I first made the transition to inverted the motor
quit. So, I began gliding it down for an inverted landing. Once I got back to level
(inverted still) the motor refired! Bob G was there and he couldn't believe it.
I think the extended intake with the venturi sitting on top of it starved the motor.
I should have left the NVA at the base of the intake before extending it. After the motor
refired and I was able to finally stop laughing I flew out the tank and landed. In an
effort to try to get more power out of the system John and I fabricated a fiberglass
extension for the fan unit. Our thinking was that the unit was so short that if we extended
it and slightly decreased the size of the exit maybe this would compress the exiting
air and give us more power. Wrong! This didn't work, and it actually had less power.
We cut the extension down to only about 2 or 3 inches in length and this helped greatly.
Still not enough power to properly stunt, though.
All in all it was a lot of fun to goof around with and was a blast to fly. The entertainment
factor alone made it worth it. As Sparky said earlier, with the proliferation of EDF units
available there just might be a way to get one (or two) working in a stunter. I think the
main problem would still be as Doug described, getting any drive out of the corners.
Later, Steve
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For a while I was fascinated by the thought of making a scale model of an X-14 (after all, what's not to like about an open-cockpit VTOL jet whose flight data was used to develop the Harrier?). Putting together an EDF and airframe that has a thrust:weight ratio greater than 1:1 should be doable (and is necessary, I think, for CL stunt). Doing so without getting something that runs away on the level is going to be much more difficult.
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Just not nearly enough thrust for CL stunt. You have to have lots of thrust to not bogg and stall in the corners.
Try and un-ducted fan :-)
Randy
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Thinking about it, it just might work. Banjock's Dynajet stunter will stunt, its main problem is carrying 18 ounces of fuel for just 4 minutes of powered flight. With electric power it just might work.
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OK, guys, next time you accuse me and everyone else of picking on people, remember that no one responded directly to this post.
Brett
Words fail me.
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I've seen a c/l ducted fan Mig 15 scale ship fly and for that it was OK but I think there would be many problems. The big one in my mind is no acceleration out of a corner-turn and die so to speak. That scale ship wasn't all that heavy but came up to speed very slowly.
Dave
Hey Dave, I remember that Mig 15. It was the Abel boy from St Louis that flew it at Swope Park on our small circle. I say small as 65 ft lines was about max unless you liked to back up. I remember that once he got the plane on the pavement it took off in about half lap. We have to remember the ducted fans back then were still new and didn't have the engines of later years. But, with the newer ducted fans of today and designing a plane for it, it just might work doing big open maneuvers.
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Thinking about it, it just might work. Banjock's Dynajet stunter will stunt, its main problem is carrying 18 ounces of fuel for just 4 minutes of powered flight. With electric power it just might work.
I thought for sure the jet stunter would bog in corners. Then I saw how fast it flies and that went out the window. I think if you slowed it down to even a fast stunt speed it would start to bog. Not to mention the whip-up would be something to behold!
Mike
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Robert,
Let them laugh! LL~ LL~ LL~ LL~ LL~
I've been working, on and off, mostly off, with this model for sometime. I may even have a build someplace?
Electric DF.
And it will stunt. Probably not do the pattern as described in Nats compitition, But I don't care. At any field it'll still be the center of attention.
I'll get it done one day.
Charles
That's pretty wild looking right there....if you decide not to finish it, box it up and send it to me...I'd like a shot at that! LOL
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Hey Dave, I remember that Mig 15. It was the Abel boy from St Louis that flew it at Swope Park on our small circle. I say small as 65 ft lines was about max unless you liked to back up. I remember that once he got the plane on the pavement it took off in about half lap. We have to remember the ducted fans back then were still new and didn't have the engines of later years. But, with the newer ducted fans of today and designing a plane for it, it just might work doing big open maneuvers.
Man, wonder if it was the same plane I saw in Lincoln Nebraska at an RC airshow/demonstration in the late 70's, early 80's?. Think it was a Byron RC Mig converted to CL. Looked like it pulled like a mule. Pilot had two hands on the handle, and was leaning back as far as he could. Think it was painted red & silver IIRC.
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Yeah guys I think we are all thinking about the same airplane. John your brain is better than mine, I would never have been able to put a name with that plane. Probably hanging in somebody's old garage somewhere. It WAS impressive at the time. Vaguely think it had a something or other .55 in it.
Dave
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I thought for sure the jet stunter would bog in corners. Then I saw how fast it flies and that went out the window. I think if you slowed it down to even a fast stunt speed it would start to bog. Not to mention the whip-up would be something to behold!
Mike
Hi Mike
It would be a very different story if he did the maneuvers at 45 degrees, you would see some serious bogging and stalling, try a true size square 8 with the jet stunter, it will not like that one ....ouch!!!!! ;D ;D ;D ;D ;D
Randy
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Dick Sarpolus just published a plane called the Leaf Blower in Flying Models. uses a 70mm fan. It has similar performance to the propped version.
I suspect that a couple of 100mm fans would provide enough oomph. The limiting factor might be the battery weight required. These things tend to pull a lot of watts- 2700w for a 100 mm fan. Like Dan's Dynajet, flight time might be limited. At 2700w it is probably putting out nearly 4 lb. of static thrust so the governor would have to be used a lot to keep it from turning into a rocket in level flight.
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Hi Mike
It would be a very different story if he did the maneuvers at 45 degrees, you would see some serious bogging and stalling, try a true size square 8 with the jet stunter, it will not like that one ....ouch!!!!! ;D ;D ;D ;D ;D
Randy
Hi Randy,
I'm not sure the wings would like it either. You make a good point.
Mike
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I suspect that a couple of 100mm fans would provide enough oomph. The limiting factor might be the battery weight required. These things tend to pull a lot of watts- 2700w for a 100 mm fan. Like Dan's Dynajet, flight time might be limited. At 2700w it is probably putting out nearly 4 lb. of static thrust so the governor would have to be used a lot to keep it from turning into a rocket in level flight.
One of the drawbacks of fans for this application is that the power to static thrust ratio drops as the diameter of the propeller drops -- and this is more or less true whether the propeller is enclosed in a duct or not. So attaining a thrust to weight ratio greater than unity with a (relatively) small diameter fan is just going to take more power than with a prop.
All in all I think that the whole effort to use a fan would come aground on a whole bunch of nasty technical issues. But oh, if you could make it work it'd certainly be cool!
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A friend found this video.
It's short, but it shows exactly the lack of power... :X
http://www.youtube.com/watch?v=eXhL2vCrW_I&feature=youtu.be
Marcus
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A friend found this video.
It's short, but it shows exactly the lack of power... :X
http://www.youtube.com/watch?v=eXhL2vCrW_I&feature=youtu.be
Marcus
Fun to watch even with the bad camera work. Love the Scott Joplin music in the background.
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Yeah, for a scale model, I thought that was pretty well executed for flying off a not to good grass field. He was airborne in half a lap as it was. On pavement I'll bet take off is pretty smooth. Once in the air it looked pretty stable and the pilot didn't look like he was being over worked. Not a stunt model, but pretty nice just the same. Is it a ducted fan? They spent a ling time on the ground for it to be a dyna-jet.
Next time you are searching You Tube, check out the section for movies. I accidently found an old Glenn Ford movier called "Gallant Journey" I think it was. It's about pioneer aviator John Montgomery. It opens up with a you teenager flying an R/C P-80 that gets shot down by some other kids with a .22 or something, and when the wreckage is picked up, a charred dyna-jet slides out of the fuselage. Pretty corny but it's a decent movie and I haven't seen it since I was a kid.
Type at you later,
Dan McEntee
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If we had the sound of the power instead of the music, it would have been easy to tell. I too think it was a ducted fan as they held it on the ground a long time. Dyna Jets is fire up and release.
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It is a ducted-fan.
The guy likes scale models. He's from the neighbor country Argentina.
Here's a couple more videos of his models
http://www.youtube.com/watch?v=XboU-OChpO0&feature=youtu.be
http://www.youtube.com/watch?v=sfpEDMhghSk&feature=youtu.be
Marcus
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Now everybody can see the whole flight, here's the link
http://www.youtube.com/watch?v=eXhL2vCrW_I&feature=youtu.be
Anyway, I liked the model. It seems like the engine/ducted fan is not really proper for the model.
Now, with eletric ducted fan, speed control.... Maybe not the pattern, but a nice toy for sure...
I can't help but imagine one jet, like one F16, marked as the Thunderbirds, and doing a few things like inverted and lazy eights.... S?P S?P S?P
Marcus
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That's pretty wild looking right there....if you decide not to finish it, box it up and send it to me...I'd like a shot at that! LOL
John,
Thanks for the interest in my C-101 Aviojet. My all time favorite jet.
The model is actually scale or really close to it. Was designed for R/C around a Rossi 61 RE prop engine.
Decided on a fan and redid the nose to scale appearance. Looks much better. The airfoil is 1 15/16" thick.
If I had the money to purchase the stuff needed, I'd be working on it. Although, I do, from time to time, search for a good used fan. E Fans are technical.
Hey! You wouldn't just happen to.. never mind.
Thanks for the interest.
Charles
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Found a couple of pics of the Twist-O-Jet: