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Old Jul 17, 2008, 10:03 AM
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United States, AZ, Queen Creek
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SU-35 or any twin EDF with thrust vectoring

Anyone here experimented with an EDF SU-35 (or any twin EDF) using thrust vectoring nozzels? I figure that with tail flaperons, it would be a fairly straight forward modification to extend the control linkage for nozzel control....that way each nozzel would only rotate around one axis for pitch and roll control. Vectored rudder control would be the challenging part, but could be done by programing my DX7 with counter thrust (not very effective on my GWS A-10 though). Curious if anyone out there has contemplated this idea in an EDF.

I've seen the profile foamies and turbine OVT options, but I'd like to try this in the EDF arena.

Clint
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Old Jul 18, 2008, 09:12 AM
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Bellflower, Calif.
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Hi Clint...

I used a twin ducted fan system mounted on the elevons of a swing wing TomKat, and it was a lot of fun with the increased control in the pitch and roll modes, but, of course, they were not any help in the yaw mode.

Bob Reynolds
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Old Jul 18, 2008, 09:21 AM
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Got any pictures

Bob,

Would you happen to have any pictures of your work...lookin to drum up some ideas to make this work and a picture works the best. Thanks.

Clint
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Old Jul 18, 2008, 12:50 PM
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A few guys are experimenting with thrust vectoring on their SU-27 EDF twins in this thread http://www.rcgroups.com/forums/showt...7#post10169629 . One has had a few flights on his setup and claims it works very well.
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Old Jul 18, 2008, 07:53 PM
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Take a look at how the real SU-35 does it. You don't need the variable size nozzles, of course, but Sukhoi only pivot the nozzles on one axis. The trick is, the axes are turned inward at almost a 30° angle, which gives them much more roll moment. You could do the same thing with vanes on an EDF, or you could move the whole nozzle.

No, I haven't done this myself, but my next project is a parkflier '35, so I will be going there soon.
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Old Jul 18, 2008, 09:05 PM
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Bellflower, Calif.
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Hi Clint...
Always glad to share some of my work !!! I am more of a gadgiteer, then I am a builder (more function then form).

I developed a line of swing wing TomKats, ranging in size from 16" to 42", and in weight from 1/2oz to 16oz, and single and twin, using mostly GWS 30 and 40mm fans.

I tossed in some background pictures before the "vectored" one...

Bob
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Old Jul 19, 2008, 01:24 AM
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Very cool BB

Great stuff BB....do you get a wicked center of pressure change from WOT to cut-off? Same consideration with the swept wings changing from spread to swept. How does it perform power-off?

Andrew....not looking to shape the nozzel. Just want to direct the thrust with a single axis gimble mounted cone....I'm looking to do something fairly basic in design.

I've looked around on google, rc sites, etc. and havent found much out there along the lines of this interest....anyone come accross anything scale (non profile) EDF thrust vectoring in nature?

I did find this.....
EDF thrust vectoring (0 min 27 sec)


I'm looking for minimal servos so a single gimble should work fine, connected to the elevons. Thoughts?

Clint
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Old Jul 19, 2008, 01:49 AM
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Well, something like that with the scale pivot alignment should work just great. I can't find a picture right now, but the nozzle pivots are turned inward by 16° on each side (so when you pull up, the nozzles converge). You could do that by linking the nozzles to the servo with their own linkages to allow the different angle of rotation. I gather the reason they did this was to give an automatic yaw moment with roll.
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Old Jul 19, 2008, 02:17 AM
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Wow: http://www.rcgroups.com/forums/showthread.php?t=808482
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Old Jul 19, 2008, 09:20 AM
Kat Builder
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Bellflower, Calif.
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Hi Clint...

The thrust line of the EDF's placement on all of my designs is on the center of drag line, so there is very little, if any, trim change with power variations.

The wings center of pressure change was solved by NASA, and Grumman. NASA found that if the wing's pivots where about i/3 of the extended span apart, a full flying elevator would handle the trim changes without undue drag penelty.

Gruman found out that the placement of the hortz stab below the wing, would pick up a down load, as the wings swung aft, taking care of most of the trim change needed, automatically.

And that all works very well at model scales, at least it does for me. The trouble with a lot of the model swing wing aircraft, is they are designed by power plane pilots, so the CG is always located TOO far fwd.

Us Glider Guiders, know the benifits of a more rearward CG, for controllability and efficiency (the plane flies "lighter", less down load on the tail to be carried by the wings).

Bob
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Old Jul 19, 2008, 09:55 AM
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Andrew....thats an incredible link, thanks. 3 servos is the way to go, but I like your idea of altering the gimble throw (yaw direction) to get the desired effect....you could simply make a set of slightly angled guide tracks to mix yaw in with pitch....maybe have it on an adjustable mount IOT make small tweeks on the ground.

BB...great stuff. I learn something new everyday in this hobby.

Clint
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Old Jul 21, 2008, 08:32 AM
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Figure skating in the air

Quote:
Originally Posted by dash8pilot
Anyone here experimented with an EDF SU-35 (or any twin EDF) using thrust vectoring nozzels?
Clint
TV is awesome! Hanging in the air, sudden 180 turn...

Here's http://www.rcgroups.com/forums/showt...7#post10167823
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