VT-ICE

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deskpilot

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This is a new one for my 'stable'. Something a little different and an update on a suggestion to Mark Skull of Ringtail fame.

VT (Vectored Thrust) - ICE ( Inverted Chunnel {CHannel/tUNNEL} Experimental.

Why? why not. The channel or tunnel wing was a successful design in it's day but didn't survive due to cost and complexity. I've inverted and modified it to bring the center of lift forward a bit without having the wing tips so far forward that you loose sight of the airstrip in a turn. It will also keep the sun off your bonce at times.

VT? Gotta try something new. As for gyroscopic problems....a pair of contra-rotating props should cancel each other out, and to get get around the 'one engine, one prop argument' (Australian rule), it's a single propulsion system on a common shaft.

Nay Sayers will no doubt raise the question of it falling off etc. No more dangerous than a helo or gyro plane. If their 'Jesus nut' comes off..................................

You may also note that my model has finally taken on some nice curves. Amazing what you can learn by reading the rules.

View attachment 10955View attachment 10954View attachment 10958View attachment 10956View attachment 10957View attachment 10953View attachment 10952

 

Rom

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VT would give good manuverability. The down side is stability. Mark had difficulty at first maintaining stable trim.

Since I can't view your attachements I don't know if you are vectoring the prop or just the airflow. If the prop, you would be fighting gyroscopic force with every control imput. If not, how would you trim such a craft.
 

JamesAero

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I can't view the attachments either. I know the RC world doesn't scale well, but look at this take on thrust vectoring at the aft end of an electric ducted fan on an F-35 from Hobby Lobby. The maneuverability during slow flight is impressive. There is a good view of the nozzle about 15 seconds into the video.


 
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deskpilot

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That's exactly what I'm after. As for gyroscopic precession effects, I've already said, contra-rotating props within the duct. The only down side is the weight of the VT unit. Possible remedies would be to shorten the boom tube but run the risk of becoming too short coupled, move the wing aft but there's no room for a neat attachment, or simply lengthen the cockpit and move the pilot forward.

As to why you don't see the attachments................? I'll try again. Resized them.

PS Sorry Mark, got your surname slightly wrong.

VT-ICE iso.jpgVT-ICE low front threequarter view.jpgVT-ICE rear three quarter view.jpgVT-ICE front view.jpgVT-ICE side view.jpgVT-ICE top view.jpgVT-ICE rear view.jpg
 

wsimpso1

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Vectored thrust works great when your thrust is similar to or greater than your airplane weight.

Prop ingesting wash from the wing is 2*# blades per rev. It looks like four supports for the ring, so that is 4*# blades per rev. Then you will have the firing frequency. To avoid resonance issues, all of the resonant modes of the powertrain and the duct system have to be outside of those frequencies driven over the operating rpm range. Non-trivial. Particularly with a CV joint and that long shaft.

Billski
 

Rom

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Gyroscopic force exists regardless of the rotational direction of the props. The force is about .5mV^2/r more or less. A typical prop, even counter-rotating, will develop many thousands of pounds of force.
 

Rom

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Gyroscopic force of a vectoring thrust prop can be overcome with hydraulic assist controls. Normal pushrod/cable sytem would have incredably high stick forces. As far as stability goes, unlike a vectoring shroud, your craft could be stable in all kind of conditions since the prop will remain fixed on its' axis while the craft is affected by outside forces.

A fixed axis of the prop may do just the opposite, causing an increasing turn, climb or dive.
 
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deskpilot

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Wow, a bolt out from the blue. No mate, gave it away so to speak. The more i looked at it, the more difficult it became to harness the torque and gyro-graphics etc. Seemed a good idea at the time but.

I doubt any one else has attempted it either. It is a bit 'out side the box'

You going to give it a go?
 

bmcj

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I think one of the difficulties of a vectorable prop is that as you tilt the disk, the initial gyroscopic reaction will be 90 degrees from the expected effect. Once you tilt and stop, that 90 degrees will disappear in favor of the desired thrust vector angle. Perhaps what you need is an automated control system that takes the gyroscopic effects into account and uses them. This would require a system that (approximately) makes its initial movement 90 degrees fromt the desired effect, then changes the tilt progressively from the gyroscopically dictated selection to the vectored thrust dictated selection.

(Sorry for the awkward wording, but I think you'll understand what I'm trying to say.)
 

Topaz

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On another note entirely, you might want to consider opening up the gap a bit between the channel wing and the fuselage pod. That close together, you're going to get an unnecessary drag rise from interference drag. Neat visual concept, though.
 

Joe Fisher

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I don't know why you would want to vector thrust with a propeller. But it would be easy to do with no gyroscopic loads on the engine, propeller or airplane. By making the propeller hub so it can teeter and putting the teeter pivot at an angel. When the propeller disk it out plane is not perpendicular to the rotating shaft the low blade has more pitch the high blade has less pitch so the propeller would fly it self into alinement.

DSC00912.jpg
 

deskpilot

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Having been 'scared off' by all the talk about gyroscopic loads, I went with a fixed prop and a vectoring duct. For your interest, this is as far as I took it.

3 quarter front view [800x600].jpg

Showing general arrangement (pitch control only. Yaw control is identical)

Side view [800x600].jpg

Ball pivot.jpg
Ball in slot pivot

X-ray top assembly [800x600].jpg

X-ray view.

Whether this would actually work is anyone's guess. Weight was increasing and the fact that the duct was only held in place by the control wires....................... Hmm.
I'm interested in your thoughts though.
 
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