STOVL idea

cray2602 · Oct 29, 2009, 01:53 AM

I was thinking of an easier way to control a STOVL EDF jet than useing ducted fans on the wingtips for roll control and useing differential throttle on numerous fans for pitch roll etc. Ive tried this a few times and just seems to be too many issues to be simple.

What if you put a large single EDF centered on the CG for vertical lift only, and use a second EDF in the conventional location at the rear of the jet but use thrust vector paddles at the exhaust exit to control pitch roll and yaw? Why couldnt a single thrust vectoring setup work to control all three axis while the main lift fan simply prvides vertical lift? I cant think of a reason why this wouldnt work. Granted the rear fan will be pushing the model forward continuously while the center fan lifts it, which is why i think it would only work for STOVL and not VTOL. But you could theoreticaly hold it in a high alpha with both fans provideing some vertical lift for a vertical landing.

Unless someone here tells me im crazy and explains why this cant work i think i will use this as my next experiment in the search for a successfull STOVL / VTOL.

swami · Oct 29, 2009, 10:36 AM

You would hardly have any roll control.

To keep the plane from flying forward because of the tail fan, you could rotate the main fan over 90°, so it blows down and a little forward too.

Not too sure that would work though.

I've been thinking of the wingtip fans for roll control myself for a while.
It doesn't seem such a bad idea, especialy since they provide some extra lift too.

The VERTIGO uses this method too, and it's not the first version.
The first version had a propeller, and since he still uses this method it must have good results.
http://video.rc-model-airplanes.com/...ne-Powered-Jet

Dirk.

cray2602 · Oct 29, 2009, 11:06 AM

Ive tried the fans in the wings for roll control a couple times, it can be made to work obviously, but it just adds to the complexity IMO. Im just looking for something simpler. And im trying to come up with something that still represents a jet model.

Why do you think there wouldnt be much roll control?
Twin rear fans would have much more roll control than a single but that creates a ton more weight etc. etc. . I have seen a single that had twin thrust vector paddles split down the center which suposedly worked to control roll as well as pitch. Thats what i am stuck on in my mind right now is whether that would be enough leverage to control roll. Also since it would be a STOVL there would be air moving over the wings from the forward momentum which would help to control roll from the conventional ailerons, right?. Does that sound feasable?

swami · Oct 29, 2009, 05:17 PM

I don't think so.
Twin paddles close to each other won't have enough authority to reliably roll the plane.

I am thinking of a 2-2.5 kg aircraft.
Maybe if yours is a lot lighter you could get away with it.

Since you are counting on some airflow over the wings maybe you could just use large ailerons.

I've been thinking about paddles in the main nacelle/fan to control the aircraft, but since the vertigo doesn't use them, i won't bother.

Maybe, very "maybe" i'll test that later, after i have a succesfull hovering aircraft.
But since i haven't even started drawing the plans, i wouldn't hold my breath if i were you.

Keep us updated on test results please.

Dirk.

Oct 29, 2009, 01:53 AM	#1
cray2602 I ABUSE LIPO'S Join Date: Jan 2008 Location: Plain ole KS Posts: 1,354	STOVL idea I was thinking of an easier way to control a STOVL EDF jet than useing ducted fans on the wingtips for roll control and useing differential throttle on numerous fans for pitch roll etc. Ive tried this a few times and just seems to be too many issues to be simple. What if you put a large single EDF centered on the CG for vertical lift only, and use a second EDF in the conventional location at the rear of the jet but use thrust vector paddles at the exhaust exit to control pitch roll and yaw? Why couldnt a single thrust vectoring setup work to control all three axis while the main lift fan simply prvides vertical lift? I cant think of a reason why this wouldnt work. Granted the rear fan will be pushing the model forward continuously while the center fan lifts it, which is why i think it would only work for STOVL and not VTOL. But you could theoreticaly hold it in a high alpha with both fans provideing some vertical lift for a vertical landing. Unless someone here tells me im crazy and explains why this cant work i think i will use this as my next experiment in the search for a successfull STOVL / VTOL.

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Oct 29, 2009, 10:36 AM	#2
swami Registered User Join Date: Jul 2001 Location: Ursel, Belgium, Europe Posts: 110	You would hardly have any roll control. To keep the plane from flying forward because of the tail fan, you could rotate the main fan over 90°, so it blows down and a little forward too. Not too sure that would work though. I've been thinking of the wingtip fans for roll control myself for a while. It doesn't seem such a bad idea, especialy since they provide some extra lift too. The VERTIGO uses this method too, and it's not the first version. The first version had a propeller, and since he still uses this method it must have good results. http://video.rc-model-airplanes.com/...ne-Powered-Jet Dirk.

Oct 29, 2009, 11:06 AM	#3
cray2602 I ABUSE LIPO'S Join Date: Jan 2008 Location: Plain ole KS Posts: 1,354	Ive tried the fans in the wings for roll control a couple times, it can be made to work obviously, but it just adds to the complexity IMO. Im just looking for something simpler. And im trying to come up with something that still represents a jet model. Why do you think there wouldnt be much roll control? Twin rear fans would have much more roll control than a single but that creates a ton more weight etc. etc. . I have seen a single that had twin thrust vector paddles split down the center which suposedly worked to control roll as well as pitch. Thats what i am stuck on in my mind right now is whether that would be enough leverage to control roll. Also since it would be a STOVL there would be air moving over the wings from the forward momentum which would help to control roll from the conventional ailerons, right?. Does that sound feasable?

Oct 29, 2009, 05:17 PM	#4
swami Registered User Join Date: Jul 2001 Location: Ursel, Belgium, Europe Posts: 110	I don't think so. Twin paddles close to each other won't have enough authority to reliably roll the plane. I am thinking of a 2-2.5 kg aircraft. Maybe if yours is a lot lighter you could get away with it. Since you are counting on some airflow over the wings maybe you could just use large ailerons. I've been thinking about paddles in the main nacelle/fan to control the aircraft, but since the vertigo doesn't use them, i won't bother. Maybe, very "maybe" i'll test that later, after i have a succesfull hovering aircraft. But since i haven't even started drawing the plans, i wouldn't hold my breath if i were you. Keep us updated on test results please. Dirk.