Txmustangflyer

If anyone still peeks in here and has input or ideas, post em.

Considering trying to build an rc version of the Rockwall XFV-12.

The full scale was supposed to be a thrust augmented STOL. It failed because Pratt and Whitney goofed. Seriously. Had Pratt and Whitney properly designed the engine, the US Marines would have flown F-12s for years instead of Harriers.
So..here's the questions.

1. Would an RC Turbine produce enough thrust to make thrust assisted STOL work
2. How would you do it?

Txmustangflyer

Wrong thread

Ron S

My Feedback: (2)

I think the real one failed, mainly because the performance of the ejectors in the wings and canards was much lower than what was calculated. I'm not sure if those numbers were developed by the engine manufacturer, or the airframer (North American Aviation).

I've looked at this project too in the past, but not too deeply. The duct work would be a nightmare. One could replace the ejectors with EDF fans perhaps, but that would lose the looks of the model (or atleast I would think).

Good luck, if you decide to proceed!

mongo

My Feedback: (15)

replacing the ejectors with edf, might be a quick way to get a proof of concept model flying, before one does all that nightmarish engineering on the ducting system.
would also give you a realistic idea just how much thrust they would have to produce.

Txmustangflyer

Been tossing it around..If I do do it, I think it would be standard take off with simulated nozzles maybe. IThe problem with the prototype was pratt and whitney miscalculated on the exhaust ducting. When thrust was transferred to the nozzles, the engine could only produce 15% of its thrust. They were too restrictive.
to fix it would have meant starting from scratch so the Navy cancelled it.

Still mulling it over.

Txmustangflyer

Done some more research about an RC version of this.
Even reached out to Jonathon at thelightersideofrc to get his take. The consensus is, the ducting to make the thrust assist work could not be done at scale, sufficiently, to pull it off.

Its an absolutely gorgeous aircraft, though, so still considering, possibly a 1/8 using something close to a xicoy x45 turbine..Nothing huge, just sleek, quick, and easy to transport.
Seeing if Rumen Chakarov would consider doing a short kit for it, glass it, and simulate the wing nozzles. Be light enough it would appear STOL capable maybe...

I dunno. Still tossing it around.

Probably end up just waiting to see if a manufacturer tackles it. From ehat I've read, despite the miscalc on the thrust nozzles in the wings, it flew very well. Could have made a nice, standard, carrier borne fighter.

Boomerang1

One of the American RC model magazines published a plan of a VTOL model called the Vertigo powered by a glo engine mounted
around the middle of the model.

The main feature was the whole engine nacelle tilted to achieve vertical thrust.

Could your model use the turbine engine mounted to pivot & blow downward to provide a lift component to shorten the take off run? Obviously you would have no control at very low speeds unless you fitted a vectored thrust nozzle so it would purely be
to assist take off when airflow over the normal control surfaces would exist. On the Vertigo two movable vanes controlled the vertical thrust direction.

https://www.rcgroups.com/forums/show...10-years-later!

Txmustangflyer

That would destroy the scale look..

Boomerang1

That would destroy the scale look..

Only from the bottom.

I've seen quite a few scale model jets which have been fudged to include turbines in non scale
locations & some have been difficult to spot when the model is flying 100 metres in the air.

Sometimes it's a compromise between weight, complication & cost especially on smaller models.

Your choice.

Txmustangflyer

True, but was hoping fpr a 1/7 to 1/8 scale competition bird unlike any other. Still researching. Trying to figure out where P and W goofed

Txmustangflyer

And I may have figgered that out...

The problem they caused, was when they tried to use the thrust assist, the engine would only develop 15 percent of its normal thrust..

A jet engine is basically a high pressure air pump..it sicks air in, adds fuel, ignites it, and sends it out the back. Thrust being generated by the expansion of the resulting gases to keep it simple.

in thrust assist stol mode, the engine basically got constipated. If you block any engines exhaust, it can't run for snot..the burnt exhaust gasses had nowhere to go..this caused a build up in the engine and a partial sputtering, stall of the engine..Normal take off and flight, the engine ran flawlessly.

I don't think that it would be possible to do turbine assisted stol and keep a scale shape to the wing, It would have to be a much thicker wing to contain the tubing required to make it work.

So..its back on yhe possible list, simply because of that. An rc turbine would, potentially, flame out.

so..to do a scale WORKING version..the outlet size to the wing nozzles and the nozzles themselves wpuld need to be equal in volum in their sum total, to the main engine exhaust outlet in normal flight mode, this means that thrust would be the same in either mode...or should be. I think P&W goofed on that calculation and made the thrust assist outlets and nozzles way smaller than they should have been.

Had they done it correct, the resulting wing would have been much different. So, to make it scale, it would HAVE to not work...if that makes sense.

mongo

My Feedback: (15)

so, we, who do scale, been making overly thick wings on projects for decades...

what's your hold up?

Txmustangflyer

As much as 3 to 4 times as thick....no. We fudge the scale and airfoil on a wing to make an rc managable at rc speeds. The alteration needed to contain the ducting to make the stol work would make it a non contender in scale comp and the resulting drag, nearly unflyable imo
However, if it was built light (structure) and sufficient thrust..with a good airfoil, it could appear stol capable.
Then, theres the weight. The wing load would be very high, airframe weight overall difficult to overcome.
Then theres the heat..

Txmustangflyer

I have an idea...think A-7 or F-8. Changing the AoA of the main wing, actiating the wing mounts in the fuselage...
maintains scale profile and gives it STOL capability. It wasn't a vtol, but a thrust assisted STOL.
keeps airframe weight and wingload manageable and within the capability of an rc turbine.