F-117 R/C rocket glider

[burkefj]

I think I got my mojo back... I haven't wanted to design a new RC rocket glider for about 3 months, but some postings of the North Coast free flight kit piqued my interest again. Based on some plans for a 1/20 scale model I have, It's a 6 mm depron airframe and I'm going substitute 3 mm for the fuselage cover/shell to save weight. Current weight as shown with upper covers is only 4 oz, ready to fly should be about 11 and a half painted with E6 installed. This version won't eject anything but it's fairly large with a 39 in long and a 25 and a half inch wingspan and a pretty scale outline, it should glide pretty slowly. I've got only about two and a half hours into it so far, mostly thinking about how I was going to modify the plans and changing slot dimensions for the different foam thicknesses. My daughter holding the 6mm airframe, and a photo showing test fitting the 3mm upper shell plates as a dry fit. Wing loading will be about 4.25 oz/sq foot which is pretty light even for my builds. I'll have to install the radio and rail button mounts before a glue everything in place and put a battery hatch near the front.

 

[hermanjc]

That is awesome! Please continue to post progress. Can't wait to see it fly.

 

[neil_w]

That looks amazing.

 

[BABAR]

That is awesome! Please continue to post progress. Can't wait to see it fly.

It’s a real challenge to make a flying unpowered glider designed after an airplane that was so inherently unstable it could only be flown with a computer interface!

 

[burkefj]

In keeping with mothers day, I feel like I've just given birth after an intense 7 hour labor the RC equipment is installed and I balanced it with the rocket motor in the tail and it's coming out right at 11 oz, so should be just about 11 1/2 painted.

 

[Brian V]

When’s the kit coming out????????

 

[tab28682]

It’s a real challenge to make a flying unpowered glider designed after an airplane that was so inherently unstable it could only be flown with a computer interface!

Not to take away from Frank's excellent work, but it is not that much of a challenge. Yours is a common misconception. There have been a good number of RC models of the F-117 built and flown, and several foam RC ARF electric ducted fan models that have been and are commercially available. None required stabilization if the CG was properly located.

All you have to do is put the CG in the right place to make it stable. Sometimes the vertical tails are made a bit larger, but not always required.

Free flight F-117 models work out well, usually. There have been a few commercially available foam small F-117 and they fly fine. When I was with HobbyLab in the 1990s, we developed a prototype 1/32 scale F-117 model in molded Depron that was a good F/F model, launched as a parasite on a BT-60 booster with D-12 power.

 

[tab28682]

In keeping with mothers day, I feel like I've just given birth after an intense 7 hour labor the RC equipment is installed and I balanced it with the rocket motor in the tail and it's coming out right at 11 oz, so should be just about 11 1/2 painted.View attachment 463462

Looks great!

 

[Blast it Tom!]

See, this is what I have to get onto, glider stability. CP behind GG is easy for a rocket, but I've never gotton on to what makes a glider glide nicely. What I see Frank doing here spurs me on, but may have to wait until I can get me retired here... My gliders usually swoop & stall, swoop and stall - very seldom do I get a good glide, and then I can't figure out why! Fiddle with the nose weight, wing position, even fold the ends of the elevators, ahem, horizontal stabilizers up or down... Anyway, great and inspiring work, Frank - I have some papers on the subject that I can read, so back to your regularly scheduled thread!

 

[burkefj]

That is usually the key That and thrust line versus trim for boost.....

When I first was experimenting in around 2007 or so a number of us were trying to get scratch profile F-117's to fly right, it turned out having a mid mounted pusher with the battery right next to it led to problems, all the mass in the center caused some stability issues even with a properly balanced model, turned out we needed to move the motor and battery away from the CG a bit to get the stability back in control. At least that was my experience. Same CG but the motor moved back 4" and the battery moved forward the same, otherwise it would do sudden divergence at times....it was weird but probably explainable with inertia and damping if I knew what I was talking about.

All you have to do is put the CG in the right place to make it stable.

 

[tab28682]

That is usually the key That and thrust line versus trim for boost.....

When I first was experimenting in around 2007 or so a number of us were trying to get scratch profile F-117's to fly right, it turned out having a mid mounted pusher with the battery right next to it led to problems, all the mass in the center caused some stability issues even with a properly balanced model, turned out we needed to move the motor and battery away from the CG a bit to get the stability back in control. At least that was my experience. Same CG but the motor moved back 4" and the battery moved forward the same, otherwise it would do sudden divergence at times....it was weird but probablyyaw explainable with inertia and damping if I knew what I was talking about.

If you are talking pitch divergence, that is interesting. Some profile models exhibit odd divergence in yaw due to too much forward fuselage side area.

Given that the CG was never changed, I would be inclined to say that the location of the prop slot had an effect on stability. I have seen that on other prop in slot profiles. Likely odd airflow issues.

Concentrating the main masses of the aircraft near the CG tends to improve inertia related effects and not cause them.

Early in the F-117 program, the engineers would catapult 1/20 scale wooden free flight F-117 models across a large hangar into a net as they experimented with various static stability margins. Even though the real aircraft has static stability so relaxed that it is unstable without the flight control computer functional, this experimentation gave useful stability insights in terms of just how statically unstable they could make the aircraft and have it work the way they wanted it to.

 

[burkefj]

Here you go....
Here are the first three F-117 flights of my scratch build 1/20th scale version, now ready to paint the top flat black...Flew like a sweetheart, nice glide and controllable flare.

 

[aerostadt]

This is terrific! The bottom paint scheme is cool. If this is a kit, sign me up. What kind of stick moves do you use, to make your sharp turns?

 

[burkefj]

This is based on somebody else's plan so I don't feel comfortable making a kid of it. For the controls I use pretty gentle stick movements and it's very responsive I'm using about an inch of aileron throw in about 2 in of elevator throw at the tips of the surfaces.

This is terrific! The bottom paint scheme is cool. If this is a kit, sign me up. What kind of stick moves do you use, to make your sharp turns?

 

[BABAR]

This is terrific! The bottom paint scheme is cool. If this is a kit, sign me up. What kind of stick moves do you use, to make your sharp turns?

Ironically, especially with that ventral pattern, as flown here this is among the LEAST stealthy rocket gliders you’ve posted!

very nice execution of a unique aircraft. Not quite a Klingon Battle Cruiser, but it’s up there.

 

[burkefj]

I know, I just really like that scheme and it allowed me to put some vinyl on the bottom which gives a little road rash protection.

Ironically, especially with that ventral pattern, as flown here this is among the LEAST stealthy rocket gliders you’ve posted!

very nice execution of a unique aircraft. Not quite a Klingon Battle Cruiser, but it’s up there.

 

[burkefj]

Final glam shots after paint and vinyl trim, cutting the stars out by hand was a drag but it only took me about half an hour...

 

[Brian V]

VERY NICE!!!! Frank looks great!!

 

[BABAR]

Final glam shots after paint and vinyl trim, cutting the stars out by hand was a drag but it only took me about half an hour...View attachment 463596View attachment 463597

Of course, with only 28 stars, technically this can’t be flown in any state admitted to the union after Texas, in 1945......
https://www.enchantedlearning.com/usa/states/statehood.shtml

 

[BABAR]

Did you make your weight target?

 

[tab28682]

That is the ONLY F-117 scheme to use on an RC RG! Well done as always!

 

[burkefj]

If I had not put the stars/stripes on the bottom I would have been at 11.6 oz, but the vinyl added .4 oz so I'm at 12, which is still good for this motor....

Did you make your weight target?

 

[burkefj]

I think the US officially was complete with the admission of Texas right?

Of course, with only 28 stars, technically this can’t be flown in any state admitted to the union after Texas, in 1945......
https://www.enchantedlearning.com/usa/states/statehood.shtml

 

[burkefj]

Here are some post painting flights from this morning.....

 

[BABAR]

Nice.

would have been fun to have a video with the sound dubbed.

starts with cut to an empty pad. Countdown, camera follows the invisible plane up, pans left and right, finally comes in for a landing. You’d have to time the bogus video right, but it would be fun.

I know, I need to get out more.

 

[Brian V]

Hey Frank I heard you last night on that Podcast you did an excellent job you had those two guys all fired up wanting to really get into the R/C Rocket Gliders. Thanks again for your kit designs and for what you do for the hobby. Just let me know when you get a new kit so I can make sure I keep up of having all your current kits.

 

[burkefj]

Thank you. Btw I just re released the Iron Cross, looks great in the air or display!

Hey Frank I heard you last night on that Podcast you did an excellent job you had those two guys all fired up wanting to really get into the R/C Rocket Gliders. Thanks again for your kit designs and for what you do for the hobby. Just let me know when you get a new kit so I can make sure I keep up of having all your current kits.

 

[burkefj]

Another launch from this weekend in the Tri-Cities Washington

 

[Brian V]

Hey Frank I received the the Iron Cross kit. I’m currently on travel with the airlines working on some broke airplanes so it will be a little while before I can get built. I am going to surprise you on the paint scheme I’m also trying to get off work to come out at the end of the month to fly with you in Colorado Nice flight on the F-117

 

[Ez2cDave]

Frank,

Extremely cool !

Dave F.