MP FunJet R/C Rocket Glider

ORIGINALLY POSTED IN THE MPR DISCUSSION PAGE

I haven't seen too many R/C plane conversions to rockets. I really wish I had taken better care of my AT Phoenix kit when I was young and dumb but I guess I can't dwell on the past. I'm going to attempt a Multiplex FunJet conversion. The FunJet was designed to go fast. I have one that will go over 100 MPH but I've seen them get as fast as 200 MPH. Never as fast as a rocket though. I hope I don't leave the wings on the pad. I haven't seen this plane converted except for a guy who piggybacks his on an r/c plane then drops it and ignites the motor. That one already has momentum so I kinda worry what kind of forces I'm looking at from a static launch position...

Any ideas? Do I need to be stopped before I hurt myself?

Lots of folks have converted stuff like Zagis and Strykers to rocket power. There's gonna be a slight CG shift from boost to glide if you just pop the motor tube around the same place as the electric motor would go.

Just like any fast RC plane, small control inputs are best on boost when it's going fast. Helps to have a dual rate or flight modes on your transmitter.

kj

Thanks KJ!
I'm a proficient R/C pilot and I know all about dual rates (I think I learned the hard way). Good stuff to keep in mind. The E-motor vs. rocket engine are within 2 oz. (29mm rocket motor is heavier) so hopefully I won't take much to balance it. What about motor size? I'm thinking about using a 29mm mount with a 24mm adapter so I can start out small and work my way up depending on how it handles. Any formulas out there on determining weight vs. impulse power? Black powder vs. composite 24mm?

I would think that something like the E15-P from aerotech would be about what you want. That's a 24mm motor without an ejection charge. If you want to do some 29mm F flights you'll have to come up with a way to vent the ejection charge.
Normally you want to shy away from high initial thrust spikes (check thrustcurve.org) but you may be able get away with it with this model.

kj

If you want to fly higher thrust composites (not the D7 E7 E6 and E12 R/C reloads), then just get a 24/40 or a 24/60 reload case and leave the red powder charge out. Make sure you include the delay grain though.

A neighbor of mine flies a FunJet as a rocket glider. It's carried aloft by an electric-powered plane then it drops and an Aerotech G motor powers it. Both pilots use First-Person View cameras, so there are some neat videos of it online:

https://vimeo.com/search?q=quadstar+funjet

Most of the time, they fly out of the schoolyard across the street from my neighborhood, so you can spot my house in some of the videos.

-- Roger

jadebox said:

A neighbor of mine flies a FunJet as a rocket glider. It's carried aloft by an electric-powered plane then it drops and an Aerotech G motor powers it. Both pilots use First-Person View cameras, so there are some neat videos of it online:

https://vimeo.com/search?q=quadstar+funjet

Most of the time, they fly out of the schoolyard across the street from my neighborhood, so you can spot my house in some of the videos.

-- Roger

Click to expand...

I've seen the videos before. It looks like fun.

TheAviator said:

If you want to fly higher thrust composites (not the D7 E7 E6 and E12 R/C reloads), then just get a 24/40 or a 24/60 reload case and leave the red powder charge out. Make sure you include the delay grain though.

Click to expand...

Great Idea. That's what I wanted to do with it.

Some Pics...

The first flights of my rocket SkyFun are on E15-P. Your FunJet weighs about the same. I recommend this motor. It gives me enough altitude to recover safely, but keeps me low enough that I don't worry about losing the plane.

I have two settings on my TX--one for boost, one for glide. The boost setting has the elevators at zero lift. I stay on that setting--and going straight up--under boost. I only interfere with it if the plane strays from vertical. After motor burnout, especially with larger motors, the plane keeps going up, and it may take awhile to the speed to dissipate. I like to take over only when the plane slows down enough that I'm sure I'm not going to strip servos or break elevon linkages (bitter experience here).

I wish you success with your SkyFun, and I'm looking forward to your photos!

Ari.

Sweetrex,

Dont sweat the motor issue, I have just done a Funjet conversion and its awesome. Using 32mm AT F16 & G12 reloads I balanced the model on the moulded dimples on the lower wing surface using a 1oz wieght in the motor case to simulate a fuel grain. Ended up with 2ozs in the nose,this is removeable to revert to my 4s electric setup anytime I choose. I made it slightly tail heavy loaded so it wouldnt go too nose heavy as a glider this I can pick up with the elevator trim after the boost phase.

Maiden was done on the F motor and it flew clean of the launcher, I then did two more launches on the G motors. I think this gives nearly 1000ft and the model is real small, the paint jod saved the day. Ill tryto post a video

Good luck with your project

That's awesome to know. Post the video. I'd like to see it.You just omit the ejection charge? I cut an exhaust port in the top and blocked off the front portion so I can store my R/C electronics up front.

Planecrazy said:

Sweetrex,

Dont sweat the motor issue, I have just done a Funjet conversion and its awesome. Using 32mm AT F16 & G12 reloads I balanced the model on the moulded dimples on the lower wing surface using a 1oz wieght in the motor case to simulate a fuel grain. Ended up with 2ozs in the nose,this is removeable to revert to my 4s electric setup anytime I choose. I made it slightly tail heavy loaded so it wouldnt go too nose heavy as a glider this I can pick up with the elevator trim after the boost phase.

Maiden was done on the F motor and it flew clean of the launcher, I then did two more launches on the G motors. I think this gives nearly 1000ft and the model is real small, the paint jod saved the day. Ill tryto post a video

Good luck with your project

Click to expand...

Hi ya

I've used the dedicated r/c motor casing that comes blanked off. The ignition uses a 35amp brushed speed controller (GWS product), this is plugged into the throttle channel on the reciever and triggers the igniter at about half throttle.

I am using a JR DX 9 transmitter but any programmable tx should do the job. My plan for the next flying day is to set up a new flight mode for the glide segment of the flight to reflex the elevons to save retrimming after the motor is burnt out.

I also change batteries for Rocket launches, this is a 450mah 3s lipo plugged into the speed controller, a lot lighter than the 4000mah battery for the electric set up, I also take out the 90amp esc that that system uses. If its not in the plane it wont get burnt.

Sorry about the video I did make an attempt at posting the video but Im a newbie at this computer stuff and need to learn more, the forum wouldnt accept the video because it was too larger file. Give me a hint and Ill have another go at it.


Cheers!

This is interesting. I never thought about remote ignition. It would certainly make things easier to stand at a better vantage point.

Hoorah,

found some footage one of my friends took on the day hope you enjoy watching as much as I enjoyed flying it. The funjet starts about 1min in, the 1st flight is on a F 13rc the other 2 flights on G12 rc,

https://www.youtube.com/watch?v=ka5On5aEoWE

Cheers Planecrazy

Got a flight in this weekend with my Funjet. Had an altimeter two on board this time which reported the following numbers (G13 reload): 641ft & 265mph. Kind of not believing the speed thing but will try to do some number crunching on the rest of the data to confirm the speed.


It was a bit gusty on sunday which made the boost phase a bit of a handful but we got her up there.


Might make the next project to set a flight mode on my transmitter to pick up the elevator to retrim a bit quicker for the glide phase. I had the C of G set a lot better this time which improved the glide speed and handling. Im sure on the right day a thermalling flight will be possible.

Regards Plane Crazy

Good job on your flights! Altimeter Two reports some incredible numbers on my gliders as well. I think it integrates the accelerometer, and if you pull reasonably hard in a turn, you confuse it into thinking you're going up really fast. I remember it reporting something like 230+mph on my FunJet, which I find hard to believe.

I use the throttle stick as elevator trim in addition to ignition. With the stick fully forward, I have ignition and zero-lift trim. With the stick back, I have glide trim. It's easy to mix throttle into elevator on your JR. The liftoff procedure with this setup is:

throttle stick back (ignition: no current, elevator trim: glide)
load on the pad
insert igniter
count down
throttle stick forward (ignition, elevator trim: takeoff)
as the motor burns out, bring the throttle stick back to trim for glide

Keep the videos coming!

Ari.

Gidday All

After a couple of months break(changing jobs, bad weather, excuses, etc) I gave the funjet a couple of boosts on the weekend. We have our National Rocket Day next month and wanted to make sure I can still fly, before I do something dumb in public .


I thought a party trick of some sort would be good for the public viewing. I found that when the tracer smoke burns out that there is just enough energy to to complete 3 very fast rolls and finish of the boost phase with a loop of the top.

With a bit of conservative flying I found I could stretch the glide out and need to work on my soaring skills so that I can maybe catch a thermal on the way down.

The other tweak before our big day next month is to increase the control throws on the glide mode of my transmitter, as I had trouble pulling into loop whilst in the glide phase.

Keep an eye open in early Feb as a new cameraman has volunteered to film the flight

Cheers from the bottom of the world.

Planecrazy

YOu asked about 29mm motors Apogee offers a 29mm long burn endburner single use (or at least used to) I cant remember the designation but it has like a 10 second burn.. might be a good choice if you can find them!

ok its 8 seconds F-10 you can get them here!

https://www.apogeerockets.com/Rocket_Motors/Apogee_Medalist/29mm_Motors