R/C FunJet Rocket Conversion

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Thomas0840

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This is a brief description of my conversion to rocket power of a Multiplex FunJet Ultra. The plan was to use the Aerotech E15-PW motor or the RMS 24 mm R/C reloadable.

I took a used 24 mm D sized motor tube and modified it to center in the 40 mm I.D. FunJet fuselage. Centering rings would have been easier, but I didn’t have any.

I installed a plywood bulkhead in the fuselage so that the motor to would rest against it and the nozzle of the motor would extend about ¼ inch beyond the plastic tailpipe.

I then assembled the FunJet according to the instructions and glued the motor tube into the rear of the fuselage. I added two plywood-mounted 1010 rail buttons to the bottom of the fuselage for launching.

Since I use a one-cell, 500mah LiPo battery to power my Spectrum receiver and servos, I needed to add about 1.5 ounces of lead to the nose for proper balance with an empty motor casing. Ready-to-fly weight is 16 ounces.

My launch system is a 6-foot 1010 rail set at a 30° angle down from vertical. Since the plane takes off at tremendous speed with the E15 motor, it is necessary to add some down elevator trim for launch or it will try to make a large loop.

The launch is exciting, but you need to be quick on the controls to keep it tracking straight. The airframe handles the acceleration well and will reach a respectable altitude. It will glide for quite a while and is easy to fly.

I will try the RMS motor as soon as it becomes available. That will prove to be easier to handle at launch because it has less thrust and longer burn time.Motor tube A.jpgMotor tube B.jpgMotor tube C.jpgMotor tube D (1).jpgFunJet.jpg
 
I have a similar project with one of the FunJet clones with swap-able 24mm and 32mm motor mounts. I will take some photos of the mounts to post.

kj
 
There have been several similar threads with general success using these types of arfs, although the funjet is a little more expensive as a starting platform than others like the radjet...one of my first rc rg's was a conversion of an old 55mm Mirage 2000 foamy.

https://www.rocketryforum.com/showthread.php?40169-MP-FunJet-R-C-Rocket-Glider

https://www.rocketryforum.com/showthread.php?67519-Hobbyking-Radjet-800-conversion

I think you can't beat the E-6 for these size gliders, they are just so much easier to control on boost.
 
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Welcome to TRF!!! Thanks for joining us, and sharing that project (along with photos)... I'll be watching this one. :pop:
 
Thanks for the forwarded information… The FunJet Does cost more, but I found it to be much stronger than some of the other foamies. In the past I have had two Estes E motor explosions That destroyed two of my early rocket gliders, so I don’t really trust them. With the Aerotech E15 PW the plane does launch straight, But I have to use very low rates to control the climb angle. It’s a learning process… I Really want the 24mm RMS R/C motor, But I can’t find one anywhere. Do you have any ideas?
 
I've been pushing on Aerotech to get more casings made but they have said cash flow issues are preventing it, the machinists don't want to make less than 100, aerotech only sells maybe 20 a year and they don't want to put that much $$ into it right now. I was not willing to front $5k for 100 casings. I'm pushing on them to certify the E-6 reload using the standard case with the following caveats, fill the forward closure with JB weld(this is a must have due to flame front propagation and the forward closure is a $15 part so very cheap), and the addition of a single .03 washer and 1/16" o-ring from the standard 24/40 loads which gives the right internal length to properly seal both ends. They seem willing to consider this as of Narcon. I've done tests and it seems to work fine, although not certified, I did the tests at my own private field. I've also ordered a batch of 100 single use E-6P motors to be made for me which will be more expensive than reloads but are certified and don't require a casing.
 
Thanks for the detailed reply. I have the information on how to modify the standard case for the E-6 load, but can't find a standard case to buy. When you receive your single-use E-6P motors will you make them available to others? Appreciate your advice...
 
Yes, they'll be on the dynasoar website when I get them in, they'll be around $12.50 each.

Thanks for the detailed reply. I have the information on how to modify the standard case for the E-6 load, but can't find a standard case to buy. When you receive your single-use E-6P motors will you make them available to others? Appreciate your advice...

Ok
 
My version was based on an EDF funjet clone. I made two mounts for 24mm and 32mm rocket motors that swap in and are held by the removable locking hatch.

kj

75452255-A686-47DE-AC7C-2421B4588F17.jpg
 
Did you actually fly it on G-12's or just f's? That would most likely scream on a G-12.....


My version was based on an EDF funjet clone. I made two mounts for 24mm and 32mm rocket motors that swap in and are held by the removable locking hatch.

kj
 
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