Multiplex FunJet Ultra RCBG

[ckreef]

I've not seen precisely how he does it, as he covers the mount with a plastic shroud after fixing it in place. I believe that he uses a pair of carbon rods mounted vertically to the bottom of the motor tube that nest in a pair of tubes in the tail boom. A few wraps of tape on either side of the boom is enough to hold it on boost. When it is where you want it, wick thin CA between the tubes and then back up with some 5min epoxy. Clip off the excess that sticks out of the bottom of the boom. Add a plastic fairing for awesome aerodynamics.

That is a totally kewl idea. Seems like you would need a minimum of 2 sets mounted at 90 degree angles to each other or preferably 3 sets in a triangle fashion in order to adjust for all thrust line offsets (if I understand this concept.) This would require you blasting through a bunch of motors in order to get it dialed in perfectly. Also with a glider where you have a wing hanging off two sides, fins off a third side and nothing off the forth side you would need to do all the tests on totally windless days otherwise you might be adjusting for windage without really realizing it (same issue with trimming out an rc plane on a windy day.)


Currently I have 9 successful flights out of 9 launches (success measured in landing without breaking anything.) After seeing how she rolls during the motor burn phase I know my offset is off by a smige. Not off by enough to worry about it as she is easy to fly her through the thrust line offset (just wait for motor burnout before making major adjustments or performing aerobatics.)

 

[TheAviator]

You should really only need to adjust the pitch axis. Roll and yaw are taken care of with careful alignment and piloting. Also, you should always launch into the wind, but I'm pretty sure you knew that already.

Also, as they say, any landing you can walk away from...

 

[ckreef]

You should really only need to adjust the pitch axis. Roll and yaw are taken care of with careful alignment and piloting.

Brian, I somewhat agree with you except I feel both pitch and yaw needs to be adjusted with the thrust line. With pitch you either come back on yourself or slam into the ground going down. With yaw you can easily slam to the ground left or right.If pitch and yaw axis is right then a roll will be straight and true otherwise something is off.

Both pitch and yaw can be adjusted with the thrust line or piloted. I am in the mode, TLAR and I can easily pilot (wih dual rates) what ever axis is off by a smige.

Also, as they say, any landing you can walk away from...

So true !! With a rocket glider (a rocket that glides around on it's own to landing) then you are flying a rocket. If you are launching a RCBG then you are really flying a rc airplane with a rocket motor for thrust.

 

[ckreef]

I went to the rc field today and got the video from flight #2. This was taken on a windows based tablet. She flew off a AT 24/40 E18. On this flight I was just trying to get her up and then back down without incident. Getting use to RCBG flights and checking out the trim settings.

The commentary is another person also trying to video the flight and his grandson telling him how to do it

[YOUTUBE]emkyWz_NSUg[/YOUTUBE]

 

[Planecrazy]

For what its worth, looking at the above video you may be running a little nose heavy. The gentle nose over is what I got on my first flights and the very fast glide just looks to me like you could loose some wieght out of the nose. I've found by trimming mine a fraction tail heavy with the motor loaded it comes right once the motor has burnt out. You can if you wish to extend the glide, go with a lot more nose up trim on the glide mode, the Funjet does slow way down if you want it to.

Still a fun project though. I'm thinking about building a 4" H powered booster with R/C seperation for my next developement of my Funjet.

I'm also a little jealous as we move into winter here. Last launch was washed out!


Cheers Planecrazy

P.S. Keep up the good work

 

[ckreef]

For what its worth, looking at the above video you may be running a little nose heavy. The gentle nose over is what I got on my first flights and the very fast glide just looks to me like you could loose some wieght out of the nose. I've found by trimming mine a fraction tail heavy with the motor loaded it comes right once the motor has burnt out. You can if you wish to extend the glide, go with a lot more nose up trim on the glide mode, the Funjet does slow way down if you want it to.

Still a fun project though. I'm thinking about building a 4" H powered booster with R/C seperation for my next developement of my Funjet.

I'm also a little jealous as we move into winter here. Last launch was washed out!


Cheers Planecrazy

P.S. Keep up the good work

The nose over was me on the sticks. It actually want's to come back on itself a little. My 1st flight I didn't nose it over soon enough and she stalled at apogee. I had to let her free fall down a bit before I was able to gain control so on this flight I was a little paranoid and probably nosed her over a little early.

Will hopefully get a few more flights this Sunday if weather permits. I fly at an rc field so no need to wait for a launch -- I just fly when work permits and the weather is good.

 

[ckreef]

For what its worth, looking at the above video you may be running a little nose heavy. The gentle nose over is what I got on my first flights and the very fast glide just looks to me like you could loose some wieght out of the nose. I've found by trimming mine a fraction tail heavy with the motor loaded it comes right once the motor has burnt out. You can if you wish to extend the glide, go with a lot more nose up trim on the glide mode, the Funjet does slow way down if you want it to.

Still a fun project though. I'm thinking about building a 4" H powered booster with R/C seperation for my next developement of my Funjet.

I'm also a little jealous as we move into winter here. Last launch was washed out!


Cheers Planecrazy

P.S. Keep up the good work

I've been giving what you posted a lot of thought. That video was flight #2 on a E18 (only my second RCBG fllight.) I have tweaked it a little bit since then (total of 9 flights to date) and now only launch her on F24's (the F24's are a slightly different flight profile.) Will fly her 2 more times on the F24's and tweak her some more. I can easily move the battery back a bit in order to make the nose lighter/tail heavier although with the F24's she noses back over on herself a bit more then with the E18's (slightly off, thrust line is what I suspect.)

Will try to get a new F24 video or at least post a flight report next time I get some nice calm weather.

Charles

 

[ckreef]

So far I have flow the Funjet for 20+ flights. Today I had 3 motors loaded and ready, so off to the field we went. The first flight was awesome. Did a bunch of rolls on the way up. I let her stall and come back straight down. I recovered her, did a few more rolls and then landed her on the runway. I was feeling pretty good about that flight.

I loaded the 2nd motor, put her on the pad, turned on the electronics and tested the control throws. All was good to go. I gave a count down and hit full throttle (on-board ignition). She ignited immediately so I know I had a good radio connection at that point. As soon as she blasted off the pad I no longer had any rc control. All I could do was sit back and watch the show :y:

She went up ..... and well ---- what goes up, must come down. And down she came

Anywho not sure what went wrong but I'll try and figure it out. I think I can straighten her out and glue her back together. I have to go to FL next weekend so it might be a few weeks before I get her straightened out. Once I do I will report back my findings and hopefully a re-maiden flight.

A sad day at the field :cry:

 

[Planecrazy]

My deepest condolences. My funjet went a similar way about 6 weeks ago. I think it may have been sitting in the car too long and warped. Couldn't get the nose up or hold of a roll to the right and it went in underpower. It will not ride again! however I have ordered a Me 163 Komet that will fly on all the R/C gear and motor that was in the Funjet. I will also have dual power on it ie rocket and 14v electric.

Take heart that most foamies can be rebuilt in the time it takes to charge the batteries.

Best of luck with the rebuild
Plane crazy

Ps Thats what my park flying buddies would call a flesh wound:wink: I suggest some cabon fibre strips to reinforce the cockpit sides and I think that canopy may be straightened with a hot towel. (Check RC groups)

 

[TheTellurian]

Ouch! If you do find the cause do let us know. Might help another to avoid a similar ouchie. Had a similar issue that nearly treed an Electra glider yesterday. Rx was stuck in range check mode. S*** happens even when one tries to do it right. :flyingpig:


Richard

 

[ckreef]

Thanks for the condolences. It sucks as she was a fun/stable flyer. I had 20+ decent flights on her before this one. If I wreck because of dumb thumbs that's one thing but it is a real bummer when all you can do is sit back and watch the destruction.

When I get back in the next week or so I will try and figure out what went wrong. Not sure if I'll ever know as the impact definitely shifted things around a bit.