Hobbyking Radjet 800 conversion

I am working on my first RC conversion and wanted to ensure that some of the assumptions I have made are not problematic. I purchased a HK Radjet 800 and spent some time getting it sorted out to use it as a rocket glider.

My question is this: with the rocket loaded up with a 24mm motor, to get the rocket to balance at the CG, I need to use the battery pack that was intended for the motor and prop. This seems kind of heavy, but it does "fly" when I toss it. When I scale back to a much lighter battery, the plane does not fly at all and just dorks into the ground with no control. I am hoping that Ari (or anyone else who has attempted this madness) might be able to give some insight on how they sorted out their Radjet and what they used.

I just want to ensure that I'm not flying more weight than I need to, especially when that weight is in the form of LIPO batteries. i would hate for it to have a crash and then have this rather large battery pack be a potential safety issue.

Other than that the plane is looking good! It has been an absolute challenge trying to trim this plane - I can't toss it hard enough to get the airspeed to where lift is generated. I just worry about sending up something which I am unsure of the recovery. Since there is not a whole lot of info on conversions like this I figure that I need to ask some questions that might be "dumb". Any other tips people have, I would love to hear them! No sense in learning "the hard way" when there is a good possibility that someone on here has already learned some tough lessons.

Thanks!

Some pics? You know we love pics...

Hi there,

I did the same thing about 2 years age with the Multiplex Funjet. I think the the Radjet is a knock off of that design. I used the CoG from the instructions and had it set up a little tail heavy with a loaded motor, then needed some up trim to hold a reasonable glide. I also made the motor mount so I could switch it back to electric when I wished.

For boost/glider I just used a 2s 450mh lipo to power the radio gear and an 8oz sinker right in the nose to get the CoG correct with the lighter battery on board.

Hope you have a good run, it is a hoot. I was getting 650ft with a 32mm F12

Cheers Planecrazy

I had a RadJet 800 RCRG conversion. Yes, throwing it by hand to test-glide is very difficult. With an electric motor, you just kind of drop your hand out of its way and let the excessive thrust take it away. Yes, I ended up with almost the same size battery in the nose to balance it, and it yes it felt like a huge waste to remove all that motor and ESC weight and still require that much balalst.

Ari.

Ari and Planecrazy,
Thanks for the info! Just making sure that I'm not crazy (well I am crazy, but that is in the good way). I need to get a few things sorted out and maybe, just maybe I'll maiden it up next weekend. Right now the ESC is still in there as I'm trying to rig up a way to use that to light the igniter rather than drag my "ground support (plus, this is the only plane and battery i have with the XT-60 connector. One of my biggest complaints about RC flying is the dizzying amount of battery connectors you can possibly use. It is very frustrating to a new flier).

Matt,

If you want to see the Radjet 800, just check out HobbyKing The only changes I have made to the out of box is removing the motor and replacing it with a motormount, adding on 2 mini rail buttons and putting some reinforced packing tape on the wing-to-fuselage seam. However, I'll try to get photos and video of the first flight (or crash as it is likely to be).

Hi Matt

Flying wings and deltas are notoriously fussy about CG location, so if it was balanced with a motor and you remove the motor then that mass must be replaced in order to maintain balance. The battery, same thing, however it can be made a bit lighter by increasing the lever moment. That is if battery mass is X@4" then 1/2 X@8" is the same thing but 1/2X lighter. I've drilled out the nose of some to put mass [lead&epoxy] in there to get the mass as far way from the CG as possible. Of course to put the old battery back in the nose mass must be removable.

Hope that helps and the first flight is a good one. Oh and don't use too much motor at first. Ok I'll shut up now.


Richard

Hi again

Rather than using an esc for ignition, get an RC kill switch. This is either off or on. For my current boost gliders this is what I prefer. These RC switches are used by the guys who fly with gasoline engines and are required to have a ignition kill switch on thier transmitters. I have mine assigned to the trainer switch on my Tx so that it is only on when I am holding the trainer switch on.

Hope this is of some help

I just picked up one of these from HobbyKing and am sorry to see that this thread died off over a year ago. As was the OP, I'm looking for info on what the acceptable range of CG's are for boost (rearward location) and glide (forward location). Who here are flown these successfully and what guidance are you willing to provide? Thanks.

JMZawodny said:

I just picked up one of these from HobbyKing and am sorry to see that this thread died off over a year ago. As was the OP, I'm looking for info on what the acceptable range of CG's are for boost (rearward location) and glide (forward location). Who here are flown these successfully and what guidance are you willing to provide? Thanks.

Click to expand...

I just setup the CG with a loaded motor in it per the instructions. It flew "OK" but my build was way too heavy and it flew more like a brick. I added packing tape to help make it crash-proof and was using a very heavy LI-ON battery. On the BP D motor we were lucky enough to get it back close to us. On the BP E motor we had a little more luck but it didn't fly all too well. Once we loaded it with an AP F motor we got the altitude necessary for the plane to get enough speed to overcome the weight and let the control surfaces work. However, it was a VERY short flight and I need to go back to the drawing board over the winter and lighten it up and start from there. I suspect once i ditch the excess weight it will fly better.

how about this conversion..

I am in the process right now of converting my sig wonder over to a pulsejet... (insert evil laugh)

[video=youtube;t93KmnNtWv8]https://www.youtube.com/watch?v=t93KmnNtWv8[/video]

stickershock23 said:

how about this conversion..

I am in the process right now of converting my sig wonder over to a pulsejet... (insert evil laugh)

Click to expand...

Sa-weeeet!

I promise you if that was my plane it would have augured in after 15-20 seconds and there would be a pleasing resultant fireball for all to see at the field!

yeah thats the fun part...

im nervous already!!

ill post it up when its done in another thread..

I do want to see what HIS radjet is like as a boosted glider... very cool idea!~