RadJet800 conversion

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iter

HPR Glider Driver
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I flew my RadJet conversion today. The kit is here: https://www.hobbyking.com/hobbyking/store/__19690__Hobbyking_Radjet_800_EPO_800mm_PNF_.html

My version has none of the decals (they are thick and tend to peel off at leading edges) and a 24mm mount. It's a very straightforward build, since the original design is for 24mm brushless pusher motors.

First flight today on D12-7. From the looks of it, the glider might do OK on C11 and E15 as well.

Ari.

[video=youtube;DLjkwcIWzJA]https://www.youtube.com/watch?v=DLjkwcIWzJA[/video]
 
That looks like a decent boost and glide Ari. What is your all up weight? I'm assuming you are plugging the D-12-7's or venting them, or are you ejecting them?
 
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Thank you Frank. I land with the motor. Throwing a casing off the back of the glider would move CG forward in addition to what burning propellent off the back has already done.

There are people here who frown on "modifying" a motor by plugging it, so I'm just going to stay with the sentence above.

Pad weight with a D12 is 257g. I use a single-cell 400mAh lipo for the receiver.

Ari.
 
Ok, I was trying to get you to admit your sins��
What rx are you using that runs reliably off of a single lipo? My spektrums are supposed to be marginal below 5v..

Frank
 
Spektrum Rxs are good down to 3.5V. That's not much margin from the nominal 3.7V of a 1S LiPo, but the F3K guys use big (1Ah+) single cells for their birds all the time. I'm sure Horizon support wouldn't suggest it, but I've done it too and it works okay.
 
I use FRSKY almost exclusively. I love their stuff. The RF modules are from TI, and the hardware makes sense. I've used Taranis as my primary TX for a year and a half now, and love the fact that the firmware is open source. Let me know if you want to hear more about my experience. The specific RX in this glider is V8R4-II, 3V to 16V nominally (https://www.frsky-rc.com/product/pro.php?pro_id=11)

Ari.
 
Interesting, I was also concerned about driving the servos with 3.7

Normally they are pretty slow below 5v as well..it would be nice to not have to carry/buy a bec...I know there are hv servos to work directly off of 2s, but I thought 1s servos were usually micro..

Frank
 
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Interesting, I was also concerned about driving the servos with 3.7

Normally they are pretty slow below 5v as well..it would be nice to not have to carry/buy a bec...I know there are hv servos to work directly off of 2s, but I thought 1s servos were usually micro..

Frank

You lose power and speed, but they will still operate. As always, test before you fly.

I use FRSKY almost exclusively. I love their stuff. The RF modules are from TI, and the hardware makes sense. I've used Taranis as my primary TX for a year and a half now, and love the fact that the firmware is open source. Let me know if you want to hear more about my experience. The specific RX in this glider is V8R4-II, 3V to 16V nominally (https://www.frsky-rc.com/product/pro.php?pro_id=11)

Ari.

I've heard good things about the FRSky equipment as well, and I'm glad to hear that you are enjoying it. I may have gone that way now, but I've been pretty committed with Spektrum since I got into R/C.

Sorry for derailing a little. That RadJet looks like a lot of fun and it glides pretty well too!

Are you using onboard ignition or ground? Also, if you have an Aerotech 24/20-40 case, an F12 (~50N-s) would give it a pretty good ride too.
 
Ok, I just hadn't heard of people doing this with larger servos(non ultra micro)...was just curious if anyone is designing with 1s in mind, or if it was just use at your own risk...on the servo side...I'll have to do some tests, I am curious about load under boost control, I hate to have something not work under boost even if it works on the bench. It woul be nice to go to a single thin cell and dump the bec. Of course the other option would be 2s direct, but I think then the servos are the limiter...

Frank
 
Great flight Ari. :D

Frank; I use 1S in my Snaggletooth [Delta RCRG] and have been for over a year. Typically a 400mah but as low as 160mah. It has D60s controlling 1x20" elevons and flys with D11 and E9p motors. I'd say its safe with park flyer sized models. I do check all incoming servo on the bench with a servo tester and a spare 1S lipo [ < 3.7V @ times] and even the big standard ones respond, but if you need that size there should be no worries about a BEC's weight.

The Aviator; FrSky [FreeSky] Taranus will take a Spec module or Orange module in the rear [JR] module bay. You can fly both but be warned many people sell off their Spectrum stuff after trying FrSky only keeping the Spec module for the BNF models. :surprised:

Ari; Have you thought of putting a 808 Keycam on the Radjet? Would be cool.


Richard
 
Ok, I'll have to experiment then. I'm running typically AR-400's and two hs-55 servos by default. It sounds like that should probably be ok then, although they are a bit less torque by spec than a D-60, my small models probably don't have that much surface area/load.

Frank


Great flight Ari. :D

Frank; I use 1S in my Snaggletooth [Delta RCRG] and have been for over a year. Typically a 400mah but as low as 160mah. It has D60s controlling 1x20" elevons and flys with D11 and E9p motors. I'd say its safe with park flyer sized models. I do check all incoming servo on the bench with a servo tester and a spare 1S lipo [ < 3.7V @ times] and even the big standard ones respond, but if you need that size there should be no worries about a BEC's weight.
 
I use Turnigy "9-gram" servos (https://www.hobbyking.com/hobbyking...gy_TGY_50090M_Metal_Gear_9g_Analog_Servo.html) in my parkfliers. Another option is a 2S LiFe battery; most servos can operate on 4-cell NiCDs, or 6V, and do fine on 6.6V. I used this setup on SkyFun until it blew up on G65. I've been flying my SW Mega Baron on 1S setup for almost three years now, and it's one of my most reliable gliders ever.

I use a ground battery for ignition, but actuate it from the same TX I use to fly the glider. I can post some photos when I get home tonight. I use a locking, return-to-neutral, three-position switch for ignition and a chain of safety interlocks to prevent accidental ignition.

The fire control box uses two channels, 7 (ARM) and 8 (FIRE). Channel 7 closes a transistor when it's on. Transistor switches power to a relay that closes when channel 8 is on. Both channels have to be on to fire. Either channel being lower than a threshold prevents firing. Arming the box (ch. 7) also actives a loud buzzer.

On the TX, the ignition switch has three positions: safe, arm and ignition. It's a locking switch, meaning you need two hands to pull it from "safe" to "arm." It takes only one hand to push from "arm" to "ignition," but the switch has a spring and returns to "arm" as soon as I release it.

In addition to all these, I also program the TX so it arms only if elevator trim is in "boost" position. I once launched a glider with the elevators set for glide, and had two very low altitude loops right off the pad. My setup prevents such a launch.

Ari.
 
Ignition box has, in addition to features above, a safety interlock in series with the launch switch (1/4 phono jack with LED indication insertion) and a continuity indicator (smaller LED on right). Transmitter has a launch switch that returns to the "off" position when released. It's this part from DigiKey: https://www.digikey.com/product-detail/en/M2019LL1W01/360-2671-ND/1027457. I modified it slightly; arming requires two hands, going to ignition form armed requires only one so I can have my right hand on the right stick as I launch. I launch with my left thumb, which would normally be on the throttle, for an idiomatic control.

Ari.

IMG_4122.jpg

IMG_4121.jpg
 
Had 3 good flights today, all on AT Blue Thunder reloads. Very little flame and less smoke, but here's a still from the video.

Ari.

RadJet.jpg
 
Three more happy flights today, all on E11Js. This glider now has 12 flights on it.

Ari.

vlcsnap-2015-11-26-17h27m07s425.jpg
 
3 more flights today, E11J, F12J and C11 (BP). This glider now has 15 flights on it, on motors in 4 impulse classes.

Ari.
 
Ari, although I'm not a huge fan of the shape of the radjet personally, I know a lot of guys love these, and it looks like it has pretty good performance, is pretty versatile for motor usage and for a plug and play, with only minor mods, pretty reasonable as well. The motor isn't far off from the CG and that's a nice plus.

Frank
 
Thank you Frank.For the price and ease of construction, this plane is hard to beat. This is what I now recommend to R/C pilots who want to try RCRGs. Strange thing is, on the motors I fly, the plane is very slow (I mean, E6, right?). Nonetheless, the comments I get at the R/C field all have to do with how it really went, how fast it is, etc. People really want to believe.

Ari.
 
Ari, have you flown it on pusher as well, you could do a quick pod like I use to plug into the mount, but then you'd need to rig up the esc and battery for it, just curious if you were trying that at all.

Frank
 
I left the door open for that. The motor mount is open at the front, and I could build a pod like you describe. I haven't.

I used to slope one of my SkyFuns. The first one I built, I went to great lengths to make the engine mount "reversible," i.e. so I could mount an electric motor back on. I never did that either.

These foamies, if you take out the heavy stuff (motor, lipo) make excellent slopers.

Ari.
 
What Cg locations do you find flight worthy for launch and glide respectively? I have not started on my conversion yet and it would be good to try not to wander too far from what is know to work (at least initially).
 
Hi. Contrary to what some posters are saying in the other RadJet thread, I find the CG envelope very forgiving. I can take out the motor casing entirely and fly the plane at the lope all day without compensating for the CG move.

I settled on two US quarters taped to the front inside cockpit wall for CG. Without a motor in the back, this results in CG about 1/2" ahead of the fingergrips' front edge. With a full E9, the CG is about the middle of the fingergrip cutout. I have flown th glider without the quarters, but I find that it tracks much close to vertical in pitch with the extra ballast.

Ari.
 
Thanks for the guidance. I'm eventually planning to fly some of the larger CTI 24mm motors - eventually, but this should certainly get me started. I really do not wish to radically alter the fuselage just to move the motor mass closer to the desired CG.
 
This one has flown on AT F12J. It got very small on that motor.

As far as altering the fuselage for CG purposes, it's easy. I did a fuller build-and-fly thread on a similar foamie conversion: https://www.rocketryforum.com/showthread.php?63582-SkyFun-III-new-ideas-for-managing-CG-shift . It appears unnecessary though. Any motor big enough to push CG out of the envelope on the RadJet probably flies it out of sight. The bigger SkyFun flew great on CTI F30s, but shredded on a G65.

Ari.

ImageUploadedByRocketry Forum1394180535.268754.jpg
 
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