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Old Aug 18, 2012, 06:16 AM
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Originally Posted by colin269 View Post
i have F-35 Lightning II 2.4GHz RC Jet Plane Brushless.The F-35 Lightning II is a single-seat, single-engine stealth multirole fighter can perform close air support, tactical bombing, and air defense missions. Lightning can perform a multitude of aerobatics in skilled hands, but due to its stability, it is a good choice for someone who wants to learn the thrills of model jets.
Jets RC
That's great Colin, but just what does that have to do with the radjet?

I've decided to (try to) set my jet up with a CG 393mm back from the nose tip, which seems to be what many recommend. I tried putting thumb tacks at this point to balance my finger on, but found that wasn't accurate enough so I ended up using my coat hanger CG rig (see attached pics)

For me to achieve the CG I wanted with a 3S battery 1300mah nanotech I need the battery pushed so far back that it touches the ESC. The battery is so far back that the only way to get it out is by pulling on the wires.

Radjet fliers, is that seriously how far back all of you keep your batteries? Doesn't that make it hard to get the battery out?

Also, how on earth do people like Rattlesnake fly with 1000mah 6s packs? Rattlesnake, i noticed you can remove your whole top deck, is that so you can mount your battery closer to the middle of the airframe and still have access to it?
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Old Aug 18, 2012, 06:51 AM
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USA, TX, Lumberton
Joined Oct 2005
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I didnt have to put my 3s that far back. My 3s 1300mah was about a little over 3/4 deep, but not that far back. With stock gear it balanced right were they recommended. But once I put a heavier motor on my cg went back about 10mm, but still flys the same as before.

Are you running stock motor and esc? You won't be going fast enought to need a lot of carbon fiber support if you're basically staying stock. I used fast drying white colored gorilla glue and have no trouble with bonding and it's lighter than epoxy.
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Old Aug 18, 2012, 07:32 AM
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wow, that's weird that my lipo seems to need to sit so far back to get the thing to balance right. Any ideas on why that might be?

My setup is 100% stock. I am using a turnigy 9x receiver which is a bit of a brick, and I've got it right up the front of the 'battery compartment' because I don't have room for it anywhere else.

The CF support I'm adding is one of the lightest weight options available as far as I know, and the thin spars are really easy to install cos you just need to make a cut in the foam, pry the cut open a little with a screwdriver and slip in the epoxy coated CF. It may not be as important to start with, but it will be good to future proof it now while I'm in the mood for building. I have a 2836 2300kv that's waiting to go in if I can master flying it with the existing powerplant.

I just fired mine up with a 6x4 prop and it only drew 15.5 amps max, that was less that I was expecting. There's a video on the hobbyking website for the radjet 800 doing prop comparisons and that indicates that a TGS 6x4 draws 17 amps
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Old Aug 18, 2012, 08:02 AM
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Joined Oct 2005
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Taking a closer look at your where your wire hanger CG is, it looks like it's about 10mm back from where I had mine when it was stock. Basically it's where my CG is now with my heavier motor. You should be fine with it 10mm further forward, which means you could move your battery forward.

CF supports are a good upgrade to do if you do plan to go with more power down the road, which it looks like you want to do.

This jet is really a easy throw together jet, you may be putting more thought in it than needed. lol Get your CG in the recommend area, make sure your control surface move correctly and your power system works and go fly. But a word of caution, these jets don't need a lot of aileron and elevator throw. My first flight was squirrelly getting it trimmed and after landing I had to tame the throws.
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Old Aug 18, 2012, 08:31 AM
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Dillzio -

Don't know what kind of CA you use, but the gap-filling (purple cap) CA I have stuck fine to the wing joints, vert stabs, servo covers and belly pan. Did use a bit of white gorilla glue to fill in the small gaps, but after 8 flights everything stuck on with CA has stayed stuck.

The location for the CF strip looks good to me, though I used a 4mm CF rod through the fuse into both wings so haven't gone this way.

The CG on mine (3s 1300 nano-tech, orange 6-ch RX in the front of the cockpit wired to a satellite behind the battery) is just in front of the lowest (faint) line in your pic. Basically a few mm forward of the middle of the forward wing-to-fuse tab. I use my fingers to check CG, close enough I figure.
I do need a touch of up elevator to fly level, but after 8 flights I'm happy with how she handles. Doesn't seem nose heavy, and can still snap up with full up elev.
Dial in a few clicks of up elevator trim before you first toss her in the air and you should be fine!
Beautiful day for flying here today so off to the field!
cheers
Kurt
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Old Aug 18, 2012, 08:34 AM
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Quote:
Originally Posted by Dillzio View Post
For me to achieve the CG I wanted with a 3S battery 1300mah nanotech I need the battery pushed so far back that it touches the ESC. The battery is so far back that the only way to get it out is by pulling on the wires.

Radjet fliers, is that seriously how far back all of you keep your batteries? Doesn't that make it hard to get the battery out?
I removed the turtle deck and carved out the bottom of the "cap" a bit, so there's about 1" of the 3s nano-tech 1300 45-90c (seems like an excellent battery so far, takes about 9 minutes of flying at various throttle to use 900mah) sticking out into the cockpit.
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Old Aug 18, 2012, 08:39 AM
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Quote:
Originally Posted by setxws6 View Post
CF supports are a good upgrade to do if you do plan to go with more power down the road, which it looks like you want to do.

But a word of caution, these jets don't need a lot of aileron and elevator throw. My first flight was squirrelly getting it trimmed and after landing I had to tame the throws.
CF is also nice to have in a crash

+1 on the aileron (have mine set up so low is 40 expo/70% DR, med is 20 exp 85% DR, high is 10 expo/100%DR, mostly fly on med) while elevator is always at 15 expo/100%. Ailerons are much more sensitive than elevator.
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Old Aug 18, 2012, 08:44 AM
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I've added a couple of coins to the back of my model as ballast now, not sure if I'll keep it on there or not.
It does make the battery much more accessible, as you can see from the pics, but it adds 30g (1oz) of weight to the model.

Kurt, the CA glue I used was hobbyking brand. I used it on my funjet ultra (may it RIP) and it worked beautifully, but it wouldn't stick to this foam at all, even with accellerator. Maybe I needed to sand back the foam first?
Oh, and Kurt, could you plz post a pic of how u have ur batt mounted? it's hard to visualize from a written description
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Old Aug 19, 2012, 11:04 AM
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A couple of questions on setting the control surface throws.

Should i copy the settings for the funjet ultra and use reverse aileron differential, and more up elevator than down? It would be great if someone could give me some figure to aim for in terms of travel

Funjet ultra manual says:
Up-elevator (stick back towards you) 10 mm
Down-elevator (stick forward) 8 mm
Aileron travels +8 / -11 mm
(negative differential)


So far I've set mine up as
ailerons 7mm up 9mm down,
elevators 9.5mm up 8mm down

I expect that it may make things a bit twitchy, but I'll have the dual rate switch (or switches I should say) to make things nice and docile for my first flight.

Also, anyone know if my ballast is going to cause problems for the little stock motor?
With ballast in place the jet weighs 450g with battery, assuming i get about 600g thrust from my TGS 6x4 that will give me a power weight ratio of 1.33 which I figure is still pretty good, all be it not as good as the ballast-free figure of 1.43 but still OK.
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Old Aug 19, 2012, 11:39 AM
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Not sure on the differential. That aileron sounds peepy but like you said you can switch to lower rates. I'd have the ailerons on lower rates and the elevator on high is fine.

It would be much nicer not having to use the ballast. But it should still fly fine. The vertical with the stock motor setup on 3s wasn't outstanding, but okay. When I swapped motors and went from 150watts (stock setup) to 350watts on my new setup, the radjet finally woke up on verticals. But nothing like my 1500watt funjet lol
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Old Aug 19, 2012, 01:14 PM
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Originally Posted by setxws6 View Post
Not sure on the differential. That aileron sounds peepy but like you said you can switch to lower rates. I'd have the ailerons on lower rates and the elevator on high is fine.

It would be much nicer not having to use the ballast. But it should still fly fine. The vertical with the stock motor setup on 3s wasn't outstanding, but okay. When I swapped motors and went from 150watts (stock setup) to 350watts on my new setup, the radjet finally woke up on verticals. But nothing like my 1500watt funjet lol
1500w funjet? holy moses! My ultra with turnigy 2826 was faster than I could handle and that was only 280w. What did you do with all that power?

I take it most of you fellas with super fast jets fly at clubs or out whoop whoop? I'm more of a parkflier myself.
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Old Aug 19, 2012, 01:29 PM
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Originally Posted by Dillzio View Post
1500w funjet? holy moses! My ultra with turnigy 2826 was faster than I could handle and that was only 280w. What did you do with all that power?

I take it most of you fellas with super fast jets fly at clubs or out whoop whoop? I'm more of a parkflier myself.
My funjet ultra is my newest jet, only about 6 or so flights on it, but it's a blast. Flat out it's in the 140-150 mph range, and verticals are literally unlimited. And no I don't fly at a field, I fly down the street at a big church parking lot area, and land in a long stretch of grass in front of the church. The FJ slows down well.

280 watts in an ultra? I have more watts pushing through my little radjet lol...Speed planes/jets can be addictive
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Old Aug 20, 2012, 04:40 AM
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Originally Posted by Dillzio View Post
I've decided to (try to) set my jet up with a CG 393mm back from the nose tip, which seems to be what many recommend.

Also, how on earth do people like Rattlesnake fly with 1000mah 6s packs? Rattlesnake, i noticed you can remove your whole top deck, is that so you can mount your battery closer to the middle of the airframe and still have access to it?
Its not for the battery its just for ease of installation/ changing things.

I thought most people were using 400mm back 393 seems to far forward to me.
I use 1300mah 6s not 1000mah :P
It just fits right in, no need to move it back for CG because the
motor is bigger.

Its a 36mm not 28mm like most people.

Quote:
Originally Posted by Dillzio View Post
I've added a couple of coins to the back of my model as ballast now,
Take the coins off and put a bigger motor on!

Quote:
Originally Posted by setxws6 View Post
My funjet ultra is my newest jet, only about 6 or so flights on it, but it's a blast. Flat out it's in the 140-150 mph range,
Same speed as my Radjet on 1200watts
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Old Aug 20, 2012, 01:46 PM
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Originally Posted by The_RattleSnake View Post
Take the coins off and put a bigger motor on!



Same speed as my Radjet on 1200watts
Agreed take the coins off and up the motor!

And the radjet and FJ ultra are on a totally different playing field. The FJ Ultra is a much stronger better built foam jet, with better cooling, and much more room for electronics...
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Old Aug 21, 2012, 12:50 AM
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Actually bought the funjet ultra as my first jet cos of it's excellent quality, and I really regretted getting it as my first jet. I wish I got a normal funjet like I wanted but the guys at the hobbyshop talked me into getting the ultra instead.
I found the ultra was too hard to hand launch, and it needed too much room to land for me to fly it at the local park... the funjet ultra weighs about twice as much as the radjet, and it has about 7 ounces on the normal funjet!

My funjet ultra lasted two flights (not counting the failed hand launch attempts). I was flying it around OK, and my mate that was filming said I was flying too far away for him to get a clear shot so he asked me to fly closer. I went to fly past about 15m away about 5m high- I wanted to get a good shot of the ultra going really fast cos there were a bunch of idiots on here that were telling me my turnigy 2836 wasn't powerful enough. anyway, the combination of being too close and going too fast was just too taxing for an inexperienced jet pilot such as myself. After my high speed pass I pulled up, but my plane must have somehow ended up inverted cos when I pulled up the ultra when down nose first into the ground at about 150ks.

Here are the before and after pics:


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