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FUNJET

Old 08-05-2008, 06:27 PM
  #251  
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Default RE: FUNJET

Post all your stuff your putting in the plane I'll run the numbers
CP
Old 08-06-2008, 01:20 PM
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Default RE: FUNJET

Ignore that last post the numbers are off. I think my inputs are wrong. More later
Old 08-06-2008, 01:30 PM
  #253  
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Chipped~

Turnigy 60a esc-
Cont Current: 60A
Burst Current: 80A
BEC Mode: Switching
BEC : 5v / 3A
Input: 5.6v-22v
Weight: 60g
Size: 80x31x14mm
Supported motor speed for all TURNIGY ESCs is;
(Maximum): 210000 RPM (2 poles), 70000 RPM (6 poles), 35000 RPM (12 poles).

Zippy-h
Capacity: 2500mAh
Voltage: 3S/11.1v/3 cell
Discharge: 30C ~ 40C
Weight: 239g
Size: 143x45x17mm

Graupner spinner hub and prop
5.5X5.5 cam speed prop

KB28-47-09S
Shaft Size: 3.17mm x 12mm
Motor Dimensions: 27.6mm x 47mm
Weight: 135g
Motor Spec.
Kv: 4900
Idle Current: 2.4A
Resistance: 0.0119
Max Current: 45A

Here is all of my info: purchased it prior to all of the conversation and advice. I will see what does and doesn't work.
Old 08-07-2008, 03:24 PM
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Default RE: FUNJET

slicktop.

Higher KV swings smaller props...given fixed voltage
Higher KV can handle more amps.

Lower KV swings larger props at less RPM...given same voltage.
Lower KV can handle more voltage.

As voltage goes up, each motor needs to run smaller props to keep amps from jumping higher too.

Power is expressed in watts.
746W=1 hp

1Watt = 1 Amp X 1 Volt (But volts read while motor is running).

Battery pack voltage drops with motor running.


Yes with 3S, high KV motor makes more power. If the KV is way too high, the prop diameter is too low.

Too small a diameter prop will make less thrust.

At high speed the drag of air frame goes up and if the prop is too small to make enough thrust to overcome the drag at high speed, it makes no difference if it is making all the power in the world if it cannot transfer that power to the air to make enough thrust to overcome the drag to get more speed.

***So too high KV with too small a prop will not fly as fast as proper setup with less power.

_________________________

Your numbers above may get you to 120-125 MPH but it'll need 100A or more from battery and your pack can not deliver that...your ESC is not good for that either.

To max out your ESC, you need a lower KV motor and higher voltage.

You can run (2) identical 3S packs at 6S and prop for 60A....that would be serious power.

you need to find a motor that can handle as close to 60A as possible while being able to swing a prop that is not too small so you will not become drag limited.

Your combination is bad. That high KV motor cannot be used with this single battery pack to swing any reasonable prop size.......

I guess you might be able to run 4.5X4.1 prop check using a wattmeter...MIGHT be just fine for up to 110 MPH flight?????? Forget about any Psycho climbing rate though.
Not sure if that motor is 4300 or 4900KV? Motocalc constant might be off, if so then may be 4.1X4.1 prop.

The parts you listed are not a very good match together.

Consider the longer version of the same motor...the 57 length versus the 47 length. It'll handle more power while running cooler. It can make more power and be more efficient than the shorter one.

How about KB28-57-17L 1700KV on (2) 3S-2500 packs in series as 6S-2500 swinging APC E 6X5.5 prop?
Also KB28-57-16L 1800KV
Or KB28-57-15L 1900KV swinging 6X5 prop?

Above setups might get to 130-135 MPH with your 60A ESC.

Those are my guesses using Motocalc...vary things carefully using measuring tools such as wattmeter and radar gun.

I don't know your speed goals in level flight and no wind.

There is a cubic relationship between speed and power required.
To fly 10% faster you need 1.1X1.1X1.1=1.331 33% more power
To fly 20% faster you need 1.2X1.2X1.2=1.728 73% more power for 20% more speed.
To fly 30% faster you need 1.3X1.3X1.3= 2.2 times the power for 30% more speed.

Good luck,

Gryphon
Old 08-08-2008, 09:15 AM
  #255  
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Default RE: FUNJET

Thanks Gryphon

I would suggest the Medusa V2 on a 4 cell 5.5x4.5 and hold on to something !!!!
CP
Old 08-12-2008, 03:58 PM
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Default RE: FUNJET

Thanks for all the input. I really need to get smarter because Gryphon is making me look stupid. I guess i need to get a motor that will run a 5.5x5.5 with a 2500 3s well and with the 60esc. The motor is the cheapest change right now out of what I have. Got the carbon rods in the FJ but can not upload the pics for whatever reason.


SSSHHHHHHHH! It is quiet! Hunting wabbits?
Old 08-12-2008, 11:52 PM
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ORIGINAL: slicktop

I guess what you guys are saying is I shouldn't spend the time and effort, and comprimise the weight, to glass this FJ. I have assimilated the info. and it took. So I will buy some carbon instead. Tubes or strips? Which is easier.....better?

Thanks Guys!
M reason for the strip is so that I can stiffen a bigger area of the wing, I think the f/g tube is ok but if you fly at absurd speeds and turn like a maniac like some here (not me) then yeah the CF tube will be nice.

Don worry about Gryphon ... you wanna see the PMs he sends to me? Its a darn lecture! He is detailed, very detailed. WE LOVE YOU GRYPHON!!!

To run the 5.5 x 5.5 I think you want a motor like the 28-47 in the 2,100-2,500 KV range. You might be pulling about 50A then. I say take the HobbyCity KB28-47 of 3,000 KV, use a 5x5 ... she will pull about 50A and is decently fast.
Old 08-16-2008, 11:38 PM
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I just wadded up my FJ today and want to build another one. I was running a Multiplex bl-480/4d and could easily get 100+ with it but it was pretty heavy (24 oz with battery). Do you think this is too heavy? Pretty hard to hand launch at this weight.
Old 08-16-2008, 11:52 PM
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Default RE: FUNJET

The difference in weight for the FJ using a BL 480 and BL400 is a lot. Just give her a really hard toss on full throttle.
Old 08-17-2008, 08:32 AM
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I'm thinking about switching to the E-Flite Six Series 2700kV. Much lighter. I still don't know really what happened to make her crash. The right elevon was somewhat warped and I attempted to straighten it before flying. On launch both times I tried she did a roll to the right to the inverted position right into the ground. It's was always hard to hand launch even with the stock motor but once in the air with either motors it was a perfect flyer.
Old 08-17-2008, 10:20 AM
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Default RE: FUNJET

Mike ... the prop usually makes her roll to the LEFT. As for the launch on a heavier set up you need to give her a very good toss. Might it be your launch is not level and perhaps not hard enough and she is stalling?
Old 08-17-2008, 10:36 AM
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The wing and elevon look pretty warped. I've got a 0utrunner 4200kv that I've got mounted in te stock motor mount and am ready to try building another one. This motor is the stock 4200 kV motor from my SAPAC T-45. I test ran it with a 5.5 prop and came up with 45 max amps and 355 watts ( 3s TB 2200 extreme). Do you think this is way too much power? The weight difference from my last motor (Permax BL-480/4D) is huge. The 480/4D came in at 4.3 oz and the B3830 4200kV comes in at 2.3 oz.
Old 08-17-2008, 02:41 PM
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Default RE: FUNJET

355W for the FJ is not too much power, its only more like entry level for power! Some have exceeded 1KW.
Old 08-17-2008, 03:44 PM
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cool then I'm safe. I'll try a 4.5 prop also
Old 08-18-2008, 12:25 PM
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I tell you the truth........soldering deans connectors is enough to make you leave the sport forever!!!!!!!! That sucks! Is there a secret I do not know. the soldering tabs need something to grip the solder. Any way, I will be in the air this weekend.......hopefully. Thanks for everyones help.
Old 08-18-2008, 05:06 PM
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Default RE: FUNJET

Hey ones so wise in the ways of FJ's~

Do I need to do anything to the hinge points to make them stronger? It seems to be just foam...
Old 08-18-2008, 05:08 PM
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How do you post pics? I was born yesterday!!
Old 08-18-2008, 05:28 PM
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Default RE: FUNJET

@slicktop ,
you need to tin thetabs with solder first.
afpe45.

Old 08-18-2008, 06:03 PM
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SLicktop

I hold my connector in a vice or pair of pliers, making sure not to touch the metal taps which will suck the heat out. Next I tin both the tabs and the wire. Hold the wire with a clothes pin to keep from burning your fingers. Remember to be carefull not to overheat the tabs or they will melt the housing.
Old 08-18-2008, 08:06 PM
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Yeah! I did tin the tabs but did not have a clamp or a clothes pin, burned my thumb an made a mess. But it is done and I am ordering them pre soldered from now on. A huge 5 bucks for a lot less aggrivation. Any one know how to post pics? Still have not learned that one....
Old 08-18-2008, 10:16 PM
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Default RE: FUNJET

Slicktop ... ROFL!!! You are funny ... hot iron and no extra set of hands! Heheheheehee ... get a little table vise, its so cheap and you need not spend time with your fingers in iced water! Remember to also tin the wires so it attaches much faster.

To post pics, look at the bottom left of your messaging bos, you will see CLICK HERE TO ... click on it, then brows for your pic, attach it.
Old 08-18-2008, 10:19 PM
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ORIGINAL: slicktop

Hey ones so wise in the ways of FJ's~

Do I need to do anything to the hinge points to make them stronger? It seems to be just foam...
No need to do anything but if you want to then use some THIN CA on it, I did that a lot with my MicroJets as they tend to get bumped a lot and it keeps the hinges from tearing so easily. Use a very light amount of CA only and DO NOT use any accelerator. Careful that it does not drip on you ... get some tissue ready.
Old 08-19-2008, 09:28 AM
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OK hopefully this worked! Any way....... these are from last week and I have the rudders in and the servos and everything in but the power. What else do I need to do to this thing to make it strong?
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Old 08-19-2008, 09:36 AM
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slicktop ... I would use carbon fibre cloth to lay it all over the plane, then you dissolve the foam and waaaaalaaaaaa, a CF FJ!!! Seriously, just teasing you, I think you got enough there. Enjoy the flight ...
Old 08-19-2008, 04:53 PM
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Thanks tIANci~

I am looking forward to flying it too, but freakin Hobby City AKA Hobby King has had my order now for 4 weeks and I still do not have it. So as soon as I get my stuff I am good. Should I do anyhting to the motor mount area to beef it up? It seems flimsy.

Slicktop

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