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Old Dec 21, 2008, 09:42 AM
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bighead93's Avatar
Sacramento
Joined Apr 2005
5,554 Posts
Quote:
Originally Posted by rstein9
I bought one of those helicopter motors from Scorpion....he told me it would scream in the funjet.

Problem is you have to reverse the shaft so it will mount.....then you have the wires in the way.....you have to thread them up past the motor.....

maidened it yesterday....but i think the wires are touching....made a hideous sound...althought it flew ok....but not fast??

My friend is using the same motor (and it is super fast.......but he mounted it with one of those trick devices that swivels the motor.

i could mount it sticking out the back....but then will have to add weight up front.....and i hate doing that.

any ideas?
Check to make sure the prop is on the correct way...I have made that mistake before and it sounded terrible
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Old Dec 21, 2008, 09:48 AM
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bighead93's Avatar
Sacramento
Joined Apr 2005
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I am getting ready to fly my Second FJ...and still wonder if the 4.7X4.7 prop was the issue that caused the destruction of my my first FJ. My set-up is the same as last time...Mega 16/15/3 CC 60 Amp ESC and 3S 2200 25C lipos (plan to use 4S 2200 25C's down the road). Please give me an idea what will be the best prop for all around performance and will make it easy to hand launch. Thanks guys!
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Old Dec 21, 2008, 09:55 AM
I buy, I fly, I buy....
Wingwrecker's Avatar
United States, OH, Toledo
Joined Feb 2008
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Well I know your battery can handle 55 amps!

Thanks again, Ben
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Old Dec 21, 2008, 09:58 AM
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Ben D Wing's Avatar
The Peak District
Joined Dec 2006
2,882 Posts
Quote:
Originally Posted by Wingwrecker
You're right, that is easy! Thanks.

So how do you know if the battery's c-rating is inflated? Just by the battery getting hot during what should be a normal load?
I guess there is no way of telling for sure if the manufacturer is exagerating his 'C' rating, but I think that most these days are fairly accurate.
A battery will get warm under normal usage and as long as it can be comfotably held in the hand after a flight you could assume that all is ok. The higher the Amps drawn and the longer the duration this is level is used for (a pylon racer for example), the hotter the battery will be. This is where the better quality LiPo's score as they can stand more abuse than the budget ones, but of course there will always be exceptions.
Ideally an Ampmeter should be used when trying different props, or setting up initially to ensure that that the LiPo's or ESC's maximum aren't exceeded, and if at all possible don't run at the max rating for more than a few seconds. Also, when dealing with larger capacity LiPos it is extremely important to use a balancer when charging otherwise the cells will soon be out of phase and that's when problems start.
Apologies if I'm teaching you old tricks, but there may be newbies reading here too.
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Old Dec 21, 2008, 10:18 AM
I buy, I fly, I buy....
Wingwrecker's Avatar
United States, OH, Toledo
Joined Feb 2008
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No worries, all good info there.
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Old Dec 21, 2008, 10:24 AM
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Ben D Wing's Avatar
The Peak District
Joined Dec 2006
2,882 Posts
Quote:
Originally Posted by bighead93
I am getting ready to fly my Second FJ...and still wonder if the 4.7X4.7 prop was the issue that caused the destruction of my my first FJ. My set-up is the same as last time...Mega 16/15/3 CC 60 Amp ESC and 3S 2200 25C lipos (plan to use 4S 2200 25C's down the road). Please give me an idea what will be the best prop for all around performance and will make it easy to hand launch. Thanks guys!
I think you need to prop up a bit to get the best out of that motor. These are well known for being underated by the manufacturer and can take a whole lot more Amps than they quote.
I am using the same spec Mega in my Simprop 'Turn Left' pylon racer and am using the following prop: An APC 5"x5" which is drawing 37 Amps (static) for about 400 Watts on a 2200 mAh 3s LiPo. This plane really burns air on this setup so I can only guess what it going to be like in a Funjet! Just be careful if you use a 4s on that motor as you will need to prop down to about 3.75"x3.75" and then you will lose some efficiency as the rear of the Funjet isn't much smaller!
Re. Launching: The lighter your Funjet is the easier it will to be to launch, but the secret is to toss the plane wings level (very important), and at an angle of about 5-10 deg above the horizon. If you look on Youtube you will see all manner of launches that really don't give the plane a fighting chance, and it's no wonder that lots of folks complain of torque rolling etc.
I use the above technique and have never had torque issues on any of my (3) Funjets.
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Last edited by Ben D Wing; Dec 21, 2008 at 10:32 AM.
Old Dec 21, 2008, 10:34 AM
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bighead93's Avatar
Sacramento
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Thanks for the info Ben! I will start with the 5X5 and see how it goes...I think I will stick to 3S for now...I just bought 8 or them (Tenergy's) and they are working great so far!
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Old Dec 21, 2008, 11:14 AM
Spritual Pilot
Silicon Valley, CA
Joined May 2001
677 Posts
Quote:
Originally Posted by gotboostedvr6
Using the 1.5 with a 6x4 on a 2200 4s lipo will smoke the battery in short order. 72-76 amps is what a 6x4e draws on that motor.
I don't agree with the battery issue. If the battery is high dischaging rate, it should be fine with proper throttle management. The battery is rated 25C (constant) and 35C (15s burst). It can handle 55A (constant) and 77A (butst). So, the range of 72-76 amp seems ok as long as I don't do WOT for more than 15sec.

Now, only concern for me seems the 70A esc. However, if it is really 72 to 76 amps, then it should be also fine because the 70A esc is rated as 80A max for 10 sec.

Seems like 'Good to GO'... with some throttle management.

Thanks for the good information.
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Last edited by jnyoun; Dec 21, 2008 at 12:30 PM.
Old Dec 21, 2008, 11:22 AM
To drive or to fly......BOTH!!
FresnoJay's Avatar
USA, CA, Clovis
Joined Apr 2007
6,196 Posts
Wing, to be on the safe side I always run at 80% of the stated rating to be safe and prolong my lipo life. Take the stated rating say 2200 25C = 55A*.8 (80%)=44A safe long life limit.

Jason
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Old Dec 21, 2008, 11:24 AM
To drive or to fly......BOTH!!
FresnoJay's Avatar
USA, CA, Clovis
Joined Apr 2007
6,196 Posts
jn, Even with TM he will destroy the LiPo in short order. I know this from experience.

Jason
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Old Dec 21, 2008, 01:27 PM
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gotboostedvr6's Avatar
USA, NJ, Mt Laurel
Joined Oct 2007
3,691 Posts
Quote:
Originally Posted by Wingwrecker
gotboosted, How does the c-rating of a lipo and actual amperage draw correlate?
its based on voltage drop over given time. Dr. Kiwi might be able to shed light on it if you pm him
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Old Dec 21, 2008, 01:28 PM
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gotboostedvr6's Avatar
USA, NJ, Mt Laurel
Joined Oct 2007
3,691 Posts
Quote:
Originally Posted by jnyoun
I don't agree with the battery issue.

Well i strongly do what kind of lipo is it?

Actually it doesn't matter your max amp draw will be around 50 amps constant. if your fly 40 amps constant you can burst 60 for maybe 25 seconds before you have to resume 40
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Old Dec 21, 2008, 03:12 PM
Annoying people since 1970 :)
United Kingdom, England, Taunton
Joined Nov 2005
1,677 Posts
Looks like Numb Thumb may have some competition from Italy!

Fast Funjet
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Old Dec 21, 2008, 03:38 PM
Lloyd Robinson
fishboy77's Avatar
USA, MO, St Louis
Joined Jun 2007
780 Posts
One more for the fleet

Well, I maidened my FJ the other day. I certainly agree with everyone else that this plane is appropriately named. I'm starting off with a very tame setup just to get used to the way it flies: Suppo 2212-06 (2200 kv), Dynam 30A ESC, APC 5.1x4.5E prop, HXT900 servos, and Mystery 2400 mAh 15C lipos. It pulls about 18 amps at WOT in the air and has decent thrust. Already hungering for a bigger motor, perhaps an Arc 28-37-2.5 or a 47-1.5.
Funjet, fifth flight (5 min 31 sec)
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Old Dec 21, 2008, 04:10 PM
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Ben D Wing's Avatar
The Peak District
Joined Dec 2006
2,882 Posts
That's a nice paint job and video fishboy, and no offence intended, but your launcher is demonstrating the exact way not to launch a Funjet! He launches at too steep an angle from the horizontal and swings the plane left with the torque. This is a natural trait for most right handed launchers and is not easy to overcome. Try getting a southpaw to launch your plane and increase the power progresively, it might just save you from those pucker moments!

Check out how this guy launches his Funjet...... http://www.rcgroups.com/forums/showa...mentid=1099744
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Last edited by Ben D Wing; Dec 21, 2008 at 04:19 PM.
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