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Old Sep 30, 2012, 07:25 PM
Row 0, Seat A
G550Ted's Avatar
Savannah, GA
Joined Jan 2008
2,706 Posts
Quote:
Originally Posted by Joe 1320 View Post
They had one prior to all these new models, I can't understand why it went away. It was about these same size as the current models and had a 64mm fan crammed in there. Performance was great!
Well, that one was actually an F-4B/N not a J or hard wing S. Either way it was a b!tch to launch but flew OK if you ever got it going. Mine ended up going straight in from about 100' due to a control failure (suspected broken clevis). What remained of the EPS airframe was low grade packing material.

Ted
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Old Sep 30, 2012, 09:51 PM
Warbird Fanatic
jchtr3a's Avatar
United States, PA, Coraopolis
Joined Jun 2012
272 Posts
F-86 cog

The manual for the F-86 puts the CG at 107mm back from where the leading edge of the wing meets the fuse. About 4 and 1/4 inches. Seems pretty far back. Even so I am having a hard time getting the plane to balance.
Most flyers seem to want it a bit nose heavy. I'm using a Turnigy Nanotec 950mah which just fits under the canopy.
Is that 107mm COG right? If so where is the best spot to put some weight in the nose?
It's a great little plane, and I can't wait to fly it. Just a bit worried that if it is too tail heavy, I'll wreck it.
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Old Oct 01, 2012, 06:09 AM
cmd
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cmd's Avatar
Niceville, FL
Joined Oct 2004
1,212 Posts
Look here:
http://www.rcgroups.com/forums/showthread.php?t=1480110



Quote:
Originally Posted by jchtr3a View Post
The manual for the F-86 puts the CG at 107mm back from where the leading edge of the wing meets the fuse. About 4 and 1/4 inches. Seems pretty far back. Even so I am having a hard time getting the plane to balance.
Most flyers seem to want it a bit nose heavy. I'm using a Turnigy Nanotec 950mah which just fits under the canopy.
Is that 107mm COG right? If so where is the best spot to put some weight in the nose?
It's a great little plane, and I can't wait to fly it. Just a bit worried that if it is too tail heavy, I'll wreck it.
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Old Oct 01, 2012, 07:55 AM
we can take off without that
green_flyer's Avatar
London, UK
Joined Nov 2008
824 Posts
Its amazing what a difference balde design makes!
I decided to remove the JPower-like 6-blade rotor I was using with a 30g 4900kv inrunner (the F35 flew quite well with it so I was a bit hesitant).
In its place I put in a cut-down HK Alloy fan rotor, aka Lander 53mm alloy fan.
The thing i noticed about this rotor is that the blades had a reducing pitch towards the tips, similar to the Wemo rotor. I had a gut feeling that this was a better blade desing than the simple paddle-like 6-blade rotor copy of JPower 5-blade.

It turns out I was right, 3A less, 20W less, but 16g more thrust at peak and settling to higher stable thrust. Not bad at all.
If only HK or someone would sell the separate adaptors as well as the rotors (which are only around $2), I would get more of these.

Here are some numbers and video to back up claim:
Motor: Neutron 705 4900kv 30g inrunner
ESC: Phoenix 25
Lipo: Hyperion 3s 850mah 25C

HK Alloy Fan rotor cut down to 50mm in JPower clone housing
Thrust--Amps-----Volts----Watts--WOT time elapsed
333g----15.24A---11.05V---168w---0s
290g----13.72A---10.50V---144W---14s

JPower clone 6-blade fan
Thrust--Amps-----Volts----Watts--WOT time elapsed
317g----18.34A---10.40V---189W---0s
279g----16.63A---9.92V----165W---8s



Static thrust test JPower 50mm F35 with 5-blade cut-down rotor from Lander 53mm alloy fan (0 min 30 sec)

Static thrust test JPower 50mm F35 with Neutron 4900kv 6-blade clone fan (0 min 19 sec)
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Old Oct 01, 2012, 08:13 AM
Registered User
United States, AR, Jacksonville
Joined Jul 2004
448 Posts
Nice results, and that just goes to show that comparing whats Watts between different power systems is not reliable.

I had tried the HK Alloy cut down to fit in the stock housing along with the paired 3S 4800 kv inrunner in my F-35. I was so disappointed in the performance that I went back to the stock power system on 3S.

After that I tried the 4S on stock and that's currently my favorite setup.

I think what happened in my experience is that eflux has been sacrificed for higher thrust and less amp draw. Basically all the numbers we regularly use are advertised to be better, which they are, but the one that we can't reliably measure and are never provided with has been diminished.
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Old Oct 01, 2012, 08:28 AM
we can take off without that
green_flyer's Avatar
London, UK
Joined Nov 2008
824 Posts
Thanks.
I agree, watts to me is a almost useless measurement when comparing fans. I dont want more watts, I want less watts more thrust
I think the Lander 40g inrunner, although it is long, is weak. I tried my Lander/HK alloy inrunner in its original alloy fan and got only 343g peak (outside of an airframe). Inside an airframe its going to suffer losses and produce less thrust. Of course the HK alloy fan is 53mm inner diameter, so by cutting down to 50mm diameter we are losing approx. 14% fan swept area.
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Old Oct 01, 2012, 09:50 AM
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Joe 1320's Avatar
United States, FL, Sebring
Joined Feb 2006
7,426 Posts
Picked up the Katana from the post office, they left me a notice on Saturday. That's usually the way the timing works for me. sunday would have been a great day to do the build. Oh well, at least the fun starts tonight. Everything looks good, no warps or damage. I just can't help myself, I'm going to put in an order to hobbyb for a few more airframes and motors/fans, I've gotten hooked on the 35mm series, the only 35mm planes I don't have now are the F-16 and T-45.

As soon as the EDF madness stops, I'm going to start hitting the prop planes. I've managed to resist myself for the longest time on those and I'm getting weak.....LOL.

great test BTW on the 6 blade. It's basically what I found some time back. The rotr is fairly stong, but not very effecient. In fact, all the haoye fans I ever tried were amp hogs for the output they made. Not very effecient at all.
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Last edited by Joe 1320; Oct 04, 2012 at 03:44 PM.
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Old Oct 01, 2012, 10:22 AM
chuck
santa barbara, CA
Joined May 2009
4,113 Posts
well i agree w/ u guys , there is a lot more to rotor design than meets the eye. that being said whiskey hit the nail on the head, its easy to get more static thrust w/ less amps. same with a prop , just reduce the pitch and add blade area. but eflux speed goes away, so it depends what u want. the over all performance is a combo of static thrust, eflux speed, and cfm , which is important as well.

very few manufactures give us much tech info on there rotors / fans, making informed decisions difficult at best. so the watts are still the easiest way to judge basic needs. one thing i know , there is no magic rotor/ motor combo cuz i have tried a bunch. so it still comes down to watts / pound , and for me 250 -300 / pound is minimum for a fun ride.

i have bench tested lots of bits combined w/ other bits and then installed them in a test jet . interestingly mostly a watt is a watt if and only if the motor is not overloaded. i had the same feelings about certain rotors , ie , man this has got to be better, only to find out that ya it's different ,maybe not better.

what would be cool would be to have different pitch rotors of the same type so u could tune the fan the the airframe, like u can w/ a prop. but for now i just go w/ the low blade count/ high pitch for fast , low drag airframes and higher blade count/lower pitch rotors for draggy planes.

so keep testing and reporting and will all benefit.

chuck.
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Old Oct 01, 2012, 10:25 AM
chuck
santa barbara, CA
Joined May 2009
4,113 Posts
Quote:
Originally Posted by Joe 1320 View Post

As soon as the EDF madness stops, I'm going to start hitting the prop planes. I've managed to resist myself for the longest time on those and I'm getting weak.....LOL.
good luck w/ that joe and if u find the cure let my wife know.

chuck.
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Old Oct 01, 2012, 10:28 AM
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Joe 1320's Avatar
United States, FL, Sebring
Joined Feb 2006
7,426 Posts
Quote:
Originally Posted by chas650r View Post
well i agree w/ u guys , there is a lot more to rotor design than meets the eye. that being said whiskey hit the nail on the head, its easy to get more static thrust w/ less amps. same with a prop , just reduce the pitch and add blade area. but eflux speed goes away, so it depends what u want. the over all performance is a combo of static thrust, eflux speed, and cfm , which is important as well.

very few manufactures give us much tech info on there rotors / fans, making informed decisions difficult at best. so the watts are still the easiest way to judge basic needs. one thing i know , there is no magic rotor/ motor combo cuz i have tried a bunch. so it still comes down to watts / pound , and for me 250 -300 / pound is minimum for a fun ride.

i have bench tested lots of bits combined w/ other bits and then installed them in a test jet . interestingly mostly a watt is a watt if and only if the motor is not overloaded. i had the same feelings about certain rotors , ie , man this has got to be better, only to find out that ya it's different ,maybe not better.

what would be cool would be to have different pitch rotors of the same type so u could tune the fan the the airframe, like u can w/ a prop. but for now i just go w/ the low blade count/ high pitch for fast , low drag airframes and higher blade count/lower pitch rotors for draggy planes.

so keep testing and reporting and will all benefit.

chuck.
And to add to that, everyone has different ideas as to what they want. Some want only the lowest amp draw coupled with the largest battery for long flights. Some want blazing speed and could care less about flight times, others want the sound of a turbine without regards to amps draw. There are soooo many choices.
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Old Oct 01, 2012, 11:31 AM
we can take off without that
green_flyer's Avatar
London, UK
Joined Nov 2008
824 Posts
True, there are so many possible set ups.

Just to check my understanding, if everything else is kept the same (fan diameter, intake area, exit area, fan swept area, etc) but the static thrust is higher for one set up, does that mean the efflux speed is higer too?
I'm thinking more air has to move through the same size hole per second?
(thrust being the volume of air moved per second)
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Old Oct 01, 2012, 12:13 PM
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Sunnyvale
Joined Feb 2009
5,025 Posts
I am going to order an RClander fan from Toysonics and then a Katana Airframe from HobbyB and try it out. I already have the 4s 25c 1550 mah gens ace packs....
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Old Oct 01, 2012, 12:21 PM
Augermeister
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United States, TX, Keller
Joined Jul 2011
2,662 Posts
Might get a chance to maiden the Katana later today. I have the Don's Wicked 4800KV Wemo set up with balanced fan. 40 amp esc came with the combo deal. Too chicken to go with 4S from the start but will later if all goes as expected. Goony, everytime I look for a gens ace packs from Nitroplanes, they are out of stock. Not 100% sure about the throws.Re-reading manual. Looks like they need to be dropped a notch or two on the TX.
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Old Oct 01, 2012, 12:24 PM
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Sunnyvale
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Just ordered my Katana. $77 shipped is a steal!!! Can't wait to get started on it....
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Old Oct 01, 2012, 06:34 PM
chuck
santa barbara, CA
Joined May 2009
4,113 Posts
Quote:
Originally Posted by green_flyer View Post
True, there are so many possible set ups.

Just to check my understanding, if everything else is kept the same (fan diameter, intake area, exit area, fan swept area, etc) but the static thrust is higher for one set up, does that mean the efflux speed is higer too?
I'm thinking more air has to move through the same size hole per second?
(thrust being the volume of air moved per second)
u are correct , but only regarding static eflux speed, as one type of set up may unload more than another .

if EVERY thing is equal and let say u change timing on the esc and u see more static thrust then u have more eflux speed and most likely more unloaded speed.

chuck.
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