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Old Nov 28, 2012, 07:46 PM
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The weight of a 3000mah 3S bat is similar to a 2200mah 4s, so it wouldn't be overkill. You'd have longer flight times and better air penetration, as well as a little more power.

I've had a number of people ask if I was running 4S they were so impressed with the speed, that really says something about this airframe. It's just a lot of fun.
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Old Nov 28, 2012, 08:08 PM
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Des Moines IA
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Originally Posted by Znybar View Post
The weight of a 3000mah 3S bat is similar to a 2200mah 4s, so it wouldn't be overkill. You'd have longer flight times and better air penetration, as well as a little more power.

I've had a number of people ask if I was running 4S they were so impressed with the speed, that really says something about this airframe. It's just a lot of fun.
Ok what motor and prop are you running then we can discuss further.
How do you figure more power?
I'm just trying to educate myself.
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Old Nov 28, 2012, 08:13 PM
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I'm using a 5.5x4.5 sport prop and an NTM 2700kv 2836 motor on a 3S2200mah 45-90C nano-tech. From memory I think it pulled around 550W and around 45A.

Larger lipos have higher possible discharge rates, which theoretically means more amps/watts. Basically, if your lipo is limiting the power output in any way (which is more than possible on a small 2200), a larger lipo should give you more power. In the case of speed, more weight means better air penetration and inertia (i.e. speed coming out from a dive will be much greater than something very light).
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Old Nov 28, 2012, 08:20 PM
Gravity? No, the Earth sucks
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United States, IA, Des Moines
Joined Apr 2011
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Originally Posted by eckace1 View Post
Ya tough bird it is and after repair we clocked it at 9o mph.
Now if I can only get him to upgrade to 4s I think it would be in the 130 range with a 32gram motor

Before crash we clocked him at 100 mph.

I think he just wants to see me hit the ground at 130mph !!! I need a few more flights with 3s and some more 90mph practice before I up my game- it is just a little different kind of flight from the Radian sailplane i love- but fast is fun too...and anyone that knows me just a bit- knows i am not afraid of a crash or two-or ten..
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Old Nov 28, 2012, 08:28 PM
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I would love to see a wattmeter of that for sure as your motor is running about 120% efficient.
I have run a few motors in my day and lets look at mine via a wattmeter.
4s1800 lipo 206 grams compared to almost 400 grams for a 3s1p3300.
My MD 2505-2800 motor 2800kv runs at 14.6 volts under load at about 730 watts and 48amps.
Running the same motor with 3s gives me 32amps at 11v and 350 watts.

Not saying your figures are wrong but unless you run a wattmeter its just a guess.
So if you look at voltsxkv there is a difference in rpm that translates to pitch speed
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Old Nov 28, 2012, 08:37 PM
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Originally Posted by scottdearinger View Post
I think he just wants to see me hit the ground at 130mph !!! I need a few more flights with 3s and some more 90mph practice before I up my game- it is just a little different kind of flight from the Radian sailplane i love- but fast is fun too...and anyone that knows me just a bit- knows i am not afraid of a crash or two-or ten..
I'm sure that plane would do 130 but we need to dial down the throws so you have more control at 130 instead of the stock 40.
Then when you become comfortable at that then start to increase the throws.
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Old Nov 28, 2012, 08:47 PM
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http://www.hobbyking.com/hobbyking/s...00KV_595W.html
Hk specks tell somthing diffrent
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Old Nov 28, 2012, 08:53 PM
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Originally Posted by eckace1 View Post
I would love to see a wattmeter of that for sure as your motor is running about 120% efficient.
I have run a few motors in my day and lets look at mine via a wattmeter.
4s1800 lipo 206 grams compared to almost 400 grams for a 3s1p3300.
My MD 2505-2800 motor 2800kv runs at 14.6 volts under load at about 730 watts and 48amps.
Running the same motor with 3s gives me 32amps at 11v and 350 watts.

Not saying your figures are wrong but unless you run a wattmeter its just a guess.
So if you look at voltsxkv there is a difference in rpm that translates to pitch speed
700 watts could be possible. I have a watt meter, but like I said I'm just running off memory. I'll test it during the week and give you the actual figures if you want.

Regarding your lipo weights, I clearly stated a 22004s vs a 30003s. A turnigy nano 3300 3s is 357g and the equivalent 4S 2200 is 295g. That's less than a 20% difference. So a 3000mah 10% smaller than the 3300 would be roughly the same weight.
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Old Nov 28, 2012, 08:55 PM
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Originally Posted by eckace1 View Post
Wow, if there's so little trust in this case I'll go take a pic of it and show you.

Actually I don't even have to. The HK specs completely agree with what I said: the 5.5x4.5 prop is for all intents very similar to a 6x4 but faster RPM. HK specs for that are 6x4 - 11.1V / 520W / 46.8A / 1.2kg thrust, which is along the lines of what I stated initially.

The current and wattage you draw at 3S is so much lower because you've obviously got a high-rpm prop that's not adapted to 3S.
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Old Nov 28, 2012, 09:15 PM
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Originally Posted by Znybar View Post
Wow, if there's so little trust in this case I'll go take a pic of it and show you.

Actually I don't even have to. The HK specs completely agree with what I said: the 5.5x4.5 prop is for all intents very similar to a 6x4 but faster RPM. HK specs for that are 6x4 - 11.1V / 520W / 46.8A / 1.2kg thrust, which is along the lines of what I stated initially.

The current and wattage you draw at 3S is so much lower because you've obviously got a high-rpm prop that's not adapted to 3S.
Ya a vid would be great a pic not so much.
Please tell me what prop I should use then. please be specific.
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Old Nov 28, 2012, 09:33 PM
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Well what prop are you currently using?

If ultimate speed is what you want you should stay 4S. If you want to use 3S you'll likely need a bigger prop to compensate for the lower voltage.

And seriously? Pic over a vid? What, I would photoshop one to lie about the wattage? That has to be a troll.
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Old Nov 29, 2012, 12:12 AM
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It's been some time since I flew a Skyfun so I had to go look up an old spreadsheet. I was flying with a Turnigy 2836 2350kv (which tested out a 2800kv) a 2200 40c lipo and a 6x4 prop. The wattmeter showed 50.3 amps and 744 watts. Never did get a radar gun on it.
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Old Nov 29, 2012, 06:38 AM
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Originally Posted by Rich in ILM View Post
It's been some time since I flew a Skyfun so I had to go look up an old spreadsheet. I was flying with a Turnigy 2836 2350kv (which tested out a 2800kv) a 2200 40c lipo and a 6x4 prop. The wattmeter showed 50.3 amps and 744 watts. Never did get a radar gun on it.
Been running the same 4s setup with a plush 60a esc on mine for about a year. Average high speed pass with a radar gun is 108-110mph. I do a lot of cruising around with 4-5 full speed passes and mange about 6-7 min flights. I chopped off the back third of the canopy to expose the esc to more airflow and now everything comes down cool to just warm. Hate messing with a good thing but I'm going to try a few props with a little more pitch. I've broken it into multiple pieces a few times while figuring out hand launches and getting to know her, but even with all the epoxy scars, it flies beautifully! I ordered another kit and the same motor after one of the crashes and guess what... They're still in the box. This thing is like the energizer bunny!

Norm
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Old Nov 29, 2012, 04:13 PM
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Originally Posted by Norm62 View Post


Been running the same 4s setup with a plush 60a esc on mine for about a year. Average high speed pass with a radar gun is 108-110mph. I do a lot of cruising around with 4-5 full speed passes and mange about 6-7 min flights. I chopped off the back third of the canopy to expose the esc to more airflow and now everything comes down cool to just warm. Hate messing with a good thing but I'm going to try a few props with a little more pitch. I've broken it into multiple pieces a few times while figuring out hand launches and getting to know her, but even with all the epoxy scars, it flies beautifully! I ordered another kit and the same motor after one of the crashes and guess what... They're still in the box. This thing is like the energizer bunny!

Norm
Amen to that, the number of times I've crashed and gone 'surely that's the last of it' only to have it fly just as well as before...
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Old Jan 01, 2013, 09:27 PM
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Marshall Islands, Enewetak Atoll
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Mounted an Eflight 80mm ducted fan on my Skyfun, maidened it today. Crashed bad.
Cause: I think the FY30a. Too much vibration. After perfect launch it kept wanting to flip onto its back. Then it would flip back upright again, hold that position for a second then flip over again.
Nosed into pavement. In the process of putting it back together.


Any experience with vibration induced FY-30a problems?
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