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› 10s vs 12s and flight times
06-03-2012 04:47 AM  6 years agoPost 1
love for scale

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Omaha, Nebraska U.S.A.

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i fly scale, no 3d or stick banging, or smack whatever the heck it is!!! on 600, 700 and larger vario heli's. i have read on forums that 12s provides longer flight times. i realize a lot more comes into play then just battery voltage. i fly low headspeeds, like 1350 to 1600 max. just curious for any comments or input. thanks for educating me! greg

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06-03-2012 04:58 AM  6 years agoPost 2
Band1086

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Kennewick, Wa. USA

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Yes, for the same wattage used, if you bump the voltage up 1/5th, the amps used should drop about the same amount. However, adding voltage, ie. more cells, may add slightly more weight than adding capacity, ie larger cells. Also, you must be able to gear properly, instead of just adding voltage to the ESC rather than letting that voltage actually get to the motor through gearing changes.

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06-03-2012 05:13 AM  6 years agoPost 3
love for scale

rrVeteran

Omaha, Nebraska U.S.A.

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11t and 12t are only slant gear options. But flying scale, and low HS maybe straight gears ok. I will run the demo mode and see!

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06-03-2012 05:25 AM  6 years agoPost 4
Band1086

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What KV is your motor?

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06-03-2012 06:04 AM  6 years agoPost 5
love for scale

rrVeteran

Omaha, Nebraska U.S.A.

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I have an align 700MX 470 kv, and a scorpion 4035-400kv that I coulds use, I think at the time of my post, I ran numbers on the 470kv with the 11s. But the 400kv on 12s ran about the same. What target of percent of full throttle at zero pitch should I be looking to get? With enough headroom, but not governing down to low?

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06-03-2012 02:42 PM  6 years agoPost 6
Band1086

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Kennewick, Wa. USA

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If you target about 15% headroom, your system should work well. The Align 470 with 11T pinion on 10S or the Scorp 400 with 12T pinion on 11S would be your best bets for 1350-1600 headspeed. Check out this HS calc for further info. I usually use it for "set RPM" gov modes, and it works very accurately for that.

http://www.myrclog.com/ecalc/

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06-03-2012 05:22 PM  6 years agoPost 7
Gregor99

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Western Wa

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i have read on forums that 12s provides longer flight times.
12s can be more efficient, but that alone is not what increases flight times. As an example, there some guys going from 12s to 6s and doubling their flight times.

How are they doing it? Lowering their headspeed, reducing the aggressiveness of their flying style and reducing the weight of the model. These factors have far more influence on flight times than cell count.

In the end, for a given headspeed, and flying style the model will consume a roughly fixed amount of watts. For example if hovering takes 100 watts, except for a slight increase in efficiency, doubling the cell count will not reduce the amount of watts required to hover.

Last year, I converted my 600 from 8s to 12s. With 8s on my slowest headspeed I was already getting 8 minutes. The reason I converted was for a little more power and so I could share the packs with my 500. To figure out what size packs I needed I made the chart below, which normalizes the power from each pack for direct comparison. This is done by converting 80% of the packs power into watt hours.

I had been using 8s 5000 packs which comes out to be 118wh. The same wh on 12s ends up with a pack size of 3300. I would have preferred to go down to 3000. But was unable to find suitable packs in that size.

The result: Because the of limited motor choices, I ended up with a higher wattage (and heavier) 12s motor than the 8s motor. Also to keep the same watt hours, the equivalent 6s packs (times two) ended up being heavier than the 8s packs they replaced.

In the end I added more weight and slightly reduced the desirable flight characteristics of the model. Also because of the shape of the new packs and motor placement on this particular model, vertical CG was slightly lowered reducing the models willingness to roll and flip on axis. Its not a huge difference, but not a change for the better. Of course power is now quite good. But my flying style is more as a collective manager a than power user.

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06-03-2012 06:13 PM  6 years agoPost 8
love for scale

rrVeteran

Omaha, Nebraska U.S.A.

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Thank you! I am doing a trex 700nitro, converted to electric, it will be going in a scale body, so I do not fly aggressive at all! But the fuselage will add some weight.

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06-27-2012 01:11 AM  6 years agoPost 9
love for scale

rrVeteran

Omaha, Nebraska U.S.A.

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Ran that ecalc, and actually pm'd the guy who made the ecalc, he quoted me like 41 percent headroom! Wow!

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