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Old Jun 03, 2015, 04:21 PM
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Big Glider motor option for 136" wingspan

If i had a 136" glider and have to swing a 18-20" folding prop which outrunner kv choice should i choose for 4s 3300?

Should it be around 700kv?

Im not gonna use a gearbox like a hacker b50 with 5:2:1

Im using direct drive. Going the cheaper route.

I just wanna throw in a 100amp esc a motor and 4s

Theres gotta be a direct drive option instead of a gearbox option
.

Thanks
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Old Jun 04, 2015, 06:43 AM
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Kv of 700 will be way too high for 4S and 18", let alone 20".
Assuming around 90-100A, rough ballpark is up to Kv of around 440 for a nominal 20x14 and 520 for an 18x12 - these estimates are based on Scorpion 4025.

That's a big prop and a lot of power for 136" - what's the model?
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Old Jun 04, 2015, 06:52 AM
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This would be tons of power for a 136" sailplane in the 50 oz. or so weight class
http://www.espritmodel.com/mvvs-40-4...ess-motor.aspx

I used this in a 3.6 metre (141") Pulsar. 136" isn't really big anyhow, more like middlin size.
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Old Jun 04, 2015, 08:03 AM
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I have a DragonFly Strong I just built which is 137 inches. I did a GliderDrive from HobbyKing 3858 4.6 1120kv. I used a 4s 3000 pack and it hauls the glider up with no issues. I used a 11x6 Graupner prop with a YEP 80 ESC. I also did a 3 meter Albatros from Top Model with the same setup and the Albatros goes vertical on that setup.

http://hobbyking.com/hobbyking/store...dProduct=71400

http://hobbyking.com/hobbyking/store...dProduct=36919

DragonFly thread:
http://www.rcgroups.com/forums/showt...ight=dragonfly

Albatros thread:
http://www.rcgroups.com/forums/showt...light=albatros
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Old Jun 04, 2015, 09:59 AM
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The Kv question is not the first item in the decision list.
First determine the approx. all up weight and from there calculate the Watts/lb for the performance you would like.

Check out my blog for more information on motor selection.

Iain
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Old Jun 04, 2015, 11:11 AM
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Quote:
Originally Posted by rev.iain View Post
The Kv question is not the first item in the decision list.
First determine the approx. all up weight and from there calculate the Watts/lb for the performance you would like.

Check out my blog for more information on motor selection.

Iain
Thats true watt for pound

Id have to see what the model weighs with electronics in her.
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Old Jun 04, 2015, 11:21 AM
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Quote:
Originally Posted by scirocco View Post
Kv of 700 will be way too high for 4S and 18", let alone 20".
Assuming around 90-100A, rough ballpark is up to Kv of around 440 for a nominal 20x14 and 520 for an 18x12 - these estimates are based on Scorpion 4025.

That's a big prop and a lot of power for 136" - what's the model?
Fvk graphite.

Yeah i figured 700 would be too much. 500ish would be the ticket for a big prop.

Maybe ill take the dragonflys setup and run it from there
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Old Jun 04, 2015, 11:37 AM
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Is there a reason for such a large prop? My DragonFly goes great on a smaller prop. My DragonFly weighs 4.48 without battery, with a 4S3000 it weighs 5.26lbs.

I have GliderDrives in many of my newer sailplanes with zero issues. The model I use also comes in a lower kv. Here is the 840kv version:

http://hobbyking.com/hobbyking/store...dProduct=48054
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Old Jun 04, 2015, 11:47 AM
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Quote:
Originally Posted by gquiring View Post
Is there a reason for such a large prop? My DragonFly goes great on a smaller prop. My DragonFly weighs 4.48 without battery, with a 4S3000 it weighs 5.26lbs.

I have GliderDrives in many of my newer sailplanes with zero issues. The model I use also comes in a lower kv. Here is the 840kv version:

http://hobbyking.com/hobbyking/store...dProduct=48054
Ehh well...the manufacturer fvk calls for a large prop via website. I know yours haul butt up to the moon.

I may do that with a smaller prop. Who knows we will see. Ive checked HK and the 840kv gliderdrive motor looks good!!
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Old Jun 04, 2015, 12:14 PM
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I run that motor (glider drive 850) on my Mystique, 2.9m plane. 148 prop and 4s. A little over 800 watts. Climbs to ALES height in 18-20 seconds. For a 35 dollars motor... I am 100% happy with its performance.
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Old Jun 04, 2015, 12:20 PM
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Thats what i ran on my mystique. It was all stock except for a 4s lipo.

She climbed good.
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Old Jun 05, 2015, 02:06 AM
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Ok clear the chalkboard.

Heres some parts ive found in the garage to make this 136" bird fly

Older 100amp esc german made
18x10 cam carbon prop not pictured
15x16 rfm slim
12x8 cam carbon

Just trying to get parts. Whatcha guys think on battery or that HK glider drive motor?

Maybe 4s 840kv and 15x16 RFM. <----might be way too much amps, 3s 3300 maybe
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Old Jun 13, 2015, 12:34 PM
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I think im gonna use this 840kv motor (MVVS 40 4.6/840)

It has ducted cooling fins and just is a great piece of art and craftsmanship

http://www.espritmodel.com/mvvs-40-4...ess-motor.aspx
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Old Jun 13, 2015, 12:46 PM
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I would like to heat from you about the difference between the Glider Drive and the MVVS motors if they are comparable in size and prop.
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Old Jun 13, 2015, 01:54 PM
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Quote:
Originally Posted by XtremeWingRC View Post
I think im gonna use this 840kv motor (MVVS 40 4.6/840)

It has ducted cooling fins and just is a great piece of art and craftsmanship

http://www.espritmodel.com/mvvs-40-4...ess-motor.aspx
You really do not need the cooling fins. This is a glider, not a powered plane, you are going to run the motor for about 30 seconds or so. Cooling is not necessary. You could buy 3 GliderDrives for 1 MVVS motor.
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