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PIPER L BIRD GRASSHOPPER

gangreen

Junior Member
#1
Piper.png

Hey guys,

I am building my first balsa plane(photo and specs in attachement) and i am new to choosing motors,props,Esc,batteries myself as i have always bought bnf or plug and play airplanes.
Could someone please help me find a good setup (electric) for this airplane ? Can be Hobbyking or another brand.

Thanks very much!
 

earthsciteach

Moderator
Moderator
#2
Choosing the proper power setup for an electric plane can be (and usually is) a bit confusing. I blame the inconsistent nomenclature and ratings used for brushless motors. If you live in the US, my first recommendation is contact headsuprc.com. Provide them with the above specs and they will give you a solid power system recommendation. I believe the contact email is headsuprc@yahoo.com.

Based on the info above, I think this motor will work:
http://www.hobbyking.com/hobbyking/store/__19025__Turnigy_G32_Brushless_Outrunner_600kv_.html

I'd go with a 70 amp esc:
http://www.hobbyking.com/hobbyking/..._70amp_OPTO_ESC_with_5_Amp_External_UBEC.html

And 13x4 prop.

But, I have no idea about the ground clearance of the prop with this plane, so it may be too big in diameter. Hopefully, others will weigh in on this thread with their own thoughts.
 

Ak Flyer

Fly the wings off
Mentor
#3
1850mm converts to 72". I think you would be cutting it close with a 13" prop. I have a 76.5" cub and 6" foam wheels on it and I run a 12" prop. With the stock wheels it's a bit closer but I also fly in an unimproved area with big rocks and sticks etc. If you have a nice field you should be good. That same cub uses a .46 nitro engine and it's got good power. I would say find a motor that's about the equivalent of a .46 nitro. I think that a .30 would be too small unless you build it light and are going for slow scale type flying.


I think this one on 5 cell would work beautifully. On 4 cell you'd need a bigger prop but it would actually pull harder. Depending on your weight, clearance and desired flight characteristics you may be better off with 4 cell.
http://www.hobbyking.com/hobbyking/...y_G46_Brushless_Outrunner_550kv_46_Glow_.html

A 60 amp plush would work well.
http://www.hobbyking.com/hobbyking/store/__2166__TURNIGY_Plush_60amp_Speed_Controller.html

These master airscrew props have a nice scale look but you can't beat the way an APC prop pulls.
http://www.hobbyking.com/hobbyking/store/__8073__Master_Airscrew_propeller_15x8.html
HTML:
 
Last edited:
#7
Note the description.....although I personally think you could drop kv a bit and bump on up to a 4s lipo.....perhaps bit lengthier flight times.

 

earthsciteach

Moderator
Moderator
#8
Also, this question reminded me of how much I still need to learn in the world of electric motors. It took me a good while to come up with the combo I suggested, and I still didn't have a lot of confidence in it. So, for that, Thanks. It made me dig around a bit and was helpful for me, as well!
 
#9
Actually I am sorta surprised it is flying as well as it is on 3s in the vid.....I would have for sure thought this would be a 4s hands down.
 

Ak Flyer

Fly the wings off
Mentor
#10
Here's the thing with that. You could fly that plane on a 1S, but it would take a lot more amperage and your KV would be a lot higher. The difference between flying it on 3S and say 5S is the amount of amperage you have to pull to make it work. Because the higher cell count has more voltage, the amperage draw is less to do the same work. The inverse is true as well. If you lower the voltage, it takes more amperage to do the work.

Since KV is revolutions per minute per volt, a 1000 kv motor at 3S or 11.1 spins 11,100 rpm at full throttle.
That same motor on 4S or 14.8 volts would spin at 14,800 rpm at full throttle.

To prevent over speeding the prop, you need to lower the kv accordingly which is why you always see larger motors have lower and lower kv based on the higher voltages they are supposed to be matched with. This all keeps from running ridiculously huge esc's with massive amp draw, heat, and battery sizes.

Looks like the guy in the video has a successful setup. You could go with that. Personally if it were mine I would stick with a 4S or possibly a 5S setup with a smaller esc. Actually the esc I recommended was a 60 amp because it's oversized for safety. The setup I had called for a 50 amp but it's better to run one a bit larger than required.
 
#11
Thanks again you all for taking the time to help me! Really appreciate your help.

I'm still waiting for the plane to be delivered to me (US to Belgium).Ill post some pics when its build and ready to fly.

Take care