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Dec 13, 2017, 07:19 AM
Never too old to learn
Discussion

Motor/Esc for bipe


Hey guys:
I am converting a Northeast Aerodynamics Belair 60. I was running a Saito 72 on it with a 13x6 prop.
Now I have a Power Up 46 620 kv motor with a Hitec 60 Amp ESC .
AUW should be close to 7 lbs.
962 sq inch wing area 52x9.25x2.
Specs with a 14x7 E prop on 4s 55C are:
112 oz of thrust
47 Amp draw
740 watts.

Should fly it, right?

Tom
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Dec 13, 2017, 11:19 AM
A man with too many toys
7 lb and 962 sq" may be a bit much for a 46 size electric motor with a 4s LiPo. It will fly OK as a easy flyer but it won't have the power for those fantastic aerobatics that biplanes are famous for.

If it were my airplane I would use a 60-80 size electric motor, 100 amp ESC, 16" prop and a 6s 4000/5000 LiPo.


.
Dec 13, 2017, 02:18 PM
Registered User
scirocco's Avatar
At 300g, the motor is big enough to handle that power and more - up to 1000W should be pretty comfortable.

The problem I see with your proposed setup is not thrust, but pitch speed. I'd suggest using a 14x10 instead. That will give you a lot more excess thrust available at comfortable flying speed. and should load the motor about the same (ie 800W) as the 15x8 in the Powerup prop test sheet.

At 7lb, lots of wing area and that sort of power I reckon it will fly pretty well. Assuming you get about 10000rpm with the Saito/13x6 - the 4S 14x10 should have about the same thrust and speed.
Dec 14, 2017, 07:13 AM
Never too old to learn
Thanks guys.
WOW..two different views.
RCMan..I see where your coming from but I have no need to burn holes in the sky with this plane..I have an extra and a skybolt for that.

Scirocco..The Power up 46 sure has a wide prop range which will give me some flexibility with a 4s pack. I'll pick up a 14x8 and a 14x10 prop. I already have a 15x8.
I'll have my watt meter attached to compare the props.

Thanks to you both

Tom
Dec 14, 2017, 07:47 PM
Laughs at un-boxing videos...
basicguy's Avatar
I have 80" cub that flies on 405 gram 510kv trex motor. With a 17x8 prop on 4s it maxes at 50 amps.

It flies like this.
RC Cub (2 min 41 sec)


Everyone says it is too big but it fairly easy on batteries and has good power. The motor is rated at 90 amps. Got it used. I have put in a new 8mm shaft and bearings.
Dec 15, 2017, 09:28 AM
Never too old to learn
Basicguy..........good flight........land often?
Dec 15, 2017, 09:39 AM
Laughs at un-boxing videos...
basicguy's Avatar
Yeah it manages to land every time.
Dec 18, 2017, 03:50 PM
Never too old to learn
Quote:
Originally Posted by basicguy
Yeah it manages to land every time.
One way or another...lol
Dec 18, 2017, 04:16 PM
Laughs at un-boxing videos...
basicguy's Avatar
At any rate it gives you a data point for powering your stork. No sense in flying it with too little motor or have to buzz the motor to high rpm and too little prop. I keep the battery in the cockpit area under the CG to make the size fairly irrelevant, Smaller battery shorter flights, larger battery longer flights.
Dec 18, 2017, 04:27 PM
Never too old to learn
I flew the Belair today with the Power up 46 on with a 14x7 prop. I had 930+ watts at 59 amps. It flew ok but at about 80% throttle. I'm thinking a 13x8 prop may be a better choice.
On a 4s 6000 mah pack I was at 3.8 volts after a 5 minute flight.
I'll need to experiment with props.

Tom
Dec 19, 2017, 03:39 PM
I just want to go fly!
walter3rd's Avatar
Iím planning on rimfire 80 on 6s batts for my current build. A bit heavier than yours but I think itís a good combo based on others comments.
Dec 19, 2017, 08:24 PM
Registered User
scirocco's Avatar
Quote:
Originally Posted by iflircaircraft
I flew the Belair today with the Power up 46 on with a 14x7 prop. I had 930+ watts at 59 amps. It flew ok but at about 80% throttle. I'm thinking a 13x8 prop may be a better choice.
On a 4s 6000 mah pack I was at 3.8 volts after a 5 minute flight.
I'll need to experiment with props.

Tom
A lot more current than suggested by the Heads Up test data.

But anyway, more pitch! You're seeing the symptom of pitch speed too close to stall speed.

620 rpm/V on 4s is just too low max rpm to work nicely for a sports model with anything under 8" pitch.

While you should see an improvement with 13x8, 13x10 should only load the motor a fraction more than 14x7 and will give you the pitch speed margin above minimum flying speed for comfortable part throttle performance.

For aerobatic models flying with about the same max rpm (6s, ~ 400 rpm/V) I find 10-12" pitch comfortable. I'd only come down to 7" or below on 4s with Kv at least 750 rpm, and that's for a lightly loaded Cub
Dec 19, 2017, 10:59 PM
Laughs at un-boxing videos...
basicguy's Avatar
Regarding the cub statement
My cub has about 1000 sq in of wing and weighs about 8 pounds. The motor is drawing 50 amps at full throttle. I fly it in circles will fly fine at half throttle. But what the fun is that. The helicopter motor is capable of continuous 90 amps on 10s as it has a built in fan. I am barely idling it at 25% of the rated power. Here it is:


I fly all my planes about the same. Have a small home field and like them to climb well. Initially before I flew it thought it might need a 6s battery but am fine with it as is. I have lflown it with props from 16x8 to 17x10 but it doesn't seem to make any difference as I am usually not at full throttle. Have zero desire to put fine details or a doll in the plane. I am flying it from the ground
Dec 20, 2017, 05:47 PM
Never too old to learn
Scirocco, maybe a 60 class 400kv motor on 6s would be a better option?

Tom
Dec 20, 2017, 07:30 PM
Laughs at un-boxing videos...
basicguy's Avatar
How is the balance with the motor you have?

Nice thing about electric that should not be overlooked is that if you have a 300 gram motor pulling 65 amps it will not put out the thrust that a 400 gram motor at the same current.

Are you limited to a 14" prop because of current landing gear?


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