FT Simple Cub not flying

[tartiflette]

Hi, I recently built a simple cub and it doesn't fly. I think it's because of the motor. It is equipped with a 2200 kv A2212 motor with a 6035 propeller. Is that the problem or it can come from something else and if so what should I put instead?

 

[luvmy40]

Can you elaborate? When you say "it doesn't fly" what exactly do you mean? What radio are you using? Have you set the RXs up correctly? Have you set the throws? Etc.

 

[tartiflette]

Can you elaborate? When you say "it doesn't fly" what exactly do you mean? What radio are you using? Have you set the RXs up correctly? Have you set the throws? Etc.

When I throw it by hand it directly stall. I'm using a FS-I6 with FS-I6a and everything is correctly set up

 

[luvmy40]

I'd say you are under powered. FT recommends 2212, 1050kv and 9x4.5 prop for the Cub. I'm running a 2212 1000kv and 9x4.5 on mine. While I cannot say it flies great(my lack of skill and stick time), it definitely does not stall on launch. The plane design does tend to tip stall at low speed.

 

[Hondo76251]

Have you tried taking off from the ground? Sometimes its hard to get enough speed on a hand throw, particularly when trying to do it by yourself. That can be even worse if the plane is under powered, though i dont think yours should be unflyably under powered with that setup.

 

[tartiflette]

I'd say you are under powered. FT recommends 2212, 1050kv and 9x4.5 prop for the Cub. I'm running a 2212 1000kv and 9x4.5 on mine. While I cannot say it flies great(my lack of skill and stick time), it definitely does not stall on launch. The plane design does tend to tip stall at low speed.

Do you think a 1000kv with a 10x6 prop will work ?

 

[tartiflette]

Have you tried taking off from the ground? Sometimes its hard to get enough speed on a hand throw, particularly when trying to do it by yourself. That can be even worse if the plane is under powered, though i dont think yours should be unflyably under powered with that setup.

I don't have a landing I used to have a 3D printed one but I don't use it anymore because it was to hard to take-off on the ground

 

[luvmy40]

I'm definitely not the guy to ask about motor/prop selection. I just go with the designer recommendations and haven't had any serious issues with them in my limited experience.

 

[Hondo76251]

Ive got an 1808 2400 that runs a 6x4 just fine on a tiny trainer. Id think you should be able to get in the air with that setup. Hows the CG?

 

[tartiflette]

Ive got an 1808 2400 that runs a 6x4 just fine on a tiny trainer. Id think you should be able to get in the air with that setup. Hows the CG?

A bit tail heavy. I used to have a 2200 kv with 6x3.5 on my tiny trainer and it was perfect but the tiny trainer and the simple cub are two different plane

 

[Hondo76251]

A2212 2200kv should pull 732 grams with the 6x3 prop on 3s

Are you running 3 s?

 

[tartiflette]

Yes I'm on 3S

 

[luvmy40]

Yes I'm on 3S

Maybe a stupid question but, did you calibrate your ESC and/or make sure your connections are solid? You may not be at the throttle position you think you are.

 

[Aslansmonkey]

The FT Simple Cub is a larger plane than the Tiny Trainer and they should not be compared for motor selection. There's a reason the Tiny Trainer is in the "Mighty Mini" section and the Simple Cub is in the "Swappable" section. ALL the Mighty Minis fly on smaller higher KV motors with 6" or smaller props. Everything in "Swappable" flies on larger, lower KV motors with 8 to 10" props.

If you don't want to buy the B or C (proper sized motors) from Flite Test, buy something in the 22xx/1000kv size range like this (which is between the Flite Test B and C size)...

https://www.amazon.com/gp/product/B0799HRLGZ/?tag=lstir-20

For brushless motors, the first 4 digit number can be broken into two parts **## where the ** denotes the stator width and the ## denotes the stator height (so the linked example as a 22mm wide by 16mm high stator). So larger numbers mean bigger motors which equates to more torque and more current draw.

The "KV" number roughly equates to the motor speed per "S" (cell count) of your battery. So the linked motor, at 1120kv, would rotate at about 3360 rpm (unloaded) on a 3s battery.

To swing a bigger prop, you need a bigger motor, and generally these also spin slower.

There's more to it than this, of course, and I am by no means an expert in it all. But I do know the linked motor should be sufficient to fly the Simple Cub on a 9" prop.

The motor you are using, with a 6" prop, is NOT sufficient.

 

[Hondo76251]

@Aslansmonkey I beg to differ. I do agree that the motor is not ideal but it should not be 100% unflyable. I really dont think thats the problem hes having IMHO.

As far as motor recommendations, you pretty much have to check the specs on the motor.

These 2212s for example will make even less power with 930kv and 10x6 prop, although it would be very efficient. According to this sheet, that motors sweet spot is 1400 and 9x5 prop at 910 grams of thrust but that is still only 180 grams of thrust more than he has now, about 25%. A 25% decrease in power is not enough to be unflyable.



Just dont want to send the poor fella to get another motor if that is not 100% the problem...

 

[Aslansmonkey]

@Aslansmonkey I beg to differ. I do agree that the motor is not ideal but it should not be 100% unflyable. I really dont think thats the problem hes having IMHO.

As far as motor recommendations, you pretty much have to check the specs on the motor.

These 2212s for example will make even less power with 930kv and 10x6 prop, although it would be very efficient. According to this sheet, that motors sweet spot is 1400 and 9x5 prop at 910 grams of thrust but that is still only 180 grams of thrust more than he has now, about 25%. A 25% decrease in power is not enough to be unflyable.

View attachment 223994

Just dont want to send the poor fella to get another motor if that is not 100% the problem...

As I said, I'm am by no means an expert, but 25% more thrust can make all the difference in the world if 100% at your current set up is just under what's needed. He's flying the 2212 on a 6" prop. He could try a 9" prop on this motor to see if that helps. If so, I'd be checking the motor to see if it gets too hot from swinging that bigger prop. But the 2212 2200kv motor he's using is NOT the recommended motor for this plane.

Mathematically, however, the loaded Simple Cub (battery, electronics, etc) likely is under the 1000g max weight on the chart so maybe. If the OP has a 9" prop, it's surely worth the try.

The Simple Cub, I'll add, isn't the best flyer. I've had several and it was the plane I had my first successful flights on, but there are easier birds to fly. If cost is the factor, he might be better off building the Mini Trainer, which will fly fine on the motor he's using, and you can still google and find the plans. Two sheets of dollar tree foam board is cheaper than a new motor OR a 9" prop.

 

[Ligbaer]

You need a bigger prop as the motor you are using is what ft recomends

 

[Ligbaer]

The Simple Cub, I'll add, isn't the best flyer. I've had several and it was the plane I had my first successful flights on, but there are easier birds to fly. If cost is the factor, he might be better off building the Mini Trainer, which will fly fine on the motor he's using, and you can still google and find the plans. Two sheets of dollar tree foam board is cheaper than a new motor OR a 9" prop.

the motor that is being used is ppc the tiny trainer would be really nose heavy. i think a storch would be better

 

[Piotrsko]

Back to the original issue: if it is balanced properly and everything is set neutral, it will glide and not stall no matter what size motor is used assuming it was thrown fast enough ( stalled, yup thrown fast enough) One heck of a glide if it's a tiny motor but it still shouldn't stall, ever. Notice the key word stall? Says cg is too far aft or too much up trim/ incidence... if it won't climb, then yeah the motor is too small but it still shouldnt stall.

 

[tartiflette]

Thanks for all your answers. I think I'm going to put a 1000kv with a 10x6 prop do you think this should work ?