HELP - Nano Flerken - Just Nose Dives! :_(

[craigan]

Hello - I need some help please

Below is a picture of the Nano Flerken my son built. This is his first build. As you can see it's taken a few nose-dives and the nose is crushed.

We have tripple-checked everything, and all seems to be fine. However, each time we launch it, it goes about 6 feet (from being tossed/launched) and then just nose-dives into the ground.

What could be causing this?

Thank you in advance for your help!!

 

[CappyAmeric]

What battery (size) and what motor? Also where are you determining the CG?

The Nano Flerken flies great- but only within a narrow CG band. It is very pitch/CG sensitive. Normally, however it tends to be tail heavy, so diving seems suspicious. Could be any of the following or combination:

1. Out of CG with too heavy a battery
2. Bad thrust angle on the motor
3. Incorrect configuration of the elevons

 

[craigan]

What battery (size) and what motor? Also where are you determining the CG?

The Nano Flerken flies great- but only within a narrow CG band. It is very pitch/CG sensitive. Normally, however it tends to be tail heavy, so diving seems suspicious. Could be any of the following or combination:

1. Out of CG with too heavy a battery
2. Bad thrust angle on the motor
3. Incorrect configuration of the elevons

Battery: Tattu 800mAh 7.4V 45C 2S1P Lipo
Motor: Gremlin 1304 5500kv
CG: the two triangle support pieces on the front of the wings (as shown in FT's build video)

Attached is a picture of where the battery was mounted (also as shown in FT's build video)
It was hard to get a picture of the motor angle, but here's the best I could do. I'd say the top of the motor is tilted slightly forward. (They called it upward in the build video.)

 

[CappyAmeric]

All of those look normal and that is the correct place to balance.

Personally, I think 2s is a little on the weak side. All the Flerkens need lots of speed to fly stable. I run a 1606 motor on 4s on mine. I have tried many different variants, and I discovered it wants power and a nose down CG.

 

[HVB79]

Do you have the correct amount of up reflex in the control surfaces?
See:

Try a power off glide test. With the receiver plugged in and the throttle cut on, stand 6 feet apart and try to glide the plane to each other. Adjust the trim until you can glide the plane back and forth.

 

[craigan]

Do you have the correct amount of up reflex in the control surfaces?
See:

Try a power off glide test. With the receiver plugged in and the throttle cut on, stand 6 feet apart and try to glide the plane to each other. Adjust the trim until you can glide the plane back and forth.

Thanks for your reply, but my post is for the Nano Flerken, not the regular Flerken. Does that make a difference to your reply? Because if we tried to toss it to each other, it would just nose dive, the Nano is very nose heavy.

 

[HVB79]

Nose heavy = center of gravity (CG) is in front of the specified point in the plans.
If the plane is nose heavy you need to move the battery back to fix the CG.

If the CG is correct, but the plane still pitches down, the plane is not nose heavy. Instead the plane is pitching down because it is out of trim. You need increase the up reflex by trimming the elevator.

 

[skymaster]

i think since you made it smaller the cg goes back a little more. and you need speed to get a stable flight there is less control surface. you will not be able to fly slow with a mini

 

[CappyAmeric]

Battery: Tattu 800mAh 7.4V 45C 2S1P Lipo
Motor: Gremlin 1304 5500kv
CG: the two triangle support pieces on the front of the wings (as shown in FT's build video)

Attached is a picture of where the battery was mounted (also as shown in FT's build video)
It was hard to get a picture of the motor angle, but here's the best I could do. I'd say the top of the motor is tilted slightly forward. (They called it upward in the build video.)

View attachment 229853
View attachment 229854

Another thing of note. I just noticed you have an Aura on it. MAKE SURE that the Aura is correctly oriented and It is moving the controls correctly. Either that, or turn it OFF to figure out what is going on - it is likely just causing confusion.

 

[craigan]

i think since you made it smaller the cg goes back a little more. and you need speed to get a stable flight there is less control surface. you will not be able to fly slow with a mini

Well.... thing is.... he followed the FT Nano Flerken build video to a "T" - with no doubt. And, after having these issues, we have gone back and tripple-checked things such as this, and confirmed it seems to be built right. Also, it was built with the battery and motor that FT recommends and that FT has as the option choices when buying the Nano Flerken. So this is just perplexing.

 

[HVB79]

It is one of four things.
Work though this list point by point in order and you will find your problem:

1. The control surfaces are moving in the wrong direction with elevator input
2. The Center Of Gravity is wrong (to far forward)
3. The control surfaces are not trimmed correctly
4. The Aura board is setup incorrectly causing the control surfaces to be:
   1. trimmed wrong
   2. move in the wrong direction with elevator input
   3. correcting in the wrong direction without elevator input

 

[craigan]

Another thing of note. I just noticed you have an Aura on it. MAKE SURE that the Aura is correctly oriented and It is moving the controls correctly. Either that, or turn it OFF to figure out what is going on - it is likely just causing confusion.

How does one verify that the Aura is correctly oriented?

 

[CappyAmeric]

How does one verify that the Aura is correctly oriented?

The best way is to put the battery in, then move your Flerken left, right, nose up, nose down, and see how the Aura moves the control surfaces in response.