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Spitfire doesn't feel like flying...

#1
Hi everyone!

This is my first post on this forum, so if I had to post this thread in another forum, please let me know!

Now, I've been into rc-flying for about 2 years now, but only during the summer holidays, as the weather in Belgium isn't RC-friendly during the rest of the year :rolleyes:

Last winter I discovered Flite Test, and immediately, I was sold to the amusing videos... :D

So, this year, I wanted to build the FT Spitfire, my first non-profile airplane!

As exited as I was, I build this airplane in 1 day (normally I need several days as I quickly lose my concentration :eek: )
So, after building the spitfire with a detachable wing, I went to the field behind my house and tossed it into the air...

BUT:

The airplane just rolled to the left and crashed into the ground, braking a propeller (my first time I brake a propeller) and the fuselage, at the point where the rubberbands hold onto the front bbq-skewer.

dispirited as I was, I left the broken airplane in my basement for about a week...

But, as an aerospace engineer at the TU Delft, I just couldn't leave a broken airplane lying around!
So I began repairing the fuselage, and put another prop on the power pod, and tried to fly it again.
And it all happened all over again.
The airplane just looks like it wants to torque roll to the left, and then crashes into the ground (softer ground this tiem, so it isn't broken anymore!).

This has been more than 2 weeks ago now, I again, I just want this plane to fly like they do amazingly in the videos.

So, is there anyone who can help me with this problem?

My powerpod:
Emax GT 2812/05 1840kv
1800mAh 3-cell
50A Emax ESC

the first time I used a 8x6 prop, so I though this was the cause of the torque roll...
the second time, I used a 7x6 prop, but the airplane seemed a bit underpowered, beside the torque toll-thing.

I really want to fly this siptfire, so if there's anyone out there who can help me... :(
 

earthsciteach

Moderator
Moderator
#2
That seems like a big motor for that plane, producing 1400 grams of thrust with an 8x4 prop. And, with a mass of 105 g, I bet it does torque the plane around. Are you launching at full throttle? Perhaps launching at 1/2 to 3/4 throttle would help.

Here are a couple of other thoughts:
1. Are your control surface moving in the correct directions?
2. Is the cg correct?
3. Is the wing warped?

Good luck and welcome to the forum!!!
 

colorex

Rotor Riot!
Mentor
#3
Have you checked the CG between the nose and the tail? There might be more weight on one side of the wing.

Also have you tried trimming it? Will it respond to control?
 
#4
@earthsciteach: I though the plane would need a motor like that, as the suggested prop is a 8x4...

And, I'm launching the plane at 1/4-1/2 throttle, and it still rolls to the left...
I also checked CG, CS direction and throws, wing looks good.

@colorex: I also checked the CG in that direction after the first crash, and trimming won't help...


I'll make a powerpod for my other motor (don't know the specs), but I think that motor won't have enough power...

Anyway, thanks for the quick replies!!!
(and sorry for any mistakes concerning language, but my english isn't perfect yet :D )
 
#6
this is the other motor I have (yeah, Emax is nearly the only brand my locas hobby shop sells).
With a recommended 7x4 prop, it looks a bit to small for the spitfire...
 

earthsciteach

Moderator
Moderator
#9
I think you will find that motor does pretty well with the spitfire. I have flown my combat wings with the 2812 and 7x6 props. They move along pretty well.
 

earthsciteach

Moderator
Moderator
#11
The max recommended prop is a 7x6. You could probably get away with an 8x6 if you are very careful with the throttle, but that is pushing your luck.
 

xuzme720

Dedicated foam bender
Mentor
#12
Have you thought about a little flatter pitch on the prop? Like an 8x4...Seems like it would be less susceptible to torque effect, at least until you get some fight time on it. Then go for the hot combo.
 

xuzme720

Dedicated foam bender
Mentor
#14
I would think so, but it's always best to check. Hold the plane firmly in your hand vertically while you throttle up. The plane should start to feel a little light at around half to 3/4 throttle. If it's trying to lift your hand up, then you really have too much thrust for anything but 3D or a speed demon. You'd be surprised how little thrust you can get away with on some airframes. I know some guys will say you can never have too much power, but there are times you really can have too much...
 
#15
..., but there are times you really can have too much...
I rahter like a 1:1 weight/thrust ratio, it's fun to fly like that :p but I'll check if that would solve the problem ;)


Now, when I was testing my new powerpod with the smaller motor on it, I encountered another problem:
Something's broken :p

When I plug my hobbyking SS 25-30A into my Spektrum AR6115e reciever, the motor makes the startup sound, and then keeps beeping rapidly.
However, when I connect it to a reciever which isn't binded, it keeps beeping slowly, as if it's waiting to be binded.
I'd think that, when the ESC is burned, I would smell it or the motor would beep anyway, binded or not.

As the motor and battery looks fine, it looks like it has to be the reciever causing the problem.

I remember I was playing around with some cheap servos last year, and burning some of them due to connecting them the wrong way.
Is it possible I burned the recievers? recieverS as my spare reciever won't work too... (I'll try the third one tomorrow)

Update: I tried my 3th reciever, a AR6210, which works. So I'm going back to my LHS and see if they can help me with the other 2...
 
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