J3 Cub Old Timer from hobby king doesnt want to fly.

[Dude]

Hi to all

I recently bought the J3 cub old timer from hobby king and I was very excited. It was an easy build, but when trying to fly it, the plane always tended to nose dive into the ground or it just went crazy in the air. I adjusted the elevator for max throw but not even like that it flew. I ended up crashing it and very disappointed and frustrated. It is still repairable but I want to be sure next time it will at least try to fly. Any recommendations??


Thanks in advance and happy flying!!

This is the link to the aircraft:
http://www.hobbyking.com/hobbyking/store/__12971__J3_Cub_EP_Old_Timer_ARF_.html


Spec I had set it up with:
1300 kv bell motor
18amp esc
1000mah 25c battery
2*9g servos

 

[earthsciteach]

Did you verify that the CG was correct? Did you make sure the controls were operating properly (not reversed)?

 

[Fishbonez]

Definitly sounds like the CG is off and if your contols are not reversed maybe overcorrection. Are you flying upwind?

 

[Dude]

Yes the Controls were ok and the cg was about 30% from the edge of the wing.

 

[Fishbonez]

Yes the Controls were ok and the cg was about 30% from the edge of the wing.

I assume you mean the leading edge of the wind. Have you tried to balance it with 2 fingers at the CG point?

 

[Dude]

Yes upwind and downwind hahaha I tried it all hahaha.

 

[Fishbonez]

Hmm she is a small plane how much wind?

 

[Dude]

yes, leading edge.

 

[Dude]

It was a bit windy but I would assume it was about 10 - 15 mph at certain point

 

[Fishbonez]

Well INMHO that was too much wind for such a small plane. FIx her up and wait for a calmer day. Is this your first plane?

 

[teflyer]

Did you check if it is laterally balanced? What angle of attack did you take off at?

 

[FlyingMonkey]

Where do you live? Maybe there's a forum member that lives close by that can help you out.

 

[Dude]

yes but i have done some scratch build previously.

 

[Fishbonez]

After posting I learned that you fly Helis so I guess without some more detail I am not sure how we can help you. However possibly muscle memory kicked in and maybe you flew it like a heli? Just a shot in the dark

 

[pgerts]

..the plane always tended to nose dive into the ground or it just went crazy in the air. I adjusted the elevator for max throw but not even like that it flew. I ended up crashing it and very disappointed and frustrated. ..Any recommendations??

This is exactly what to expect from an oldtime CUB with max throw. You are definitive not alone to have experienced this.
The CUB needs enough speed and small throws. Get it gently up to hight against the wind before any turns.
Try to move the CG from your 30% to 25% from the leading edge to make the plane a little more gentle to fly but the CUB is still a plane you need to be careful with.
Other CUB "look alike" planes like EasyCub and FunCub are much more easy to fly.

 

[lobstermash]

I've got (or should I say my wife has) an Old Timer, and it's a beauty. I did find, though, that the plane wasn't anywhere near balanced with a 1000mAh 3s battery, so I managed to squeeze a 1600 3s right up into the nose. The CG came out at about the front wing spar with this setup, which seems to be at the back edge of balance. I've got a fair bit of down trim programmed in, although I wouldn't need it if I wasn't lazy and built a little downthrust into the motor mount.

I don't find that mine (or should I say hers...) needs much speed to fly well. It doesn't get blown around too badly, but I wouldn't take it out in more than about 20kph winds. One little trick to this one is making sure the struts are in properly. Occasionally in transport the hooks can push too far through and make the dihedral unbalanced.

I hope you have some success with this plane, as it's a gem, especially for the price.