Simple Cub not flying

Foamforce

Elite member
Thank you I will try them and report next week
Good luck!

Also, since a couple of us suspect the prop, can you take a few very close up shots of the prop, both from the front and side? With good lighting, well enough so that we can read the writing on it.
 

Piotrsko

Master member
Since it runs flat until you get some speed I now suspect one wing panel isn't set the same as the other probably the right one has gotten a warp, leading edge high at the tip or the left one has leading edge low. It's definately rolling left at speed as opposed to turning left. It's accelerating straight pretty well so backwards prop or not, thrust isn't the issue. Crooked wing to fuselage alignment just causes odd loops and slow turns towards the retreating side. Doesn't look to be tip stalling, it just a nice fast roll to the left at flying speed. You could attempt a flight at full right aileron trim to see if that changes anything but check alignment first.
 

MasterEpic

New member
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MasterEpic

New member
Since it runs flat until you get some speed I now suspect one wing panel isn't set the same as the other probably the right one has gotten a warp, leading edge high at the tip or the left one has leading edge low. It's definately rolling left at speed as opposed to turning left. It's accelerating straight pretty well so backwards prop or not, thrust isn't the issue. Crooked wing to fuselage alignment just causes odd loops and slow turns towards the retreating side. Doesn't look to be tip stalling, it just a nice fast roll to the left at flying speed. You could attempt a flight at full right aileron trim to see if that changes anything but check alignment first.
Yeah one wing is slightly higher than the other, how would you fix that
 

MasterEpic

New member
That was just lifting up too soon and stalling. You need a lot more speed and pull up more gradually. You absolutely should not have to push it like that. You have a thrust problem. Try the other steps outlined above.
Would buying a 9 by 5 prop fix the problem?
 

Foamforce

Elite member
Would buying a 9 by 5 prop fix the problem?

That prop looks just fine and the direction is correct. With your 1400kv motor that should provide adequate thrust. Just to double check though, hold the plane nose up and go full throttle. It should be almost able to lift out of your hand.
 

skymaster

Elite member
Did you calibrate your ESC. and make sure your motor bell is not loose. make sure the screw is grabing on to the shaft.
 

chrisvdv

Active member
Adding a shim (piece of balsa, foam or cardboard) between the lower side of the wing and the fuselage until you get even height on both sides.
 

Piotrsko

Master member
Yeah one wing is slightly higher than the other, how would you fix that
If you can, put the wing on a table or the floor with one panel touching the flat surface. If it points up at the front on the tip, that panel has an upward twist. if the back part of the wing points up at the tip it is a downward twist Repeat with other panel. End result is they should either have the same amount exactly of upward twist or none at all. You don't want any downward twist right now. Gently slightly bending the panel in the correct direction, some times with the aid of a steam kettle or slightly overbending and application of tape or paint. Won't be perfect and if you get carried away and crease the wing just put a layer of packing tape both sides on it so it's flat. Doesn't have to be 100% perfect, THAT is what you use trim for

Worse case is make a new wing that's flat.

Did you try full right aileron trim?
 
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kdobson83

Well-known member
That video of it trying to take off without you pushing it looks like you are having a thrust issue. That 8040 prop your using with that motor could be your issue. Do you have any other props you can try? Preferably any SF (slow fly) props? My simple cub using a 2212 motor with a 8045 SF prop had plenty of power to take off but lacked power with my parachute guy hanging underneath. I would 100% try a better prop if you have one. 8045 SF or maybe go with a 9045 but increasing the size also increases your amps.
 

MasterEpic

New member
I have fixed the wing and I will try today the plane and I did FoamForce's advice and it has enough power at half throttle to support its own weight
 

quorneng

Master member
MasterEpic
If your plane really has enough thrust to support its weight, especially at a reduced throttle, then you will not need to push your plane for ground take off. It would accelerate like a sports car all by itself!
So either nothing like full power was actually being used or it really doesn't such a level of thrust.
An SF prop may produce a bit more thrust but the 9x6 you are using should be quite adequate.
At full power it should be quite a handful to just hold the plane.