hi
I'm new to rc and learning to fly my first model- pelikan piper cub with axi 2212/26 and 1900 lipo. before i started flying i practiced every simulator and could fly every model including taking of and landing.
my problem is with taking of the real thing...
after a short run full throtle i pull the stick gently. only for a couple of time i managed to take the plane in to the air and then had no problem flying and landing.
the problem is that MOST OF THE TIME as the plane leaves the ground it is rolling to one side and falling on the back
what am i doing wrong?
not enough speed?

If it's rolling onto its back and not always to the same side it's most likely a snap that is being caused by not getting enough airspeed before taking off and/or pulling back too much to take off. Gently does it!.

Take a look at the balance (both fore and aft and lateral), make sure the balance is where it says in the plans and that it is neutrally balanced 'sideways'.

If the balance is OK, wait a little more when taking off, to get more airspeed and/or be a little more gentle when pulling back on the stick.

Other than that, it could be a warped wing or an alignment problem with the tail. Look at the model from the front and see if there are any obvious mis-alignments.

Hope that helped!

-David C.

Sounds like you are trying to take the plane into the air too soon. Let it build up more speed first and climb at a very shallow angle. Get good at that, then you can start to push the shorter landings.