Hi guys,
Thanks Downunder,
and thankyou George,
I've been out of touch for some days ,
my plane weights around 13.5 oz and the engine runs well - about 12400 to 12800 rpm- with FAI fuel and 7x4 prop.
but it has not been trimmed yet
there is an old guy here who used to fly U/C in the late past , and i guess he is the only one near me who can help me to deal with the problem in the flying field , he did test my bird and of course saved it from crash, cos the plane was somehow unstable during the flight , and tended to climb with frontwind

Regards,
Ehsan