First of all, welcome to the forum.
Do you mean on takeoff? The Simple Cub is a tail dragger & when power is applied to tail draggers with the tail wheel still on the ground it causes the plane to turn to the left due to P-factor. Right rudder is required to correct it until you get the tail elevated to level attitude. P-factor is from the angle of attack difference between the prop blade going up as opposed the the greater angle of attack of the prop blade going down. On an RC, depending on which way your prop turns P factor could possibly pull you either way but normally to the left.
If your plane is pulling right in flight it’s probably a trim issue or a matter incorrect motor mounting system. If the plane is crabbing it could be a rudder trim issue or if it’s turning right it could be too much right angle force in the mount. Most foam board models I’ve built need down force built in to the engine mounting & a few degrees of right angle force as well. If the airplane just banks right it might be aileron trim if it’s a 4 channel with ailerons. Otherwise, if it’s a 3 channel, sight down the wing & see if the lower surface is flat on both sides, no warp or twist.
Good luck & be sure to post the results of your fix.