Try standing on one foot on the beam in releve in the turn shape, and holding it for 5 seconds, and then step out like you finished the turn. Until you can do that easily, you won't be able to turn well. Also, try to look for the end of the beam when you go around. One thing you can do to try to control it is start the turn already on one foot, and just pull in your arm, go up on toe, and turn. (eliminating the step into the turn) How are your full turns on floor? Good luck! Full turns on beam are ALWAYS hard! Lots of repetitions will help you!