NMAC BTWN A C152 TAKING OFF AND A PA28 TAXIING ON THE RWY AT A NON TWR UNCTLED ARPT. THE C152 TRAINING FLT WAS ANNOUNCING ON UNICOM HIS INTENTIONS BEFORE TAKING THE RWY AND SUBSEQUENTLY BEFORE TKOF. THE PA28 WAS BACK TAXIING ON THE RWY AND HAD NOT BEEN HEARD USING THE UNICOM TO ANNOUNCE INTENTIONS.

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WE WERE PRACTICING TKOFS AND LNDGS AT W29. MONITORING AND SELF-ANNOUNCING ON UNICOM. LCL WX CONDITIONS INCLUDED WINDS DIRECTLY ACROSS THE RWY; SO DIRECTION WAS PLT'S DISCRETION. HOWEVER; SEVERAL OTHER ACFT HAD USED RWY 29. WE LANDED ON RWY 29 AND TAXIED TO RUN-UP AREA TO ACCOMPLISH BEFORE TKOF CHKLIST. AFTER ACCOMPLISHING LIST; WE PREPARED FOR A SOFT FIELD TKOF FOR PRACTICE. NO OTHER ACFT WERE ANNOUNCING IN PATTERN AND AFTER TFC CHK AND ANNOUNCING THAT WE WERE DEPARTING RWY 29 FOR A CLOSED PATTERN. WE TAXIED ONTO RWY AND STARTED TKOF ROLL. THERE WAS NO TFC ON RWY. THE NOSE ON THE ACFT OBSTRUCTED OUR VIEW DOWN THE RWY. AFTER LIFTING OFF; WE LOWERED THE NOSE TO ACCELERATE IN GND EFFECT AND SAW THE PA28 TAXIING ON THE RUNWAY; JUST FINISHING HIS TURN FROM THE MIDFIELD TXWY TO BACK TAXI TO RWY 11. WE TURNED SLIGHTLY TO THE R BUT DID NOT HAVE SUFFICIENT AIRSPD TO SAFELY CLB. WE PASSED SLIGHTLY OVER AND TO THE R OF THE OTHER ACFT. WE DECIDED TO DEPART THE PATTERN FOR SAFER PRACTICE ELSEWHERE. THE OTHER PLT SHOULD HAVE BEEN MONITORING UNICOM AND OBSERVING OTHER TFC IN THE PATTERN. IN ADDITION HE FAILED TO ANNOUNCE PRIOR TO PULLING ONTO THE ACTIVE RWY TO BACK TAXI. WHEN PRACTICING MANEUVERS WHERE VISION MAY BE OBSTRUCTED SUCH AS SOFT FIELD TKOFS; I WILL MAKE SURE I VISUALLY CHK FOR THE POSSIBILITY OF OTHER ACFT THAT MAY CHOOSE TO USE A DIFFERENT ACTIVE RWY AT UNCTLED ARPTS.