PIPER 140 PLT HAS AN NMAC IN THE PATTERN AT BVS.

Narrative

I WAS #3 ON L DOWNWIND; RWY 28 AT BVS; ABOUT 3000 FT BEHIND THE CESSNA IN QUESTION. THE CESSNA WAS FOLLOWING ACFT #1 WHO WAS EXECUTING A BASE TO FINAL TURN FOR A LNDG ON RWY 28. DUE TO A R XWIND; THE CESSNA'S TRACK DRIFTED CLOSER AND CLOSER TO THE EXTENDED RWY CTRLINE DRASTICALLY REDUCING THE LENGTH OF THE L BASE LEG. ONCE THE PLT OF THE CESSNA REALIZED THIS; HE BEGAN TO EXECUTE A R 270 DEGS TO THE EXTENDED DOWNWIND IN ORDER TO PROVIDE HIMSELF ENOUGH SPACING FOR A L BASE LEG. AS I WAS FOLLOWING THE CESSNA ON THE DOWNWIND; I WAS EXPECTING HIM TO TURN TOWARD FINAL WITH AN ABBREVIATED OR NO L BASE LEG. I WAS NOT AT ALL PREPARED TO HANDLE THIS UNEXPECTED MANEUVER AND ABOUT 3 SECONDS ELAPSED BEFORE I REACTED. I ATTEMPTED TO RADIO THE CESSNA TO WARN HIM OF MY POS ON THE DOWNWIND. HOWEVER; I WAS NOT ABLE TO COMPLETE THE RADIO CALL AS I HAD TO REACT IMMEDIATELY BY GOING FULL THROTTLE AND EXECUTING AN IMMEDIATE L CLBING TURN IN ORDER TO AVOID THE COLLISION. IT APPEARED THAT THE CESSNA WAS NOT AWARE THAT I WAS BEHIND HIM UNTIL HE SAW ME PASS OVER HIM; CLRING HIM BY ONLY 100 FT.