C170; DEPARTING; FLY IN UNDER CTAF PROC; FAILS TO OBSERVE ACFT ON SHORT FINAL.

Narrative

FLEW MY C170B TO A VERY LARGE FLY-IN AT A GRASS STRIP; RWY 20/2; WITH RAMP SPACE AT THE RWY 20 APCH END. THE PATTERN AND CTAF WERE FULL OF PLANES AND POS RPTS. A MALE VOICE ON THE GND OFFERED ADVICE TO ANY PLTS WHO SEEMED UNAWARE OF THE PROX OF OTHER PLANES AND SEVERAL TIMES INTERVENED TO HELP PLANES DEPART; ASKING PLTS IN THE PATTERN TO CIRCLE WHILE SEVERAL PLANES BACK-TAXIED THE SINGLE RWY. IT WAS UNCLR TO ME WHETHER HE WAS AN AUTH; BUT HE WAS VERY HELPFUL GETTING US IN AND OUT OF THE STRIP. THERE MAY HAVE BEEN AS MANY AS 80 PLANES ON THE FIELD AT THE HT OF THE FLY-IN. THE APCH END OF RWY 20 HAD BEEN USED ALL DAY AS A PRIMARY PEDESTRIAN XING AND PEOPLE WERE PASSING BTWN MY PLANE AND THE ONES ON EITHER SIDE; AND ALSO XING IN FRONT OF MY PLANE FROM SIDE-TO-SIDE. I BECAME VERY CONCERNED ABOUT THE POSSIBILITY OF SOMEONE WALKING INTO MY PROP; AS I WAS NOT PART OF THE LINE OF MOVING AIRPLANES AND THE GENERAL NOISE MADE IT LIKELY THAT MY PROP MIGHT NOT BE NOTICED ONCE IT WAS TURNING. SEEING NO ALTERNATIVES TO INCREASE THE SAFETY OF THE SIT; I DETERMINED TO MOVE MY PLANE INTO THE DEP SEQUENCE AS SOON AS WAS PRACTICAL AFTER STARTING UP. I HAD SEEN NOTHING BUT DEPS FOR THE PREVIOUS 1/2 HR AND DURING THE LONG AND NERVOUS MIN BEFORE I PULLED OUT TO DEPART I HEARD NOTHING BUT POS RPTS OF PLANES DEPARTING THE PATTERN IN VARIOUS DIRECTIONS. FOR THE MOMENT THERE WERE NO PLANES IN LINE TO LEAVE THE RAMP AREA ACROSS FROM ME AND THE PLT OF THE CESSNA THAT WAS FIRST IN LINE ON MY SIDE OF THE RWY WAS TURNING AROUND AND ADDRESSING SOME SIT IN HIS REAR SEATS. I LOOKED TO THE N; BEYOND HIM AND COULD SEE NO PLANE ABOVE THE TREE TOPS WHICH WERE ABOUT 200 FT AWAY. I PULLED OUT AND ROLLED R INTO A SOFT-FIELD DEP; STAYING IN GND EFFECT TO BUILD UP MY SPD. AS I RAISED THE NOSE TO CLB; I SAW A C172 PASSING ABOVE ME; IN LINE WITH THE RWY; ABOUT 100 FT ABOVE ME. I WAS DOING ABOUT 65 MPH (MY ASI DISPLAYS MPH) AND HE WAS CLBING; DOING ABOUT THE SAME SPD; JUST AHEAD OF ME. I CHKED TO BE SURE I WOULD CLR THE TREES AT THE END OF THE RWY AND HELD THE PLANE AT ABOUT 150 FT AGL AS HE CLBED; STAYING ONLY A WINGS LENGTH TO MY R BUT RAPIDLY INCREASING HIS LEAD AND ALT ABOVE ME. I KEPT MY PLANE LOW UNTIL HE TURNED XWIND IN FRONT OF ME AND I DEPARTED TO THE S; AS PLANNED. I MADE AN ASSUMPTION (TO CALL AN ASSUMPTION FOOLISH IS REDUNDANT) THAT THE STREAM OF DEPARTING PLANES WOULD CONTINUE UNINTERRUPTED. I COULDN'T SEE FAR ENOUGH UP FINAL TO SPOT A PLANE ON A LOW APCH. I ALSO ASSUMED THAT A MIN OF RADIO LISTENING WOULD HAVE WARNED ME THAT A PLANE WAS LNDG. I ALLOWED A SINGLE SAFETY CONCERN TO SO DOMINATE MY ATTN THAT MY DANGEROUS IMPATIENCE SEEMED TO ME PRUDENCE. THE NEXT TIME I FEEL SO OVERLOADED AND PRESSED BEFORE TKOF; I HOPE I REMEMBER TO PULL MY TAILDRAGGER OFF ONTO THE GRASS; SHUT IT DOWN; CLB OUT AND TAKE A FEW BREATHS AND REASSESS THE SIT; AND IF ANY IMPATIENT FOOL PULLS OUT ONTO A RWY I'M ABOUT TO LAND ON; I'M GOING TO DIRECT MY GAR WAY OFF TOWARD THE UPWIND SIDE OF THE PATTERN; TO AVOID THE POSSIBILITY THAT HE MIGHT CLB INTO ME.