PA24 PLT DEPARTS ARPT AFTER HIS DEP CLRNC VOID TIME EXPIRED.

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AFTER RECEIVING A FULL RTE CLRNC; I ASKED FOR A CLRNC VOID TIME. THE CTLR BECAME AUDIBLY STRESSED AND ADVISED ME THAT I WOULD HAVE TO CALL BACK LATER UNLESS I WAS PREPARED FOR DEP. I WAS FULLY PREPARED AND HE ISSUED MY CLRNC TIME AT XA12 FOR A TKOF AT XA16 VOID AT XA21. I ACCEPTED THE CLRNC WITH CONFIDENCE THAT I COULD START THE ACFT; PERFORM A RUN-UP; PREFLT SYS CHKS AND TAXI FOR TKOF ON RWY 14 (WX BRIEFING WINDS STRONGLY FAVORED THIS RWY) WELL WITHIN MY CLRNC LIMIT. AT THIS POINT; I WAS 40 MINS BEHIND OUR PROPOSED DEP TIME DUE TO THE DIFFICULTIES OBTAINING OUR CLRNC. DARK CLOUDS WERE BEGINNING TO DEVELOP NEAR THE ARPT AND RAIN DROPS WERE NOW PELTING MY NOTEPAD. I WAS CONCERNED THAT A DELAYED TKOF WOULD RESULT IN A SIGNIFICANT WX HOLD THAT MIGHT PRECLUDE THE ATTENDANCE AT THE WEDDING. ACFT START AND TAXI WENT NORMALLY AND I TAXIED THE ACFT INTO THE RUN-UP AREA OF RWY 14 WHERE I PERFORMED A CAREFUL AND METHODICAL RUN-UP AND IFR SYS CHK. I MOVED INTO POS FOR TKOF AND SAW DARKENING SKIES BEYOND THE END OF THE RWY AND A WINDSOCK NOW FAVORING RWY 32. I PERFORMED A QUICK MENTAL CALCULATION OF THE TAXI TIME TO THE OTHER END OF THE 4100 FT RWY AT ABOUT 3 MINS -- JUST IN TIME TO MAKE MY CLRNC VOID TIME OF XA21. DURING TAXI; I KNEW THAT TIME WAS AN ISSUE AND AGAIN ATTEMPTED TO RADIO DULLES. NO RESPONSE. IT WAS MY INTENTION TO NOTIFY DULLES THAT I WAS COMING CLOSE TO MY VOID TIME AND TO CHK WITH THEM TO ENSURE THAT MY DEP WOULD NOT CREATE ANY DIFFICULTIES. I DISABLED RADIO SQUELCH AND ATTEMPTED ONCE AGAIN. NO RESPONSE. BELIEVING THAT I WAS CLOSE TO BUT WITHIN MY VOID TIME; I MOVED INTO POS ON RWY 32; PAUSED FOR A MOMENT TO STABILIZE MY SCAN AND SITUATIONAL AWARENESS AND DEPARTED NORMALLY. I CHKED IN WITH DULLES CLBING THROUGH 700 FT FOR 3000 FT. AFTER A SHORT DELAY; DULLES ANSWERED AND INSTRUCTED A 270 DEG HDG. AFTER A FEW MINS FLYING TIME AND BEFORE REACHING MY CRUISE ALT; I WAS TOLD BY DULLES TO PREPARE TO COPY A TELEPHONE NUMBER. THE CTLR DIRECTED ME TO CALL REGARDING A POSSIBLE PLTDEV FOR MISSING MY CLRNC VOID TIME. I CHKED MY GARMIN 430 FLT TIMER FEATURE AND SAW THAT IT BEGAN RECORDING MY FLT TIME AT XA23 (IT IS SET TO LOG FLT TIME ONCE THE ACFT ACHIEVES 30 KTS OF GND SPD). THE CTLR LATER TOLD ME THAT I WAS OFF AT XA24. SUMMARY OF CONTRIBUTING FACTORS: INSUFFICIENT ATTN AND ADHERENCE TO CLRNC VOID TIME. POORLY CALCULATED TIME REQUIRED FOR TAXI AND RUN-UP. CLRNC DELIVERY ISSUING A 'CALL BACK LATER' VICE 'CALL BACK IN X MINS' FEEDING INTO MY IMPULSIVE 'TAKE IT NOW WHILE YOU GOT IT' ATTITUDE. DETERIORATING LCL WX CONDITIONS FEEDING MY IMPULSIVE 'GO NOW OR NEVER' ATTITUDE. REMOTE CLRNC FREQ NOT MONITORED BY DULLES. DELAY IN CONTACTING FSS (SATURDAY MORNING).