THE PLT/OWNER ARRIVED ABT 1.5 HR BEFORE SUNSET TO TAKE DELIVERY OF THE ACFT AFTER IT WAS GIVEN A NEW PAINT JOB. NEWLY UPHOLSTERED FRONT SEATS WERE REINSTALLED & THE ACFT WAS PREFLTD & GIVEN AN ENG RUN-UP ON THE RAMP TO AVOID A RUN-UP OVER GRAVEL. THE PLT INITIATED A TAKEOFF ON RWY 34, WHICH WAS ONLY 1650' LONG. THE RWY SURFACE CONSISTED OF SOFT DIRT & SAND. A WITNESS RPRTD THE ACFT BECAME AIRBORNE AT THE DEP END OF THE RWY & REACHED AN ALT OF ABT 30 FT. IT THEN SETTLED IN A LEVEL ATTITUDE, COLLIDED WITH YUCCA TREES & BURNED AFTER COMING TO REST. AN INVESTIGATION REVEALED THE DENSITY ALT AT THE ARPT WAS ABT 5700'; ABT 15 MI WEST AT GEORGE AFB, THE WIND WAS FM 200 DEG AT 12 KTS. A WITNESS NEAR THE ACDNT SITE ESTD THE WIND WAS FM THE SW AT 2 TO 5 KTS. THE STABILATOR TRIM WAS FND IN A FULL NOSE DOWN PSN. NO PREIMPACT PART FAILURE OR MALFUNCTION WAS FND. FLAPS WERE FND IN THE FULLY RETRACTED PSN.