TAXIING ACFT HIT THRESHOLD LIGHT MOVING ONTO RWY.

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ON THE MORNING OF THE OCCURRENCE; I WAS DELAYED DEPARTING CRAIG WHILE WAITING FOR THE FOG TO BREAK. MY FLT WAS TO BE IN AN SMA TWIN WHICH IS PRONE TO WINDOW FOGGING ON THE GND DUE TO THE FACT THAT IT HAS NO FAN NOR A COMBUSTION HEATER. THIS IS PARTLY THE REASON OF THE OCCURRENCE. BEFORE MY ORIGINAL DEP TIME I WASHED THE OUTSIDE WINDOWS WITH WATER AND WIPED DOWN THE INSIDE OF THE WINDOWS. THIS USUALLY IS ENOUGH TO GET YOU TO THE RWY FOR DEP; AFTER WHICH TIME THE AIR FLOWS FREELY THROUGH THE DEFROSTERS. HOWEVER; WE HAD TO WAIT BECAUSE THE FOG WAS SLOW TO LIFT. MY PAX AND I WENT INSIDE TO WAIT. WE WAITED FOR OVER AN HR BEFORE THE FOG AT BOTH OUR DEP AND DEST ARPTS LIFTED. AS WE BOARDED THE ACFT AND BEGAN OUR TAXI; THE WINDOWS FOGGED UP. I WAS ABLE TO KEEP A SECTION OF THE WINDSHIELD CLR BY USING MY HAND OUT THE VENT WINDOW. THIS ALLOWED ME TO SEE FOR TAXI; HOWEVER; IT LEFT A RATHER LIMITED FIELD OF VISION. I TAXIED TO THE RWY WITHOUT TROUBLE. WHEN I WAS CLRED FOR TKOF; I PROCEEDED TO THE END OF THE RWY NOT THINKING MUCH ABOUT THE RWY THRESHOLD LIGHTS WHICH STICK UP ABOUT 1-2 FT ABOVE THE GND. AS I HEADED TOWARD THE THRESHOLD I EITHER DID NOT SEE OR MY MIND DID NOT REGISTER THE LIGHTS. NEEDLESS TO SAY; AS I TURNED TO THE RIGHT TO LINE UP FOR TKOF; MY L PROP STRUCK THE LIGHT. ONE BLADE WAS DAMAGED AND THE LIGHT WAS SHATTERED. WE TAXIED BACK TO THE RAMP WITHOUT FURTHER INCIDENT. I BELIEVE THAT THIS COULD HAVE BEEN AVOIDED BY NOT USING THE LAST 100 FT OR SO OF RWY BEFORE THE TXWY. IT WOULD ALSO BE NICE TO HAVE SOME TYPE OF FAN INSTALLED FOR BETTER DEFROSTING ON THE GND. ALSO; MY ERRONEOUS BELIEF THAT THE SMALL AREA OF THE WINDSHIELD THAT I CLRED WAS ENOUGH TO SEE EVERYTHING.