The private pilot reported that he completed an emergency off-airport landing, in mountainous terrain, to avoid poor weather and fog during a cross-country flight in the single engine helicopter. He reported that he sat in position for about forty minutes to burn off fuel and "…lighten the aircraft." The pilot then lifted off and repositioned the helicopter to a nearby dirt road. The pilot sat in position for an additional hour to "burn off as much fuel as I could to lighten the ship." The pilot departed a second time; however, during the takeoff the helicopter "didn't have enough lift" and subsequently settled and collided with the terrain. The pilot reported that he thought he was taking off into the wind, instead he took off with a tailwind. The helicopter sustained substantial damage to the fuselage and tailboom assembly. No preimpact mechanical failures were reported.