The pilot reported that, during flight, the engine lost partial power. He applied carburetor heat and adjusted the mixture, but the engine did not respond. The engine continued to lose power, and the pilot conducted a forced landing on rough terrain, during which the right wing struck the ground. The airplane sustained substantial damage to the right wing spar. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. The pilot reported that the temperature about the time of the accident was 30°F and that the dew point was 34°F. The atmospheric conditions at the time of the accident were conducive to the accumulation of serious carburetor icing at cruise or climb power settings. The pilot stated that the accident could have been prevented if he had "checked for carb ice sooner."