The airplane sustained substantial damage at about 1813 Pacific time during a forced landing following a reported loss of engine power. The flight instructor and private pilot receiving instruction were not injured. Visual conditions prevailed. During cruise flight at 3500 feet msl, the engine began to surge and partially lost power. The flight instructor took control of the airplane and began troubleshooting. Despite numerous attempts to restore full engine power, the flight instructor initiated a forced landing to a nearby field. As the flight descended, the flight instructor realized they would be unable to reach his initial intended landing area and selected a second field adjacent to his position. During the landing flare, the left wing struck terrain and the airplane subsequently landed hard. Examination revealed the left wing was separated from the airframe at the wing root and the outboard three feet of the right wing was bent upwards.