On August 1, 2011, at 0920 central daylight time, a Bellanca 14-13, N74260, contacted trees and the terrain during takeoff from the Matson Airport (2WI6), Stoughton, Wisconsin. The private pilot and the passenger both received serious injuries. The airplane sustained substantial damage to the fuselage and both wings. The airplane was owned and operated by the pilot under the provisions 14 Code of Federal Regulations Part 91. The personal flight was operating in visual meteorological conditions without a flight plan. The planned destination for the flight was the Worthington Municipal Airport (OTG), Worthington, Minnesota. The pilot reported that he performed an engine run-up prior to takeoff and everything was normal. He had the flaps extended 2 notches when he initiated the takeoff to the north on the 2,500 foot long grass runway. The airplane became airborne about half way down the runway. The pilot stated that upon reaching 65 to 70 miles per hour, he reduced the flaps to 1 notch to maintain best climb. He stated the airplane cleared the initial group of trees, then the airplane began to descend. The airplane subsequently contacted the trees and came to rest in a clearing. The pilot reported that he did not get the landing gear retracted prior to impact. A relative of the pilot’s who watched the takeoff reported that the airplane was about 25 to 30 feet above his head when it passed near him at the north (departure) end of the runway. He stated the airplane looked “mushy” as it crossed the highway, and the nose remained high until the right wing dropped and the airplane contacted the trees. This witness reported that he did not hear any unusual engine noises. A second witness who heard the airplane for 1 ½ to 2 seconds reported hearing the engine sounded like it was “stumbling” prior to it backfiring immediately before the sound of the impact. According to a FAA inspector, the runway was dew covered at the time of the takeoff. The north half of the runway sloped downward, and the highway and the terrain on which the trees were located were higher than the elevation at the departure (north) end of the runway. The inspector reported that pieces of the right wing were located near the treeline and there was a slash in the terrain at the initial ground impact. There was a piece of broken propeller blade located near the slash mark. The winds at the time of the accident were variable at 4 knots. A postaccident inspection of the airplane and engine revealed the left fuel tank was ruptured during the accident and the fuel level in the right tank was about 4 inches below the filler cap. Both magnetos produced spark when turned by hand. Fuel was present in the fuel pump. The fuel pump check valves functioned normally and the pump diaphragm was intact. The carburetor was partially separated from the engine due to impact and it did not contain any fuel. The carburetor accelerator pump functioned normally. The only anomaly noted with the fuel system was that the inner sleeve at one of the end fittings on the fuel line that ran from the fuel pump to the carburetor was crimped, which decreased the inside diameter of the fuel line at the end fitting. A postaccident examination of the airplane and engine did not reveal any anomalies that would have resulted in a loss of engine power. The field elevation at the 2WI6 is 915 feet. Density altitude at the time of the accident was approximately 2,600 feet. The pilot reported that the gross weight at the time of the accident was about 1,910 pounds and the maximum gross weight was 2,100 pounds.