On June 19, 2005, at 1255 mountain daylight time, a Cessna 172N, N733RL, piloted by a student pilot and under the supervision of a commercial certificated flight instructor, was substantially damaged when it nosed over while performing a touch-and-go landing at Platte Valley Airport (18V), Hudson, Colorado. Visual meteorological conditions prevailed at the time of the accident. The local instructional flight was being conducted under Title 14 CFR Part 91 without a flight plan. The instructor and student pilot reported no injuries. The flight originated at Boulder Municipal Airport (1V5), Boulder, Colorado, at 1210. According to the instructor, the student was asked to perform a touch-and-go landing. After touching down on the runway, the student did not add power because he thought he was making a full-stop landing. The instructor asked if the student was going to take off. The student then added full power and the airplane lifted off. The instructor did not feel that the airplane was climbing at the proper rate, so he took control. He closed the carburetor heat control and noticed the flaps were still extended. He said he got "hasty" and retracted the flaps completely instead of in gradual increments. The airplane settled, touched down on soft ground and nosed over. The vertical stabilizer was crushed, the nose landing gear was broken off, the propeller was bent, and the firewall was buckled. The temperature at the time of the accident was 92 degrees F. Density altitude was calculated to be 7,713 feet msl.