The private pilot with an airplane single-engine land rating was learning to fly his son's experimental amateur-built helicopter and had accumulated about 20 hours in type. His plan for the day was to conduct solo hover practice. After about 20 minutes of hover practice on a grass runway at the non-towered airport, he began hover-taxiing the helicopter back to its hangar. As he approached the hangar area, he realized that the helicopter had excessive speed for an upcoming turn, and the pilot tried to slow the helicopter. However, instead of just decelerating, the helicopter settled to the ground. At the time the helicopter contacted the ground, it had some lateral translation. One of the skids caught on the ground, and the helicopter rolled over onto its left side. The pilot shut down the helicopter and extracted himself. The main rotor blades, tailboom, and one skid were substantially damaged, and the pilot was uninjured. The pilot stated that there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation and that his inexperience in the helicopter resulted in his inability to control it during the taxi.