The pilot stated that he was practicing stop-and-go landings when during the second takeoff, as the airplane was about 10 feet above the runway, the cockpit canopy began to open up and rotate forward. The pilot reached up with his right hand to the canopy handle, located above his head, to hold the canopy down. He decided to abort the takeoff and pointed the airplane back toward the runway. With one hand on the stick and the other on the canopy he could not manipulate the throttle and the airplane landed faster than normal. During the landing roll, the airplane departed the runway, substantially damaging the left wing root and buckling the fuselage behind the firewall. Post accident examination of the canopy locking mechanism revealed that the canopy latch and handle was functioning correctly.