The pilot stated that the preflight and engine run-up were satisfactory prior to the departure from the 1,641 foot long grass runway; the grass was a little high (estimated to be 5 to 6 inches) and soft due to rain from earlier that week. He consulted the POH and confirmed no flaps for the takeoff. After the engine run-up he taxied onto runway 32 and with the flaps retracted, applied full throttle noting 2,200 rpm, then released the brakes; the wind was from the northwest at 3 to 5 knots. He did not begin the takeoff roll utilizing soft field takeoff procedure of aft control input but did as the takeoff roll continued; later reporting that he "probably didn't initially have the yoke back enough." After a little more than ½ way down the runway at an airspeed less than 50 mph, he aborted the takeoff. Unable to stop, the airplane impacted a guard rail at the end of the runway causing the airplane to nose over. He further stated that there was no preimpact mechanical failures or malfunctions with the airplane that would have precluded normal operation. He did state in the Recommendation Section of the submitted NTSB Pilot/Operator Aircraft Accident/Incident report that the accident might have been prevented by better assessment of the conditions/effects of the grass (softness) and length of the runway, and to either not initiate takeoff or abort sooner. He also indicated that the accident might have been prevented if, "…a perfect soft/short field technique was used." Postaccident inspection of the airplane by a Federal Aviation Administration airworthiness inspector revealed substantial damage to the right wing spar and structure adjacent to the left main landing gear attach point. Another FAA inspector reported no obstructions at the departure end of runway 32. A review of the airplane Owner's Manual indicates 0 flap extension is specified for normal and maximum performance takeoff; however, 10 degrees of flaps is specified to be used for minimum ground runs or for takeoff from soft or rough fields with no obstacles ahead. The takeoff performance chart does not indicate distances for grass runway. Excerpts of the Owner's Manual are contained in the NTSB public docket.