The pilot was making his first flight in the aircraft which he had just completed building. He was using runway 17 right and the wind was a light southerly of about five knots, tending to the southwest. He reported that he misjudged the first approach to land, so made a go-around. On the next attempt he touched down about half way along the runway. There was plenty of runway remaining after landing so the pilot decided to let the aircraft run through to the end rather than to brake for a shorter turn off. At this stage the stick was full back. Suddenly the aircraft started to veer to the left. The pilot said he was unable to correct the situation. The aircraft continued the swing and was almost sideways by the time it entered the grass on the left of the runway. The right main landing gear leg buckled in the soft ground and the right wing hit the ground.