Shortly after lift-off the pilot heard several loud bangs and saw pieces of fibreglass from the cowls fly past the canopy. Believing the cowlings may have come adrift he decided to land in a small paddock, just outside the aerodrome perimeter fence. The aircraft landed heavily on the soft, wet surface and the propeller struck the ground after only five metres of ground roll. The aircraft came to rest after travelling 34 metres. Investigation revealed that the upper and lower sections of cowling had come apart, following failure of the fibreglass at the connecting screw holes. This allowed the upper cowl to move forward and contact the propeller. The failure was partly due to incorrect placement of the screw holes.