The pilot reported that just after liftoff, at about 60 knots, the engine lost power without warning. He described the power loss as a wind-down of RPM over four to five seconds and not a sudden cut. There was no abnormal engine indication before the failure. The aircraft landed heavily on the runway causing the right canard to fail and damaging the rear fuselage. Inspection of the aircraft revealed that the carburettor float bowl had been fitted with four perspex windows which had been glued to the outside of the bowl. Two of the windows were found on the floor of the trailer which had been used to recover the aircraft while the remaining two were still in place. The pilot, who built the aircraft, fitted the windows to assist in setting the carburettor float level. The windows were not a standard fit, or an approved modification. The adhesive used was 24 hour Araldite. This substance is known to deteriorate when in contact with aviation gasoline. Had the windows fallen from the float bowl during the takeoff, fuel would have escaped and possibly resulted in the symptoms described by the pilot. However, the investigation was unable to determine whether the windows became detached before, or as a result of, the accident. No weather observations are recorded at Proserpine. However, at Mackay (93 km to the south-east) at 0800 hours on the day of the accident, the wet and dry bulb temperatures were 6`C and 7`C respectively. Under these conditions, there is the likelihood of serious carburettor icing occurring at any engine power. It is possible, therefore, that the engine lost power due to carburettor icing.