Weather conditions were fine with a 5 knot westerly wind. The pilot had completed his dual conversion training on the aircraft type and was authorised to make a solo flight. He successfully completed one solo circuit with a landing into the west, as planned, on to a grass flight strip on the southern side of the runway. When the aircraft had decelerated to about 10 knots, the pilot decided to immediately take-off again. He applied power but, after travelling about 250 to 300 feet on a take-off path which, undetected by the pilot, was diverging to the left from the heading of the strip, the aircraft struck a gable strip marker and then overturned.