By closely examining drawings of ships with known good sailing qualities Chapman realized that the framework should be divided in a certain progression. The frames should decrease from the place of greatest width in the same relation as the ordinates 0, 1, 2, 3, 4 etc (pictured), where the arc ABC is a parabola, AD is the axis and A is the vertex (the "peak"). This construction method is called the "parabola method". Chapman also introduced the so called "relaxation method", but preferred the former himself.