The apparatus is mainly an acrylic made rectangular pontoon with a sail having five rows of V-slots at equal heights on the sail. The V slots center are equally spaced. The height of the centre of gravity and the angle of the sail can be changed by positioning an adjustable weight into V slots, consisting of two cylinders which can be screwed together.
Weight can be moved horizontally and vertically causing the sail to deflect. Degree graduation is provided at the front with a pointer to directly read the deflection of the sail. A plumb weight provided can be used for identification of center of gravity.