Finding the Center of Effort Prepared by Marilyn Vogel and Dan Miller.   The Center of Effort (CE) of a sail is the point through which the sum of the driving forces appear to act. To determine the CE of a triangular sail: Lay your sail on a flat surface Find the center of the luff, foot and leech. Take a line from the tack to the center of the leech, a line from the head to the center of the foot, and a line from the clew to the center of the luff. Where these lines intersect is the CE. To find the center of efort of a quadrilateral sail, draw a diagonal dividing the sail into two triangles. Determine the CE of each of the resultant triangles. Connect these two CEs. The CE of the full sail is at the intersection of that line and the original diagonal bisecting the sail. Back to Balancing the Rig.