The centre of effort of a single lug-sail should be about 3 in. ahead of the centre of lateral resistance of the immersed portion of the canoes hull; the correct position of the mast will therefore depend on the position of the centre board, if any, or the shape of the keel, neither of which is given. The centre of any triangle's area is the point at one-third of the line from the centre of any side to the opposite angle. Hence, if the sail be divided by line AC (see sketch) the points E and F will be the centres of triangles ABC and A C D respectively. Join these points by line E F. Again divide the sail by the line BD, find a and II the centres of triangles A B D and BCD; join G and H, which line intersects EP at D, the "centre of effort" of the sail. To ascertain the centre of resistance, let down the centre board, place the rudder amidships, and let the crew on board hold one end of a string in such a position that when the other end is steadily pulled by a second person, the canoe will approach the latter, remaining at right angles to the string. Mark this position, and step the mast in order that the sail's centre may be 3in. or 4in. ahead of it measured horizontally.

The rudder stock must not extend below the keel, but the drag may be curved to 4 in. below it and extending aft to 10 in. A nearly vertical stern-post is advisable.

Position of Mast in Canoe.