Lateral plan (sail NA)

The lateral plane in sailing naval architecture is the underwater profile area of the hull and appendages projected onto the centerplane, the area that resists leeway and provides the hydrodynamic side force balancing the sail’s heeling force. Its area-weighted centroid is the center of lateral resistance, and the fore-and-aft position of that centroid relative to the rig’s center of effort sets the helm balance: the center of effort carried ahead of the lateral plane gives lee helm, abaft it gives weather helm. Keel, skeg, and rudder dominate the modern lateral plane because a deep, high-aspect fin produces the side force far more efficiently, lower induced drag, than the shallow canoe body alone.