Definition of stability terms.

§ 28.510 Definition of stability terms. Downflooding means the entry of seawater through any opening into the hull or superstructure of an undamaged vessel due to heel, trim, or submergence of the vessel. Downflooding angle means the static angle from the intersection of the vessel's centerline and the waterline in calm water to the first opening that cannot be closed weathertight and through which downflooding can occur. Flush deck means a continuous weather deck located at the uppermost sheer line of the hull. Forward perpendicular means a vertical line corresponding to the intersection of the forward side of the vessel's stem and the vessel's waterline at the vessel's deepest operating draft. Open boat means a vessel not protected from entry of water by means of a complete deck, or by a combination of partial weather deck and superstructure which is seaworthy for the waters upon which the vessel operates. Protected waters means sheltered waters presenting no special hazards such as most rivers, harbors, lakes, and similar waters as determined by the OCMI. Qualified individual means an individual or an organization with formal training in and experience in matters dealing with naval architecture calculations. Substantially altered means the vessel is physically altered in a manner that affects the vessel's stability and includes: (1) Alterations that result in a change of the vessel's lightweight vertical center of gravity of more than 2 inches (51 millimeters), a change in the vessel's lightweight displacement of more than 3 percent, or an increase of more than 5 percent in the vessel's projected lateral area, as determined by tests or calculations; (2) Alterations which change the vessel's underwater shape; (3) Alterations which change a vessel's angle of downflooding; and (4) Alterations which change a vessel's buoyant volume. Well deck means a weather deck fitted with solid bulwarks that impede the drainage of water over the sides or an exposed recess in the weather deck extending one-half or more of the length of the vessel.