Draft reduction system for ships

'An apparatus is disclosed for temporarily reducing the effective draft of a loaded cargo vessel in a waterway and assisting the propulsion and steering of the vessel while in a draft reduced condition. The apparatus permits a standard ocean-going cargo vessel to be loaded to a most efficient overall draft depth, and then to be temporarily buoyed to a shallower draft for the purposes of clearing restricted channels, sandbars, ocean entrances and the like. In a prefered embodiment the apparatus is two rigid, self-propelled semi-submersible pontoons having an inner cantilever lifting plate for engaging the lower hull section of the vessel to be supported. The pontoons are interconnected by a support cable system under controllable tension. The pontoons in operation are submerged to an operating depth and moved, using internal propulsion equipment, so as to pass underneath and straddle the hull of the desired cargo vessel. The pontoons are then drawn together, reduced in ballast, and raised to a floating condition, whereupon they rise simultaneously on both sides of the ship hull, engaging the ship hull with a provided cantilever pontoon edge. The cable structure does not bear the weight of the ship hull but retains the pontoons in a joined condition against the hull of the ship. The buoyant effect of the pontoons reduces the draft of the cargo vessel to a desired shallower draft for clearing known maritime obstacles. The entire vessel is then propelled by the combination of the onboard pontoon propulsion machinery and the vessel's own propulsion and steering machinery to a location where the vessel can be lowered to its natural draft. The pontoons are then submerged, releasing the vessel, the pontoons then are propelled back a next point of use. The structure disclosed permits ships to be loaded to an optimum draft for most efficient cargo handling and permits the ships to be handled in channels or rivers of shallower draft without requiring constant dredging or other environmentally damaging activities.