Title: Balanced Vector Launch and Recovery of Small Boats
Author(s): Steven Halpern and Joseph Urciuoli
Abstract: Most vessels with stern ramps require the small boat being launched or recovered to be unguided during both launch and recovery. In high sea states, the relative motion between the mother ship and the small boat is unpredictable and significant. The successful launch and recovery relies on human judgement and potentially puts human lives at risk, particularly during the recovery phase. The concept discussed herein, “Balanced Vector Launch and Recovery” is derived from proven and in-service MacTaggart Scott helicopter traversing systems. It uses a system of three balanced vectors via two wires at the bow of the boat being recovered and additional drag or reverse thrust of the boat, maintaining controlled relative position between the mother ship and the boat. Because of the higher risk during recovery, the following only describes the recovery process. The final presentation will, also, describe the launch process. Critical to the recovery is the attachment of the two wires to the boat being recovered. This is accomplished using a “bow engager” that is deployed to a safe distance from the mother ship. The “bow engager” is fitted with a vertical grid of engagement openings and the boat is fitted with a single engagement probe. The boat is driven into the engager at a speed sufficient to fully engage the probe into one of the grid openings. The engager will be capable of sensing full engagement and will activate a locking mechanism. If full engagement is not made, the boat backs away and makes another attempt. Once attachment is made, the boat is winched in. The two cables are synchronized to allow the boat to be winched in along the center line of the stern ramp. The cables, as they enter the stern ramp, are guided over sheaves that are positioned higher up in the ramp’s opening. As the boat approaches, increased stability is achieved with increasing angle between the two bow cables and as the cables lift the bow of the boat to a height that eliminates any possibility of ramp bottom or stern impact. The boat is being “dragged” safely behind the mother ship. The boat is then pulled into the stern ramp via cable sheaves which has the capability of running inboard. The moving cable sheaves run in unison with the take up velocity of the winches. The speed of pulling the boat into the stern ramp is much faster than the speed of traversing the boat from the engagement point to the ramp opening. The capability of higher speed is the result of maintaining stored energy for the final stage of recovery. As the boat approaches full recovery position, the sheaves stop and the over running of the sheaves by the boat pulls out cable at an increased tension and brings the boat to a stop. The defined concept offers a safer capability for launch and recovery of small boats in high sea states. This concept should be considered for vessels such as the National Security Cutter and other vessels with stern ramps where, over their lives of 30 years, there will be numerous incidents which will require launch and recovery in high sea states.