Recovering long sediment gravity cores from the seabed was a hallmark of marine geology research in the 1970s but was abandoned by the U.S. oceanographic community by the mid-1980s. With renewed interest in long term sediment records of environmental change, WHOI researchers envisioned a new long core system to be installed on the research vessel Knorr that could recover 50 m long cores from full ocean depths of 7500m.
Deck Space, Core Handling and Winch Loads
The performance requirements of the new Long Core system required an unusual level of vessel modification and the development of new oceanographic tools. The 50 m core length exceeded the available deck length. The break strength of the synthetic coring line exceeded available winch capacity and underlying deck strength. There were no existing models for the conceptual deck gear to overboard a 50 m horizontal core barrel stored on deck to a vertical positon hanging under the stern A-frame.
New Tools, New Deck Plate
Working with the concepts described by WHOI researchers, the Glosten team was able to develop engineering designs and specifications for a suite of specialized Long Core deck gear. Key systems included a core handling davit to carry the core from starboard alongside to the transom, a special A-frame with a telescopic line handling boom, and a winch line sheave socketed into the Knorr’s transom.
A new class of traction winch was purchased to handle 48 mm Plasma line. These line loads required removal and replacement of the main working deck with a new strengthened “Superdeck”. A shipyard modification package was developed that included a new seven meter slot in the starboard superstructure to fit the 50 m core barrel on deck.
Increased Vessel Utilization and Better Science
The Long Core sea trials began in 2007 and the retirement cruise of the R/V Knorr in 2015 is scheduled for a final Long Core campaign. The system has become a standard mission component in evaluating new research vessel capability within the national and international fleet. The data quality within the cores has opened new opportunities in high resolution sedimentology due to the minimal disturbance of the samples by using the high modulus winch line.
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