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NTSB Report Highlights the Peril of Doubler-Plated Hull Repairs

Grace Marie underway before the sinking. Source: Paul Spillane via NTSB

NTSB Report Highlights the Peril of Doubler-Plated Hull Repairs

Mike Schuler
Total Views: 3964
July 12, 2023

The use of doubler plating in the repair of an uninspected fishing vessel’s hull eventually led to its sinking off Gloucester, Massachusetts, last year.

The NTSB this week released its report into the loss of the F/V Gracie Marie with seven crew members on board. All crew were rescued by a Good Samaritan after abandoning ship as the vessel sank. No injuries were reported, but the total loss was valued at $650,000.

The NTSB investigation focussed on the failure of the doubler-plated hull under the engine room as the likely cause of the incident, highlighting the potential peril of such repairs. Doubler plates are small pieces of plate welded to the hull to provide strengthening in a specific location.

The F/V Grace Marie was transiting to fishing grounds on July 8, 2022, when its engine room began flooding. The vessel’s bilge pumping system couldn’t keep up with the intrusion of water, forcing the crew to abandoned the vessel in a life raft.

According to the NTSB, the external area of the hull along the keel and under the engine room was covered with steel doubler plating installed 8-10 years prior to cover and reinforce areas of deteriorated steel. Although a marine survey in 2018 found the Grace Marie’s to be in “overall good condition for a vessel of its age,” the use of doubler plating can make it difficult to assess the true condition of the hull.

“The hull plating under the engine room cannot be visually inspected without drydocking the vessel. The bilge under the main engine and other equipment would not have been easily visible to the captain and deckhand 2 during the investigation due to floodwater,” the report said.

The NTSB said while it is common for uninspected commercial fishing vessels, such as the Grace Marie, to use doubler plating to repair and reinforce damaged or wasted underwater hull sections, doubler plate repairs can lead to increased stress in the area of the repair, leading to failure.

Although the source of the flooding could not ultimately be determined for certain, the NTSB said the probable cause of the flooding and sinking of the Grace Marie was uncontrolled flooding of the engine room likely from a failure of the doubler-plated hull below the engine room.

“Although doubler plating can be used as a temporary repair solution, it is not generally suitable as a permanent repair for a vessel’s hull,” the report said. “Vessel owners should crop out wasted steel on the hull and replace it by inserting new plating instead of covering it up with doubler plating.”

Marine Investigation Report 23-13 can be found on the NTSB’s website.

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