Skip to main content

Stability monitor could avert capsizes

The $4,000 device tracks rolling motion, alerting crew to potentially deadly shifts in weight and balance

Coast Guard investigators say the 93-foot fishing vessel Katmai sank off Alaska's Aleutian Islands, with the loss of seven crewmembers, because it was carrying too much cod in its hold and the crew couldn't stop water from unaccountably pouring into the engine room.

The Katmai was struggling in 35-foot seas and winds of more than 60 knots in an October 2008 storm. It was carrying 120,000 pounds of Pacific cod - more than it had ever carried and twice what was factored into its most recent stability test in 1996. The overloaded hold, coupled with the engine room flooding, lowered Katmai's freeboard and trim aft, causing the vessel to take on more water and sink.

"Of the 11 crew on board, four were ultimately rescued, five deceased members were recovered, and two remain missing and are presumed dead," the May 2009 Coast Guard report says.

The cause of a sinking usually is not just one failure or accident or error but a combination or series of them. In the case of the Katmai, the Coast Guard found that one contributing factor was the fishing boat's stability, which was compromised under the very difficult conditions it faced that night.

Could the skipper have known sooner that his vessel might be in jeopardy? Hook Marine, a Scottish company that manufactures stability monitors for cranes, has come out with a prototype monitor for boats called the SeaWise Stability Monitor ( The device continuously monitors a vessel's rolling motion and gives early warning of developing situations that could lead to a capsize.

Though conceived primarily for the fishing industry, the $4,000 monitor could also have pleasure-boat applications, says David Yell, whose firm, Ocean Technical Services of Bellingham, Wash., field-trialed the product for the manufacturer. Yell says he can see applications for yachts over 100 feet that carry potentially destabilizing cars and helicopters on their upper decks, as well as a 55-foot sportfisherman whose owner upgrades to a larger tender and stores it on deck above the saloon. SeaWise would detect and document any noticeable change in the boat's stability characteristics.

Yell says he found significant interest in the product among marine surveyors. If one of them surveys the same boat multiple times during a period of years, that person can track changes in stability as the boat is refit, refurnished, renovated and repowered. "Over time, as owners do changes, they can see what the change is in stability," Yell says.

The device consists of a small black box with an inclination sensor inside and a display screen about the size of a laptop that shows the boat's GM - its metacentric height, a measure of stability - both as a number and in a graph depicting significant changes.

The monitor "carries out what is in effect a continuous roll test while the vessel is at sea ... while the installed software filters out the less significant rolling motions to which the hull is subjected by wind and waves," Hook says in its SeaWise literature.

The screen displays a vessel's stability at any moment through a color-coded signal - green for safe, yellow for caution, red for danger. SeaWise keeps a record of GM readings so that long-term changes are documented.

"It's useful for a number of reasons," says Jerry Dzugan, director of the Alaska Marine Safety Education Association. It gives the skipper a continuous readout of the vessel's changing stability, sets parameters for adding or removing weight in different parts of the boat, and alerts the skipper to potentially dangerous stability problems.

Dzugan says a fishing boat's weight tends to increase by 1 percent a year as more equipment, rigging, stores and accessories are added - and, if it's a wood boat, as the hull absorbs water. A boat's stability may change significantly if it is refit for new uses - a different type of fishing, for instance. To remain competitive, many boats "wind up operating in four or five different fisheries," he says.

The National Institute for Occupational Safety and Health, which has an office in Anchorage, has acquired two SeaWise monitors to evaluate their effectiveness and applicability to commercial fishing boats, says Jennifer Lincoln, an injury epidemiologist at the agency who monitors commercial fishing safety and has helped develop safety gear and education programs for fishermen.

"It's a very easy system to set up," she says. She says the agency wants to know if it works and whether the fishing industry sees a need and a use for it. "I'm definitely intrigued by it. I'm intrigued by the simplicity of it."

Hook developed SeaWise after Britain's Marine Accident Investigation Branch published a study of fishing vessel accidents in the United Kingdom from 1992-2006. The report indicates that about 60 percent of vessel losses at sea are attributable to foundering or capsizing.

The United Kingdom Sea Fish Industry Authority and Scottish Enterprise Ayrshire, a government development agency, sponsored the development of SeaWise. Last fall, the device won the prestigious Lloyd's List Global Award for innovation, presented by Britain's leading shipping industry newspaper.

This article originally appeared in the April 2011 issue.