COSMOS analysis leads to revolutionary design change that alters theory of boat design

Company FBM Babcock Marine Industry Marine Location U.K. Product Used COSMOSM™ Type of Analysis Linear Static, Fatigue More Details

The Challenge

The jets used in today's very fast ferries move up to 24 tonnes of water per second at top speed. They are also subjected to great stress during low speed maneuvering and docking procedures.

FBM Babcock designs and builds a wide variety of vessels including workboats, patrol craft and fast jet-powered ferries that carry passengers at worldwide locations. They were challenged with the redesign of their ferries in that many similar designs experienced cracking around the transom and its junction with the hull. Conventional wisdom suggested strengthening the joints and adding bracing material in this area.

The Solution
John Kecsmar, a naval architect with FBM Babcock Marine, used COSMOSM to assess the effect of reducing the amount of material instead. He found that the more material they removed, the stronger the structure became. "We found that all the loading sent through the duct, and not the transom, and we could change our structure to suit this fact by taking all the strengthening members off the transom," said Kecsmar.

FBM Babcock found that several new design avenues opened up with the reduction of the structural strength of the transom. Now the transom frame requires no cut-outs, allowing one continuous weld. "Because the ends of welds attract stress and are subject to fatigue, the new design has reduced overall stress and the possibility of fatigue even more," Kecsmar said.

Summary and Metrics:

• Developed safer, stronger, faster and more fuel-efficient ferries
• Reduced manufacturing time
• Made it possible to design a single optimum scantling that would withstand the varying stresses that apply at different locations in the boat
• Revolutionized their boat designs with ability to build stronger structures using less material