UM Wave Craft
Overall length: 27 meters
Load line length: 23.9 meters
Width: 9 meters
Draught: 0.7 / 2.9 meters (transit / hullorn)
Cargo: 10 tonnes
Propulsion: Water jets powered by high-speed diesel engines
Transit speed: Over 35 knots
Range: Over 500 nautical miles
By Tea Tramontana
It all began with air-cushioned vessels developed and produced for different purposes for the Norwegian and US navies. With its latest invention of an active heave damping system, the Umoe Mandal shipyard is now beginning tests on their model of a future vessel for offshore turbine servicing.
“The truly new thing about this vessel is the active heave damping system. In short, the air cushion lifts the vessel out of the water and thereby ensures that the vessel is less affected by the waves. When waves pass the vessel, they normally force the vessel to move up and down. We are actively controlling the air cushion pressure to counteract these wave forces”, says naval architect Trygve Halvorsen Espeland.
The UM Wave Craft uses an air cushion to actively damp heave motion – the system is an adaption of naval vessel technology. Illustration: Umoe Mandal
Espeland is the project manager behind the UM Wave Craft. The vessel is designed for accessing offshore wind turbines and is a surface effect ship, a type of vessel with both an air cushion and twin hulls. The air cushion is enclosed by rigid side hulls and flexible rubber sealing aft and in the bow. The active heave damping system concept originated in UM T-Craft development work for the US Navy. Since 1989, Umoe Mandal has specialized in producing surface effect ships for the Royal Norwegian Navy at its 47,000 m² yard on the southernmost tip of the Norwegian coast facing the North Sea. Calculations show that utilizing the active damping system will reduce heave motion by more than half:
“By controlling the air flow in and out of the cushion, we greatly reduce the vertical motion of the vessel and can therefore operate towards offshore wind turbines in high sea states”, says Trygve Halvorsen Espeland.
“With support from the Carbon Trust and the Norwegian Research Council, we have developed the design of the vessel and a simulation tool for active heave damping, and we will now proceed with testing the vessel’s motionreduction capability”, says Trygve Halvorsen Espeland, revealing that they are currently initiating their model test program. “Our main focus right now is the testing of a model”.
Computer simulations so far show that the UM Wave Craft service vessel will offer improved access to offshore wind turbines. The Wave Craft will also offer safer, more comfortable, and faster personnel transfer compared with today’s solutions. For instance, it will be able to conduct transits at 35 knots with 25% less fuel consumption than a conventional catamaran travelling at the same speed.
How it works
Illustration: Umoe Mandal