Feature 1 | SHIPBUILDING TECHNOLOGY, MATERIALS & METHODS Grasping shipping’s Holy Grail
Aluminium foam sandwiches are set to revolutionise shipbuilding. Finnish yard LaffComp and its partner the Fraunhofer Institute in Germany have innovative designs for woodchip, passenger and bulk carrier vessels and a container ship equipped with its own loading and discharging system.
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ntil now it has been accepted that the hull weight of a ship will be set by the thickness of the steel plate and
the amount of steel used in the design of the ship. Fast ships have lightweight aluminium bodies that reduce the power to weight ratio necessary for driving the ship forward. Lighter ships mean that a vessel can operate
at a given speed with less power and that means fuel savings. Finding a material that is light enough to substantially reduce the weight of a ship while maintaining enough strength to operate in icy conditions such as the Baltic or the lake regions of Finland is the Holy Grail for ship designers and that material has now been developed. New shallow draſt designs for vessels
able to operate in icy conditions lake areas where the safe sailing draſt is only 2.4m with the ability to carry enough cargo to make the vessel economically viable (up to 6900m3
of peat or woodchips) requires
a new lighter material. Enter the Fraunhofer Institute for
Machine Tools and Forming Technology in Chemnitz, Germany, which has developed an aluminium foam compound that with a steel plate either side forms a sandwich creating a metal which when applied to ocean going vessels can reduce the lightweight of the ship by up to 30% and strong enough to allow the ship to be awarded ice class status. Te material itself was first developed in 1961 said Dr Thomas Hipke who helped to develop the material and its possible applications at the Department of Lightweight Structures at the Fraunhofer Institute during the 1990s. An Aluminium Foam Sandwich (AFS) or
a Steel Aluminium Foam Sandwich (SAS) is manufactured by mixing aluminium powder with a blowing agent, in this case titanium hydride, the mixture is then placed through an extrusion machine to produce rods of around 20cm x 25cm.
24 By placing these rods between two steel
sheets and heating the material to more than 600°C the aluminium melts, fusing itself to the steel and the titanium hydride creates hydrogen bubbles, “it’s like baking bread dough” said Dr Hipke as the mixture forms a dough that hardens when it cools, but its properties are immensely strong and comparatively light. Another property of the material is that
it bends more readily which also allows for the flexing of a ship. Two test projects using ALF and SAS are now under way, with the German yard Blohm + Voss developing a rudder and machinery for the drive of a passenger vessel using the foam, but more spectacularly in Finland the Laffcomp Oy yard has a hull design, the Bioship, that can be used as a bulk carrier, a log carrier, a woodchip carrier or a container vessel. Each vessel will be so light that new and innovative designs will allow these vessels
to compete in new markets that were hitherto unavailable to the maritime sector. Te container ship will have a gantry crane, also constructed from ALF, mounted on rails on deck with extendable legs that stretch out to the quayside. Tis crane will allow the ship to handle its own cargo at any shallow port, including river terminals even if the terminal does not have its own gantry cranes. Ships will be powered by liquefied natural
gas (LNG) engines that will further reduce the emissions from the vessel, including SOx, NOx, particulates and CO2
. Vessel development will be through
LaffComp’s sister company, BioLaivat KY, which was established to offer transportation “for bulk cargoes, liquid cargo and containers around the inland and coastal waters of Finland, Scandinavia, Europe and Russia,” according to Veikko Hintsanen, director at Laffcomp.
The Naval Architect July/August 2011
A cross section of the Aluminium Foam Sandwich and Steel Aluminium Foam Sandwich created by the Fraunhofer Institute, Germany. The material is extremely light weight and very strong, ideal for new ship designs.
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