German companies said they are to order four new high technology ships which will be able to lower stilts 50 metres to the seabed and jack themselves up. Cranes on the vessels may need only about a week to assemble an offshore wind turbine, according to details from civil-engineering company Hochtief in Bremen. The windmills will be built on concrete artificial islands. The new fleet, operated jointly with the Beluga shipping company of Bremen, would be able to erect 160 wind turbines a year.  Hochtief already operates such a ship, the four-year-old Odin, which has been contracted to put in place a 45-metre high foundation for a transformer in the middle of the Alpha Ventus wind farm in German coastal waters of the North Sea.  A Beluga spokeswoman said a contract would be signed next week to spend 800 million Euro on the new-technology ships, with all four to be in operation by 2012. Each will have four stilts and will take all the components out to the watery building sites and accommodate all the workers.