1. Foss creates new propulsion design by adding z-drives to cycloidal tugs; 2. Seabulk will double its fleet of saucer-shaped SDM tugboats; 3. Vane Brothers snapping up tugboats as fast as Thoma-Sea can build them; 4. Wilmington tractors undergo changes as company plans for a new tug; 5. Gulf Coast tug companies embark on aggressive program. Foss Maritime of Seattle has created a dramatic new mode of tug propulsion by adding a single azimuthing z-drive to the stern of two of its cycloidal-drive tractors. The Voith-Schneider cycloidal-drive tugs Wedell Foss and Henry Foss, built in 1982, have been made much more powerful and more maneuverable with the addition of a z-drive unit weighing about 39,000 pounds. Placed about a quarter of the way forward from the stern, the z-drive is powered by a Cummins KTA50-M2 diesel engine. The change boosts the rated horsepower of the tug from 3,000 to about 5,000, with attendant boost in bollard pull from 35 tons to 57 tons, according to Don Hogue, director of engineering for Foss.
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