Sanmar Launches New Variable-Drive Tug Design

Turkish shipbuilder Sanmar has launched its first tug with Caterpillar's "advanced variable drive" hydraulic propulsion system, which decouples running speed from engine RPM and allows the operator to use both auxiliary and main engines for propulsion. The tug also marks a 25-year milestone: it is the 200th tugboat that Sanmar has built to a Robert Allan Ltd. design. The newly-launched Bo?açay XXXVIII is an evolution of the RAmparts 2400-SX.

The CAT AVD system consists of a pair of dual-input, continuously variable transmissions located in the shaftlines between the main engines and the Z-drives. AVD offers many of the advantages of diesel-electric, but with lower cost, according to Cat. 

"AVD incorporates a planetary gear set allowing seamless clutch engagement of main engines, auxiliary engines, or both to provide a scalable power installation,” said Nathan Kelly, Caterpillar marine product definition engineer. “This also allows propeller speed independent of engine speed so optimal engine efficiency can be achieved leading to fuel savings of fifteen to twenty percent. Basically, all the benefits of a variable speed diesel electric propulsion (DEP) system at a fraction of the cost and size."

Robert Allan Ltd. and Sanmar both worked with Cat on the product's deployment in a tug application, its first commercial use. The Bo?açay XXXVIII is entering service in Sanmar's own fleet in Izmit Bay, Turkey.  

Bo?açay XXXVIII has been painted with a bright green hull and colorful flowers on the deckhouse, inspired by Andy Warhol's "Flowers" print. The livery was selected to reflect the increasing focus on environmentally-friendly operations. "This regalia . . . is bound to attract much attention in the usually moribund world of tugboat aesthetics!" Robert Allan Ltd. said in a statement.