VESSEL REVIEW | Kapena Bob Purdy – Hawaiian inter-island barge-towing tug

The oceangoing tug Kāpena Bob Purdy, built for Young Brothers of Honolulu, Hawaii, a subsidiary of Foss Maritime Company, is now in service.

'Kāpena" means Captain in Hawaiian, and the Kāpena Bob Purdy is the fourth in a series of US-built tugs, all named for captains in Young Brothers' 100-year history of operation.

Young Brothers operates as a public utility, charged with transporting cargo between islands. The company needed efficient, ocean towing tugs capable of towing cargo barges inter-island in Hawaii as part of its service. The vessels will renew the fleet and replace older vessels that have been or will be retired from service.

The vessels were built to a Damen design, primarily using materials and equipment purchased and consolidated by Damen, then provided to the shipyard for construction of the vessels. Exceptions included the hull steel and the main engines.

According to Foss Maritime, this proved the biggest challenge in building the vessel, as it represented an unusual way of working for the shipyard. Foss said it required more communication and material-handling than on most builds.

The Kāpena-class vessels are Young Brothers' first use of the GE EPA Tier 4 emission engines, which require no urea dosing due to their exhaust gas recirculation system. Avoiding the urea tank and associated dosing system simplified design, purchasing, installation and commissioning.

Two GE 8L250 MDC main engines, with total power of 4,500 kW (6,027 bhp) at 900 rpm, were installed. They turn a set of counter-rotating 3.2-metre-diameter propellers in "Optima" nozzles after passing through two Reintjes WAF 3455 gearboxes.

The bow of the tug has a Markey WESD-16-16-26 electric bow winch, dual windlass, dual warping head combination unit.

The towing winch is a Markey TESD-34 100hp (75kW) electric towing winch with dual drums each capable of handling 2,500 feet (760 metres) of 2.25-inch (5.7cm) diameter tow wire.

The tow wires are handled on the aft main deck by Smith Berger flush deck shark jaws and tow pin table. The shark jaws provide safe barge connections and disconnects by securely capturing the towing gear before personnel enter the aft deck.

Finally, the operator reports that the Damen-designed accommodations for the vessel are very nice, and particularly quiet.