(Published by TOWLINES Offshore Newsletter May 11, 2022)
Diversified Marine in Portland, Oregon has been building Robert Allan RApport tugs since 2000 for local operator and charterer Brusco Tug & Barge. The latest was named Athena– the tenth in this line—that was recently delivered to Brusco before being turned over to Crowley Maritime for a long-term charter in the Port of Seattle. This is the latest version of the design called the RApport 2500 D with beam extended from 36 feet to 40 feet to handle the increasing power of the latest Tier 4 Caterpillar 3516e diesels. It has a hull length of 78 feet (23.77 meters)—below 24 meters that requires compliance with the ABS load-line rule. Overall length including fendering of 25 meters (82 feet). Draft is 17 feet with a shallow fin keel forward.
This is the third tug to this design that Diversified has built for Brusco but the output of the 3516e (C Rating–Maximum Continuous) over this short period has increased from 88 tons bollard pull for the Hercules (2020) to 94 tons for the Apollo (2021)and 96 tons for the Athena (2022),which is reported to be “the most powerful tug of its size in the world,” with the latest rating increasing maximum output to 2 x 3386 bhp (1865-2525 bkW) at 1600-1800 rpm. (Total output 6772 hp)
According to Frank Manning, Diversified’s director of business development, the biggest issue with these small Tier 4 tugs is finding the space to accommodate this additional SCR units required by the strict Tier 4 regulations. The added beam has created enough space for the two 1,250-gallon stainless steel diesel-exhaust (DEF) tanks at the aft end of the engine room to port and starboard, while the SCR’s are housed on the main deck in the stack compartment. The Caterpillar “Cat Clean Emissions Module” provides precise control of the engines’ timing and combustion cycle, and meters the injection of diesel exhaust fluid (DEF) into the selective catalytic reduction (SCR) units.
The air-set brake with manual over-ride can hold 678,000 pounds. Like all Markey winches, this unit incorporates anti-condensation heaters within electric motors, auto-brakes, and electrical panels. The overall weight is about 30,000 lbs. The tug’s staple is fitted with a plaque that gives the maximum load at all angles of pull, up to 45 degrees from centerline at 155 short tons. This is controlled by Markey’s proprietary “Render/Recover” automatic tension package controlled from the winch station or the helm. I was invited on board to inspect the Athena shortly after launch from Diversified’s dry dock where it was assembled. The 40-foot beam does give a spacious feel to the engine room, which is dominated by the large-diameter exhaust piping leading to the SCR chambers. The carbon drive shafts are by the Spanish manufacturer Vulkan. In the stern, the Swedish Berg MTA 628 thrusters installation is very clean without a clutch, which is on the main engine that also provides the electric power to turn the ASD’s, eliminating multiple belts and pulleys.
Electrical power is supplied by a pair of Caterpillar C7.1 150 kW gen-sets on the center line. These also power the 112kW electric motor that pressurizes a Carver fire pump supplying over 1,000 gallons per minute to the fire monitor on the port side of the wheelhouse. The helm station is equipped with a full suite of Furuno electronics including two FR 8125 radars and an SC 30 satellite compass with plotter, autopilot, sonar etc. and a Transas integrated navigation system. Closed-circuit cameras provide remote coverage of all the machinery spaces.
A major change for the crews in the new, wider tugs is the increase in space that permits more accommodation, changing them from day boats with a couple of bunks into a proper overnight layout with a complete galley and mess, laundry and heads on the main deck, and three double cabins below deck to sleep a full crew and a second watch if necessary. Diversified sent a representative to visit the previous tug Apollo in San Francisco and talk to the crews to find out if they had any ideas for improving the placement or utility of the numerous shelves and lockers around the boat. This led to several changes and useful adjustments that they will incorporate in the next Rapport, which they have already started.
“We’re proud of the incredible Hercules Class vessels our partnership with Brusco and Crowley has produced. We’ve worked closely with Crowley to incorporate operator feedback into each build while increasing horsepower on each tug. Athena will be an excellent boat, and we’re excited to see it working for a forward-thinking company like Crowley,” Frank Manning commented.