Caden Foss: 110′ Multi-Purpose Tier 4 Tug

The Pacific Northwest has been at the forefront of North American tug design since the 1980’s, and has brought many innovations to both ship-handling and long-haul tugs. Over the years, a handful of boats have attempted to combine both these functions in one hull, but the goal of a truly“multi-purpose tug” has remained elusive. Vessel Chartering LLC of San Francisco is the latest operator to take on this challenge with a 110′ x 40′ tractor design. It was jointly developed by Baydelta Navigation and Jensen Maritime, the Seattle naval architects who have produced many successful tug designs in this size range.

Construction began early in 2016 at JT Marine in Vancouver, Wash., who had previously built three 120′ Jensen-designed Titans for Hyak Marine, one of which is chartered to Foss. The new 110′ l was launched in May 2017 in Foss colors with the name Caden Foss and entered service at the end of July for an initial three-year charter. Baydelta operations manager/port engineer Peter Zwart was responsible for this project, which utilized all the experience gained from the company’s previous new-build program of six versatile 100′ tractor tugs delivered from 2006-2014, They were built by Nichols Brothers to a class design from Jensen with a 90-ton bollard pull. The Delta Billie and Delta Cathryn were retained for the company’s own use, while four more were long-term chartered to other SF Bay operators Foss and Crowley.

Baydelta was formed In 1993 by three San Francisco Bar Pilots who brought all their experience to bear in their choice of tugs and gear. They provide ship assist, petroleum escort and general towing services throughout the San Francisco Bay area as well as undertaking offshore assignments. Baydelta completes 500 to 600 escorts annually as part of a system that is heavily regulated by California’s Office of Oil Spill Prevention and Response (OSPR). The ships pass under three bridges with a tug tethered at the stern, navigating through narrow channels with strong currents and winds, passing heavy commercial and recreational traffic.

Environmental Considerations

Zwart explained that Vessel Chartering co-owner Captain Ron Charlesworth recognized in 2014 that several factors, particularly a court ruling on Chevron’s Richmond refinery modernization project, had created an opportunity to build and bare-boat charter a new tug on the Bay. The ruling required Chevron to cap greenhouse emissions at current levels and provide electrical supply (“cold ironing”) to tankers at the dockside. National environmental regulations would require the new tug’s engines meet Tier 4 emission controls and the use of a ballast-water treatment system. However, recently launched tugs had demonstrated the feasibility of using diesel fuel as movable ballast.

The decision was made to start with a clean sheet and build on the proven Delta 100’s with some ideas from Jensen’s proven 120′ Titan ocean-going class. Finally, Zwart was able to return to Jensen with a full-fledged concept for the multi-purpose boat. His check list now included a full-length keel with an 18′ draft for escort w0rk, the ability to turn 11,000 TEU ships in the 1400-foot width of the Port of Oakland turning basin, and a deck layout that could safely moving barges around the bay or offshore.

Fuel capacity was also an issue. The Delta 100’s can carry 70,840 gallons of fuel, but the new design would need a capacity of over 120,000 gallons to give it real long-distance towing ability. That 70% increase definitely required greater length to support the extra weight, Jensen’s engineers pointed out, and 110′ was the absolute minimum. The aft deck was laid out for barge towing with a double-drum winch that could handle both wire rope and a synthetic hawser for towing on the hip, and the foredeck was raised by four feet for offshore work and to allow full crew accommodations in the foc’sle.

These were just the first of many changes and compromises that were made to achieve the multi-purpose ability. According to Zwart, the key to a successful charter is to anticipate where the industry is heading and find new design features or technology that are likely to add value, safety or efficiency in the future, and incorporate these in a complete package to present to a potential charterer.

Caterpillar Selective Catalytic Reduction

A pair of the newest version of Caterpillar’s 3500-series diesel, the 3516e Tier 4 engine, came packaged with two Selective Catalyst Reaction (SCR) chambers. These neutralize the harmful NOx in the exhaust by scrubbing it with a spray of urea solution carried in a 4,600 gallon stainless steel tank–enough to treat the maximum fuel capacity of 123,000 gallons at the standard 5 percent rate. (The crew will transfer some of the 123,000 gallons of fuel between tanks in order to maintain proper trim.)

The power is increased slightly to 3,385 HP and the engines and entire space are painted while—a Baydelta tradition. They specified additional air filtration for the engines, plus Centa flexible couplings and carbon fiber shafts with a single bearing. On Jensen’s first Tier 4 build, the 120′ Titan Earl W Redd, the 6.5-feet x 5.25-feet x 3.3-feet SCR unit is placed on the main deck in the fidley, but on the 110, there was enough overhead space in the engine room, forward of the engines. With the extra depth of hull, this installation is remarkably clean.

The SCR module is wrapped in a standard insulation blanket, and is equipped with sensors to measure the percentage of the exhaust gases before and after treatment. However, the exhaust flow builds up more heat in the chamber than was initially predicted. This has been a real challenge, said Johan Sperling, a Jensen V.P. He had to go back to the drawing board to increase the size of the ventilation ducts. Sperling stated that the vessel’s length is sufficient to give it the towing performance and range of the Titan class, while still providing the maneuverability and feel of the Delta class tugs.

Two Cat 71-150 kW gensets are located forward and to port of the mains next. Like the Delta class, the 110′ has firefighting ability with a Stang 900 GPM Monitor driven by a 125 HP electric motor, giving it a FiFi Class 0 rating ​​​​​​​​​​?The main switchboard is to starboard, and the third gen-set required by the OSPR for back-up during tanker escorts is a Cat C4.1 75 kW installed aft in a insulated cover to reduce noise when not under way.

There is also a centerline compartment aft of the engine room that is dedicated to housing the switchboards and controls panels for all accessories, including both winches, the twin Rolls Royce 255/3800 FP ASD’s, pumps, hotel loads etc. On one wall, Woodward’s easYgen-3000™ Series paralleling genset controllers combine generator control and protection with advanced paralleling function through the LogicsManager™ programmable logic function that can easily integrate with SCADA or PLC-based control systems.

On the bow is an electric Markey Model DEPCF-52-75HP Class II Hawser Winch. It has a drum capacity for 600 ft. of 3” diameter synthetic line and has a rated performance of 30,800 LBS at 378 ft/min, giving it a 91 short-ton bollard pull—enough to handle container ships up to 18,000 TEU. Included in the package is the Markey Render/Recover feature that allows for hands free operation at up to full rated line-speeds and line-tension.

For barge towing, the aft deck is fitted with a 100 HP electric, double-drum Rapp tow winch. It can pull over 75 tons on the first layer, and wind 2,500′ of 2.5” wire on the port side and wrap a shot of chain on top of it via an offset level-wind. Bollard pull is 92 short tons.The Rapp pin box holds four pins with hold-down hooks. To fulfill the dual-purpose demand, the starboard winch drum carries a synthetic hawser used to snug a barge up on the hip through the small 50-ton staple on the aft deck. There is a back-up come-home drive if the primary motor fails, and all controls are pneumatic. This new design is a significant addition to Rapp’s range of tug winches, says Johann Sigurjonsson, president of Rapp USA.

The Caden Foss is well-protected on the bow by an unusual double row of Shibata rubber cylinders above a laminated -rubber wrap-around, all supplied by Schuyler. Closer to the waterline are eleven vertical strips of D-rubber. Two layers of D-rubber are wrapped around the stern, with tires amidships. This is to accommodate ships and barges of any size and draft.

The spacious wheelhouse provides all-around visibility and also meets the multi-purpose description: while the pilot has a conventional ASD helm station, the aft end of the house is devoted to the boat’s offshore function with matte black overhead paneling, a chart table, with an aft-facing set of duplicate helm controls plus the towing winch control panel. This uses Rapp’s patented PTS Pentagon Control System providing the operator full control and data tracking of winch use for maximum safety at sea. Navigation electronics are by Furuno and the ergonomic helm chair is a Bostrom Sea Post.

The deckhouse is large enough to accommodate a spacious galley, mess and lounge, and officers’ quarters. The four crew cabins in the forecastle under the raised foredeck are also very well furnished. The maximum capacity in the five rooms is ten, but Zwart expects the most crew will be six to eight when offshore. Fresh water capacity is 12,000 gallons, with a water maker available for the long hauls.

“We’ve done our best to give the Caden the ability to handle practically every type of tug work on the west coast that we can foresee. We think the industry will be watching it with interest,” Zwart told Pacific Maritime after the tug arrived on San Francisco Bay in July.

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