VESSEL REVIEW | Giles S – Versatile dredging support tender for Australia’s Port of Brisbane

The Port of Brisbane (PBPL) in Australia recently welcomed a new harbour tender into service. The vessel has been named Giles S in honour of the late Giles Stimson, who formerly worked as Manager of Hydrographic Surveys at PBPL.

The custom workboat was built by BtB Marine to a design by Global Marine Design (GMD). Measuring 8.7 metres (29 feet) long and powered by twin Suzuki 110kW (150hp), four-stroke petrol outboard engines, the vessel can transport a maximum of six passengers plus two crewmembers at speeds of up to 32 knots. The petrol outboards are fitted on a specialised transom that can also accommodate larger diesel or hybrid outboards in the future.

"We required a new support vessel to accompany our flagship vessel, the trailing suction hopper dredger (TSHD) Brisbane, as it works in our port and along Australia's east coast, servicing other Queensland ports, local councils, and infrastructure projects," Andy Perry, PBPL's Executive General Manager Marine, told Baird Maritime. "The vessel can be stowed on Brisbane's deck and transported between ports. It also replaces the previous support vessel Qua."

When in port, Giles S is returned to the water for the campaign and used to transport personnel, equipment, and stores to the TSHD, covering distances of 30 nautical miles, which is far beyond that of normal dredging operations. Perry remarked that the vessel needed to be robust enough to come alongside the larger Brisbane while the TSHD is underway and be light enough to be lifted and stowed safely via a six-tonne deck crane. The tender also needs to be stowed on board the existing deck of the 7,000-tonne TSHD while allowing safe access to all areas around the latter.

Compact boat serving multiple roles

"Significant investigation and preliminary designs were undertaken to identify the appropriate arrangement and GA of a suitable boat," added Perry. "Key design considerations included NSCV 2C compliance; the size not exceeding the working capacity of Brisbane's deck crane; the ability to accommodate storage and personnel out of the weather; access stairs for safe boarding to the TSHD's main deck for crew transfers; redundancy and contingency in mechanical operation offered by dual outboards; a substantial equipment carrying capacity; and simplicity in operation for a multitude of crews."

The tender also needed to have level flotation and buoyancy in the event of overturning, polyurethane fendering, Nylac internal and external coating to preserve the aluminium hull, and a design cruise speed in excess of 25 knots. The flotation requirement was satisfied by the use of foam-filled bulwarks that will allow the vessel to float level if fully "swamped". The walkways are meanwhile kept flush and wide and handrails are fitted to permit safe crew transfers.

"The vessel was specifically designed for crew transfer, so there are interchangeable steps from port and starboard to allow easy access for the crew to enter and exit the vessel onto the larger dredger," said Chris Hough, founder and owner of BtB Marine. "Apart from the GMD hull, the owners had some specific requirements. PBPL also wanted custom windows in the forward roof to improve visibility for the coxswain, so they can look upwards at the ship. The owner also required double continuous welding throughout the vessel, which means all stringers, frames are continuously welded on both sides."

"We conducted a significant amount of research to find a vessel that would satisfy those parameters." said Perry. "This also included researching other vessels of this design and talking to owners and operators. We sought feedback from commercial operators from as far afield as Western Australia as well as other port operators that had this design of vessel, and the feedback was very positive."

"To achieve the main criteria of stability and load carrying capability, the 'cathedral hull design' was quickly identified, as opposed to the conventional monohull," said Perry. "Also, to avoid a one-off design, we inspected GMD boats and conducted test runs. Aurora Marine provided GA drawings and preliminary design criteria to ensure the new boat can fit within the deck space on the TSHD."

"The owner selected the 'cathedral hull' for its safe and predictable seakeeping and soft landings," said vessel designer GMD. "Of particular interest was the boat's excellent stability at rest, underway, and while transferring personnel at sea."

The 32-knot sprint speed means transfer times are greatly reduced. This is an important attribute, as the owner's previous tender vessel was not considerably faster than the TSHD. The displacement was also kept below five tonnes to ensure suitability with the TSHD's existing crane.

The outboards feature stainless steel propellers and power-assisted hydraulic steering. This offers added safety due to the dual engines having separate fuel tanks and electrics. The electronics suite includes a Simrad navigation package while purpose-built mounting pads are available for the installation of hydrographic survey equipment.

The outboards also have a charging line. This can automatically charge the tender's house batteries while in operation. The electronics are integrated to enable data to be continuously transmitted to PBPL's base in Brisbane. This back-to-base monitoring system fitted into the electronics system allows PBPL to assess the tender's operation without having to be physically present on the vessel.

"All cargo and crew transfers between the shore and the ship happen 24 hours a day, seven days a week on this," Hough told Baird Maritime. "The tender fills the gap of having a vessel that is compliant to take passengers but still compact enough to be lifted on and off the dredger."

Safety and durability for extreme operation conditions

BtB Marine custom-fabricated the deck layout in compliance with NSCV rules. The aft boarding steps were designed so that these could be easily handled by the deckhand, whereas on PBPL's earlier tender, the coxswain needed to temporarily leave the helm to assist the deckhand in moving the steps from one side of the vessel to the other.

"We also custom designed, fabricated, and certified a dedicated cradle for stowing the tender on the TSHD's deck. To do that and ensure that the vessel was going to fit perfectly in the space, we went down to Brisbane and we did a three-day scan of the area. We then used CAD to generate the cradle design."

GMD added that the design, construction, fendering, and fit-out are extremely robust, with the vessel capable of withstanding the harsh working environments characteristic of push-on and pilot-style transfers, plus being lifted onto the TSHD Brisbane. The vessel is lifted from three points, carefully positioned such that it is level when lifted.

"As with most smaller vessels," said GMD, "allocating space for crew, passengers, fuel, deck cargo, and stores while maintaining suitable trim and stability compliance is a challenge, particularly when the wide bulwarks are foam-filled for level flotation. Through multiple discussions with the port and the builder, we arrived at a sensible arrangement that will result in a boat able to serve the port for many years. Also, as it is our first design project with PBPL and BtB Marine, we took the time to learn how these organisations operate to know which requirement and detail preferences we can apply to our future builds."

"We worked constantly with PBPL throughout the build to ensure the vessel met or exceeded all their requirements," Hough added. "This included ergonomics and everything related to the skippers. We had people coming and going to understand the entire layout of the vessel, how to operate everything, and ensure workplace safety, so a lot of thought was devoted to incorporating features that satisfied the owner's requirements."

Hough remarked that the fendering system incorporated on Giles S is now being used extensively across BtB Marine's range of vessels. The diesel outboard-ready fuel system is also starting to be incorporated into the company's future builds for environmental reasons. Other plans include continued collaboration with GMD in the future following this and an earlier project that made use of GMD's proprietary hull design.

"The fit-out is very simple but very practical," Perry told Baird Maritime. "The internal bench seating can be readily removed to give space to stow stores and equipment out of the weather, and there is space to lay a full-length stretcher for medical evacuations. The fendering system is a proprietary polyurethane D-mould custom made to the shape of the entire vessel bulwarks."

The mould is made from closed cell foam coated with a "leather-like" outer skin. Perry said this has proven effective as it is neither hard nor soft and is able to absorb impact during alongside manoeuvres.

Following the hand-over to PBPL, the owner took Giles S on a 100-nautical-mile round trip to run in the engines ready for their first service. According to GMD, initial feedback from PBPL revealed that the vessel is able to easily keep up with the larger TSHD during personnel transfers and also offers improved comfort and seakeeping.

"For an 8.5-metre vessel, Giles S has an incredible ride," Perry remarked. "The vessel seems to power through the waves, and it is exceptionally dry. The overwhelming response from the many PBPL masters that operate the vessel is that it is 'awesome'."