VESSEL REVIEW | Indigo – Long-range, multi-purpose security vessel was a challenging design project

BtB Marine designed and developed the 7.5-metre ultra-long-range patrol boat Indigo for one of its clients in Gladstone, Australia.

This company was in need of a gas-compliant security vessel that had very low maintenance requirements and was outboard powered by diesel fuel, with compact dimensions for inshore and offshore operations.

It had to have a very long range to minimise refuelling requirements and still be a compact trailable vessel to allow it to be taken out of the water to service the outboard.

The vessel also had to have a large enough cockpit to allow a navigator position for a crewmember to monitor the FLIR camera for night-time security work.

One of the unique features of Indigo is that it is powered by a diesel outboard and has a 900-litre fuel tank, for a range of over 600 nautical miles. This allows the vessel to undertake long-range reconnaissance and patrol work (if called on to do so) and offshore dive work.

The vessel is designed to carry out both offshore and inshore operations in a variety of duties such as harbour patrol, hydrographic survey, reconnaissance, dive construction, port security and environmental monitoring.

Being one of the first gas-compliant, outboard-driven vessels fuelled by diesel, Indigo is easily maintained and road transportable if required for remote operations.

BtB told Baird Maritime that having a long range and large operational envelope with such a small vessel was quite a design challenge.

It took many man-hours to work through all of the relevant Australian Maritime Safety Authority (AMSA) regulations, and was also required to have double continuous welding on all impact zones so as to be able to be a fast craft under AMSA regulations.

The hull is also protected against impact by a custom fendering system from France's Océan 3.

"We learned from building this vessel how to design vessels which suit heavier diesel outboards, and all of the rules and regulations around diesel fuel tanks on small vessels with outboards," commented BtB.

The vessel has a large cabin with room for additional storage or desk space. It also features a large and comfortable sleeping bunk. Depending on operation, Indigo can be crewed by a coxswain only.

The vessel is equipped with an Oxe 200hp (150kW), two-litre diesel outboard driven by belts instead of vertical shafts and a bottom end gearbox to deliver 420 rpm to the propeller.

CZone Electronic switching is used to operate all of the electrical components of the vessel. An all-Garmin layout was selected, offering complete electronic and electrical integration as well as dual range radar and MARPA for safe navigation, plus a customised screen layout.

The master and navigator both have a screen available, each of which can be operated from their seats.

Indigo is used for port security and has a FLIR thermal camera for night-time security operations.

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