Diving into a niche

Frustrated by the lack of tailormade dive support craft of the right size, B Marshall Marine's long-standing client - Tony Curtis of Sub Aqua Diving Services - admitted to Barry Marshall he was reduced to taking catamarans or fishing vessels and adapting them with containerised equipment.

“So having just finished our first two vessels, we told him we would build him one,” said Chris Jakeman. Easier said than done: he wanted something under 24m yet it had to be able to hold accommodation for a full dive team, have a completely integrated dive control unit and most explicitly, a decompression chamber – all without having to give over a large amount of deck space.

So the design for the Curtis Marshall, initially outlined by naval architect SC McAllister & Co, had to answer a lot of needs.

“The benefit of having a monohull over a catamaran is, in a word, space,” said Mr Jakeman. “With a catamaran you have very little for anything bar the engines and propulsion below deck, with a monohull like ours you can have a design that actually works for everyone.”

The hull shape, said Mr Jakeman, is almost a split between a trawler and a barge with a steep hull that curves under to a flattish bottom: twin skegs help mitigate any rolling while a bulbous bow stretches the waterline for both economy and lends a comfortable ride. He added the extra length also made easier to place 150hp Kort thrusters on the bow, increasing manoeuvrability.

The main engines are a pair of Doosan 4V158TIHs supplied (in a package that covered transmission and gensets) by Watermota. Each has an output of 530bhp and coupled to very capable 60" Teignbridge propellers the set up yields ample thrust. “The benefit of these particular engines for us is that they are one of the last not to be controlled by global electronics. It isn’t run by computer and you don’t need a technician to come and plug a laptop in when something fails," said Mr Jakeman: "Sadly, engines like these are a dying breed.”

Unusually, the craft also benefits from a four-point mooring system with 7 tonne winches from Hardy Engineering and it’s also been fitted out with a bespoke load sensing bow assembly: “The boat is around 200dwt so it seemed wise to monitor – and log – exactly how much load we are putting on things like turbine towers,” explained Mr Jakeman.

On the deck there is a three-diver system from Sub Aqua Diving including 175m umbilicals and diver CCTV – importantly it is linked by Clear-com communications to the entire vessel as well as bridge through a system put together by Amber Sound. Alongside this, supplied as an integrated hydraulics package by Hardy, is a 25 tonne winch and 12.5 tonne Atlas crane plus a very handy 5 tonne A-frame for everything from recovering cable, towing a dredge plough to ROV operations. The deck area comes to 75m²: with or without a standard container this still adds up to a big, usable space; one of the vessels first jobs will see it fitted with a large compressor to airlift sand and debris from the seabed.

Although the bridge has a mix of Furuno navigation systems with PLC-based Stephenson Controls monitoring and Helmsman Systems equipment, there is an ‘added extra’ that Mr Jakeman is proud of. This is the ‘walkabout vessel control’, an innovative piece of kit put together by B Marshall Marine itself. He explained: “Rather than being limited to the fixed steering stations, there is a strap on chest pack which gives you control of all four winches, engines, bow thrusters and steering, wherever you are.”

It’s obvious that the whole vessel design is a considered one: the decompression chamber is easily accessible from the deck, and likewise there’s an easy transition from the outside into the wet rooms and showers; this has space to keep the air bottles and hang up the dive suits. “It seems like a small thing but you don’t have to tramp through the dry areas with wet gear and having the showers and toilets close to the deck really helps,” he explained. The galley itself has room to seat 10 people and behind this is a mess room with TV and comfortable seating.

The accommodation too tips the balance toward efficiency as there’s room for a dozen people in six double berths below deck, while above there are two double berths with ensuite facilities for the crew. “Other vessels tended to cram the dive teams into tiny little bunks, but these are a bit more like the standards you would find on a commercial ferry with a TV and sink in every room,” he said.

Along with capacious tanks that can hold 14 tonnes of fuel and plenty of space for provisions there is also room for 22,000 litres of fresh water: “The idea is that we can accommodate two six-man dive teams on-board and stay out at sea for around three weeks.”

But this vessel also had to be competitive to charter – and with the fuel economy “around half that of the faster catamarans” Mr Jakeman reckoned it’s going to do well: “Although on one hand we are quoting against people who normally just put the diving gear and dive control inside 10 foot container - bending the safety rules by relying on a land-based decompression chamber – we are doing everything that a 40m vessel would be able to do on a 25m boat, with all cost savings that that implies.”

By Stevie Knight