Norway’s long coastlines present a few challenges to small survey vessel designs explains Rob Voskuil of DutchWorkboats. It’s not just the long, cold transits, there’s also a lot of seabed to cover during surveys, preferably at a brisk pace.
After 15 years, Parker Maritime’s nearshore mapping vessel was coming to the end of its service life. Rather than adapting another cabin cruiser, the company realised that there were advantages to a customised build.
Parker was already interested in DutchWorkboats’ small survey vessel designs as DWB has a knack for producing a very light, trailerable aluminium boats: the 7.50 for example only weights 2.7 tonnes. But Parker needed something a little different to deal with the coastal waters around Norway and its customers: it wanted to be able to take clients out onsite, getting immediate feedback. Further, the boat also had to be transportable, coming in at under 4m high (with its antennae lying flat) including the bed of the crane truck which hoists it in and out of the water, “a deployment method we’ve been using since 2001” said Rolf Arne Ueland of Parker Maritime: "It's proven to be very effective".
This places certain demands on the design: “It has to be compact while also providing a comfortable office on water - and it has to be quick at its job,” said Rob Voskuil. Firstly, the original 7.50 hull, which is something between a semi-planing and fully planing form “gave it a very dry ride and stability when sailing slowly.”
And like the 7.50, the 8.5m version has large trim plates which makes it possible to level the boat “when it’s ‘riding the hump’ of the bow wave” he said. “This means you can carry out surveys while at mid-range, semi-planing speeds; depending on your equipment, you can double most normal survey rates making it very efficient at covering large stretches of water”.
Still, there are important differences between the 7.50 and 8.50: Norwegian survey vessels face potentially lengthy transits around the coast between the launch point and the work site; moreover Parker Maritime wanted the boat to be able to handle longer duty cycles.
Taken together this meant that while the 7.50 design had a Volvo Penta D3 engine and the associated DPS system, the 8.50 saw this replaced by a D4, 225 horsepower model and DPH Duoprop sterndrive. While both the DPS and DPH are pretty robust and the counter rotating propellers “give good directional stability without pulling to one side,” he added the DPH unit “is more of a work drive” able to handle higher torque. This gives White Beauty a transit speed of around 22 kn.
At the front there is also a bow thruster said Mr Voskuil: “This isn’t really needed for general manoeuvring, the sterndrives are flexible enough for that, but it’s very useful to have a thruster for handling the sharp turns that come with surveying a quay wall or inside a marina.”
Mr Ueland explained the new 2.9m beam survey craft has two separate moonpools behind the cabin, “a little bigger than on the original 7.50” he said. As the length was extended by a metre in all, this gave a 6m2, open rear deck which also helped fulfil Parker’s desire for enough flexibility to expand services in the future with a small A-frame and ROV, plus of course, it allows plenty of room for the very capable Kongsberg EM2040 multibeam echosounder.
Like the 7.50, the hull is shaped to allow for a clean water flow across the sensors. However, Mr Ueland added that rather than having two sets of transducer survey heads positioned at different angles, Parker Maritime has developed a housing that can switch the heads between a flat 6° attitude for normal operation and a tilted position of 30° which gives swath coverage to 90° from nadir for coastline surveys, saving space and investment costs. Further, these survey heads have been flexibly mounted, retracting into the hull in order to keep safely out of the way during transport – an option for both the 7.50 and 8.50 designs “as the survey equipment can often cost more than the boat” added Mr Voskuil.
There has been some clever work with electrical loads: besides a starter battery the boat has a separate, utility battery of 260Ah that feeds a Victron inverter, yielding 3,000VA at 220V AC. This gives a nice, even power source, very useful for the precise Seapath 330RTK, GNSS positioning and attitude sensor along with the other survey equipment. It also gives operations another layer of reliability: “We can run the instruments for an hour or two from the batteries alone”, explained Mr Ueland “so effectively it gives us an uninterruptable power supply”.
There’s also the cold weather to think about: “In Norway you need good heating in the cabin spaces but it’s also necessary around the engine – so the boat has a dedicated diesel heater built into the engine housing. This will automatically switch on if the temperature dips beneath a certain level and so even if there are freezing conditions overnight, everything will still work as it should in the morning,” said Mr Voskuil. Further, although the standard hull is a 5mm aluminium plate, the boat’s hull needed to be increased to 6mm in order to cope with the occasional piece of floating ice.
However, he admitted the real challenge lay in the cabin arrangement: “These boats need relatively large and comfortable office working areas, with surveyors normally situated along the port side with room for multi-beams or single beam scanners built into the aft superstructure,” he explained. However, Parker had a lot of experience with its previous boat and had some clear, somewhat individual ideas about what was needed, including the ability to take its clients out on surveys.
This limited the space and layout: with the passenger’s seats toward the rear of the cabin, the surveyor’s working area, along with its Hatteland Display monitors, were pushed up beside the pilot, both benefitting from Cleemann suspension seats. Added to this there’s a small wash basin, freshwater tank, and small fridge, so fitting it all together took effort, and needless to say, a lot of communication between DWB and Parker in order to give the cabin no less than four, distinct workspaces. Mr Voskuil concluded: “Our slogan is, ‘tell us what you need and will tell you what we know’...”
The new boat is an investment, certainly – but even given tough market conditions, it’s one that Parker Maritime believes will pay off.
By Stevie Knight
