TMD’s E-FINN Hull is the Next Generation of Energy Efficient Boat Design
The Hull Design Efficiency Challenge — a joint initiative of The Atlantic Canada Opportunities Agency (ACOA) and Impact Canada — was launched in July 2019 to encourage Atlantic Canadian boatbuilders and designers to come up with innovative fishing boat hull designs less than 15 metres to reduce fuel use and greenhouse gas emissions.
ACOA also partnered with the National Research Council of Canada’s Ocean, Coastal and River Engineering Research Centre in St. John’s to provide scientific and technological expertise to test and validate the applicants’ proposed solutions. On May 12, 2021, TriNav Marine Design Inc. (TMD) was selected as the Hull Design Efficiency Challenge grand prize winner.
We knew that to have an accepted and successful design in the fishing industry, our hull design, the E-FINN, would have to be one that was easily recognizable, practical and diversified. To achieve this, we reflected on the designs we have already completed over the last 25 years and what was commonly used in the industry.
In the less than 15-metre category, the most common design throughout Atlantic Canada is the Nova Scotia-style lobster boat. We worked with this basic shape and dimensions to develop a more efficient hull.
One of the great features of this basic design is that it can and is used by fishers involved with pretty much all species, but particularly lobster, crab, scallop, groundfish and seining. We knew the vessel had to be a displacement type hull since most fisheries require a large fish hold and carrying capacity, particularly when carrying lobster and crab in live well tanks and when seining. Also, this type of hull has great stability characteristics and handles well in heavy weather. Hence, the reason there are thousands of this style of vessel currently in the industry.
The E-FINN hull design has many features that improve on efficiency — most notably an increased waterline length and refined entry angles at the bow. The TMD design has a reversed bow rake to help achieve this, while introducing bow flare to reduce spray and green water on deck.
A refined or sharper entry angle makes it easier to push the vessel through the water, requiring less energy to do so. We also refined the stern shape to reduce waterline breadth to reduce drag, without affecting stern buoyancy and trim.
A large contributor to inefficiency is drag, as many tonnes of water are dragged behind the vessel in its wake. Reducing this means less energy is required to move the vessel forward. In addition to this, we arranged the vessel in a traditional manner with the fish hold aft and the propulsion machinery and accommodations forward but allocated the spaces so that trim was less extreme in various loading conditions. Trim by the stern in particular increases hull immersion and drag, increasing energy consumption.
key feature of the vessel that improves efficiency is an efficient propeller.
We will be consulting with regional suppliers to optimize the design and efficiency of the propeller, to ensure as much as possible, that the maximum power produced is actually used by the propeller. This will be accomplished by optimizing propeller diameter, blade area ratio and pitch.
The rudder design for the E-FINN vessel is improved to create better water flow. A foil design rudder, similar to an airplane wing, is more efficient than a basic plate rudder with stiffeners. The design also incorporates stern post fairing to improve water flow to the propeller and this will improve performance and efficiency.
The E-FINN hull will be built with minimum or no exterior attachments or protrusions (a clean hull).
All attachments will be recessed with appropriate fairing. This will reduce surface area, frictional resistance and drag — all which add to hull efficiency.
We will also be recommending to builders to use low friction gelcoat, now available on the market, as a final finish. This will create a very “slippery” hull surface that will make it easier to push the vessel through the water.
The structural design of the hull is optimized to ensure structure is of an appropriate size and location to optimize strength. No wood structure will be used in the construction if the hull is to be built from a mould.
If a mould is not used during vessel construction, only minimum wood materials, such as plywood, will be used to create the shape for the hull frames. All other structure and plating will be solid fibreglass or structural foam cores.
Optimizing structural design is important to reduce hull weight, material cost and the associated labour cost. Every aspect of the hull and vessel is improved to reduce resistance. This leads to a reduced requirement for power to move the vessel forward. We estimate that as much as a 20 per cent reduction in fuel consumption can be achieved with the combined effects of the E-FINN hull design features.
Equally important in the hull design is that the E-FINN vessel can be fitted with a hybrid propulsion system, where high-efficiency diesel generators will supply power to batteries where it will be stored and used on an as-needed basis.
Battery power will supply power to electric motors connected to a gearbox which will drive the shaft and propeller. Alternatively, the MAN Hybrid Smart system, or similar, which uses a high efficiency diesel engine coupled to an electric motor and gearbox to drive the propulsion system. The electric motor can be clutched in and out as required to charge batteries which could be used to drive the vessel and the systems onboard.
This arrangement will consume only the fuel needed based on the demand. The hybrid system will supply power to drive the vessel, but also fishing equipment and carry loads such as lights and galley equipment.
When demand is low, a reduced amount of fuel will be consumed, plus the batteries can be charged at dockside from clean energy sources such as hydro electricity. We estimate that as much as a 20 per cent reduction in fuel consumption can be achieved with the hybrid propulsion system. That’s a 40 per cent total reduction in fuel consumption and greenhouse gases with the combined benefit of the efficient hull and hybrid system.
We are optimistic that clients for the E-FINN vessel will choose a hybrid propulsion system, particularly when access to government funding to assist with green energy projects becomes more available.
In the meantime, TMD is working with qualified boatbuilders to develop a mould so the hull can be mass produced. We are also currently compiling a list of interested clients in the fishing and aquaculture industry who want the E-FINN hull.
We are now working with three clients who have decided to proceed with the E-FINN vessel. We are expecting that the first vessel will be completed within the next 12 months.
