F/V Raven Sees Notable Gains


raven

By changing to a Nautican propulsion system, the F/V Raven saw significant gains in speed and fuel economy:

  • A measured increase of 13% in bollard pull,
  • A measured reduction in horsepower to achieve same vessel speed,
  • An increase in speed on average of over 1 knot and reduced fuel consumption at a given RPM,
  • A net average increase in fuel economy (nm/gal) of over 20%, and
  • A significant improvement in steering noted by the crew.

With all the challenges of staying in business in the commercial fishing industry, the owners of the F/V Raven were looking for ways to reduce their overall operation costs and decided to look at options for improving the vessel’s performance. They approached Nautican with their goal sof increasing thrust at towing speed, improving overall fuel economy, and maintaining RPMs while turning during a tow.

The existing engine, gear, and shafting were to be retained to minimize costs. Additionally, there would be no investment in new equipment without assurance of a significant gains of 10%+, particularly since the existing nozzle and rudder were in good condition.

“We were excited to take on the challenge,” said Elizabeth Boyd, owner of Nautican.“This is exactly the type of engineering Nautican has done since 1976.”After evaluating the vessel’s operational needs and analyzing the current system’s performance, the Nautican Ocean Series Integrated Propulsion Unit(IPU) showed a minimum of 10% increase in bollard thrust as well as an overall increase in thrust for any given horsepower. This could all be accomplished by replacing the existing nozzle and rudder with a Nautican IPU, which includes the Nautican High-Efficiency Nozzle, Pre-Swirl Stators and Triple-Rudders. Also, by trimming down and repitching the existing propeller, Nautican was able to save on the cost of a new propeller.

With the proposed results in hand, the Raven’s owners decided to go forward with the upgrade. Nautican worked in conjunction with the shipyard, Fred Wahl and naval architects, Hockema & Whalen Associates, to assure an on-time schedule and avoid any delays or extended haul-outs.

Prior to haul-out, the Raven performed a sea trial in open waters noting the vessel load condition. Data for the vessel speed, fuel consumption and exhaust was recorded from the ship’s instrumentation at 100 RPM increments. Before the haul-out, a bollard pull test was conducted at the shipyard, by a third-party testing team. In addition to the ship’s instruments, data was logged from a shaft strain gauge and rpm log. After re-launch, another bollard pull test and set of sea trials were conducted with the same vessel load condition and similar environmental conditions.

The results of these tests showed a 13% increase in the bollard pull, exceeding the promised 10%. The speed trials showed that the vessel gained over a knot in speed, while pulling less power and using an average of 1.5 gph less fuel. This combination of getting more speed while using less fuel works out to a significant reduction in the fuel per nautical mile, giving the Raven over a 20% average gain in range and fuel economy over the speed range.

In addition, the Raven reported significant improvement in steering performance both on their way to the fishing grounds and while towing a net. “The Nautican Triple-Rudders have excellent course-keeping ability, which has meant less corrective rudder to keep course,” said Elizabeth. “But the most notable improvement has been while towing a net.” The Raven previously had a conventional single rudder that while towing a heavy load, would restrict the flow through the nozzle and overload the propeller in a turn. This would then lug down the engine RPMs, slowing the vessel’s speed making it difficult to negotiate turns while towing. The narrow Nautican Triple Rudders keep water flowing through the nozzle while turning without overloading the propeller, resulting in minimal or no lugging of engines and an increased steering effort, and maintaining speed in the turn.

“Over my years of being in this industry seldom does the actual performance of a product meet or exceed expectations,” said Robert Smith, Owner and Captain of the F/V Raven. “Nautican not only met what they predicted, they exceeded it! We’re very happy with our decision to upgrade and are continuously realizing the benefits of switching to a Nautican system. Also, it was a pleasure to work with the Nautican team – who offered fantastic support throughout the project.”

VESSEL:
F/V Raven

OWNER:
Raven Enterprises, Newport, Ore.

VESSEL SPECS:
1,200-hp, Midwater Trawler

PRODUCT USED:
High-efficiency Nozzles, Stators and Triple Rudders

EXPECTED GAINS:
High bollard pull without loss to speed and power, with fuel efficiency gains

F/V Raven – Before and After Results of Speed (knots) and Fuel Consumption
raven-graph-1

F/V Raven – Percent Change from Before w/19a Nozzle to After Re-Propulsion w/Nautican IPU versus Engine RPM
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F/V Raven – Comparison of Vessel Speed (knots), Fuel (gph) and Range (nm/gal) versus Engine RPM – Before w/19a Nozzle and After Re-Propulsion w/Nautican IPU
raven-graph-3

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