“Hull Vane To Be Fitted On Royal Netherlands Navy OPV” –Naval News

Hull Vane hydrofoil solution integrated on a Holland-class OPV model (Credit: Dutch Ministry of Defense)

Naval News reports that,

Today, June 8th, the first Hull Vane for the Royal Netherlands Navy has been delivered in Den Helder. This Dutch invention consists of a submerged transom wing which renders ships more efficient and quieter, while improving their seakeeping.

This Hull Vane will be installed in early 2023 on the aft ship of the HNLMS Groningen, an ocean-going patrol vessel of 108 meter, pertaining to the Holland Class.

This decision is a strong endorsement for an innovation that appears directly applicable to US Coast Guard cutters. The Holland class Offshore Patrol Vessels are similar in size, power, speed, and hull form to the Bertholf class NSCs and particularly to the Argus class Offshore Patrol Cutters.

The hull vane reportedly recovers some of the energy that would normally be lost in creation of the wake. Fuel savings of 10% or more are reported. It also is reported to reduce pitch make for improved boat and helicopter operations.

Besides energy saving, which automatically leads to a reduction of CO2 emissions, the Hull Vane® also offers many tactical advantages for the ship. Due to the suppressed stern wave, the vessel leaves much less visible wake, making her less visible to satellites, drones and even certain types of torpedoes. Helicopter landings will be safer in rough weather, and it is expected that the slipway in the stern can be used more frequently to launch and recover the FRISC, a fast daughter craft. The ship will have a higher top speed, and will be able to cross a long distance faster, e.g. when being deployed for calamities. But above anything else, the goal is to reduce the dependency on diesel fuel. That is valuable in peace time, but even more so during war.

“Wake behind transom on patrol boat at 11 kn without Hull Vane® (left) and with Hull Vane® (right), leading to 25% lower fuel consumption”

We have been following this promising innovation for the last seven years. Previous posts on this topic were:

Results of a 2018 test on the 172 foot, 409 ton French patrol vessel Themis, a vessel similar to the Webber class FRCs, included a “comparison with the benchmark sea trials – conducted in January in exactly the same conditions – by CMN’s sea trial team showed a reduction in fuel consumption of 18% at 12 knots, 27% at 15 knots and 22% at 20 knots. The top speed increased from 19.7 knots to 21 knots.”

“MOL’s fuel saving PBCF sets Guinness World Record” –Marine Log

PBCF installed on a propeller

Marine Log reports,

Mitsui O.S.K. Lines, Ltd. (MOL) reports that the propeller boss cap fin (PBCF) sold by its group company MOL Techno-Trade, Ltd. has been certified as the “Best-selling Energy-Saving Ship Appendage Brand (Cumulative)” by Guinness World Records and received an official certificate on December 23, 2021.

On sale since 1987, the PBCF was the first device in the world to be commercialized to recover the energy wasted in the vortex that forms behind a rotating propeller and increase the thrust by breaking up this vortex. Analysis has shown that equipping a vessel with PBCF results in energy savings of 3% to 5%.

Such a device would not have much effect on speed, but it might improve range and fuel economy.

“Wärtsilä to bring gate rudder technology to global market” –MarineLog

Evaluations of the innovative gate rudder assembly have shown improvements in both efficiency and maneuverability. (Image: copyright: Yamanaka Shipbuilding)

Marine Log reports that,

“Wärtsilä has signed an agreement that will enable it to integrate patented gate rudders into its propulsion product designs. Unlike the traditional arrangement of the rudder in the propeller slipstream, the gate rudder is a twin arrangement around the propeller, allowing improved fuel efficiency and reduced emissions. The concept is applicable to all current vessels equipped with conventional propellers.”

“…the rudder will realize synergies in capital and operational savings for ship owners by increasing fuel efficiency, improving maneuverability and course stability in both calm and rough sea conditions, while also reducing noise and vibration.”

You can see from the photo, when no rudder is required, that the rudder would not be in the accelerated flow behind the prop, thereby reducing drag, but when more extreme turns are required it would be, making it more effective.

The large bosses where the rudder shaft leave the hull might cause more drag than those of a normal rudder. There are of course two required, and it appears they would have to be more strongly built to deal with the torque resulting from the off-center drag on the rudder.