Propeller & Aft Ship 

Upgraded Alpha propeller and nozzle give superior performance

F/V Jette Kristine gained 23.5% more bollard pull

The propeller designers and PrimeServ staff at MAN Diesel Frederikshavn, Denmark could sit back satisfied on 12 October when a full-scale bollard-pull test on the Esbjerg-based fishing vessel ‘Jette Kristine’, showed an increase in bollard-pull performance of an impressive 23.5%.

The test thus verified a great propulsion upgrade advantage in relation to a „pre-test‟ performed two weeks earlier based on the same vessel, exactly the same engine output and the original propeller and nozzle installation.

The preconditions for the test were the exact same position in Frederikshavn‟s harbour basin, same water depth below keel, same draft and trim of the vessel – ensuring the realistic and best possible conditions for relative and comparative bollard pull recordings.

The two bollard pull tests of Jette Kristine gave the following results:

  • Measured before: 19.1 metric tonnes
  • Measured after: 23.6 metric tonnes
  • Corresponding to an increase of: 23.5%

General potential for greater efficiency

Propellers designed more than 10 years ago normally offer great improvement potential in retrofit projects, where fuel consumption reductions of up to 12.5% for free running propeller upgrades have been reported – simply by exchanging the existing propeller blades to today‟s optimised and advanced designs.

A relatively small investment with short payback time and radical impact on the ships‟ future operational economy, fuel consumption and exhaust gas emissions. The green impact and environmental benefit of lower consumption is not to be neglected.

In this case with Jette Kristine and in similar cases with other fishing trawlers, offshore vessels, tugs and dredgers – bollard pull is the key performance parameter. MAN Diesel‟s upgrade solutions can include bollard pull optimised propeller blades alone – or bollard pull optimised blades in connection with a propeller nozzle upgrade.

Optimised propeller blade profiles applied together with the newly designed high-efficient AHT (Alpha High Thrust) nozzle is the ultimate solution.

Optimising for bollard pull

Advanced CFD tools (Computated Fluid Dynamics) were used to develop MAN Diesel’s new AHT propeller nozzle series. The nozzle shows superior performance compared to the standard ‘19A’ propeller nozzles, which are common standard in the marine industry today.

The increased bollard pull achieved when using the AHT nozzle is not only a result of the optimised nozzle profile, which is double-curved on both the inner and outer diameter. Other contributing factors are the nozzle length/diameter ratio, nozzle support, aft ship lines, and tilting and azimuthing of the nozzle, among others.

The addressing of all these topics has been refined by MAN Diesel into a new systematic method, whereby the bollard pull can be increased by more than 12% compared to solutions with 19A nozzles. The achievements have been demonstrated both in various model tests and in full scale.

Jette Kristine ship data:

Name Jette Kristine, E 727, Esbjerg, Denmark
Owner Niels Arne Hounisen
Yard Johs. Kristensen Skibsbyggeri ApS
Yard number 178
Built year 1986
Gross tonnage 638
Length oa 43.3
Breadth 9.60
Engine type MAN Diesel 8L23/30-D
Engine output 1080 kW (1470 BHP) at 825 rev min
Gearbox type MAN Diesel 39KV11
Reduction ratio 825 to 214 rev min
Propeller type MAN Diesel Alpha VB740
Propeller diam 2650 mm

Customer feedback from the ordinary fishery operations

Today, after two fishing trips – evaluating how the propeller and nozzle upgrade has performed in real life operational conditions – the owner of Jette Kristine, Mr. Niels Arne Hounisen, expressed his satisfaction: “MAN Diesel has fulfilled my request for more pulling power, and they have delivered more than promised. Plus 23.5% is remarkable, considering the fact that Jette Kristine was equipped with ordinary propeller equipment in good condition – nothing outdated!” Hounisen continues: “When steaming, it has given me approx. 0.5 knot extra top speed, and in trawling conditions, I have experienced a clear difference with better control of my fishing gear. Most important is a reduction in fuel consumption of more than 15% recorded at trawling speed.” “Regarding the onboard noise levels below deck and in the accommodation, my crew members have stated that they experience much better conditions now – and this is not something they say just to please me”, concludes Niels Arne Hounisen.

Service Center Task at MAN Diesel PrimeServ Frederikshavn

The physical replacement and upgrade operation was performed over 14 days at MAN Diesel‟s slipway in Frederikshavn.

For more information please contact:

MAN Diesel
PrimeServ Frederikshavn
Att.: Christian Juul, Retrofit Manager
Tel.: +45 9620 4100