by Doug Woodyard
rudders
Becker highlights benefits of rudder upgrades
G
rowing demand for rudder conversions for ships in service is reported by Becker Marine Systems, which claims
its easily-installed solutions can significantly improve manoeuvring performance and reduce fuel consumption. The German specialist’s after-sales team has extensive experience in refurbishing Becker rudders that have been in service for decades. A general overhaul can reportedly turn an older rudder into ‘good as new’ condition by exchanging all wear-and-tear parts and applying a complete makeover to all the elements. Such a project benefited the cruise ship Mein Schiff 2. Becker’s after-sales business is boosted by operator interest in converting non-Becker rudder systems as well as for new solutions to enhance the manoeuvrability of vessels in service. Gearbulk Norway’s Jaeger Arrow – built in 2001 and equipped with a semi-spade Schilling Mariner rudder – is cited as an example. The worn installation was removed and replaced last June by a new full-spade Schilling Monovec rudder. As with most rudder conversion projects, Becker Marine was able to retrofit the new rudder to the existing steering gear. The ship’s crew took up Becker’s offer of manoeuvring training to experience the improved course stability. The master of the 25 year-old cruise ship Thomson Dream appreciated the results of a project in 2010 that saw the original semi-spade rudders converted to a Becker TLFKSR twisted leading edge flap rudder system. The new rudders now enable many harbour operations
Refurbishing a 15 year-old Becker flap rudder to ‘as new’ condition
The two original semi-spade rudders of the ropax ferry Stena Danica were replaced by Becker twisted flap rudder systems
to be performed without tug assistance; the formerly frequent deployment of tugs has reportedly declined by 80 per cent. Rudder conversions have also benefited Stena Line, whose ropax ferries Stena Britannica and Stena
Hollandica were fitted with new TLFKSR systems during hull elongation projects in drydock in 2007. Similar types were specified for Stena Danica to replace non-Becker rudders, the new systems demonstrating improved manoeuvrability. MP
Specialist coating solves rudder cavitation problem
Rudder cavitation problems experienced by Hamburg-based shipowner Ernst Russ on five ro-ro cargo vessels have reportedly been resolved using Ecospeed coatings. The rudders of the 1999-built vessels – originally treated with a standard epoxy coating – suffered cavitation damage due to the high propeller speed. “During the first intermediate drydocking, between two and three years after launch, we observed extensive cavitation damage on the rudders,” reports Ernst Russ superintendent, Grzegorz Girjat.
A special doubler plate was installed on
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the most affected areas as an initial remedial response and the ships returned to service. Drydocking in Antwerp in 2004, however, revealed that the doublers had not helped. “I would say that the situation had
worsened a little because the gap between the hub and the rudder was reduced by the doubler plates. Cavitation is a well known phenomenon, and it is known there has to be a certain distance between hub and rudder. If that distance is not sufficient then cavitation will be worse,” Mr Girjat notes. A glassflake vinylester STC Ecospeed
coating was applied experimentally to Elizabeth Russ during the 2004 drydocking, although there was only time to grit blast the rudder and apply two coats of the paint: the pitting and damage from cavitation was not repaired but simply covered over by the coating. The trial was successful, however, ‘beyond
all expectations’. When the ship came out of the water again in 2007 it was seen that, despite the last minute application of Ecospeed, no further cavitation damage had occurred. Similar results were achieved after the rudders of the other four roro ships were similarly treated.
Marine Propulsion I February/March 2012 I 67
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