During a routine docking, the operators of a Gunboat 80 catamaran found that the sliding bearings that they had installed on their retractable rudder were not performing optimally and they sought another solution.
The vessel had High-Density Polyethylene (HDPE) installed as the sliding bearings of the retractable rudder system, but these had only provided effective performance for four to five months.
The HDPE bearings had demonstrated significant wear and temperature sensitivity. The temperature sensitivity was particularly disruptive since the bearings expanded in warm conditions, making it difficult to move the rudder.
Vesconite has a lower thermal expansion coefficient and thus better dimensional stability when temperatures fluctuate. This means that the rudder can move freely with sufficient clearance between the rudder blade and the bearing even when sailing in regions with much warmer weather. Vesconite also offers superior wear resistance and a higher load-bearing capacity than standard polymers like HDPE.
In addition, Vesconite was preferred over various composite bearings and high-performance polymers because Vesconite bearings were more affordable and readily available.
The ship repairer noted Vesconite Bearings’ short lead times as a crucial factor in its purchasing decision: from order placement on September 30, to despatch to France on October 17 and final delivery by October 22, 2024, Vesconite Bearings’ timeline of approximately three weeks ensured minimal downtime for the vessel.
Marine application engineer Monique Potgieter highlighted the benefits of the new Vesconite bearings for retractable rudder applications.
“When catamarans operate in shallow waters, rudders can be lifted to prevent damage. It further allows captains to control the rudder blade depth based on wind speed and direction, reducing drag when steering demands are lower,” says Potgieter.
“It is of utmost importance that the sliding bearings that form part of these retractable rudder systems support smooth and quick lifting and lowering of the rudder blades,” she adds, noting that any hindrance to these operations can result in safety and performance concerns.
The complex machined bearings – measuring 587 mm by 115 mm by 60 mm for the upper sliding bearing and 620 mm by 115 mm by 70 mm for the lower – met all specifications according to the shipyard’s quality assurance department.
The vessel on which the Vesconite sliding bearings were fitted is the second Gunboat 80 catamaran to be made, and Vesconite Bearings is pleased to be a part of getting the Gunboat back in the water by November 2024. The precision and reliability of these new bearings are anticipated to enhance the Gunboat 80’s performance, offering robust, long-lasting support for its retractable rudder system.
Source: Vesconite