Fenders 30% lighter and more resistant to abrasion than typical rubber have been developed
UK-headquartered Buoyant Works has developed its FenderIT product range for the tugboat sector using its experience in supplying fendering for aluminium and composite commercial vessels. This uses new material it claims is lighter and stronger, with higher abrasion resistance than typical rubber fendering.
Buoyant Works has supplied crew transfer vessels for the offshore wind industry and now owner Andrew Wickham is targeting the tug sector. He says this design of fendering is at least 30% lighter than conventional tugboat fenders.
“I have spent many years designing and manufacturing fender systems for all kinds of vessels,” he tells Tug Technology & Business. “Most of the fenders I produced had a flexible foam core and were then sprayed or moulded with a polyurethane skin.”
These products were good for lightweight applications, but prone to damage in heavier industrial applications. However, Mr Wickham’s latest polymer construction has higher tensile and tear strength and better resistance to abrasion.
“What I have now developed is an alternative to rubber fendering using very high-performance polyurethane elastomers,” he explains.
“These fenders use a variety of internal structures to generate their energy-absorbing properties. This process enables us to reduce the weight of an equivalent rubber profile by 30-50% without compromising performance.”
FenderIT has a material density of 1,100 kg/m3 compared with 1,200 kg/m3 for rubber. It has a tensile strength of 29.3 mPa and tear strength of 96.7 kN/m. FenderIT also has abrasion loss of just 23 mm3 compared with 150-180 mm3 for conventional rubber. For abrasion loss, the lower the stated figure, the better the material’s wear and abrasion resistance is.
“The materials have excellent abrasion/wear resistance, are designed for very dynamic applications, are non-marking and available in various colours,” says Mr Wickham.
“I want to apply this fender technology to tugs and other similar commercial vessels,” he continues. “It is an opportunity to apply a more modern and engineered approach to these fendering applications.”
FenderIT could be bonded, strapped or mechanically fixed in six different methods to protect tugboats during ship contacts.
“This polyurethane elastomer material recovers much better than rubber after an impact,” says Mr Wickham. Buoyant Works can vary the material hardness depending on requirements. “We can produce a very stiff formulation, a soft one or somewhere in between,” he explains. “This enables us to fine-tune the fender for different applications.”
Buoyant Works can customise FenderIT for commercial vessel and tugboat operator requirements. Compressive strength of profile can be varied where specific performance requirements are required.
“Softer fenders generate more grip and friction, while harder fenders create more of a sliding effect,” Mr Wickham. “In certain applications it is even possible to offer a combination of hardness within the same product.”
All straight lengths of this material are manufactured to 2,500 mm, but lengths can be cut as required. Custom bow, corners and end features can be supplied as required. Standard colours are black, orange and yellow, but this can also be customised. FenderIT can be manufactured in a round-D or flat-D or rectangular profile.
Buoyant Works can produce fenders to tight weight and performance tolerances because of its consistent manufacturing process at its factory in Liskeard, Cornwall.
It offers installation assistance, repair and maintenance services, end-of-life recycling and short lead times when spares and replacements are required rapidly.
Fendering user cases
All tugs require various types of fenders to absorb shock at different velocities and angles.
Eastern Shipbuilding Group built two Z-drive escort tugs for EN Bisso & Son Inc for terminal operations to a Robert Allan RApport 2400 design with 65 tonnes of bollard pull.
The first of these 24.3-m tugs, CD White, was delivered to Bisso Offshore in early January 2020 with the second launched 31 January 2020.
Their ship-handling fenders at the bow consist of one tier of cylindrical fenders, with 812-mm outer diameter and 406-mm internal diameter, at the forecastle deck level and M-type fenders of 610-mm by 305-mm below main deck level.
Similar-sized M-type fenders are installed at the stern, plus there is a double strake of 940-mm diameter tyre fenders along the sheer lines of main deck. There is a single strake of 305-mm hollow D-shaped submarine fendering along the hull side.
In comparison, a series of escort and terminal tugs built by Gulf Island Shipyards for Bay Houston Towing and Suderman & Young have cylindrical fenders of 915-mm outer diameter and 457-mm inner diameter on the bow at the main deck level.
These Robert Allan-designed Z-Tech tugs also have double-loop soft fenders 405-mm thick between the main deck and the knuckle at the bow and along the sheer lines of main deck. On the stern is cylindrical fendering of 405-mm outer diameter and 203-mm inner diameter. The first two of these Z-Tech 7500 escort tugs, Mark E Kuebler for Bay Houston Towing and Ted C Litton for Suderman & Young, were delivered in Q1 2019.
In contrast, another Robert Allan-designed harbour tug was built on the opposite side of the world with a suite of ship handling fenders.
Lyttelton Port, New Zealand, took delivery of a RApport 2500 harbour tug, built at ASL Shipyards Ltd Singapore in 2019, with two tiers of cylindrical fenders on the bow. This tug, Piaka, is a 25.2-m long tug with 12-m beam and 4.6-m moulded hull depth.
It was built and outfitted to handle container ships at the port. Piaka has a bollard pull of 78 tonnes and free running speed ahead and astern of 13 knots.
Its bow fendering includes cylindrical fenders with 500 mm outer diameter and 300 mm inner diameter on the upper tier and larger cylinders of 800 mm outer diameter and 300 mm inner diameter on the lower tier. Piaka has a D-shaped fender fitted along the sheer lines of the main deck of 300 mm by 300 mm and W-shaped fenders of 480 mm by 300 mm fitted at the stern.
The main types of tug fenders are: