These fine, albeit small, line boats represent yet another example of the very successful Robert Allan Ltd (RAL)/Sanmar Shipyards partnership. Delivered to a Scottish owner, which will operate them on the Firth of Forth, they are rugged, stylish, seaworthy, and impressively well-finished craft.
Perhaps unbelievably for line boats, they actually look comfortable. That is unheard of in spartan Scotland.
“Gannet is the smallest twin screw tug that Sanmar Shipyards has ever built,” Sanmar’s Vice President Ali Gurun told Baird Maritime. “The challenge was to build a tug with that size, but with a greater number of roles compared to a simple mooring boat. Gannet therefore needed to possess all the equipment one would expect on a much larger modern twin screw tug, and I am delighted to say we succeeded in this regard.”
Gurun remarked that it is not easy to build a fully equipped tug with such compact dimensions, so Sanmar relied on, “a little ingenuity and drawing on expertise built up over many years,” to deliver a vessel with the needed attributes.
“The challenge posed by Gannet,” added designer RAL, “was that we needed to design a steel workboat capable of 9.5 knots full speed and six tonnes bollard pull. That is above ‘half-speed’ for a 12-metre boat, and it is difficult to achieve with a heavy steel boat and therefore needed some CFD modelling to verify.”
RAL said the six tonnes bollard pull requirement was best achieved through the installation of nozzles, but such installations are not considered ideal for ensuring high-speed performance. Also, a generous beam was needed to provide enough stability for safe towing, but the drawback with a wider beam was the impact it had on a vessel’s speed.
“A low air draught was required to get the tug underneath mooring lines and this resulted in a low pilothouse that limited visibility over the bow,” added RAL.
The work on Gannet and sister Cormorant nonetheless taught RAL some useful lessons, particularly with regards to the possibility of pushing a displacement hull past hull speed if the right hull form is used and weight is minimised.
“In order to keep the weight down to achieve the required speed, the total weight was carefully controlled during construction, including each element installed on the vessel, and since the steel plates’ thicknesses are thin, welding and having smooth surfaces was challenging. Still, it was a good opportunity for us to back to the basics and design a small, simple workboat within a very short time period. This allowed Sanmar to quickly build and deliver the boat to suit the owner’s requirements.”
When asked about the direction in which the towage industry was headed, Sanmar VP Ali Gurun highlighted the growing tendency towards vessels with electric propulsion.
“We expect more and more electric-powered tugs to be ordered. To address this need, we are collaborating closely and sharing expertise with other major players in the development of new and advanced technologies.”
Among the projects that Sanmar is working on as regards vessels with alternative propulsion are dual-fuel escort tugs and battery-powered harbour tugs.
“Turkish tug operators currently own and operate one of the youngest fleets in the world,” Gurun told Baird Maritime. “The average age of tugs in our own fleet is under three years. The Turkish fleet is very young, powerful, and modern, which is, in our opinion, due to Turkey being the leading nation as regards tug construction.”
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