Anchoring is a crucial operation that takes place on ships to keep them in place. The type of seabed and external factors such as wind, current, and tide stream play a significant role in determining the duration and location of the anchoring operation. The two most common methods used for anchoring are the “Let Go” and “Walk Back Under Power” methods.
The “Let Go” method
is widely used in a range of vessels, from smaller crafts and pleasure yachts to larger vessels with tonnage up to 100,000 GT. The principle behind this method is to let the anchor slip with the cable under its own weight from the hawse pipe. Factors such as the weight of the cable, windlass brake holding power, and the momentum of the vessel are controlled to ensure that the anchor digs in and the cable is laid out correctly. The speed of the vessel over ground is brought to zero using engines and helm, and the anchor and cable are then allowed to run out under their own weight. Once the flukes touch the bottom or chain touches the ground, the engines are moved astern or ahead to attain astern momentum with respect to the ground, which will stretch the cable. Care should be taken to not allow the full cable to run out under weight or to allow the cable to pile up, which can result in developing kink or twist in the cable.
The “Walk Back Method”
is recommended and used mostly on vessels above 100,000 GT. The working principle is the same as the “Let Go” method, but the cable is paid out using the windlass at a fixed speed. As the anchor touches the bottom, more length is paid, and engines are given astern to develop slight astern movement to lay the cable nicely as the flukes of the anchor dig in the seabed. This method is usually of longer duration than the “Let Go” method; however, it provides ship masters with better control over the amount of cable paid and weight upon the windlass. It is important that the correct assessment beforehand of tidal conditions, gusty winds, or strong coastal currents are made by ship masters to accommodate for the movement of the vessel as the cable is paid out.
In summary, the “Let Go” and “Walk Back” methods are the two most common methods used for anchoring ships. The “Let Go” method is widely used in a range of vessels, while the “Walk Back” method is recommended and used mostly on vessels above 100,000 GT. Both methods require proper assessment of external factors such as wind, current, and tide stream and careful control of the weight of the cable, windlass brake holding power, and the momentum of the vessel.
Keywords: ship anchor, anchoring methods, Let Go, Walk Back, ship operations, wind, current, tide stream, seabed, hawse pipe, windlass brake, momentum, vessel, cable, flukes, chain, shipmaster, windlass, piling up, twisting, cable, VLCC, ULCC