FOM-3.38	Fleet Operations Manual Navigation Methods of Anchoring	Doc No.: FOM-3.38 Revision: 01 Date: 15 Oct 2024 Issued by: DPA Approved by: MD

Methods of Anchoring

The two commonly used methods of anchoring are described below:

Method 1: Anchor Let Go on the Brake

• Approach the anchor position heading into the wind / tide

• Stop the ship over the ground

• Walk-out the anchor and cable until the anchor is about half a shackle off the bottom

• Hold the cable on the brake

• Take the windlass out of gear

• When in position, drop the anchor by releasing the brake

• Control the speed of cable by the brake, noting the following cautions:

• if the cable is paid out too fast, it can result in the anchor and cable piling up on the bottom and lead to poor holding
• if the brake fades or fails there is risk that the cable will run out to the bitter end, with the consequent damage.

With smaller ships, the piling of cable on the bottom may be avoided by allowing the vessel to move astern to stretch the cable as it is paid out. Additionally, after sufficient shackles have been paid out for the anchor to take hold, the brake may be applied and the ship allowed to swing round to the prevailing forces (wind or current) before paying out further cable. If necessary, main engines and thrusters if fitted may be used to initiate or check the motion over the ground.

On large, loaded ships a disadvantage of this method is that is difficult to see the lead of the cable and watch it ‘grow’. On a loaded ship, particularly one with flush foredeck, the hawse pipe is very low and the cable attitude is difficult to ascertain. The degree of engine assistance required is also difficult to estimate.

An advantage of using this method of anchoring is that the brake will render before critical stresses are reached.

Method 2: Anchor Walked-Out

• Approach the anchor position heading into the wind / tide

• Stop the ship over ground

• When in position, walk the anchor and cable out under power until the complete length of cable required is paid out on the seabed, noting the following cautions:

• this method produces a controlled cable flow, but an accurate estimation of the vessel’s movement over the ground is essential to avoid damage to the vessel’s windlass
• under no circumstances must the windlass be allowed to operate at a rate in excess of the manufacturer’s recommendation

Additional Considerations

The windlass motor is the weakest link in the system and, if the windlass over-speeds, there is a risk that the motor will be damaged. On some hydraulic systems utilizing high speed, highly geared axial motors, damage could result in catastrophic failure and risk of injury to personnel from flying debris.

Under no circumstances should the weight on the cable be such as to cause the windlass to over-speed. If this is suspected, aggressive use of main engine may be required.

In extreme case, the windlass brake may be used to assist in controlling the speed of the windlass.

The lead and weight of the cable should be closely monitored as there will be no pre-warning of windlass damage if the system is over stressed. Damage may not be evident until the windlass is next used to heave up anchor.