Stopping A Boat In The Middle Of The Ocean

Stopping a boat in the open ocean is a challenging task, especially if the ocean is too deep for a traditional anchor to be effective. In such cases, alternative methods like using bow and stern thrusters, or even cutting the engines and drifting, may be considered. This article will explore the various techniques and strategies employed by sailors to bring their vessels to a halt in the vast expanse of the open ocean, delving into the pros and cons of each approach and offering insights into the complexities of maritime navigation.

Dropping sails and drifting

If you drop sails in blue water, your boat will roll a lot more as the sails are no longer there to take the action out of the rolly seas. It is also quicker to take avoiding action when sails are up and you can see another boat on a collision course.

If you are stopping in the open ocean, it is a good idea to look at busy shipping lanes and plan your trip to stay away from them, reducing the chances of meeting other vessels. Shipping lanes are usually marked by "great circle routes", which are the shortest possible distances for commercial shipping.

If you are stopping for a celebration or a swim, it is important to remember that the ocean is too deep to drop a traditional anchor. You can use a sea anchor/parachute or drogue to reduce drift, but these are usually used in windy or stormy conditions. You can also use bow and stern thrusters to keep your position, although this is usually automated via GPS.

In general, it is not necessary to anchor in the open ocean as you are unlikely to run into anything, so it is fine to just float. Most ocean-going vessels will have some sort of autopilot, so you don't have to be actively driving them the whole time.

Using bow and stern thrusters

To understand how thrusters can stop a boat, it is important to first consider the benefits of thrusters and why they are used. Thrusters are particularly useful in busy, overcrowded, or tricky harbours, where a mariner's blood pressure may rise as they attempt to manoeuvre their vessel. With one or more thrusters on board, a sailor gains more time to orient themselves, consider their next steps, and wait for others.

The main benefits of thrusters include better control under demanding conditions, a lower risk of collision, a more attractive aftermarket value, and the ability to manoeuvre the boat alone. Thrusters are especially useful for older boaters who may struggle with handling their vessel due to age. With a bow and stern thruster, sailors can pin the boat in the desired location, allowing them to operate a large vessel on their own.

When choosing a bow or stern thruster, it is critical to select one with sufficient thrust to cover your intended use with a good safety margin, the correct location in the hull, and an adequate and sustained energy supply (battery voltage). Insufficient thrust force and noise are common issues with boat thrusters, so ensuring sufficient power is paramount.

Upgrades to thruster systems include fitting a stern thruster, upgrading to proportional variable speed control, applying higher voltage to the electric motor, installing a remote control, and upgrading to new, more quiet and efficient propellers.

In summary, bow and stern thrusters provide enhanced manoeuvrability and control for vessels in demanding conditions, such as busy harbours, and can be particularly useful for older sailors who may struggle with vessel handling. By providing 360-degree directional control, thrusters enable sailors to stop and pin their boat in a desired location, even in open ocean scenarios.

Sea anchors and parachutes

A sea anchor (also known as a parachute anchor, drift anchor, drift sock, para-anchor, or boat brake) is a device that stabilises a vessel and limits its progress through the water. Unlike a conventional anchor, which tethers the boat to the seabed, a sea anchor provides hydrodynamic drag and acts as a brake. They are normally attached to a vessel's bows, preventing the boat from turning broadside to the waves and being overwhelmed by them.

Sea anchors are typically made of fabric and are designed to be launched from the bow of a vessel. They can be bagged and easily stowed when not in use. The size of the sea anchor determines how much water it can displace and, therefore, how much braking it can provide. Multiple sea anchors can be used together to increase the braking effect.

The parachute-style sea anchor is a type of sea anchor that is shaped like a parachute or cone. When deployed, it floats just under the surface, and the water moving past keeps it filled. Some varieties are cylindrical, with an adjustable opening at the rear to control the amount of braking.

To use a sea anchor, you will need the sea anchor itself, a deployment rode, and a trip line. The sea anchor is dropped off the bow of the vessel, and the rest is optional. Sailboat owners may prefer to bridle their sea anchor for a more comfortable ride. The length and type of line or rope used to attach the sea anchor to the bow are also important considerations. A longer, more elastic rope will provide more shock absorption and help to smooth out changes in loading caused by waves interacting with the hull.

In addition to sea anchors, drogues are another type of drag device that can be used to slow a vessel. Drogues are streamed from a vessel's stern in strong winds to prevent pitch-poling or broaching in overtaking seas. They slow the boat while keeping its heading steady.

Drogues

There are several types of drogues:

• Cone-shaped drogues: These direct water through a small opening, creating controlled drag. They are typically made from reinforced fabric and are lightweight and easy to deploy, making them suitable for small to medium-sized vessels.
• Parachute drogues: These create substantial drag in the water and are often used by larger vessels or those operating in extremely rough seas. Parachute drogues are effective at maintaining a steady position and are frequently preferred for offshore sailing or during long ocean passages.
• Multiple-line drogues: These consist of multiple small cones or fabric "cups" attached along a line, distributing drag across several points and providing more stable resistance. They are especially useful in heavy seas as they minimise the risk of sudden strain on a single point.
• Buoyed drogues: Adding a buoy to a drogue prevents it from sinking and becoming entangled. This is helpful in rough seas as the buoy keeps the drogue closer to the surface, providing consistent drag.

When using a drogue, it is important to match the drogue size to the conditions, check attachment points to ensure they are strong enough, deploy the drogue gradually to avoid sudden strain, and monitor the line length to balance stability with practicality. Practising retrieval in calm conditions is also recommended to build confidence for storm use.

Autopilot

The autopilot system is one of the most advanced and technically sophisticated navigational tools on ships. It is synchronised with the Gyro Compass to steer manually inputted courses, with reference to the gyro heading. The system can also be synchronised with the Electronic Chart system (ECDIS), enabling it to follow the courses laid out in the Voyage plan.

Rate of Turn and Rudder Limits

The method of turn is the most important control of the autopilot system. The system will follow the selected turn method for course alterations. The user can input the limit of such turn methods, including the rate of turn, rudder limit, and turning by radius. It is important to consider the vessel's manoeuvring characteristics when setting these values to ensure safe operation.

Steering Gear Pumps

Steering gear pumps are used to actuate the steering gear unit, which moves the rudder in the required direction. The number of pumps running will impact the speed of the rudder movement. In areas with high traffic density and the need for sudden alterations, it is recommended to have maximum steering gear pumps running. Conversely, in open-sea navigation with less traffic, the number of pumps should be reduced to a minimum.

Off-Course Alarm

The off-course alarm notifies the operator if there is a difference between the set course and the actual heading of the vessel. The user can manually set the degree of difference required to trigger the alarm. However, it is important to monitor course changes as the autopilot may follow a wandering compass and fail to sound the alarm in certain cases.

Steering Controls

The autopilot system offers two modes: Automatic and Manual. In Manual Mode, the vessel can be hand-steered using a Follow-Up Helm or a Non-Follow-up emergency tiller. Hand steering is recommended when manoeuvring in restricted waters, channels, and areas with high traffic density. The NFU tiller moves the rudder in the desired direction but not to a specific angle and is intended for emergency use only.

Usage Recommendations

It is not recommended to use the autopilot in areas with high traffic density, narrow channels, traffic separation schemes, or other restricted waters. The autopilot may not be able to turn the vessel quickly enough to avoid a collision in such situations. If the autopilot must be used in these conditions, ensure that all steering gear pumps are switched on for better rudder response.

Additionally, the autopilot system works inefficiently at reduced speeds. It is not recommended to use the autopilot when the ship is manoeuvring or steaming at very low speeds.

Speed Synchronisation

The autopilot system can be synchronised with the Speed Log to receive feeds on the ship's speed. Users should monitor the speed log as any errors in the log speed will be reflected in the autopilot system. When manually inputting the speed, ensure that the value is as close as possible to the actual speed of the vessel.

Weather Conditions

Hostile weather and sea conditions can adversely affect the performance of the autopilot. Modern autopilot systems have a Weather Control option that automatically adjusts the settings to adapt to changing conditions. Alternatively, the user can manually set specific values to compensate for rough weather.

Alarms and Signals

In addition to the off-course alarm, a well-integrated autopilot system should have the following alarms and signals:

• Failure or reduction in power alarm: Sounds in the event of autopilot failure or a reduction in power supply to the heading control or monitoring system.
• Sensor status monitoring: Indicates with an audible alarm if any sensors in the autopilot system fail to respond.
• Heading monitor: Provides an audio-visual alarm if the heading information diverges from a second heading source beyond a set limit. It should also provide a clear indication of the actual heading source.

Important Limitations

The autopilot system should be designed so that the preset heading cannot be altered by intentional intervention of onboard personnel. The heading control system should automatically correct the course to the preset heading without overshooting its position.

Frequently asked questions