An anchor is easy to overlook when planning a narrowboat. On an ordinary canal, it may remain unused for years.
On a fast-flowing or tidal river, however, it can become the boat’s emergency brake.
If the engine fails, an effective anchor may prevent the boat from being swept towards a weir, bridge, shoal or other hazard. As Priscilla is intended for more demanding British and European waterways, her anchoring equipment must be selected as part of the boat’s safety design.
Is an anchor necessary on a canal?
An anchor is not normally required for routine cruising or mooring on a sheltered canal. Indeed, deploying one unnecessarily could damage underwater structures, cables or services.
The position changes on rivers, tidal waterways, estuaries and commercial navigations. Canal & River Trust guidance states that boats navigating rivers should carry an adequately sized anchor with a suitable length of chain and rope.
Some navigation authorities impose specific requirements. Narrowboats using the tidal Thames, for example, must carry a suitable anchor that is ready for immediate use.
Anchor weight is not the whole answer
It is tempting to select an anchor using a simple table based upon the boat’s length. However, length and anchor weight alone do not determine whether an anchor will hold.
The correct equipment depends upon:
- The boat’s displacement and windage
- The anchor’s design and holding performance
- Expected current, tide and weather
- Water depth
- The composition of the riverbed
- Manufacturer recommendations
- Requirements imposed by the navigation authority
A typical narrowboat is extremely heavy for its length. A generic recommendation of 10–20 kg may therefore be unsuitable for some boats or passages.
Priscilla’s anchor should be selected only after her final displacement, dimensions and intended cruising waters are known. Advice should be obtained from the boatbuilder, anchor manufacturer and, where appropriate, a competent marine surveyor.
Choosing an anchor type
Different designs perform differently according to the riverbed and available storage.
Fluke or Danforth-style anchors
These anchors fold relatively flat and can provide good holding in suitable sand or firm mud. Their convenient shape makes them attractive where storage space is limited.
They may perform less consistently in weed, gravel, rock or very soft silt, however, and must be correctly set to develop their holding power.
Plough-style anchors
A plough-style anchor can perform across a wider range of bottom conditions and may reset more readily if the direction of pull changes.
Its shape can make it more awkward to store aboard a narrowboat, particularly where there is no dedicated bow roller or anchor locker.
Modern high-holding designs
Newer anchor designs can offer substantial holding power relative to their weight and may set more reliably than some traditional patterns.
Whether one is suitable will depend upon its certified sizing guidance, the intended waterways and how safely it can be stored and deployed from the boat.
No anchor performs perfectly on every riverbed. The choice should reflect the most demanding conditions Priscilla is reasonably expected to encounter.
Chain, rope and the complete anchor rode
The anchor is connected to the boat by its rode: the collective term for its chain, rope or combination of both.
A length of chain next to the anchor serves several purposes. It resists abrasion, adds weight and helps keep the pull closer to the riverbed, allowing the anchor to hold more effectively.
The rope—often called the warp—provides the remaining length and some elasticity. Nylon is commonly used because it can absorb shock, although its diameter and construction must be appropriate for the boat and expected loads.
Generic recommendations such as 6–8 mm chain should not be accepted without calculation. Chain grade, link size, connectors, rope strength and every attachment point must form a compatible system capable of carrying the expected load.
The shackles and swivels can be weaker than the anchor rode if poorly selected. Each component should therefore have an appropriate documented working or breaking strength and be secured against working loose.
How much chain and rope are needed?
The required length depends principally upon water depth and the distance between the water and the boat’s attachment point.
Canal & River Trust guidance for some commercial waterways recommends a total rode approximately five times the greatest expected depth. Its River Severn guidance recommends six times the maximum depth, while specialist advice for particular exposed passages can differ again.
Current Port of London Authority advice suggests a minimum of 5 metres of chain and 25 metres of rope for the Thames Tideway. This is passage-specific guidance rather than a universal specification.
The planned route must therefore be researched before choosing the final length. Thirty metres of rope may be adequate in one location and insufficient in another.
More rode also requires more storage space and must remain capable of being deployed without tangling.
Securing the anchor to the boat
The strongest anchor and rode are useless if their final connection fails.
The inboard end—the bitter end—must be secured to a structural anchoring point capable of sustaining the load. A lightweight deck fitting or ordinary mooring attachment may not be suitable.
The arrangement should allow the crew to:
- Reach and deploy the anchor quickly
- Control the rode without becoming entangled
- Keep clear of rapidly moving rope and chain
- Confirm that the bitter end is securely attached
- Recover or release the equipment safely
- Avoid obstructing normal movement around the boat
The deployment position and structural fixing should be designed with the boatbuilder. Anchoring by the stern in a strong current can expose a low deck or openings to the flow and may be dangerous.
Ready for an emergency
An anchor buried beneath luggage or wrapped in a tangled rope is of little value when the engine stops.
Before entering a river, the anchor should be correctly assembled, accessible and ready for controlled deployment. The crew should understand the procedure and agree who will steer, who will handle the anchor and how they will communicate.
Practical instruction is preferable to attempting the process for the first time during an emergency.
The passage plan must also identify bridges, weirs, prohibited anchoring areas and suitable emergency anchorages. Anchors should never be deployed where charts or navigation notices prohibit it, except where immediately necessary to protect life or the vessel.
Planning Priscilla’s anchoring system
For Priscilla, the anchor cannot be selected from a generic weight table.
The final system will need to consider:
- Her completed displacement and windage
- British tidal and commercial waterways
- The greater depths and currents that may be encountered in Europe
- Suitable anchor type and manufacturer sizing
- Adequate chain and warp for the most demanding planned passage
- Properly rated shackles and connectors
- A structural attachment point
- Safe storage, deployment and recovery
- The possible value of a second anchor for particular routes
This will require more than buying a heavy piece of metal and storing it on the bow.
A properly designed anchoring system is emergency equipment: rarely used, but expected to work immediately when everything else has failed.
That is precisely why it deserves careful planning.