Currents, fluctuating water levels and swell place particular strain on mooring lines and can cause serious damage to the boat. However, there are a number of precautions you can take to prevent damage. Below, we outline the basic principles that should be observed in the most common mooring situations to ensure your boat is properly secured.
1. In the box at the jetty and dolphins
Normally, most boats here are moored with four lines. The aft mooring lines are looped over two dolens using spliced or knotted loops, the two bow lines are secured to cleats on the jetty, and the chosen berth is longer than the boat.
Mooring lines are not simply discarded halyards or sheets, but ropes optimised for their specific purpose. Their breaking strength and elongation must be appropriate for the size and weight of the vessel. Such lines are strong, yet elastic enough to protect both the boat and the crew’s nerves.
The bow lines are often secured to the slipway. This is disadvantageous for a number of reasons. The mooring lines have less give, chafe against the cleats on the jetty and sustain more damage with every movement of the boat. Finally, they cannot be slackened from the jetty if the water level changes. In some harbours, securing the lines to the slipway is therefore – quite rightly – prohibited by harbour regulations.
When do the various measures take effect?
The better the length of the line, the way it is routed, and the coordination between the shock absorbers and the stretch, the smoother the ride for the boat and its crew. If no shock absorbers are to hand, with a bit of improvisation the bow lines can be routed over the fenders, which can significantly improve comfort on board.
Alternatively, weights could be attached to the aft mooring lines to improve the ship’s response to sudden movements. A positive side effect is that the higher the ship floats, the further the weights slide towards the dolens, where they help to keep the lines submerged.
However, if an extreme weather event such as the recent ‘flood of the century’ – with storms and exceptionally high water levels – were to occur, the measures described would not be sufficient. After all, the rising water level lifted the boats by more than two metres. Sooner or later, in such a situation, the four lines that have been deployed will come under an ever-increasing strain.
The correct length of the mooring lines
This effect is all the more pronounced the shorter the box is, as the angle at which the lines are pulled is steeper in that case. If the stern lines are then secured only by a large eye on the stern posts, without any further securing, they will come loose at the very latest when the water level reaches the top of the dolphin heads. In practice, however, this will happen much sooner due to various other factors, such as the increased movement of the vessel caused by the rising swell. Apart from the fact that the stern of the vessel is no longer fixed in position, this immediately gives rise to the next problem: the forward mooring lines will gradually pull the boat under water, at least as long as they do not break.
A scenario that can lead to the ship capsizing, as several incidents during the last storm surge have shown. If, on the other hand, the mooring lines fail to withstand the strain and break, the ship will be left adrift in the harbour. This usually has similarly devastating consequences.
The solution to this dilemma is to use long cradles and long lines. If possible, the cradle should be at least three to five metres longer than the boat. The length of the lines can be determined using a simple trick: a telescopic boat hook and a folding rule on the foredeck. If the water is expected to rise two metres higher than normal, the ship’s cleats will also be that much higher than before. So, if you place the boat hook – cut to the appropriate length – next to the cleat, the point at its upper end will mark the approximate position the cleat will be at during the predicted high water. If you now remove the lines from the cleats and run them over the positioned boat hook, you will find the point at which they need to be reattached to the cleat so that the line does not become overly taut later on.
Setting springs: the longer, the better
The same procedure is followed at the stern, using cross-laid stern lines. Where possible, the ends of these lines are also secured to nearby winches behind the cleats. This ensures that the boat remains secured to the winches even if the cleats fail. The motto is: redundancy increases safety.
However, as long as the maximum expected water level has not yet been reached, the boat will now drift towards the dolmens or jetty, as there is far too much slack in the lines. Taut lines are needed to resolve this problem. And they must be as long as possible. To prevent the boat from drifting into the jetty in this situation, a long line is run from a stern dolphin to the ship’s mid-cleat, or better still to the bow cleat.
This line is cut to a length that ensures the boat is just short of touching the jetty. The same is done on the other side, in reverse, so to speak, to prevent the boat from drifting backwards into the dolmens because the bow lines are far too long. Due to the length of these springs and their considerably flatter angle to the boat, they can accommodate large changes in water level. As cleats on the boat and the jetty can come loose, the mooring lines should be distributed across as many points as possible.
To keep the bow centred in the berth, provided there are no neighbouring boats in the way, very long bow lines can also be attached, running from the bow at as obtuse an angle as possible to a cleat further away on the jetty. Here, too, the rule applies: the longer they are, the better they can compensate for rising water levels and peak loads.
This ensures the boat is well prepared for high water. Provided you have enough space, lines, cleats and winches, there’s no reason not to double up on mooring lines or run additional lines from a centre cleat or the mast base to the jetty. In this case, the more, the better.
When extreme weather is forecast, it must be assumed that, in addition to your own cleats, the mooring points on the jetty may also fail. It is therefore advisable not to rely solely on two cleats, as is usually the case, but to distribute the load across multiple points. Perhaps you could wrap the lines around the entire jetty or one of its supports – this is where a bit of creativity is needed. After all, particularly with such unconventional mooring points, suitable measures must be taken to prevent the lines from chafing.
You need space and long mooring lines
It is equally important to bear in mind that the lines must not come loose, even at the highest conceivable water level. Whilst this is not a problem with cleats on the jetty, this aspect of preparation requires a very careful approach when using stern posts. Whether the bollards are steel tubes covered in smooth plastic or blunt wooden bollards, the stern lines must hold fast to them. In many cases, the posts are fitted with metal brackets or similar fittings at the top. Under normal circumstances, the lines are draped over these so that they do not fall into the water. If extreme high water is forecast, it is advisable to position the stern lines beneath these brackets.
To secure the aft mooring lines to the bollard, a loop pulled through itself is often used. When under tension, this knot holds quite well, but when not under load it can come loose and slip. A stopper knot with two half-hitches is a better option.
You can also weigh down the stern lines. Weights, chains or canisters filled to the brim are well suited for this. As the water level rises, they slide towards the dolens; whilst this means they lose their function as shock absorbers, they do help to keep the mooring lines secured to the posts.
2. Moored alongside a jetty or pier
In the event of a storm surge, this situation is only advisable with an offshore wind or a headwind. In principle, the same basic principles apply as when mooring in a berth. Here, too, the secret lies in using long lines. You can see how to use them correctly by observing the fishermen in the English Channel, who have to cope with a tidal range of several metres there.
The forestay runs from the boat’s forward cleat to a point on shore as far as possible behind the boat. The aftstay runs in the opposite direction, from the aft cleat to a point well ahead of the boat.
Additional long lines should be run from the cleats on the seaward side of the ship – which are currently still free – to the front and rear of the jetty.
Lots of ropes on lots of cleats
Here, too, it is important to distribute as many different lines as possible across as many cleats as possible on the boat and the jetty, in order to provide redundancy in the event of equipment failure. The mooring lines are supplemented by two lines running at right angles from the jetty to the boat, designed to prevent the vessel from drifting too far away from the jetty. Their length is again determined using the boat hook method.
Particularly when mooring alongside, the boat should be carefully fendered. If fenders of different thicknesses are available, it is important to position them correctly: thick fenders at the bow and stern, with their diameter gradually decreasing towards the centre of the boat.
To ensure they are securely fastened, the fenders should, where possible, be attached to the jetty rather than the railing.
3. In the parcel
Wherever possible, mooring in a line – at least with several sailing boats – should be avoided when severe weather is forecast. Even if the boats are moored in a staggered formation – that is, stern to bow and vice versa – the risk of the masts getting in each other’s way and being damaged in strong winds and heavy seas would be too great.
4. At the jetty
The places that appear to be the safest during flooding are only safe as long as the jetty in question actually remains in place. During the Baltic Sea storm surge, however, floating jetties in some places were unable to withstand the forces of nature and either broke free or simply drifted away from their moorings. If unusually high water levels are forecast, it is therefore advisable to check whether a floating jetty can withstand them.
5. Bonus: The most important rules of thumb in the event of flooding
- Move the ship into a long berth
- Bow into the wind
- Extend the bow and stern lines in line with the expected water level
- Fitting a shock absorber
- Creating redundancies to cope with failures: deploying additional lines from several points on board to various locations on shore
- Keep all the ropes as long as possible
- Minimise the windage as much as possible and take down the sprayhood, the cover and the sails
- Set out all the fenders
- Detaching the shore power cable The author has published a video on the topic of ‘securing the boat against storms’ on his YouTube channel
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Mike Peuker
Freier Autor
