Seamanship: When visibility is poor - behaviour in fog (2024)

Thick fog! The harbour exit is barely visible and the wind is blowing weakly. This weather situation can be more unpleasant at sea than any storm. If you have the opportunity, stay in the harbour. If the fog appears unexpectedly during the voyage, it represents one of the last major challenges. Thanks to modern aids, an unforeseen landing is no longer to be feared, but a collision with a drifting object could have serious consequences.

In addition to being aware of this danger, there is also the panic factor: many people feel uncomfortable when their most frequently used sense, sight, is impaired. Only heavy rain or dense snowfall are even greater obstacles than fog, as even radar no longer works reliably and even GPS reception can be disrupted.

Whether fog is actually dangerous or merely an unpleasant side effect depends on various factors. In addition to visibility, the area, local knowledge and the traffic situation are decisive. If visibility is 300 metres on the Elbe, it is better not to sail. The Schlei, on the other hand, may still be navigable even with a visibility of 100 metres.

Read this article to find out how fog is created:

Where the limits of GPS lie in fog

By and large, you should still be able to find your bearings with the help of GPS even in the thickest soup - provided you have GPS. However, every skipper must decide for themselves whether they want to be dependent on a single electronic means of orientation. After all, if visibility is poor, you no longer have the option of taking a cross bearing to determine your position. Compass, plumb line and log are a help, but only if you know roughly where you are. In an emergency, you can feel your way along a known depth contour with the help of the echo sounder.

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In narrow passages, however, things can become critical even with satellite assistance. This is because the accuracy of the position in the plotter cannot be checked visually. In addition, the helmsman must also be able to follow the plotter data precisely in order to really "blindly" enter a harbour. In practice, a deviation of at least 50 metres between the planned course line and the actual route taken should be expected. And also that the chart used for planning has deviations.

What the rules require in fog

Just inconvenient or a risk - it depends on the circumstances. The Collision Prevention Regulations (KVR) clearly define behaviour in poor visibility. Rule 19 states: "Every vehicle shall proceed at a safe speed appropriate to the circumstances and conditions of reduced visibility." With regard to behaviour on approach, the following can be read: "Any vehicle which appears to hear the fog signal of another vehicle ahead rather than astern must reduce its speed to the minimum necessary to maintain steerability. If necessary, it must reduce all speed and in any case manoeuvre with extreme caution until the danger of a collision has passed."

In practice, it looks like this: If there are only other sailors in your own protected area, you are up against opponents who are fighting under the same conditions. This means that you can see just as well or just as badly, are sailing at a similar speed and have roughly the same manoeuvrability. You can take the same approach as on the road: with an intensive lookout, only manoeuvre in such a way that you can stop or evade within less than half the visual range. This procedure is also recommended by the KVR.

Things look quite different in tidal areas. The current can cause oncoming vessels to surface much faster than expected: For example, a yacht travelling "uphill" through the water at four knots will still make two knots over ground at two knots of tide. The skipper feels completely safe due to the very slowly passing pricks, after all, the current would still help with "braking".

This may be the case with fixed obstacles. An oncoming vessel now also makes a cautious two knots, but through the water; after all, it needs rudder power to follow the tide. As the current is pushing, this ship is travelling four knots over ground. As a result, instead of the expected four knots, the two ships approach each other at six knots. Anyone who is at home in tidal areas will be familiar with this effect, but for others the "speeding" comes as a surprise.

Caution with "big pots"

Where yachts are not the only ones facing each other, the calculations have to be completely different: A 200 metre long freighter with a bridge aft effectively only has 200 metres in front of the bow with a visibility of 400 metres. On the other hand, at this distance there is hardly any opportunity for the fat ship to take evasive action. And slow speed is another matter: manoeuvrability quickly becomes very poor.

Competition and time pressure often lead to commercial vessels simply continuing to sail with electronic assistance despite poor visibility. This may or may not be a good thing, but it won't change anything. The big ones see enough of each other, as a "small target" you should avoid the main shipping lanes if possible.

Which tactics are safe in fog

The best approach in busy coastal waters is to crawl into a place where no passing ships can reach, give the appropriate sound signals and wait on the spot for better visibility. Of course, you don't throw the hook away in the fairway - after all, you want to wait for better weather and not for the next steamer to pass you by. An old rule of thumb for safe spots is: where the water is shallow, no big pot will go. This applies to anchorages as well as courses.

But too flat is not good either. Because even if fog on the coast is usually accompanied by a light wind, passing ships can still generate a lot of swell. So, for fear of unpleasant encounters, you should not sail into shallower water than you would dare in the same place with good visibility.

When GPS and echo sounders were not yet a matter of course, sailors used a simple method before falling ashore in fog: they would drop the anchor overboard in deep water and then run towards the coast until it caught. They would then stay there until it cleared. Thanks to electronics, it is now possible to find a suitable spot more precisely. A spot should be chosen where there is as little through traffic as possible. This could be a bay or simply a bend in the depth contour. Of course, you have to navigate very carefully when approaching such points, as there could be other vehicles waiting for better conditions at the targeted spot or on the way there

Never anchor in the approach to the next harbour or in the approach line of prominent waypoints.

Commercial shipping also travels according to plan in fog - and rarely slower. Known courses of the "fat ones", for example ferry lines, should therefore be avoided from the outset. There are fewer potential collision opponents travelling slightly off the direct route. Waypoints pre-printed on the map are also not the first choice, as many skippers use their coordinates.

If anchoring is not possible

On the open sea, only a very vigilant lookout will help. Take regular turns, because after a while you can see all sorts of things coming towards you in the featureless fog.

Sometimes you can see from the deck that the top of the mast is obviously shining in the sun, while no rays are reaching the bottom. The idea of pulling a crew member over the fog into the rig is not a bad one.

Flawless communication between the lookout and the helmsman must be ensured, for example by means of pre-arranged hand signals. Or by walkie-talkies, which don't have to cost much. Be that as it may - high landmarks and large ships may actually be easier to see from above. However, it should always be borne in mind that other obstacles do not necessarily protrude from the fog bank: buoys, motorboats, small fishing boats, net buoys and shallow headlands remain hidden from the man in the mast.

What sound signals do in fog

Another sense helps people to orientate themselves: hearing. For this reason, there are sound signals, different ones for steamers, sailors and anchormen. However, these only help if they can be used and recognised.

Sound signalling systems are mandatory for yachts over twelve metres in length. Smaller yachts do not need them, but should carry something to make noise. This can be a compressed air fanfare (with sufficient reserve cartridges), or a frying pan in an emergency. If you are surprised by fog at anchor, you finally have an official use for the ship's bell. Incidentally, the pitch of fog signals should indicate something about the size of the ship: the deeper, the bigger. That is why authorised yacht installations have this annoyingly high squeaking tone.

Unfortunately, a yacht's engine is a powerful source of noise that deafens the crew to quiet sounds. That's why it's better in fog to only move under sail, even if it's much slower in calm conditions.

If the engine absolutely has to run, then at a speed that makes as little noise as possible. How much is a matter of trial and error. Standstill throttle does not automatically produce the noise that stands out best from the fog signals of other ships. To make sure you don't miss any collision opponents, position a listening post on the forecastle, as the engine is quieter there than in the cockpit. If in doubt, switch off the engine every few minutes to listen.

How to be seen in fog

According to the KVR, navigation lights must be used between sunset and sunrise and in poor visibility. This makes sense, because even in bright daylight, a light in the fog can be recognised at a greater distance than a yacht hull. And the colour also makes it immediately clear in which direction the target is moving.

A radar reflector must be on board anyway. And it doesn't belong in the forecastle in fog, but in the rig. The large rectangular ones are ideal because they produce the strongest echo. They usually have eyes for ribbons at the corners - which makes it tempting to set them with the tip pointing upwards. However, the correct position is the so-called rain catcher position, i.e. with a tap pot over two opposite corners so that a funnel points upwards. This produces the stronger reflections.

How electronics can help in the fog

With GPS, radar and AIS, fog at sea and on the coast has lost much of its terror. The skipper knows where he is and what is happening around him - at least approximately. But you can only be really good with a combination of technologies.

In terrestrial navigation, it was customary to use sea marks as waypoints and to actually sail to them. Firstly, in order to see the current that might be running at the buoy, and secondly, to have a safe starting point for the next stroke.

A slightly different approach is recommended for route planning using GPS, especially in poor visibility: The waypoints should not be set exactly on sea marks, but a little to the safe side of them - this reduces the likelihood of two ships heading for the same position at the same time and the waypoint becoming a collision point. Incidentally, this tactic equalises the situation when navigating on popular routes in all weathers.

Radar is of course the best equipment for fog. Those who have it are also required to comply with the KVR rule 7b: "In order to obtain an early warning of the possibility of a collision, an existing radar installation must be used, including the use of plotting or an equivalent systematic method for monitoring located objects."

This means that if you have it, you have to actively use it - and not just leave it running on the side. How helpful the electronic eyes are in an emergency depends mainly on the skill of the operator. So practise beforehand with good visibility. This is the only way to recognise the strengths and weaknesses of your own system and your own abilities. However, even if the yacht is equipped with a large radar and the crew can handle it perfectly, the following should be borne in mind: be aware that potential collision opponents may not have radar or may not be able to interpret the image reliably. And with vessels that only provide minimal echoes, such as fishing boats.

Although an AIS transponder offers help, it does not provide any real safety benefit. Firstly, not all vessels are equipped accordingly, and secondly, the display of yachts can be suppressed on large vessels. This is particularly likely in areas with heavy traffic.

Despite all the aids, tricks and precautions: The safest way to get through the fog is to stay in the harbour. Otherwise, you should always weigh up the weather, visibility and traffic conditions in the area.

Sound signals - how crews should draw attention to themselves

Vessels over twelve metres in length must be equipped with a sound signalling system and are obliged to give the signals listed below. Vessels under twelve metres in length may instead give any powerful sound signal every two minutes. However, it is also advisable for them to use the correct signals.

Ships under engine

One long tone (letter T) at least every two minutes. Two long tones without travelling (letter M)

Ships under sail, manoeuvring, fishing, towing

One long and two short tones (letter D) at least every two minutes

Anchor berth

The ship's bell rings for five seconds every minute. When other vehicles are approaching, an additional short, long and short tone (letter R)

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