Sailing lession: Sailing in fog

Sailing lession: Sailing in fogWe all know that the weather conditions are not always ideal as they are shown in catalogues of turist agencies and charter companies. I think it is  appropriate to write some words about traveling in bad weather and rough conditions.

The sea can be a very tough enviroment and it is right that we know what to do when we find ourselves in tough weather conditions and sail with our boat and crew safely to our final destination. This time I will be writing about sailing in fog. You probably won’t see it if you sail only in summer months but it might happen as well.  I think it is a right thing to know something about sailing in fog.

Facts about fog

We know that fog is actually nothing more than a cloud, which is located on the ground or water. It consists of tiny water droplets that are so dense that visibility is reduced, sometimes to only a few meters. Fog occurs when the air contains enough moisture and air temperature drops bellow dew point temperature. Because of the that moisture is present in the air, condensation begins which resulting in fog. Sailing lession: Sailing in fogFor the us who are sailing it may not be irrelevant that we at least have some knowledge about principle of fog formation. Knowing the basics we will be able to predict the formation of the fog and avoid putting our self, our crew and boat in danger. Therefore, we will first learn about types of fog. These are basically four. The first and most common is radiation fog. This type of fog is formed in basins and everyone knows it after the foggy mornings, which sometimes make it difficult to travel on roads. This type occurs usually when we have clear nights. Usually, when there is a strong anticyclone present in the area. In these days the heat of the night air and soil is losing by radiation into space. (This thermal radiation is prevented by clouds when bad weather occurs.) As there usually there is no wind along with the warmer weather which would mix cold and warm air layer the air at the ground cools overnight and so the temperature drops below the temperature of dew and fog occurs. The sun reheats the air during the day and fog disappears. This type of fog usually does not represent a threat to us, except when we are at sea. Advection fog occurs when moist and warm air passes over cold areas and thus cools. Usually it is occurring at sea in spring and early summer when the sea is still cold. Warm air comes from the land over the cold sea, where it is cooled below dew point temperature. The result is fog of course. Advection fog is most dangerous for sailors. The third example is the frontal fog, which is formed at the junction of hot and cold weather fronts. Its characteristic is that it looks more like a cloud, and that it is formed in a very thin layer between the contact both fronts. Quickly comes and quickly moves away. For general education, I will mention a fourth type of fog, which is called the Arctic sea smoke. The very name tells us where it occurs. Since not many of you who are reading this will not sail in the Arctic sea, I will not describe this phenomenon .

How to prepare for fog

When you perceive a risk of fog, immediately begin preparations for sailing in foggy conditions. We start with our radar, if we have one of course, and we check the mounting of the buffer. It must be placed at the highest possible position on the vessel. On the sailboat the best place to mount it is just below the top of the boom. If the buffer is not yet installed, now is the right moment to do so. Prepare life jackets for all crew. In the case of fog, all members of the crew have to wear life jackets. Even those who are below deck. In the event of a collision and sinking of the vessel is not the time to search and put on life jackets. If you have a dinghy along, let it go of  in the water and tie it to your stern. Preferably with a knot, which allows fast detaching! Check your life raft, if you have one. Bring aboard your fog horn or bell to be used for this purpose. Also prepare a white and red flares and red distress flares. White torch is used to draw attention when there is a possibility of collision. It gives a very strong white light and illuminates the surroundings. The red torch is used to indicate an accident site and signal rockets to seek assistance. Repeat the necessary knowledge of using horn or bell. If we sail, we will emit a long signal horn (4-6 seconds), followed by two short signals (1 second), all in an interval of no more than two minutes. Power-driven vessels will emit one long signal that is broadcasted every two minutes. We make a mark on our map on our current position which is then continually checked and marked. Today when almost every boat has a GPS unit, that is not so difficult.

When fog surrounds us

Sailing lession: Sailing in fogIf you read the advices from the previous chapter, you have already marked your vessel’s position on the map, otherwise do it immediately. Using the GPS receiver is not so difficult. Following our position when we have electronic maps in conjunction with a GPS receiver on board is not a problem but I will describe the procedure for those who do not already have these devices. Mark your current position on the map and then kept plots, where you are. You should have learned how to navigate, so I will not repeat that. All crew must be wearing life jackets. Skipper reduces the speed of the vessel so the vessel is slower while still capable of rapid maneuver. We must assess the visibility! We do thi sby throwing a piece of paper or some similar degradable object (that does not pollute the sea) into the water , which will remain in the water long enough to perform measurements. We check the speed of the vessel and then measure the time until the moment when the object disappears from our sight. As we sail with a known speed it is not difficult to calculate visibility. Perhaps even more important than the actual visibility in meters, it is time that we measured because it will tell us how many times we are at that speed away from the crash at a time when we see an obstacle. Unless it is not sailing towards us. That time is much shorter and depends largely on the brains of the other skipper. Now we can plan our travel further. This concerns mainly moving away from threats, such as coastline, islands and dense traffic routes. In tracking our position in the absence of GPS receiver depth gauge can also help. To prevent a collision or stranding of the coast, you can simply follow one of the isobaths. On the map, you first look at how the (for example) 20 – or 30-meter isobath goes and if it fits our travel plan we can follow it. Beware, there is a possibility that someone else followed the same isobath, so be careful. Choose non standard isobaths. How do we save our self when we are in a long-lasting fog, is again a matter of our position. If we are near the coast and bays, we can use smart navigation and sounders to come to shallow water where you throw the anchor and then remind the vessels in our neighborhood with appropriate signals from the bow . The signals are given in the table. If we are in the route of large ships we must try to leave these waters as soon as we can. During our trip we have to listen and observe our surroundings. If we see a ship we must immediately start a maneuver to avoid collision. Do not wait for the maneuver of the other ship, regardless of who has priority. If the ship is sailing toward you, it’s best to turn your boat with the port side or starbord side parallel to the bow wave of incoming ship. The probability that it will deduct the vessel to the side is considerable. If you see that a collision is unavoidable, try to turn the vessel coming toward you alongside with the vessel. So you’ll probably only grazed your boat and you will not suffer major damage.

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