Sea anchor
Drogue or sea anchor - historically also Lenz bag called - are on yachts used in heavy seas. They are parachute-like constructions that are used in deep water to hold the bow or stern against the wind and thus prevent the boat from standing across the waves and being capsized by them.
Another, rare possibility of use is to propel the ship through deep-lying ocean currents. For antique ships with their bad assets to the wind to sail a sea anchor was, according to some sources, the only practical way to the Mediterranean at the Strait of Gibraltar against the prevailing wind and current direction to leave, but evidence of successful trials do not exist.
A third use is the tensioning of ropes in canyoning.
terminology
Historically, the terms sea anchor and sea anchor are interchangeable, but in the meantime it has been agreed to designate anchors deployed over the bow as sea anchors or para anchors, while anchors deployed over the stern are called sea anchors . The former are intended to keep the yacht in place as calmly as possible with the bow in the wind, the latter serve to reduce the speed ahead of the wind to a reasonable level. If a ship descends too quickly from a wave, it can cross the trough due to the reversed direction of flow of the water and then be rolled over by the wave.
commitment
Sea anchors or sea anchors are used when the swell goes beyond what the ship can tolerate and there is a risk that breaking waves could capsize the ship . For all ocean-going ships, the real danger in heavy weather comes from the waves and not directly from the wind, because the wind can push a ship flat onto the water, but never beyond it. In practice, drifting or sea anchors are used when the wind is above 7 or 8 Beaufort . They ensure that the ship always faces the waves with its bow or stern, thus creating the smallest possible contact surface for the water masses. It is well known that this tactic offers the greatest likelihood of surviving the storm unscathed.
Sea anchor
Parachute or para sea anchors have been regularly used with success by various ocean sailors since the 1960s. The first sea anchors included Bu-Ord parachutes, disused parachutes of the US Army that could be purchased cheaply in California.
A sea anchor are particularly suitable for boats that are not good Heave to, or are very light and are influenced by the waves too much when trying to show up a lot of wind. Other boats, especially long keelers, can turn so well that a sea anchor hardly offers any additional security. As an alternative to the sea anchor, there is also the possibility of motoring against the sea, but this is very demanding for the helmsman, can put a lot of stress on the engine due to strong rolling movements and is not possible for as long as you want, because the fuel supply, especially for sailing yachts, is limited.
Sea anchors should be at least 35% of the ship's length in diameter to be effective. The more stable the ships are, the bigger they have to be. You can also enlarge the area by tying several umbrellas together. Too large, however, they may not be, because then it is virtually impossible to deploy or obtain and the necessary ropes and cleats on the boat exceed the reasonable dimensions.
Sea anchors are lowered into the water on long lines from the bow of the ship. The line should be at least 50 meters long, ideally even 130 meters and more on the open ocean. This corresponds to the wavelength of large waves at sea. The optimal length depends on several factors, including the design of the ship. Lines that long are difficult to handle and expensive, especially when they are wet. A piece of chain can be shackled between the connecting line and the actual anchor so that the additional weight prevents the anchor from floating. The anchor should always remain well under water, where it is unaffected by waves and spray.
At the far end of the anchor there is a so-called buoy ladder, a heavy line that keeps the end under water. Above is a float, e.g. B. a fender attached. The anchor can be retrieved more easily by means of a further line, the so-called triple line, which is attached to the first float. The position of the anchor in the sea can be determined by means of the floats.
When deploying the anchor and mooring the end of the cable to the ship, care must be taken that the line does not rub through the bow. Because of the ship, which works hard in the waves, the line could otherwise break in a very short time and the sea anchor and hawser sink into the tide. Pieces of tubing over the line or additional lines to distribute the force to several attachment points can counteract this. The latter also prevents the cleats on the ship from being overloaded and torn out.
Sea anchor
The sea anchor system has been known for a long time. Various objects were dragged along early on in order to reduce the speed to a safe level when the sea was lagging behind - i.e. when the ship was sailing ahead of the wind. In the simplest case, you drag as long as possible a hawser behind the boat. It is also possible to use the actual anchor with chain as a sea anchor. The steep angle creates a lot of drag. However, this method only works if the water is deep enough and retrieving it could be difficult.
Very long lines are also needed to deploy sea anchors, because the anchor should be about a wavelength behind the ship. In the open ocean, the wavelength is around 120 meters. A few meters of chain or extra weight may also be helpful for the sea anchor to keep it underwater. There have been contradicting reports about this, however, and it is always recommended to test the equipment in moderate conditions before the emergency occurs, every move requires great effort and work on deck becomes a real danger.
By using a sea anchor, the boat should be slowed down so much that it does not cross over in the waves (making it vulnerable to breaking waves), but also not so much that it can no longer be steered, because then it would be hit by the waves also thrown around at will.
Sea anchors are available in different versions. In addition to the simple line already mentioned, there are so-called row sea anchors with many small cones on an approximately 100 meter long line. These have the advantage that they always remain under tension, as they are never influenced by a single wave due to their length. With the associated ballast weight of more than 20 kilograms, they are very heavy and difficult to stow away. Galerider or Seabreak are models that are very compact and bag-shaped and funnel-shaped. Cone sea anchors are also available for purchase and achieve similarly good results. A genoa attached to the three corners performed surprisingly well in tests , but only if the connecting lines are long enough and they can open.
The Bu-Ord parachute proved to be the most effective in terms of the speed reduction achieved. However, it braked so well that it is more likely to be considered as a sea anchor, because the ship could hardly be steered.
Summary
Sea anchors are useful additional equipment for boats that go out to sea and have to reckon with heavy weather. Together with an automatic steering system , they can give the crew the necessary rest time and keep the ship's bow or stern facing the oncoming waves, thus avoiding serious damage or capsizing .
Use in canyoning
When canyoning a sea anchor is used to overcome dangerous currents. The rope tensioned by the anchor is used as a guide when abseiling, for example so that it does not get caught in the backflow of a waterfall .
Individual evidence
- ^ Meyers: Großes Konversations-Lexikon , 1905-1909: "Treibanker". Zeno.org. Retrieved March 9, 2014
- ↑ E. Ludwig: Pocket book for marine engineers and marine machinists
- ↑ Hans Joachim Schellnhuber: Self-immolation: The fatal triangular relationship between climate, humans and carbon . C. Bertelsmann, ISBN 978-3-641-17526-9 , pp. 93 ( limited preview in Google Book search).
- ↑ Ernst Steininger: Seemann, your home is the sea . Verlag Maritimbuch, 2015 ( limited preview in Google book search).
- ↑ Schult, keyword sea anchor
- ↑ Heavy weather sailing , pages 110ff
- ↑ Heavy Weather Sailing , page 113
- ↑ Heavy weather sailing, page 129f
- ↑ Comparison table , see Heavy Weather Sailing, pages 130 and 131
- ^ Treibanker ( Memento from October 17, 2011 in the Internet Archive ) at the German Canyoning Association.
literature
- Peter Bruce: Sea anchors and their use in heavy weather in heavy weather sails ; 12th edition 2014; Delius Klasing Verlag; ISBN 978-3-7688-3178-9 .
- Joachim Schult: Sailors Lexicon. 9th edition. Delius Klasing, Bielefeld 1994, ISBN 3-87412-103-8