Etmal
An Etmal (from Middle Low German : Etmal = recurring period) is the distance covered by a ship from noon to noon . Noon is the local highest level of the sun ( ship noon ).
The ship's noon must be determined for the location determination according to the astronomical navigation . This means that you only have a fixed daily noon time on board with the determination of the highest level of the sun, i.e. without a clock. So it made sense to record the distance between two consecutive noon as a measure of the travel progress of the day.
The Etmal has been preserved in this meaning to this day. So expect and get the most shipping companies of merchant shipping daily noon position and Etmal the previous day by radio or telephone. These two values, the Etmal and the midday position, are still the most important daily data of a ship for the shipping company.
Subtleties
When traveling west, you can tell with a watch, especially a chronometer suitable for navigation , that the sun reaches its highest point a little later each day. A little more than 24 hours pass between two so-called boat lunches, and a little less when traveling east. When driving west you have a few more minutes to drive the Etmal. The time difference depends on the direction of travel, speed and latitude. Every 15 minutes of length , the duration of the day changes by one minute . At the equator you have to drive 15 nautical miles to the west or east for a minute. At 60 ° north or south latitude, e.g. B. in Northern Denmark or Cape Horn , you only need 8 nautical miles. When traveling quickly near the polar regions, even with traditional sailing ships, half an hour can regularly be gained or lost and the Etmal can change by five to ten nautical miles. When crossing from Hamburg to New York on a modern container ship with over 20 knots, the usable time per trip is even extended by around 50 minutes. And on a trip from Bergen to South Greenland at 30 knots you would gain 100 minutes, which increases the Etmal by 50 nautical miles. You lose both on the fast return trip.
Another, but smaller, deviation arises regardless of the direction of travel, because the true length of a sunny day is exactly 24 hours only four times a year (see also the equation of time ). This effect depends solely on the eccentricity of the earth's orbit around the sun and the inclination of the ecliptic and is also independent of the geographical location. As a result, the true sunny day around January 1st is around 30 seconds longer and at the end of June 12 seconds longer, while at the beginning of April and mid-September it is around 20 seconds shorter. The distance (not) covered in this short time can usually not be reliably measured using astronomical navigation.
In practice, however, these variable measuring times are expressly not incorporated in order to determine the Etmal, according to the definition, so that the Etmal is only suitable for the approximate calculation of the (daily) average speed. In traditional sailing, the error was usually less than 1% and thus in the order of magnitude of the measurement inaccuracy of astronomical location determination, but in modern seafaring it is easily 5%.
Different usage of language
Racing yachts
The midday position is no longer determined on modern racing yachts, the location is determined exclusively by GPS . This means that the use of Etmal for the route covered in any 24 hours has become established in the usage of racing yachts. In English they are more correctly referred to as 24 hour distance . In any 24 hours you generally cover longer distances than exactly from noon to noon.
Cruising yachts
A different language has become established on cruising yachts with overnight stays in port or at anchor. When navigating under land, the midday position does not play a role, rather the overnight stays form the fixed points of the journey and accordingly the distance of a day is referred to as the Etmal .
Outstanding Etmale for sailing ships
The Etmal, the daily distance, is calculated from the distance between the midday positions or measured on the nautical chart and noted in the logbook. Outstanding Etmales are published and are suitable to help the shipping company, the ship or the skipper to achieve a certain reputation.
The fastest sailing ships of the 19th century were the clippers . In December 1854, for example, the 259-foot Champion of the Seas drove in the southern Indian Ocean under the command of Captain Alexander Newlands a breathtaking 465 nautical miles (862 km, average speed 19.4 knots). For the next 130 years, this is believed to be the greatest daily distance a sailing ship has ever covered.
Only the ocean yachts of the late 20th century were able to surpass the etmale of the clipper. Although they are much smaller than the clippers, they can sail more than twice as fast even over long distances thanks to new materials and new findings in fluid dynamics and navigation (e.g. weather routing). Furthermore, because of the much better chances of rescue and survival, boats that are actually unsinkable are sailed much more risk-taking.
In August 1984 the 80-foot catamaran Formale TAG drove an etmal of 512.5 nautical miles (24 hour distance record) under the Canadian skipper Mike Birch. The first monohull to break the Champion of the Seas record was the German yacht Illbruck Challenge (skipper John Kostecki ) on May 7, 2002, which sailed 484 nautical miles in 24 hours during the 2001/02 Volvo Ocean Race , which was also the "20 knot sound barrier" broke.
The record has stood at 908.2 nautical miles (average speed 37.8 knots) since August 1, 2009, when the French 40-meter trimaran Banque Populaire V achieved a record Atlantic crossing from New York to Lizard Point . The average speed of the entire 3 days, 15 hours and 25 minutes journey was 33 knots (61 km / h), which was faster than all Atlantic crossings by water before 1952 including the respective Blue Ribbon winners . The longest Etmal for single-handed sailors has been held by François Gabart on the Macif trimaran since July 2016, which improved its record from 783.46 nautical miles (average 32.6 knots) to 851 nautical miles on November 15, 2017. Shortly before Gabart's first record, Thomas Coville achieved a single-handed 24-hour distance of more than 700 nautical miles on June 8, 2016 on Sodebo , namely 718.5 nm with an average speed of 29.93 knots.
The record for monohulls so far was 596.6 nautical miles, held by the Volvo Open70 Ericsson 4 , achieved in the Volvo Ocean Race 2008/09 on October 29, 2008. The average speed was 25.11 knots (= 46.5 kilometers per hour) ). The record was increased to 618 nautical miles on July 11, 2015 by the 100-foot yacht Comanche under skipper Ken Read during the Transatlantic Race from Newport (Rhode Island) (USA) to Portsmouth (GBR). This corresponds to an average speed of 25.75 knots. For single-handed sailors with monohulls, the record time was sailed on January 16, 2017 with 536.81 nautical miles (average 22.36 knots) by the Briton Alex Thomson during the Vendée Globe 2016/17 .
Sometimes outside of the sea
The use of the word “Etmal” is not limited to seafaring alone. With the meaning “day and night” it is used in the legend “ Of King Karl and the Frisians ” by the Brothers Grimm :
- There they stood an etmal (time of day and night) in the group.
Web links
Individual evidence
- ↑ For the largest and fastest clippers with 60 to 75 meter long water lines, only on their maiden voyage were brief, one-off top speeds measured and found to be credible, in this case 19 to 21 knots, just below their respective theoretical hull speed . The Sovereign of the Seas , an almost identical ship of the Champion of the Seas from the same shipyard and the first ship ever to travel over 400 nautical miles a day, is the fastest square sailer of all time with a unique 22 knots measured in 1854. Average speeds of 17 and 18 knots are documented for some clippers, but over 19 knots and thus 95% of the hull speed must be doubted, as the swell at the necessary wind strength (approx. 40 knots, Beaufort 9, at least in the second half of the Etmal 150 meters long and 6 meter high waves) does not allow a constant maximum speed. The record time of the more modern, slightly larger, lighter, slimmer but less "sleek" Gorch Fock is 323 nautical miles (13.5 knots, 60% of the hull speed).
- ↑ Boehmer, W. Richard: TREP Analysis of Champion of the Seas One Day Record Run. Nautical Research Journal vol. 24, Washington, 1978. pp 69-71, ill.
- ^ Archive of the designer Nigel Irens ( Memento of March 30, 2010 in the Internet Archive ), under the boat name Daedalus
- ↑ A 24 hour distance record is recognized by the World Sailing Speed Record Council WSSRC. Old records are also listed there. WSSRC
- ↑ Unofficial record, as the positions were not documented with an automatic navigation protocol (e.g. GPS).
- ↑ a b c d e Publication of the WSSRC commissioned by the ISAF to manage the records
- ^ Article in the Frankfurter Allgemeine Zeitung from September 23, 2009
- ↑ See blue ribbon
- ↑ Boat info Macif
- ↑ Yacht.de: New solo record: 785 nm in 24 hours, accessed on July 4, 2016
- ↑ Yacht.de: François Gabart with a new 24-hour record
- ↑ Segelreporter.com: Comanche 24-hour record, accessed on July 13, 2015
- ↑ The fairy tale of King Karl and the Frisians at Project Gutenberg