Genealogy is the study of families, family history, the tracing of their lineages. Genealogists use oral interviews, historical records, genetic analysis, other records to obtain information about a family and to demonstrate kinship and pedigrees of its members; the results are displayed in charts or written as narratives. Although used interchangeably, the traditional definition of "genealogy" begins with a person, deceased and traces his or her descendants forward in time, whereas, "family history" begins with a person, living and traces his or her ancestors. Both the National Genealogical Society in the United States and the Society of Genealogists in the United Kingdom state that the word "genealogy" refers to the scholarly discipline of researching lineages and connecting generations, whereas "family history" refers to biographical studies of ones family, including family narratives and traditions; the pursuit of family history and origins tends to be shaped by several motives, including the desire to carve out a place for one's family in the larger historical picture, a sense of responsibility to preserve the past for future generations, self-satisfaction in accurate storytelling.

Genealogy research is performed for scholarly or forensic purposes. Amateur genealogists pursue their own ancestry and that of their spouses. Professional genealogists may conduct research for others, publish books on genealogical methods, teach, or produce their own databases, they may work for companies that provide software or produce materials of use to other professionals and to amateurs. Both try to understand not just where and when people lived, but their lifestyles and motivations; this requires—or leads to—knowledge of antiquated laws, old political boundaries, migration trends, historical socioeconomic or religious conditions. Genealogists sometimes specialize in a particular group. Bloodlines of Salem is an example of a specialized family-history group, it welcomes members who can prove descent from a participant of the Salem Witch Trials or who choose to support the group. Genealogists and family historians join family history societies, where novices can learn from more experienced researchers.

Such societies serve a specific geographical area. Their members may index records to make them more accessible, engage in advocacy and other efforts to preserve public records and cemeteries; some schools engage students in such projects as a means to reinforce lessons regarding immigration and history. Other benefits include family medical histories with families with serious medical conditions that are hereditary; the terms "genealogy" and "family history" are used synonymously, but some offer a slight difference in definition. The Society of Genealogists, while using the terms interchangeably, describes genealogy as the "establishment of a Pedigree by extracting evidence, from valid sources, of how one generation is connected to the next" and family history as "a biographical study of a genealogically proven family and of the community and country in which they lived". Individuals conduct genealogical research for a number of reasons. Private individuals do genealogy out of curiosity about their heritage.

This curiosity can be strong among those whose family histories were lost or unknown due to, for example, adoption or separation from family through divorce, death, or other situations. In addition to wanting to know more about who they are and where they came from, individuals may research their genealogy to learn about any hereditary diseases in their family history. There is a growing interest in family history in the media as a result of advertising and television shows sponsored by large genealogy companies such as This coupled with easier access to online records and the affordability of DNA tests has both inspired curiosity and allowed those who are curious to start investigating their ancestry. In communitarian societies, one's identity is defined as much by one's kin network as by individual achievement, the question "Who are you?" would be answered by a description of father and tribe. New Zealand Māori, for example, learn whakapapa to discover. Family history plays a part in the practice of some religious belief systems.

For example, The Church of Jesus Christ of Latter-day Saints has a doctrine of baptism for the dead, which necessitates that members of that faith engage in family history research. In East Asian countries that were shaped by Confucianism, many people follow a practice of ancestor worship as well as genealogical record-keeping. Ancestor's names are placed in shrines, where rituals are performed. Genealogies are recorded in genealogy books; this practice is rooted in the belief that respect for one's family is a foundation for a healthy society. Royal families, both and in modern times, keep records of their genealogies in order to establish their right to rule and determine who will be the next sovereign. For centuries in various cultures, ones genealogy has been a source of social status; some countries and indigenous tribes allow individuals to obtain citizenship based on their genealogy. In Ireland, for example, an individual can become a citizen if one of their grandparents was born in Ireland if the individual or their parents were not born there.

In societies such as Australia or the United S

Joe English (sailor)

Joe English, was an Irish yachtsman, professional sailor and sailmaker. He competed at multiple world championship level sailing events, including the America's Cup, the Whitbread Round The World Race and Admiral's Cup race series. In 1989, English skippered Ireland's first entry to take part in the Whitbread Round the World Yacht Race. Born into a seafaring family in Cobh, County Cork, English became an internationally successful yacht-racing captain and long distance offshore competitor. English was involved in the development of the sport of sailing in Ireland, from an amateur hobby into a full-time profession. In the 2014 Irish Examiner obituary, he was described as The People's Skipper. English had early success in the laser class, he won the Irish Yachting Association Junior Helmsman championship in 1974 and represented Ireland at the Youth World Sailing Championships in Largs, Scotland in 1975. English competed in the 1977 Admiral's Cup boat ‘Big Apple', on board ‘Moonduster’ for the 1979 Fastnet race.

After sailing aboard ‘Blizzard’ in the 1979 Southern Cross Cup, English emigrated to Sydney, Australia. During the 1980s, he competed in international events including the Admirals Cup, Southern Cross Cup, Sydney to Hobart Yacht Race, San Francisco Big Boat Series, Antigua Sailing Week Series and several Middle Sea Race events, including an ARC across the Atlantic. In 1981, along with friend Harold Cudmore, English won the Two Ton Cup and One Ton Cup aboard'Hitchhiker' and'Justine 3' respectively. In the America's Cup, English was involved in several Australian syndicates during the 1980s. In 1982, he signed on as part of the sailmaking team, to become part of the Australia II America's Cup Campaign. In 1986 he joined the James Hardy backed'South Australia' syndicate as mainsheet trimmer for the defence of the 1987 America's Cup. South Australia was a sister ship of Australia III designed by Ben Lexcen, although she performed quite differently. English campaigned during the 1987 Defender Selection Series with Syd Fischer on Royal Sydney Yacht Squadron Steak'n' Kidney.

English was made an Australian citizen for his America's Cup exploits. In 1989 English returned to Ireland to skipper the 82 foot, Ron Holland Maxi yacht'NCB Ireland', Ireland's first entry in the 1989–1990 Whitbread Round the World Race. Irish national expectations for the boats success ran high, but race leg wins were eclipsed by other teams, including the Peter Blake led Steinlager 2 entry that dominated the race. Gear and equipment failure dogged the Irish campaign. In the 31,500-mile race, noted for risk of loss of life and boat, NCB Ireland finished 11th out of a 23 strong fleet, he raced in the 1993–1994 Whitbread Round the World Race on ’Tokio’ with Chris Dickson and latterly with Toshiba for the 1997–1998 Whitbread Round the World Race, led by Dennis Conner and Paul Standbridge. Toshiba's crew had 13 28 America's Cup campaigns between them. English subsequently became part of the Whitbread executive committee until 2001 as it evolved into the Volvo Ocean Race. In 1991 Ireland won the Southern Cross Cup.

In 1993, English Skippered the 50 foot Jameson 1 in the Admirals Cup in that year for businessman John Storey. In 1994, with members of the Royal Cork Yacht Club he led the development of the 1720 Sportsboat, one of the world’s first boat classes aimed at delivering affordable and fun racing for local club level sailors. In 1997 he won the Round the Island Race in Cowes on his own 1720 Sportsboat. In 1999 English sailed aboard the Italian yacht'Riveria di Rimini' for the Middle Sea Race and subsequently placed second in the 1999 Fasnet Race. In 2007, aged 51, English was diagnosed with Alzheimer's disease and retired as a professional yachtsman. In 2011, English took part in the Ocean Legends Regatta in Alicante, Spain for the start of the 2011–2012 Volvo Ocean Race. Following the establishment of the Joe English Trust, with fellow America's Cup sailor, John Bertrand,English became an advocate and campaigner for better solutions to treat and manage Alzheimer's disease, by meeting the President of Ireland to highlight the cause and participating in an RTÉ Television programme in association with the Alzheimer's Society of Ireland.

Highlighting the impact of the disease on sufferers and their families. He died on 4th November 2014 aged 58, his daughter Aoife, is a world champion sailor. In 2008 she won the Student Yachting World Cup Sywoc in La Trinite, France and in 2016 she won the Melges 24 Sportsboat World Championships in Miami, Florida. Aoife along with brother Robbie English are National and European 1720 Sportsboat Class Champions, a boat developed by their father

Lift-to-drag ratio

In aerodynamics, the lift-to-drag ratio, or L/D ratio, is the amount of lift generated by a wing or vehicle, divided by the aerodynamic drag it creates by moving through the air. A higher or more favorable L/D ratio is one of the major goals in aircraft design; the term is calculated for any particular airspeed by measuring the lift generated dividing by the drag at that speed. These vary with speed, so the results are plotted on a 2D graph. In all cases the graph forms a U-shape, due to the two main components of drag. Lift-to-drag ratios can be determined by calculation or by testing in a wind tunnel. Lift-induced drag is a component of total drag that arises whenever a finite span wing generates lift. At low speeds an aircraft has to generate lift with a higher angle of attack, thereby leading to greater induced drag; this term dominates the low-speed side of the lift versus velocity graph. Form drag is caused by movement of the aircraft through the air; this type of drag known as air resistance or profile drag varies with the square of speed.

For this reason profile drag is more pronounced at higher speeds, forming the right side of the lift/velocity graph's U shape. Profile drag is lowered by streamlining and reducing cross section. Lift, like drag, increases as the square of the velocity and the ratio of lift to drag is plotted in terms of the lift and drag coefficients CL and CD; such graphs are referred to as drag polars. Speed increases from left to right; the lift/drag ratio is given by the slope from the origin to some point on this curve and so the peak L/D ratio does not occur at the point of least drag, the leftmost point. Instead it occurs at a higher speed. Designers will select a wing design which produces an L/D peak at the chosen cruising speed for a powered fixed-wing aircraft, thereby maximizing economy. Like all things in aeronautical engineering, the lift-to-drag ratio is not the only consideration for wing design. Performance at high angle of attack and a gentle stall are important; as the aircraft fuselage and control surfaces will add drag and some lift, it is fair to consider the L/D of the aircraft as a whole.

As it turns out, the glide ratio, the ratio of an aircraft's forward motion to its descent, is numerically equal to the aircraft's L/D. This is of interest in the design and operation of high performance sailplanes, which can have glide ratios approaching 60 to 1 in the best cases, but with 30:1 being considered good performance for general recreational use. Achieving a glider's best L/D in practice requires precise control of airspeed and smooth and restrained operation of the controls to reduce drag from deflected control surfaces. In zero wind conditions, L/D will equal distance traveled divided by altitude lost. Achieving the maximum distance for altitude lost in wind conditions requires further modification of the best airspeed, as does alternating cruising and thermaling. To achieve high speed across country, glider pilots anticipating strong thermals load their gliders with water ballast: the increased wing loading means optimum glide ratio at higher airspeed, but at the cost of climbing more in thermals.

As noted below, the maximum L/D is not dependent on weight or wing loading, but with higher wing loading the maximum L/D occurs at a faster airspeed. The faster airspeed means the aircraft will fly at higher Reynolds number and this will bring about a lower zero-lift drag coefficient. Mathematically, the maximum lift-to-drag ratio can be estimated as: max = 1 2 π ε A R C D, 0, where AR is the aspect ratio, ε the span efficiency factor, a number less than but close to unity for long, straight edged wings, C D, 0 the zero-lift drag coefficient. Most the maximum lift-to-drag ratio is independent of the weight of the aircraft, the area of the wing, or the wing loading, it can be shown that two main drivers of maximum lift-to-drag ratio for a fixed wing aircraft are wingspan and total wetted area. One method for estimating the zero-lift drag coefficient of an aircraft is the equivalent skin-friction method. For a well designed aircraft, zero-lift drag is made up of skin friction drag plus a small percentage of pressure drag caused by flow separation.

The method uses the equation: C D, 0 = C fe S wet S ref, where C fe is the equivalent skin friction coefficient, S wet is the wetted area and S ref is the wing reference area. The equivalent skin friction coefficient accounts for both separation drag and skin friction drag and is a consistent value for aircraft types of t