Swimfin
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Swimfins, swim fins, fins or flippers are finlike rubber or plastic shoes worn over the foot to help movement through the water in water sports activities such as bodyboarding, bodysurfing, kneeboarding, swimming, and various types of diving.
Scuba divers use fins to move through water better, as human feet provide poor thrust, especially when the diver is carrying equipment that increases drag in the water. Very long fins and monofins are used by freedivers in the search for underwater propulsion that does not require high frequency leg movements.
Swimfins are also known as "flippers" outside of North America, though scuba divers all around the world use the words fins.
Some people call them "flippers" in North America and elsewhere, because the word "fin" can also mean the fins on cars and auxiliary airfoils on tails of aircraft, which are parallel to the fluid flow. The comic book character Aquaman has had this sort of fin on the calves of his boots.
[edit] History
Benjamin Franklin made a pair of early swimfins while he was a young boy living in Boston, Massachusetts near the river; they were two thin pieces of wood, about the shape of an art palette, which let him move faster than he usually did in the water.
Other early inventors including Leonardo da Vinci had toyed with the concept of swimfins.
Louis de Corlieu in France and Owen Churchill in the United States, working independently of each other, were the first to make swimfins a practical reality. Churchill's design caught the attention of the US Navy, which wanted to issue it to their underwater demolition teams in the early 1940s; and fins of his design can still be found in just about any sporting goods store or surf shop.
In Britain, Dunlop made frogman's fins for World War II, but after the war saw no market for them in peacetime, and, after the first supply of war-surplus frogman's kit was used up, the British public had no access to swimfins (except for home-made attempts such as gluing marine ply to plimsoles), until Oscar Gugen started importing swimfins and swimming goggles from France.[1]
[edit] Specialized types of swim fins
Different types of fins have evolved to address the unique requirements of each community using them. Scuba divers, in particular, need large wide fins to enable them to overcome the water resistance caused by their diving equipment; snorkelers need lightweight flexible fins; ocean swimmers, bodysurfers, and lifeguards favor smaller designs that stay on their feet when moving through large surf, as well as allow less awkward walking on the beach. Other, more specific design trends are listed below:
[edit] Paddle fins
These are the most basic fins - a pair of simple stiff plastic, composite, or rubber blades that work as extensions of the feet while kicking. Some paddle fins have a water vent through the blade, opening backwards on the underside and forwards on the upper side, as in the third image. As the hip joint is flexed, a jet of water blows backwards out of the vent in the fin. This type of fin is sometimes called a "jetfin"; but the name "Jetfin" is correctly a tradename. Other paddle fins have convoluted channels and grooves to improve power and efficiency. Paddle fins are generally not the most efficient fins, but are widely believed to be the most versatile.
[edit] Split fins
Some swimfins have the end of the blade split. In hydrodynamic principle, split fins actually operate similarly to a propeller by creating suction and lift forces to move the swimmer forwards. [2] Water flowing towards the center of the fin's "paddle" portion also gains increased speed as it focuses, creating a "scooping" or channeling effect. Split fins are sometimes called "Biofins", but "Biofin" and "Jetfin" are tradenames. Split fins are generally regarded as among the most efficient fin designs, although there is ongoing controversy among divers as to their versatility - many report that split fins cannot be used for frog kicks and are poor for maneuverability.
[edit] Force fins
Force fins represent a type of fin that is, at present, only manufactured by the Force Fins company. They are radically different from all other fins - they have a wide upturned blade made of polyurethane, with a shallow V-shaped cut into the end like some fishes' tails. Force fins are valued for their high efficiency and acceleration, but are often chided for their poor maneuvering characteristics. Also, for divers who wear neoprene wetsuit boots in colder waters, the negative buoyancy of the lightweight Force Fins is not sufficient to counter the positive buoyancy of their boots. This leads to a condition colloquially known as "floaty feet".
[edit] Freediving fins
These are very similar to paddle fins, except they are far longer, and designed to work with slow stiff-legged kicks that conserve energy and oxygen. They can still deliver impressive acceleration if necessary, however.
[edit] Monofins
See monofin.
[edit] Trivia
Owen Churchill, already a wealthy man, became a multi-millionaire from his "invention" of the first popular swim fin, which gained in use in the late 1930s and early 1940s. The income from his then-patented and now-commonplace device let him pursue his passion of competitive sailing. Churchill became the primary patron and team captain of the United States Olympic Yachting team at both the1932 (Los Angeles) and 1936 (Berlin) Olympic Games. Churchill was also a lifetime member of the Los Angeles Yacht Club, where memorabilia of his exploits is on display to this day. During the 1984 Olympic Games in Los Angeles, special recognition was given to Churchill by Peter Ueberroth for his lifelong efforts to promote sailing. Churchill's Star Fleet yacht, The Angelita, was fully restored for the occasion and re-christened at the time in Los Angeles harbor.
