Swimfin

From Wikipedia, the free encyclopedia

This article or section may contain promotional material and other spam. This is generally not encyclopedic content, and may be removed by anyone when identified. If you are familiar with the content of the external links, please help by removing promotional links in accordance with Wikipedia:External links. (You can help!)

Contents 1 History 2 Specialized types of swim fins 2.1 Paddle fins 2.2 Vented fins 2.3 Split fins 2.4 Force fins 2.5 Delfins 2.6 Freediving fins 2.7 Monofins 3 Training 4 See also 5 References

Swimfins, swim fins, fins or flippers are worn on the foot or leg and made from finlike rubber or plastic, to aid movement through the water in water sports activities such as swimming, bodyboarding, bodysurfing, kneeboarding, riverboarding, and various types of underwater diving.

Scuba divers use fins to move through water efficiently, as human feet provide relatively poor thrust, especially when the diver is carrying equipment that increases hydrodynamic drag.^[1][2][3] Very long fins and monofins are used by freedivers as a means of underwater propulsion that does not require high frequency leg movement.

Swimfins are also known as "flippers", due to the ambiguity of the word "fin"; "fin" can reference the fins on cars and auxiliary airfoils on aircraft. Scuba divers all around the world would generally be familiar with the word "fins".

[edit] History

Early inventors, including Leonardo da Vinci and Giovanni Alfonso Borelli, toyed with the concept of swimfins.^[4]

Benjamin Franklin made a pair of early swimfins when he was a young boy living in Boston, Massachusetts near the Charles River; they were two thin pieces of wood, about the shape of an art palette, which allowed him to move faster than he usually did in the water.^[5]

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.^[6] Churchill's design caught the attention of the United States Navy, which issued it to their Underwater Demolition Teams in the early 1940s. Fins of this 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 plywood to plimsolls), until Oscar Gugen began importing swimfins and swimming goggles from France.^[4]

[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 and that allow less awkward walking on the beach. In general there are two main groups of fins; full foot and open heel. Full foot fins fit like a shoe, and are designed to be worn over bare feet. They are commonly used for surface swimming, and are in non adjustable sizes. Open heel have a foot pocket with an open heel area, and the fin is held to the foot by springs or straps. They can be worn over boots, and are common in diving. Many companies design fins with the same fin architecture but a choice of heel type. Other, more specific design trends are listed below.

Cressi-sub vented paddle fin

Beuchat Closed-heel Jetfins

Beuchat Open-heel adjustable Jetfins

A freediver using a monofin

[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 convoluted channels and grooves to improve power and efficiency though it has been shown that the desired effect does not occur.^[3][7] Paddle fins are widely believed to be the most versatile and have improved swimming economy in men.^[1][8] Tests in women showed a more flexible fin to be more economical, most likely due to lower leg power.^[3][9]

[edit] Vented fins

Vented fins were first designed in 1964 by Georges Beuchat and commercialised as Jetfins. Vented fins are paddle fins which have vents at the base of the foot pocket that allow for the passage of water during recovery kicks, but prevent passage during power strokes due to the blade angle. Recovery kicks require less effort so kick efficiency is improved. The Jetfin tradename and design were sold to Scubapro in the 1970’s.

[edit] Split fins

Some swimfins have the end of the blade split. In hydrodynamic principle, split fins operate similarly to a propeller, by creating suction and lift forces to move the swimmer forwards.^[10] The theory is that water flowing toward the center of the fin's "paddle" portion also gains speed as it focuses, creating a "scooping" or channeling effect.^[1][10] Due to the nature of the design this type of fin is also commonly used for snorkeling due to the fins being able to break the tension of the water with less effort than other designs when swimming along the surface, allowing the swimmer to conserve energy. Split fins are sometimes called "Biofins", although "Biofins" is a tradename.

[edit] Force fins

"Force Fin" is the trademark for fins designed, developed, manufactured and distributed by Bob Evans Designs, Inc. ^[11] They are distinguished by:
(1) An open foot pocket, that allows the wearer to wiggle their toes, and cantilevers the force of the kick from the large muscles of the upper thigh. .
(2) They are made of polyurethane, and the blade arcs when kicked against and the material compresses then responds by snapping back into its original shape. This snapping action generates thrust by moving water behind.
(3) Force Fins have trailing edge mechanisms ^[12], to channel and focus water behind.
(4) They have a clean or narrow side and leading edges that promote the flow of water over the fin blade without turbulence.

[edit] Delfins

This section requires expansion.

The Mor-Fin Corporation produces "delfins", which are swimfins that have a secondary fin which looks similar to a forked homocercal caudal fin. It is based on the anatomy of a dolphin's fluke.^[13]

[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. Though primarily intended for high efficiency at variable depths, they can still deliver impressive acceleration if necessary. The vast majority are made in the "full-foot" design with very rigid footpockets, which serves to reduce weight and maximize power. Freediving fins are commonly made of plastic, but are also often made from materials such as fiberglass and carbon fiber.

[edit] Monofins

A monofin is typically used in finswimming and free-diving. It consists of a single surface attached to footpockets for both the free-diver's feet. Monofins can be made of glass fibre or carbon fibre. The diver's muscle power and swimming style, and the type of activity the monofin is used for, determine the choice of size, stiffness, and materials.

[edit] Training

The upper limit of a diver's fin-kick thrust force using a stationary-swimming ergometer was shown to be 64 newtons (14 lbf).^[14] Resistive respiratory muscle training improves and maintains endurance fin swimming performance in divers.^[15]

[edit] See also

• Swimming
• PowerSwim
• Diving equipment
• Scuba equipment

[edit] References

v • d • e Underwater diving Types: Scuba diving · Surface supplied diving · Free-diving · Snorkelling · Saturation diving Specialities: Technical diving · Deep diving · Decompression diving · Mixed gas diving · Wreck diving · Cave diving · Ice diving · Rebreather diving · Solo diving · Altitude diving Equipment: Diving suit · Scuba set · Rebreather · Dive computer · Diver propulsion vehicle · Mask · Fins · Snorkel · Buoyancy control device Disciplines: Professional diving · Police diving · Military diving · Underwater photography · Underwater videography Hazards: Decompression sickness · Nitrogen narcosis · Oxygen toxicity · Barotrauma · Hyperbaric medicine · Drowning · Shallow water blackout · Deep water blackout · High pressure nervous syndrome · Dysbaric osteonecrosis

v • d • e Competitive swimwear Female suits: Racerback • Kneeskin • Bodyskin Male suits: Swim briefs • Jammers • Square leg suits • Legskin • Kneeskin • Bodyskin Accessories: Goggles • Swim cap Training gear: Training fins • Pull buoy • Hand Paddles • Fistgloves • Swimming board • Swimming machine • Inflatable armbands