Swimfin

A pair of Viper swimfins

Full foot fins

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".

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]

In 1946 Lillywhites imported about 1100 pairs of swimfins; they all sold in under 3 months.^[7]

In 1949 Ivor Howitt or a friend of his mailed to the Dunlop Rubber Company for swimfins; Dunlop answered that they had no plans to make swimfins and saw no use for them in peacetime. Howitt made his own swimfins with innertube rubber stretched across a frame of stiff rubber tube.

Types of swim fins

Types of fins have evolved to address the unique requirements of each community using them. Scuba divers, in particular, need large wide fins 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 make walking on the beach less awkward. 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

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][8] Paddle fins are widely believed to be the most versatile and have improved swimming economy in men.^[1][9] Tests in women showed a more flexible fin to be more economical, most likely due to lower leg power.^[3][10]

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. There is a hazard when swimming among debris, that long thin debris can get threaded through the vent.

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.^[11] 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][11] 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.

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.

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.

Force fins

"Force Fin" is the trademark for fins designed, developed, manufactured and distributed by Bob Evans Designs, Inc. There are over 30 models of Force Fins. They are distinguished by:

(1) An open foot pocket, that encloses over the instep, leaving the metatarsals and phalanges, toes free so the foot can flex, and cantilevers the force of the kick from the large muscles upper thigh. This eliminates a major cause of cramping from fins, which is caused by extended Plantar_flexion, having to hold toes pointed (lower leg muscles contracted) because the blade extends from the end of the toes. ^[12]

(2) Force Fins are made of Polyurethane. Polyurethane cross-links to hold to its molded shape at the molecular level, which works together with various design features, including structure on the underside of the fin blade to compress when kicked against, recoil, and responding with the fin blade snapping back into its original molded shape. This snapping action does the work for the kicker on the recovery and generates thrust by moving water behind. ^[13] Use of polyurethane allows the fin to be designed with clean, or narrow side and leading edges, and without ribbing that can generate turbulence and impede the flow of water over the blade.

(3) Force Fins have trailing edge mechanism, the most well known of which is the upcurved blade and V-shape at the end like some fishes' tail^[14], or [[4]split blade], with a curved trailing edge, others are outfitted with [[5]winglets], to channel and focus water behind.

The Tan Delta Force Fin is part of the permanent collections of the [[6]New York Museum of Modern Art] for changing the way mankind perceives moving through water, and along with the Extra Force Fin is part of the collections of The Costume Institute of the New York Metropolitan Museum of Art.

Less usual types

Open and closed heel fins are predominant, but there is a range of fins which have specialised blade attachment architecture. These include (these names are tradenames):

Delfins

This section requires expansion.

The Mor-Fin Corporation produces "delfins", which are swimfins that end short and to the end is attached a shape like a fish's forked homocercal caudal fin. It is based on the anatomy of a dolphin's fluke.

Shinfins

These fins are attached to the ankle and rest against the (anatomically) upper side of the foot, to avoid leg cramps and to reduce foot strain: commercial site.

Fins for special purposes

Flipfins

Flipfins are a modern USA-made type of open-heel swimfin designed to allow easy walking on land. Its blade and foot part are separate: the blade hinges onto the foot part at each side, roughly on the level of the metatarsal heads, and when swimming is held in line by a clip on the front of the foot part. On land or when wading the blade can be unclipped and hinged vertically so it does not interfere with walking: commercial site, with images

• Youtube video of Flipfins in use

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).^[15] Resistive respiratory muscle training improves and maintains endurance fin swimming performance in divers.^[16]

See also

• Human swimming
• PowerSwim, a device somewhat like two pairs of long thin airplane wings fastened to a scuba diver's hips and legs
• Diving equipment
• Scuba equipment

References

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