Fins

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Fins

October 13, 2011 - 23:34
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Fins provide a great way to get from point A to point B in an H2O environment. In fact, with few exceptions, it is the only way to get around with ease while diving.

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As a diver you are limited by your strength and stamina. This is when the design of the fin really can work for you. If you are an able-bodied, strong person, you will have little problem with whatever fin you happen to wear. A good blade design will merely fine tune your performance. But if you know your stamina is low, and it has been some time since you visited a gym, choosing the right fin can make all the difference between a bad or good experience. However, it is easy to get confused. Fin designs have evolved over the years. Long fins, short fins, split fins, twisted fins, stiff fins, soft fins...

How to choose?
We keep telling you to do your research, but looking at specfications in isolation will most likely just add to your confusion. To figure out what the right fit for you is, you need a step-by-step approach that will narrow down the options with a process of elimination.

Fin Formula
Begin with clarifying which kind of diving you would normally be doing. Also, consider the level of your physical fitness in this context. Then, start looking for a fin. Today, there are choices that respond to different needs. It’s a good thing. At the end, the fins need to be comfortable, and they need to perform.

So, who are you?
Will you be mostly diving in a way where you need to cover long distances and rough water during your dives? Will you be fighting current and waves on a regular basis? Is it more important for you to be able to maneuver with ease under water? Or, are you one of those that just likes to cruise along and enjoy the view?

The Mount Everest Diver
The Mount Everest Diver is a diver looking to move effectively and effortless through water, while covering long distances during his dives. He does not like to take the easy road, the tougher conditions the better. With a compass in hand, he plots the course to the dive site from the shore. Then, he endures the long surface or under water swim to the site with a smile on his face—at least, with the right fins, he does.

You need a good pair of fins that can push water effectively and move you forward without tiring you. You need a large blade with some stiffness built in. How much stiffness depends on how fit you are, but you will need a fin that can transport you and your dive equipment through the water resistance without tiring you.

The Spear Fisher
The Spear Fish Diver needs maneuverability as well as the option to move effectively through water. In fact, he needs to go from 0-60 in a split second in order to land that catch.

The Ocean Diver
The Ocean Diver is a diver who knows that any second of the dive, the current can pick up. He needs a fin that can fight the current and violent wave action on a regular basis.

The Cocktail Diver
The Cocktail Diver is a diver that just likes to cruise along and enjoy the view. He is typically found in tropical water, and cares nothing about efficiency and speed. He lives in the moment, knowing that the dive boat will pick him up when he runs out of air or time—whatever comes first.

The Explorer
The Exploration Diver is a diver on a mission. They can be photographers, wreck and/or cave divers, and the one thing they all have in common is that there is a purpose to their dive. They need full control of every movement during the dive, not to stir up silt or scare the wild life. They have to be able to maneuver with ease. A consciencious tropical diver who needs to move carefully around to protect the reef might fall under this category, too. You need a shorter, more flexible fin than the average, which still has the capacity to move you forward with ease.

The Snorkeler
The snorkeler hangs mostly on the surface. Occasionally, he takes a plunge to take a closer look at something, but the main objective of his time in the water is to observe from above.

The snorkeler does not have the advantage of using the fin while immersed. He might favor a more flexible, light weight fin to handle the occasional “air” flip in an effective way.

Gone are the days when the rubber fin ruled the world. And for all you rubber fin fans out there, don’t get offended. That is still a good design, but maybe not for everyone.

The Physics of Fins
When diving, you need a flexible fin of moderate length. When you push down on the fin when kicking, you bend it, and it is largely the spring-back force from the fin as it straightens that propels you forward. This makes the material choice and fin shape critical to getting the right spring force for optimal efficiency.

Fin Types

Paddle fins
The traditional paddle fin is a really simple design, a flat blade with a mounted foot pocket. The material of the blade is made out of stiff plastic, composite or rubber. The design of the fin generates quite a bit of resistance during the kick cycle and requires rather good leg muscle strength for effective strokes. Because of this, the paddle fins are sometimes considered to be not so efficient.

A more developed paddle fin can come with a water vent through the blade, opening backwards on the underside and forwards on the upper side, blowing a jet of water backwards out of the fin as the fin flexes. Others have convoluted channels and grooves, in an effort to improve efficiency.

In 1985, Mares developed a new feature for water fins called channels. Traditional paddle fins suffered from water ”spilling” off of the edge during the down stroke of the diver’s kick. This loss of water translated into a loss of thrust, meaning that the diver’s effort was not being fully utilized. Mares’ channels worked to maximize fluid stream channeling, keeping the water under the fin in place, so that it can be displaced during the down stroke. This increase in water displacement allowed for greater thrust levels and improved overall performance.

The addition of channels or grooves made the effort and energy expended by the diver more valuable—more thrust was generated with each stroke. But this advance in technology did not solve the energy inefficiency of the kick cycle upstroke.

Split fins
Split fins are considered one of the most efficient hydro-dynamic fin designs. However, that does not necessarily make it the best overall fin.

In the split fin, as the name indicates, the blade is split, which causes a kind of propeller movement. Using traditional fin kicks causes a suction and creates a lift, which allows the diver to move with less effort compared to using a paddle fin.

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 generally regarded as among the most efficient fin designs, although there is

Originally published

on page 57

X-Ray Mag #17

May 22, 2007 - 19:48
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Red Sea - behind the scene Egypt and Saudi Arabia. FINS + interview of Bob Evans. How coral reefs change. Kurt Amslers photoschool: Macro. Safety margins on a rebreather. The Science of Salinity. Sun protection for divers. Mermaid Matters: Mascara: Medical issues: Nasal Irrigation

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