Foil Force Fin

"Here we introduce to you to a fin that is a world novelty, which design does not leave anyone indifferent to it. We had the great opportunity to test them and to be able to discover its alternatives upon comparing it with the fin movement and the design of the conventional blade. Do not miss the results."

Foil Force Fin
by Nora Camera

Let the force be with you. It was in 1971 when Bob Evans, a submarine photographer by profession, started to observe the movement and displacement in the water of fish and the great ocean creatures. In reality he was not a true designer, but he did have experience in the making of molds and figures because his father was a sculptor, and this allowed him to develop an almost innate ability for geometric space designs. Like a good diver, Bob used to check the products in catalogs and he realized that year after year the diving industry kept the basic design of a flat and long blade in all of their fins and that the only thing they incorporated as new was the color and the insertion of pieces that in practical terms were useless for the improvement of the water displacement.

LEARNING FROM NATURE

He knew better than anyone that the responses to a man made design would never be valid in the natural environment, therefore, why not learn from the great fin experts? And that is how he started to study and understand the anatomical designs of the propelling structures of the great oceanic creatures, whether fish or mammals. It was at that point, when he realized that a design of a flat blade was unnatural and costly energy wise, and not advantageous for a diver who depends on an amount of non-renewable air supply which diminishes as the efforts increase during the flapping or strokes.

Therefore he concentrated his research on the relationship between physical effort and the hydrodynamic performance during the strokes, in the function of air consumption. Very quickly he came to the conclusion that geometry and the rigidity of the blade would be the key points to achieve the optimal objective: to create a fin that would do the greatest part of the work instead of the diver during the displacement through the water. And the Force Fin was born, from research directly from Mother Mature.

PERFECT GEOMETRY

The main difference in the design of Force Fin with respect to the rest of the fins in the market, is that they have a curved base, allowing for a greater penetration in the fluids, contrary to the general rule of the flat blade design. Why? It is very simple. Imagine a boat with a flat hull. What would happen? It would impossible for it to navigate without capsizing, since it would not have the proper penetration for the correct deployment through the water. Then in order to achieve balance while its cutting through the water one would add a million gadgets, just as it occurs in the models of flat blades, but without resolving the main stability problem.

Bob Evans has gone beyond all of that and has incorporated to the fins the equivalent of a keel on a boat, providing the main component of stability for sub-aquatic propulsion and avoiding the pronounced edges, channels and etc. Why develop alternative solutions, if one could avoid the problem itself? That is Bob Evans philosophy, who has worked hard upon the most adequate hydrodynamic design for the divers strokes and has succeeded on a model of a curved blade that better penetrates the viscosity of the fluid liquid mass.

Another aspect that surprised me but that I liked very much, was the reduced space for the foot pocket and the freedom that it lends to the instep or vamp, and if you look closely, you will notice how it extends from it the tip of the foot pocket, meaning that one does not have to do the typical hyper extension of the instep that squashes our ankles so much and produces cramps in the base of the plantar arch. When you put on the fins you notice that they fit like a glove but they do not squeeze you like the rest of the models in the market. This point is important to consider in case of injury , or in the case of bone or muscular weakness, because it frees our foot from carrying out all of the efforts during the ascending stroke and avoids the hyperextension of the instep during the descending stroke.

And here we come to one of the most criticized point- due to ignorance of course in the manufacturing of the fin; how could a fin that cost so much money be tied up with an anchoring based in a strap so stingy? Well, Force fins do not need to be anchored, and this is easily shown putting on a fin with the "stingy strap" and without it. Then we will realize that both fins are working equally well, and therefore their perfectly well researched design is shown once again. The fin fits on your foot and is the fin which does the job.

Try and do this test with a model that is not Force Fin and you will see that Bob Evans chose to invest in design and material to get this effect, instead of placing automatic clasps and other superfluous accessories. And certainly, for the anchoring system to be considered "stingy", one should have questioned the quality of the material, but I should let you know, that before mention the strap and the plastic materials for the anchoring, are more than sufficient for the function to be performed.

If you buy some Force Fins, you must have into account that the size of the fin will not be your foot size but a combination of shoe size and foot pocket size, otherwise, if you do not tie your fin you will loose it on the way in case of experimenting with "free footing".

Why then does it have straps? Very simple; it has cost quite a bit to introduce a new concept in design in the antievolution minds and if on top of it you sell them fins without straps, nobody would buy them for . fear of loosing them. It is normal, there is still a long road ahead, and I believe that today's diver is not ready for it and much less the Spanish market. The psychological effect of security in the fastening it is necessary for obvious reasons.

LIKE MADE OF GOLD

Of course they are not, otherwise they would not be so fantastic. Bob once again has search for alternatives and materials is another one of them. Force Fins are made of polyurethane, a non-plastic material much more expensive that the popular material among manufacturers, ethyl-vinyl-acetate (EVA) which is a cheaper and archaic material, but of easy manipulation during the process of mold injection.

Once again Bob Evans decide to invest in what really matters, since his material does not have the negative thermal properties of EVA. When you put them in a car or in a boat during the middle of the summer, your fins quickly get hot and begin to deform little by little and then when we go into the water they get cold and they get their new shape. If you observe worn out fins made of what normally is know as "technopolymer", you will see that they are always deformed in a concave shape, which the shape produced by the hydrodynamics of the kick, which is slowly molding the flat shape of the conventional blade. This shows once again that the flat shape of a blade it is not hydrodynamic.

Force Fin does not loose its rigidity as immersions take place and even if you store them deformed, they will not lose their original geometry .Besides, the polyurethane is much more resistant to ultraviolet radiation and to the wear due to friction and heat. Other characteristic is the high degree of rigidity, high degree of snap to return to the normal shape and high density, which provides a 10% of negative floatability.

CHARACTERISTICS

Material

FOIL FORCE

Polyurethane

OTHER FINS

ethanol-vinyl acetate- rubber

IN THE WATER WITH FOIL FORCE FIN

Up to now, all of the characteristics spoken about are the same in all Force Fin models, and now we are going to concentrate in the model named Foil, which we have tested. This fin has a division that runs 2/3 of the curved blade and gives them a comic look of "rabbit ears" and that is what they are called in several occasions. From the whole collection they are the most graceful and the smallest, and their creator has designed them for a mid size and thin body which generally is the female constitution, but of course they are unisex, but if they were to be used by muscular and better developed legs, the Foil Force Fin would not be up to the level of its abilities. In my case, in spite of using the smallest size, I had to get help from his ingenious system of Comfort Instep, which is an accessory of foam covered with a soft cloth that reduces the space of the pocket where you set your foot. This piece is easily inserted and removed with Velcro strips.

The sensation of kicking with Foil Fin Force is literally like "having no fins". Warning, before I went into the water I was taught the concept of conventional kicking strokes and its mistakes, substituted in this case by a very different kicking stroke. Here we do not work the axle ankle-knee, neither we do a low frequency stroke in where the range of the kick is less open. If do not do it so then you are not taking the full advantage.

What are the advantages of switching fins? The ankles and the calves are not overloaded, and upon reducing the range of the kick, the push effort is diminished and so is the physical effort. The main test dives took place in the Canary waters with its well known currents and I have to admit that even I am not well rounded in this type of diving - I am a Madrid Girl - I had not problems overcoming the effort but where I noticed it was in the air consumption which was less in comparison to similar dives.

These fins work well once thy reach sufficient inertia, so that their advantage is not noticeable within a dive of non-continuous or soft strokes, they are noticeable when you go great distances or with a sudden current against you. Just imagine the wheels of an old locomotive, to start they go slowly, but once inertia comes into play they are very fast. The same occurs with the strokes of Foil Force Fin, once inertia is sufficient, the effort and consumption ceases.

HOW TO KICK WITH FOIL FORCE FIN

We should not kick so with the Force Fin because we will not take advantage of their special traits. We will kick with our legs well stretched and with a minimum knee flexion, since the one working is the thigh.

DESIGN AND HYDRODYNAMISM

During the descending or inactive kick, Foil Force Fin succeeds in penetrating correctly flexing the double tip, which because it is curved offers less hydrodynamic resistance and because it is divided canalizes the produced current towards the back, which in turn produces an effect of reaction, propelling us forward. At the same time, the foot remains without doing a hyperextension, because the entire front tip remains separate from the blade, and only this is flexed.

During the ascending kick, the design itself of the fin allows again the resting of the axle ankle-foot and it is our thigh muscles jointly with our calves' muscles that are doing the pushing efforts instead of only our claves doing the work.

Advantages? The muscle mass of the thigh is greater than the calf so that with the same effort for the ascending kick, we have better stroke results with less energy expenditure. The base of the fin also facilitates the rupture of the superficial water tension thank to the Vortex Generator system, formed from small protuberances which produce mini-twirls which facilitates the penetration in the water. They do not create turbulences, but they break the lines of forces that make up the natural laminar flow of the liquid medium and in this manner they reduce the effort during the strokes.

While kicking in this manner, the frequent cramps caused from stroking against the current or on long journeys, will disappear. Because it is not a wide kick, we save in excessive effort against the water and we reinvest in greater quantity of strokes with less physical effort and the advantage of less air usage.

It is true that it is difficult to change habits that you were taught when you started diving, but if now you must use fins that function differently, why shouldn't you change your stroking ways? Success lies in adaptation and evolution.

APPROXIMATE PRICE 200 EUROS AVAILABLE IN YELLOW, BLACK, GREY, AND BLUE MORE INFORMATION ON: www.freeshark.es or Calling in Spain: 639.738.729

--- Nora Camara for Inmersion, April issue 2003

Reprinted with the permission of Inmersion © 2003