C4 FLAP VGR
FLAP, EFFICIENCY IS IN THE SHAPE
FLAP VGR blades, patented by C4, are born from the study of underwater behaviour by traditionally shaped blades, like Falcon, compared to the theoretical parabolic model of the blade under load.
Traditionally shaped blades, like Falcon, have an inherent limit to their bending that, due both to the minimum functional thickness utilizable for the material and the water quantity worked by each blade section, cannot possibly have that correct bending homogeneity, the most possibly analogous to the perfect parabolic curve C4 is since the beginning searching for its fins.
Nature evolved fish in such a way that they assume, while swimming, a bending progressively parabolic from head to tail, exactly for exploiting to the maximum degree the non-compressibility of water.
The presence, by now essential in high level fins, of lateral water channelling edges, novelty introduced first of all by C4 itself, leads to an undesired and invariably non-elastic stiffness in the terminal blade segment.
This causes a lack of bending in this section (the last 15-20 cm) that, in underwater usage, remains almost perfectly straight. As a proof, look at pictures of underwater swimming divers or, better still, one of many videoclips available. It’s easy to notice that the terminal blade section is if not minimally bended: it remains almost perfectly straight, in a very different way from fish when at their maximum bending.
The straight terminal section, due to the different inclination by this blade segment compared to the water flow, causes water vortexes on the blade, exactly in the segment that can feel more the slowing effects, because there the fluid flowing velocity is maximum.
The blade terminal section moves partially perpendicular to water flows, and it’s this that produces the negative vortexes. A diver swims like having a sucker adhering on water attached to the blade terminal segment.
It’s well known water is a non-compressible fluid and this makes more arduous to the movement all those technical situations opposing the movement itself, exactly like the vortex effects produced by a straight and not bent blade terminal section. Water channelling edges enhances this effect because they increase the quantity of water worked by the blade.
The specific patented shape C4 gave to FLAP VGR blades adds another plane to the blade itself (the FLAP) on which the water can flow and work, giving finally the parabolic bending searched by C4.
Efficiency losses due to vortexes are in this way reduced. Whats more, compared to traditional fins like Falcon, it’s increased the water flows detachment speed on the blade so to produce less turbulences on the blade terminal portion. All this creates a greater than ever swimming velocity.
On FLAP VGR blade, compared to the world wide appreciated Falcon, it has been shortened the blade lateral section, the corners, in such a way to reduce the risk touching the bottom and stucking them in it, lowering the possibility to damage the fins, in whatever material they’re built of.
Experience teaches, and logic supports, that blades are mostly broken or damaged in the maximum effort area, near the footpocket, where applied forces concentrate.
It’s very difficult that terminal FLAP, being positioned in the farthest place away from the maximum strain, can create strength problems to the blade.
The reduced area on the blade terminal segment vastly enhances fin manoeuvrability: underwater progress is in this way extremely easy and with low energy consumption.
FLAP VGR has the identical and significant angle between foot and blade, about 23°, many times tested on Falcon.
Underwater tests demonstrated that FLAP VGR gives performances constantly higher than Falcon, more or less about 15%. A diver can in this way obtain identical performances with lesser energy consumption, improving both dynamic potentials and safety in breath holding dives.
Top fiber quality : MEGAFORCE T 700
In the fins FLAP VGR the use of the new fibre MEGAFORCE T 700, HT type yarn (Hight Tensile), allows, thanks to its resistance of 40% more in comparison with the standard yarn T300 and the same elastic module (Tensile Modulus), to considerably improving the resistance to break of fins.
In order to understand which importance has, with the purpose to resist breaking, a fibre with more resistance and with the same elastic module, as MEGAFORCE T 700, it is enough to consider which are the stresses and how they are distributed. The beginning of a blade break occurs when, for too much bending, the material is stressed with a least curve ray, exceeding the resistance values.
If we suppose a blade section and the stresses on the different layers or sheets are analysed, we discover that during the bending the exterior sheet has a curve ray larger than the sheet that is on the internal side of the blade. The external sheet is so subjected to bending and traction, its opposite side to bending and compression. The sheet that will be placed in the middle of the section will be stressed only to bending.
With these stresses, the blade will start breaking when the external layer, the one more subjected to traction, stands no more applied stress. If this layer or sheet has a resistance higher of 40%, it will occur that it starts breaking for traction charges higher of 40%.
It is therefore essential that these layers or sheets (the ones external of the blade) have a strong resistance. The resistance of a sheet is improved through two parameters: the physical dimension of the blade (large and/or heavy clothes) and yarns with high resistance, as MEGAFORCE T 700.
The yarn MEGAFORCE T 700 has a percentage stretch to break of 2,1%, in comparison with 1,5% of the standard T300. This improves the flexibility and the resistance to break too; thanks to this a more accentuated fold of the fins can be reached.
It is important, both for resistance that for bending, that the yarn MEGAFORCE T 700 has got a standard elastic module as T300. A higher elastic module would make the fin very stiff. A stiff fin doesn’t bend and therefore it would not work, as it ought to do. In order to reduce the stiffness of the blade and allow its bending, thinner sheets (light cloth) and so less resistant should be used. This is the reason that makes unsuited the use of yarns HM (Hight Modulus) and light clothes for the manufacture of fins.
The carbon blades C4 are composed by more fibre layers and have a progressive lamination to get the required and needed parabolic bending curve.
Among the many possible ones, the ideal parabolic curve is the one that water density naturally imposes to fish, this is the more functional for our purpose. If we notice a swimming fish, we will remark as its head (for us the foot) is substantially firm, while the body is bending, more and more approaching to the tail, in an always more marked way.
The bending line of the fish is so parabolic, also if at a summary look it seems only the tail is bending. In the fish, as in the fin, all concerned surface is bending, less towards the head (our foot) and more in the last part of the tail (the blade end) with a bending typical of parabola (a simple parabolic function is x = y2).
If we consider a blade, as it was a shelf embedded in the foot and subjected to a uniformly distributed charge, we will remark that the section further and further from the foot bend only if the previous ones support them, that is the first ones should bend less.
A blade visibly bending next to the feet will not allow to the last stroke to work in the best way, getting so only a partial exploitation of its dimension features.
So, this kind of blades cannot work fully in a parabolic way, it is wrong to say it, but on the contrary in a quite uniform way and this is the opposite of a common believing supported by summary observations and bad information.
A blade working with a quite uniform bending surely doesn’t follow the fish swimming, to which it is certainly not taught how to bend in an efficient way the fins.
The very good sport results got by the blades C4, since 1990 until today, are the sure guarantee of the performances of our products and of the correctness of our technical choices.
VGR - Variable Geometry Rails
The water rails, invented by C4 in 1994, play the role to control, canalising it, the water on the blade. They make the swim with fins stable, the fin moves as led on two rails; the performances are enhanced by the total lack of 'derapage' effect.
In plain breath-held diving, where the performance is executed in controlled conditions, in quiet waters, in a straight path with constant charges, the performance is obtained with the matching of least energy consumption and highest speed.
The requirements for fishing are different, because an easy handling, a sudden spring and variable charges, due both to fishing needs and changing sea weather conditions, are required.
Therefore the main thing requested to fins is their adaptability to the changing work conditions to which they are subjected. As we know, the improvement of performance is always reached by adjusting in specific way the features of the tool, to the action needs.
Changing needs require modifications in the equipment. Only one thing good for all means to be satisfied with common performances and this is not our philosophy.
The water rails VGR (Variable Geometry Rails) let in a new concept in the system of control on the amount of water worked by fins. By them the canalisation of water flows is progressively modified according to the area and the fold of the blade, improving the performances.
We know that, owing to the move led by the foot on the fins, the speed of water running on the blade is increased, passing from the foot to the blade end. It is this that provokes the propulsory push of the fins. With the water rails VGR, water amounts worked are progressively modified, following the speed changes of this in the progressive sections of the blade.
A further advantage given by the water rails VGR is they take at work a special shape of the “L” sections, strongly reducing the rips between the layer of moving water on the blades, in comparison with the static one of the sea.
The water amount worked by the water rails changes according to their dimensions. Low water rails work little water, if high they work more.
With the same conditions of materials, surfaces and applied energy, more is the worked water, stronger is the push. It is for this that long blades pushes more than short ones, because they work more water.
With the same conditions, the worked water becomes the one controlled by the water rails, that are useful the largest possible, to work the maximum of water, this consistently with the elastic response of materials, hardness, geometries and dimensions of the fins. Task of the designer is to amalgamate materials, stresses and dimensions to get low consumptions of oxygen and high speeds.
Therefore the water rails VGR have the largest possible dimensions for each section of the fins, to make the maximum possible quick the worked water amounts.
What is useful, where and when it is useful, it is so that higher speeds and energy saving are obtained, as it is with the water rails VGR.
To choose hardness blade
FLAP VGR are provided in three different stiffness, 25 soft, 30 medium and 40 hard so to better adapt to several users with a variety of requirements. Blades have to be chosen the softest possible for the job they have to perform. The choice has to be made taking into account the maximum load conditions when leaving the bottom and in the swimming against current. The load situation kicking off the bottom is strictly personal, it depends by body weight, by the amount of lead we have on our belt and by the depth we are. It’s also necessary consider how psychologically we’re used to the depth we reach freediving. We counsel stiffer blades for someone in a hurry to resurface. If we manage well our breath-holding abilities and we have a great deal of tranquillity we could utilize softer fins so to save some amount of oxygen. Has also to be considered that the typical spearfisher, instead of the pure freediver, performs many dives, often with very low recover time between them. Consequently, a rather stiffer blade, even if can somewhat reduce the maximum accessible depth with maximum relaxing, will surely provide more safety.
A stiffer fin does not give more depth but surely will burn more oxygen. The velocity permitted by fins is not directly proportional to their stiffness, it depends instead by the mechanic and hydrodynamic efficiency of the man + fins system. Considering this, the blade stiffness is only one of many parameters, and not the more significant. While instead a stiffer blade has better performances and lesser oxygen utilization in our underwater movements, for example leaving the bottom, when it has to bring us from zero velocity, motionless on the bottom, to a constant ascent velocity. While resurfacing, a stiffer blade will burn up more oxygen than a softer one. This one instead will have better performances and lower oxygen consumption in the constant velocity parameters.
A traditional technopolymer fin, in its standard version, requires a muscular effort like our FLAP VGR 25, a technopolymer fin in a stiffer version requires a muscular effort harder than our FLAP VGR 40.
Every FLAP VGR blade has been permanently marked with the guarantee number on the back of the blade itself.
FLAP VGR is covered with a two years guarantee, like all other products under Italian law, following the directions of the European Community.
C4 FLAP VGR 25 soft 780 x 190 mm
C4 FLAP VGR 30 medium 780 x 190 mm
C4 FLAP VGR 40 hard 780 x 190 mm
All the C4 products are made 100% with carbon tissue MEGAFORCE T700.
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