Wahoo 09 : the plastic for C4
The blades C4 Wahoo 09
The plastic blades C4 Wahoo 09 are designed to get the wished and required parabolic flexion curve.
Among the many possible parabolic curves, the ideal 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 sections 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 foot will not allow the last stroke working 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 belief supported by summary observations and bad information.
The blades C4 Wahoo 09 stretch until the foot heel, allowing so the most energy transmission.
In C4 Wahoo 09 the flap shape of the blade end (patent C4) allows better parabolic bending curves, less energy absorptions and a more efficacious water flows detachment from the blade (for more information see the page fins C4 FLAP).
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.
Wahoo 09 – Water 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.
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 push 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 largest amount 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.
The water rails, with large section, of the fins Wahoo 09, have a parabolic profile, to better fit to the most different use conditions.
Energy transmission: foot – blade position
Which is the best position for the foot related to the blade, and vice versa?
To answer this question it is necessary to carefully notice the strain application and how the move is executed, both for the foot and the blade.
In the fins, the shoe defines the reciprocal position of foot and blade, the elements it connects.
Some technical features affecting the reciprocal positions of foot and blade are unavoidable, others can be modified.
It is easy to remark how for man it’s natural to lean against the lower part of metatarsus for applying an effort, like for example on bike pedals, climbing a staircase steps or running. That point of the foot is where it’s possible to naturally apply the maximum strength and maximum shift, that is to exert the maximum work with legs (work = force x shifting).
A fin blade is mechanically classifiable as a shelf submitted to a load homogenously distributed. So it is possible to identify, depending on bending, a centre of gravity point of the load applied and its distance from the shelf joint position, in our case where the blade bends, exiting from the shoe.
The fulcrum effect to which the load produced by the blade move is applied can be computed as the distance between the projections, on the theoretical advancement axis in a submerged diver, or longitudinal axis, of the metatarsal points and the gravity point of the load applied to the blade. This effect is directly proportional to the resistance a diver should overcome to move the blade. The lesser is this distance, the lesser the effort.
In C4 Wahoo 09, with the foot advanced on the blade of 7 cm (in comparison with standard shoes) the reduction of the fulcrum effect is more than 20%, with following advantages in reduction of required energy.
Hydrodynamics: blade position and angle
The least hydrodynamic resistance is obtained when a diver, in vertical position, head up, with completely extended fins, observed from a lateral point of view, has along only one axis all articulation theoretical rotation centres: hip, knee, ankle, metatarsus and fin blades.
This is possible only if the fin blade is placed as in C4 Wahoo 09, just under foot metatarsus, with the fitted wide angle, over 23° in C4 Wahoo 09.
Vice versa, shoes and/or blades with narrower angles, force fins away from the body axis. The diver will be compelled to arch his/her back when swimming (necessarily a symmetrical swift) for moving on a straight line.
Arching the back increases the diver’s frontal section and reduces hydrodynamics. Both arching the back and resistance increase provoke energy removal, harmful to breath-held diving duration and to safety.
When the angle between blades’ axis and diver’s axis is too wide it is possible to have damages to articulations of knees and ankles. With C4 Wahoo 09 this doesn’t happen, ergonomics is at the maximum level.
The shoes C4 Wahoo 09 are produced taking into account hydrodynamics requirements, both because they have got widely rayed shapes and a close outline of the shoe, and for the lack of side stiffeners. The lack of side stiffeners distinctly reduced the front section of the shoe, so reducing their consistent hydrodynamic resistances.
Right and left anatomic shoe
How well a fin fits is an essential feature for the effectiveness of it. The shoe is the primary component in the cinematic chain of energy transmission from foot to blade: better the connection; more energy will be transferred to the motion.
A free diving fin has an optimal performance if the shoe has good ergonomics, perfectly fitting to the foot. For this we realised anatomic right and left shoes, with a customised adjustment of the shoe lacing.
A single shoe, somewhat constricting the foot or letting it free to partially move inside it, has been so far the usual conditions every diver had to deal with, choosing between how much pain to endure or how much energy inevitably to disperse.
C4 Wahoo 09 simply eliminate these problems at their source: they significantly improve how well they fit, giving more comfort and effectiveness to athletic motion.
C4 have been shaped from the best running shoes, revised to fit free diving diver’s requirements, to guarantee excellent ergonomics.
Optimal anatomy of shoes C4 Wahoo 09 allowed the use of a strong polymer, so guaranteeing an excellent energy transmission without reducing comfort.
The shoe is planned with different thickness, obtaining varied resilience in the several parts and optimising energy transmission.
The choice to manufacture shoes without traditional side stiffeners moved the fin centre of gravity toward the foot, making them significantly lighter when swimming.
Energy absorption due to side stiffeners in traditional fins was measured in tests developed in the Engineering Department of Padua University, and it resulted to be of 55% in the hysteresis loop. In C4 Wahoo 09 this energy amount is not absorbed by the shoe with full profit for performances.
It’s evident to all the bigger comfort due to the anatomic right and left shoe in an easy comparison with the traditional standard fin with the same foot pocket for both feet.
hoe lacing adjustment
The possibility to have a millimetric and customised adjustment of the shoe, through the fitted elastic strings C4 Wahoo 09 are equipped with allows the best adaptability of shoe to foot.
It’s a system very similar to the one we’re used to with land shoes: right and left shoes, with laces to tie them up.
For the foot, underwater or on land, comfort and energy transmission are the very same thing. Having the possibility to “custom” adjust the attachment pressure is the maximum a free diver could ask his/her fins!
The lace operates on five points and the adjustment is to be made only once, on land. When decided the attachment pressure and tied up the lace with a knot (see assembly instruction) the diver can forget about it and use C4 Wahoo 09 exactly like all other fins, wearing them and taking them off like he/she’s used to.
Thanks to the possibility to loosen and tighten at will the shoes it will be possible, changing only the laces, to use thicker or thinner socks, adapting C4 Wahoo 09 to season temperature needs.
The adjustment system by elastic lace was selected after having tested countless solutions, such as zips, buckles, numerous kinds of fastenings and Velcro. No one of those, for a lot of reasons, offered better results than elastic lace.
It’s a practical, simple solution, easy to cope with even if there are problems in a far away island; it’s enough a piece of rope. It’s not metal and it will not rust, it’s not a device and it’ll not get stuck, it has not springs, it’ll not open by accident, it doesn’t carve the shoe polymer, it’s very light, it spreads out the pressure onto five points, allows an elastic distribution of pressure, it’s truly reliable, it’s an extremely “marine” solution and it’s really cheap, a good thing above all this.
If the lace breaks up when diving the breaking point will be forcedly in a stretch of it. The friction the remaining portion of it still exerts on other insertion points will prevent the sudden unfastening of the attachment: diver can so follow swimming with most safety.
The fins C4 Wahoo 09 are available in five sizes: 39/40 - 41/42 - 43/44 - 45/46 - 47/48
The fins C4 Wahoo 09 are assembled by fastening screws to guarantee an easy interchangeability.
The fins C4 Wahoo 09 are available in two stiffness ranges: soft (amber) medium (black)
The plastic blades C4 Wahoo 09 have the dimensions of 800 x 190 mm.
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