4 revolutions in one fin

We have recently presented the C4 Tank short fins for shallow and medium water, which had very interesting solutions. Let us now see the real revolution, the C4 S-990 fins. It is always great for us at Apneapassion when we are able to analyze and present a really innovative and extraordinary product. This is the case of the new C4 S-990 spearfishing fins, in the Firestone and Camu versions. Well done to C4 who has had the courage to study, invest, test and come up finally with an extraordinary product. We will soon publish a test in the sea of the new C4 S-990 fins. We can though anticipate here they indeed are a revolution and an amazing step forward in the fins sector. This revolution is in four key areas: fluyd dynamics, biomechanics, weight and construction.

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C4 S-990 fins

C4 S-990 fins

Fluyd dynamics in the C4 S-990

It all starts from the amazing new C4 200 footpocket, with a very compact design and the extremely special connection of the blade under the foot. On the fluyd dynamic side, this permits, just like the rear wing of a F1, to have a much cleaner flow of fluyd. So, all  along the blade the water flow has no turbulence and obtains an extremely higher efficiency. This is possible as the water flow passes between the foot pocket and the blade. So the turbolences generated by the foot-pocket and moving on the blade surface are extremely reduced. The consequence is evidently a much lower effort by the diver for the same thrust. In addition, the shortened blades under the foot result in a further reduction of the hydrodynamic resistance of the area, allowing easy rotations of the feet during kicking, with sensation of great agility.

C4 S-990 fins clean water flow

In addition to this, the extremely compact shape of the C4 200 footpocket permits a very high penetration of the water. This result comes from the reduced sections, low volume and smooth surface of the footpocket. This additionally improves efficiency and reduces the effort requested to the spearo.

C4 200 footpockets

C4 200 footpocket compact design

Biomechanics revolutionized with the C4 S-990

The position of the blade versus the footpocket

In line with the aim of reducing the effort by the spearo throught the maximum efficiency is also the position of the blade. The area where the force generated by the diver can be applied during the kick is key. The best solution to exercise the force from the foot to the blade is starting from the metatarsus. This is due to the fact that the human skeleton has in the area under the metatarsus its maximum power transmission. And this is what the geometry of the C4 200 footpocket generates with the attachment of the blade under the foot instead of on its tip. This permits to have a better balanced back and forth stride for good muscle performance. Also, the new geometry allows the diver to naturally keep a straight position, aligned with the direction of movement. This determines a much better water penetration. 

C4 S-990 revolutionize the posture of the spearo

Materials of the C4 200 footpocket

The C4 200 footpockets are manufactured with two distinct materials. A soft, thin and ultra resistant TPE (thermoplastic elastomer) is over-moulded on a rigid sole made in polypropilene. The upper material is softer (65 ShA) for sizes 36/37, 38/39 and 40/41 and slightly stiffer (74 ShA) for sizes 41/42, 42/43, 43 / 44 and 44/45. This guarantees the best comfort and performance. The C4 200 footpocket has 3° of inclination to perfectly adapt to the curvature of the foot.

C4 200 footpockets

C4 200 footpocket variable setup

C4 200 footpocket variable setup

Variable biomechanic setup of the C4 S-990

The connection footpocket to blade is obtained with two longitudinal fixing screws, which are the only link. This differs from the traditional two transversal ones together with the insertion of the blade in the foot-pocket. In addition, there is the interposition of a polyurethane “shock absorber” between the blade and footpocket. Such solution allows a quick assembly and protects the blades from abnormal stress.The additional option of the C4 S-990 is the variable setup of the biomechanic. In fact, the holes for the screw are 6 and not 2. So it is possible to move back and forth the blades along the footpocket in 3 different positions. The 6 threaded brass bushes are inserted in the sole during the moulding process. The blade tightening screws also feature an anti-unscrewing thread lock. This aspect permits to adapt the fins geometry to every single diver depending on their height, weight and kicking style. There is no absolute rule in this setup, and each spearo will have to test the fins directly to choose the right solution. This solution rapresents an aboslute world première as it is the first time that such system is thought and brought to market. 

C4 200 footpocket variable setup

Weight reduction

C4 200 the lightest footpocket on the market

Weight reduction is something on which C4 has been working since years. In time they have been followed by some other companies. The C4 300 and C4 400 footpockets have aimed to reduce, especially the first one, to the minimum their weight. And in the same way the C4 200 also have a very compact design that also determines weight reduction to only 198 g (measured by AP) in size 42-43. The C4 200 are today the lightest footpockets on the market

C4 200, 300 and 400 footpockets


Materials and lamination of the S-990 blades

In addition, the carbon fiber blades have intrinsecally an extremely reduced weight, and the ones of the C4 S-990 bring this quality to the extreme still guaranteeing amazing resistance. They are made of 100% carbon fiber layers produced with a new progressive lamination. The total layers are 11, an amazing effort, 7 for resistance and 4 for parabolic effect. The lamination combines 4 different types of Japanese carbon fiber, including an external layer of the C4 exclusive HT15.  Such fiber optimizes reactivity and resistance. This very difficult to find and work HT15 carbon fiber with big squares has a reduced number of knots compared to twill carbon fiber. Such structure generates a lower absorbtion of energy.

The carbon fiber blades of the C4 S-990 are offered in 3 different hardnesses: Soft (25), Medium (30) and Hard (40). C4 indicates though a chart on its website the suggested hardness depending on the weight and height of the spearfisherman, and the type of use. 

The guarantee of extreme resistance to heavy load and fatigue of the blades fo the C4 S-990 has been verified by testing them with a special machine. This has been specifically designed by the C4 technicians to produce repeated kicking cycles with 3 times the strength of a normal diver. 1.6 million cycles have been applied to the C4 S-990 fins to deliberate the quality and resistance. In addition, over 18 months of testing have been brought forward by an international team of C4 divers. These are: Giacomo Cubeddu, Andrea Calvino, Andrea Fazzolari, Luc Pillon, Giannis Pitias, Marco Rodo, Mariano Satta, Stelios Velikis, John Lopez, Gian Franco Loi, Stefano Oggioni, Ahmed Ben Salah, Fabien Renau, Marco Bardi and Eric Demontis.

Force transmission and ergonomic insoles

The C4 200 footpocket is designed to adhere to the entire foot. The idea is to transmit the force not in a single area, like many footpockets do reinforcing the are of the instep, but through the entire surface. To additionally improve this solution, together with an amazing comfort, C4 has designed ergonomic insoles. These are specifically made with materials adapt to the sea. Thanks to the asymmetrical shape the comfort increases, the planar shape of the shoes under the foot arch is greatly improved. All this thanks to the elimination of the void and thus increasing the control of kicking and optimising the propulsive force. The empy areas between the foot and the footpocket are filled and even the water sacks are so eliminated. Cold water flow is si minimized, thus keeping warmer the foot in Winter and reducing the risk of cramps.

C4 insoles for fins footpockets

Water rails with O.P.S. technology

O.P.S. technology innovation

3D shaped water rails are applied on the blades by the over-moulding technique. This has been developed by C4 specifically for the blades of the 200 series. Such process avoids any separation that can occur on glued water rails. Also, the O.P.S. (Over-moulding Protection System) of the water rails protects the blade from impact and damage.

Material of the water rails

The plastic polymer used to manufacture the water rails maintains elasticity four times more over time. The first portion of the water rail close to the foot protects the blade without overloading and limiting its elasticity. Progressively, the height of the water rails increases becoming an effective guide for the fluid threads, thus preventing load drops and skidding. The additional anti-skidding effect is obtained by the dovetail tip of the blades. 

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C4 S-990 data chart

O.P.S. Technology on C4 S-990 fins

Special water rails with variable height and O.P.S. technology

C4 S-990 fins with dovetail tips