Fins - C4
The C4 Carbon Blades
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| The aim is to use carbon fibres for diving, obtaining significant improvements in the equipment’s performance.
The sea is a hostile environment for man, so equipment is fundamental in order to operate. Movement is the first thing to be achieved in order to enable any form of operation. The flippers are the equipment which transforms our energy into movement. You may often hear about more powerful flippers, which is far from the truth. Flippers transmit energy, and since they cannot produce it, they have the same effect as a boat with a propeller rather than a motor: in this case our legs are our motor.
| There are two design philosophies regarding diving flippers: one tends to create a spoon effect, while the other creates flexible inclined planes that move by gliding through the water. Flippers with the spoon effect are inspired by fish fins. Unfortunately fish fins are connected to bands of muscles, and the form they take during movement is due to the fact that they are alive. As opposed to the scuba diver’s flippers, they also act as the motor and transmission, which is totally impossible for the scuba diver. To give these flippers their characteristic spoon deformation, some of the scuba diver’s energy has to be used in order to deform the flipper. The greater the deformation, the more energy is used, reducing energy needed for moving the scuba diver ahead. The flipper adjusted to the spoon shape uses a lot of water only when deformed to its maximum, which is obtained for a short time by flipping movement, creating an erratic, throbbing push. As we have learnt from physics, the greatest consumption of energy occurs during accelerations, a throbbing push that makes us accelerate at each leg movement. These flippers are very easy to use, as the throbbing movement required is similar to the natural walking movement, providing high performance even for those who aren’t trained in swimming with flippers.
The carbon fibres are low stretch materials, but to create a spoon effect, the materials used have to be stretchable. Only a fool thinks that a composite flipper can be deformed along two lines forming a spoon, since however many “waves” the surface of the blades can have, the laws of physics provide no alternatives.
The construction philosophy of the C4 flippers has always aimed at obtaining the highest performances, so our flippers work like flexible inclined planes with very high spring back (extremely small hysteresis loops). They glide through the water, covering a sine curve that produces a practically constant push, thanks to the different angles of the leg muscles during the flipping movement along with appropriate training. A constant push requires less accelerations, which means a lower consumption of energy necessary for moving ahead in the water. The bend of our blades is deliberately gradual, and the laws of motion in a fluid follow exponential rather than linear progressions (constant curving). As an example, just look at a fish from above: while swimming the curving is progressive, with the head almost immobile and gradually more curved towards the tip of the tail.
On the sides of the C4 flippers, there are vertical edges in rubber that serve to protect the carbon blade from any abrasions. By moving in the water, the flippers create swirls and vortexes of water along its sides, actually losing 50% of the energy that we use for moving with flippers. It is very easy to test this out: just apply coloured cotton threads each 4/5 cm long on the blades with adhesive tape, in a checkerboard arrangement. Moving with flippers, we can see which direction the water takes. If the flippers are without high lateral edges, for the FALCON C4 they are 24 mm high, the threads will be positioned at 45°, showing that half of our hard-earned energy is lost.
There are two materials making up the carbon flipper blades: resins and fibres. There are various types of usable thermosetting resins, that is epoxy and polyester resins. Epoxy resins have the best mechanical characteristics, and coupled with carbon fibre they make the best construction material known to man. Used in the aerospace industry and racing cars etc., they obviously cost accordingly. The polyester resins have low mechanical and heat resistance, and are used in the nautical sector and general industry (containers, pipes, etc.), where low weights and high resistances are not fundamental. The average cost is less than a third compared to the epoxy resins. C4 uses only the best epoxy resins for its products, as the use of economical materials lead to low results in terms of performance. For the fibres, C4 uses carbon fibres and R glass fibres, highly resistant materials that actually realize blades with low energy consumption (small hysteresis loops). There are other fibres that can be coupled with thermosetting resins, such as the aramid fibres (Kevlar made by Du Pont) and polyester yarn based fibres (Diolene, Diolen, etc.) These have an opposite elastic behaviour compared to carbon fibre and absorb energy during deformation without returning it (large hysteresis loop). The aramid fibres are used successfully as anti-projectile coverings because they absorb energy, as opposed to what is needed in the flippers. The only use for polyester based fibres (Diolene) is that they are easily coloured in black and look like carbon, whilst costing 5 times less. They are only compatible with polyester resins, and can create objects with a carbon “look” at a low cost. However, the mechanical performances for each unit of weight are distinctly lower. There are different types of glass fibres, but the R type used by C4 is the best available. It is highly resistant, costs accordingly and is compatible with epoxy resins. The S glass, normally used in the nautical sector, has lower costs and performances, and is compatible with polyester resins. Using the best materials is the basis for creating an excellent flipper. Following the success of the C4 flippers, there are now various composite flipper proposals on the market. Some of these use economical resins and fibres, retailed at similar costs to ours. The best athletes in the world continue to use our flippers without being sponsored, which proves that C4 does not even have to demonstrate the efficiency of its flippers.
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