Fins are very important in diving, but also a seemingly simple but very technical equipment. Let me talk about fins in detail.
The origin of fins
Fins are the product of bionics. What is bionics? For example, dragonflies - helicopters, tortoise shells - thin shell buildings, Fireflies - artificial cold light, fins of fish - oars, etc. the flippers are studied according to duck fins, goose fins and tail fins of ducks But the "Shanzhai" is not as good as the original one. The best flippers are not the things of the human body. Only by mastering the use skills of flippers can we really realize the use of fins.
Frog kick -- the basic kick method of traditional fins
People who often go abroad to dive will notice that when the foreign diving guides and coaches use the fin flippers, their kicking method is different from that in our country. Their movements are relaxed, beautiful and slow, but they are still far ahead. This is frog kicking.
Frog kick is not like a frog kick water, but according to the angle of about 40 ° to the left and right sides of the fins to separate and then clip, then the situation is completely different with the next swing. First of all, the fins move along the narrowest edge on the left and right sides, so as to avoid the wave making resistance and eddy current resistance caused by the wide front moving against the water. In addition, according to a certain angle, the actual opening and closing of the water clamp is to take the whole fin surface as the power surface, so that the flow direction generated during the clamping is backward, and its reaction force is just the forward thrust.
Frog kick effectively eliminates the resistance surface and increases the power surface. How can such a kick not be easy and efficient It is for this reason that jetfin fins are favored by professional divers and have been used up to now. In fact, these professional divers are all proud of their beautiful frog kick. It's also a wonderful enjoyment to enjoy their relaxed and beautiful travel in the water.
Although the method of frog kick can solve the problem of resistance and power under water, and it is very effective, there are still unsatisfactory places. The problem lies in the water surface. After the water surface, it is quite difficult for the diver to kick back to the side of the ship or the shore, because the frog kick effect is not good at this time, and the up and down kick will encounter huge wave making resistance and eddy current resistance.
So let's talk about a new type of fin at the beginning of this century, the bifurcated fin
The bifurcated flipper was invented by American Robert B. Evans. The most obvious feature of the bifurcated flipper is a slit along the middle line of the fin. This seam completely changes the resistance and dynamic composition of fins when they kick up and down. First of all, when fins kick up and down, they will no longer face the water with a wide front because of this gap, so they effectively reduce the wave making resistance and eddy current resistance. In addition, the middle joint extends the edge line, increases the edge effect area, and almost turns the whole flipper surface into a dynamic surface.
What the bifurcated fins can't do is to back off, but the back off maneuver has little significance in leisure diving and can be ignored.
Both frog kick and bifurcated fins are designed to reduce resistance and increase thrust. Frog kick is to solve this problem from the kick method, and bifurcated flipper is to solve this problem from the hardware design, which has the same magic.
The price of bifurcated fins is much higher than that of chip fins. In recent years, under the stimulation of bifurcated fins, companies have been increasing their R & D efforts and launching many innovative new fins.
People who are used to frog kicking and those who need to walk in narrow space are better to use the new fins represented by Seawing nova.
People who can't frog kick (new cadets) or are used to kicking their fins up and down (common in recreational diving) are better off with bifurcated fins.
Classification (length)
There are long fins and short fins. The length of the short fins is 3-5cm, and the area is not more than 32 × 16cm. The width of the long fins is 1-1.5 times that of the feet, and the fins are not longer than the length of the feet.
Generally speaking, long fins are recommended for diving.
