Split Fin Bashing?
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There is still pressure differential on one side of the fin to the other. That is lift hydraulic or not.
Eric Sedletzky
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Wow, those are wacky looking fins, would love to see the physics explanation behind them, not just the teliological. I also wish there was some easy way to try them out. I am pretty flexible about my fins. I have a pair of Scubapro Jets and a pair of Force Fins that I dive occasionally for a change of pace. My fin of choice these days is the Dive Rite XT. Before that, I was diving a pair of Aqualung Caravelles and could keep up with the best. I spend the majority of my time frog-kicking, about one cycle for every four or five of the divers I'm with.
Eric Sedletzky
Contributor
Those look like they might actually work quite well once you find the sweet spot or the perfect leg stroke to achieve the most power to movement ratio.
A tuna tail is actually one of the best designs for power and speed. The slender blades slice through the water efficiently while the length gives enough surface area for the tail muscles to push off for power and forward movement.
That one mono fin that looks like a tuna or dolphin tail is supposedly about the fastest fin out there currently.
Lift (force) - Wikipedia, the free encyclopedia
A fluid flowing past the surface of a body exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction.[1] It contrasts with the drag force, which is the component of the surface force parallel to the flow direction. If the fluid is air, the force is called an aerodynamic force. In water, it is called a hydrodynamic force.
That might help clear things up for you.
A fluid flowing past the surface of a body exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction.[1] It contrasts with the drag force, which is the component of the surface force parallel to the flow direction. If the fluid is air, the force is called an aerodynamic force. In water, it is called a hydrodynamic force.
That might help clear things up for you.
Dierscape.
I looks like you have answered your own question. If not then here goes. water temp is moot ,,,,vis is moot. that only leaves current and that is relevant cause you CAN NOT get the thrust from a set of split fins that you can get from non splits. No one says that splits do not have a place in diving. Only diving that requires significant propulsion. This topic, like you have mentioned is akin to asking why does everyone bash cars with a 50 mph governer on the throttle. Gevernered vehicles have thier place, just not on the interstate. With out thrust you can not fight a current ,,, push your self up to the surface with a wing or BCD failure when you are heavy, do efficient frog kicks, and the list goes on. I dont care for them. I used them for years till i went to cozumel and then hung them up or non splits. There is nothing,, that a non split can not do ,,that a split can do. The opposite can not be said. There are those that say they can do frog kicks with them,,, and they can. Ther are also those that can do frog kicks with out fins all together. That is not the debate. The question is ....which fin will propell you the most for that same effort applied. Non split fin will always win hands down. On behalf of the split fins I must say I have never had a leg cramp from using them. That is because there is much less resistance when using them. That resistance is thrust.
I looks like you have answered your own question. If not then here goes. water temp is moot ,,,,vis is moot. that only leaves current and that is relevant cause you CAN NOT get the thrust from a set of split fins that you can get from non splits. No one says that splits do not have a place in diving. Only diving that requires significant propulsion. This topic, like you have mentioned is akin to asking why does everyone bash cars with a 50 mph governer on the throttle. Gevernered vehicles have thier place, just not on the interstate. With out thrust you can not fight a current ,,, push your self up to the surface with a wing or BCD failure when you are heavy, do efficient frog kicks, and the list goes on. I dont care for them. I used them for years till i went to cozumel and then hung them up or non splits. There is nothing,, that a non split can not do ,,that a split can do. The opposite can not be said. There are those that say they can do frog kicks with them,,, and they can. Ther are also those that can do frog kicks with out fins all together. That is not the debate. The question is ....which fin will propell you the most for that same effort applied. Non split fin will always win hands down. On behalf of the split fins I must say I have never had a leg cramp from using them. That is because there is much less resistance when using them. That resistance is thrust.
DaleC
Contributor
Fish/mammal and aircraft design influencing fin design. It's hard to find example of splits in nature for efficient forward propulsion.
victorzamora
Contributor
dmoore/Eric.....I can certainly put that one to rest completely. You CAN produce lift in water, in the traditional aerodynamic lift sense. My specialty was fluid dynamics. That's what I do, and that's where my passion lies. I'm an Aerospace Engineer, and I did a lot of work with fluid dynamics. Fluid dynamicists use water all the time in tunnels for their experiments as the incompressible nature of water has nothing to do with aero characteristics below transonic speeds. Air, at any speed a human would encounter without serious mechanical assistance, is incompressible. The speed at which air DOES become compressible is measured in "Mach."
Dmoore19
I wouldnt take wiki's definition too seriously. First of all lift does not counter drag. Lift counters gravity. thrust counters drag. when lift adn thrust exceeds gravity adn drag the plane will fly. Next a wing and a foil like on a plane although yeilding the same result does it is opposite ways. the "lift from a wing is from the surface areas being different causing a change in densit of the air above as compared to below the wing. In reference tothe top surface teh wing is said to lift up. from the lower side of the wing the wing is said to be pushed up. This motion is caused by force created from differences in fluid(air) density.
Now from a water stadpoint you can not achieve the same effect by the same means. Ther is no change n fluid (water) density. The force is derived by the teh wing or foil physically interfacing with the water and only moves cause the wing mass is less than the water mass. Both the wing and water are non compressables and it is a attle of which one will give in first. You will not find a submarine with airplane like control surfaces. both sides are alike. the top surface is the same area as the bottom.
Next you could get a plane to fly with flat wings angled up instead of wings with upperand lower surface areas differing. It just takes a lot more speed to create the force to get the LIFT. The example of pushing your self off a wall is a very accurate discription of hydrodynamics. Which by the way if you were bigger than the wall the wall would move and not you.
.
I wouldnt take wiki's definition too seriously. First of all lift does not counter drag. Lift counters gravity. thrust counters drag. when lift adn thrust exceeds gravity adn drag the plane will fly. Next a wing and a foil like on a plane although yeilding the same result does it is opposite ways. the "lift from a wing is from the surface areas being different causing a change in densit of the air above as compared to below the wing. In reference tothe top surface teh wing is said to lift up. from the lower side of the wing the wing is said to be pushed up. This motion is caused by force created from differences in fluid(air) density.
Now from a water stadpoint you can not achieve the same effect by the same means. Ther is no change n fluid (water) density. The force is derived by the teh wing or foil physically interfacing with the water and only moves cause the wing mass is less than the water mass. Both the wing and water are non compressables and it is a attle of which one will give in first. You will not find a submarine with airplane like control surfaces. both sides are alike. the top surface is the same area as the bottom.
Next you could get a plane to fly with flat wings angled up instead of wings with upperand lower surface areas differing. It just takes a lot more speed to create the force to get the LIFT. The example of pushing your self off a wall is a very accurate discription of hydrodynamics. Which by the way if you were bigger than the wall the wall would move and not you.
.
Lift (force) - Wikipedia, the free encyclopedia
A fluid flowing past the surface of a body exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction.[1] It contrasts with the drag force, which is the component of the surface force parallel to the flow direction. If the fluid is air, the force is called an aerodynamic force. In water, it is called a hydrodynamic force.
That might help clear things up for you.
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