Venting for Drag.

[Bob Evans]

When

 

[Joneill]

The jet fin you show is a stepped/offset design with vents between the 2 surfaces to allow water to pass through on the back stroke to reduce drag/resistance. The spoiler on the aircraft wing you show is extending a surface out (at a very diffent angle than the rest of the wing) into the airflow over the wing to disrupt it and add drag to slow the plane - there is no venting, so really apples and oranges...

I'd also love to understand how you claim to have created a surface (a wing) that you move through the water without creating any drag?

 

[Bob Evans]

The jet fin you show is a stepped/offset design with vents between the 2 surfaces to allow water to pass through on the back stroke to reduce drag/resistance. The spoiler on the aircraft wing you show is extending a surface out (at a very diffent angle than the rest of the wing) into the airflow over the wing to disrupt it and add drag to slow the plane - there is no venting, so really apples and oranges...

I'd also love to understand how you claim to have created a surface (a wing) that you move through the water without creating any drag?

 

[Zef]

The wing of the aircraft is not providing a propulsive force...the speed differential of airflow above and below the wing creates lift not propulsion...the extension of the wing surface area creates high speed and resultant lower pressure of the laminar air flow above the wing which increases the amount of lift produced while the aircraft is traveling at a slower speed.

In contrast, the fins depicted are used for propulsion....they move through the water in a much different way with force vectors different than the airplane wing. As mentioned above, the openings are not meant to aid propulsion but to reduce resistance on the recovery phase of the kick, thereby reducing fatigue to the diver.

I am sure you make a great product but the science, as I understand it, does not support your claim.

-Z

 

[tbone1004]

@Bob Evans you answered your own question with regards to the bias on this board. Frog kicking is the predominant kick used by most people that contribute to this board. Wish you had something that worked for that

 

[Bob Evans]

@Bob Evans you answered your own question with regards to the bias on this board. Frog kicking is the predominant kick used by most people that contribute to this board. Wish you had something that worked for that

 

[tursiops]

The wing of the aircraft is not providing a propulsive force...the speed differential of airflow above and below the wing creates lift not propulsion...the extension of the wing surface area creates high speed and resultant lower pressure of the laminar air flow above the wing which increases the amount of lift produced while the aircraft is traveling at a slower speed.

This is a popular misconception of how an airplane flies, and it is not true.
See, for example:
How planes work | the science of flight

 

[Zef]

This is a popular misconception of how an airplane flies, and it is not true.
See, for example:
How planes work | the science of flight

Ok...it indicates there have been advancements in the scientific understanding of how an airfoil creates lift since I last studied aerodynamics....but unless I missed it, it did not implicate that these forces are propulsive in nature....one can argue that lift is a propulsive force in specific direction but that is not what is commonly meant by propulsion.

-Z

 

[Joneill]

This is a popular misconception of how an airplane flies, and it is not true.
See, for example:
How planes work | the science of flight

Here is another good source of info on the topic of how an airplane flies: +: How Planes Can Fly

Fins definitely work in a different way than airplane wings! And paddle fins s work differently than split fins as well!

 

[tursiops]

Here is another good source of info on the topic of how an airplane flies: +: How Planes Can Fly

Fins definitely work in a different way than airplane wings! And paddle fins s work differently than split fins as well!

Nice link!
And what is missing in all these discussion is the vortices created each time a fin starts and stops....the more times it starts an stops, the more vortices are created. Mostly, the vortices represent energy lost...the fluid is just spinning around. Split fins...and Force Fins...create oddball vortices because of their V-shape, or split. If any of those vortices come off the two sides of the fin and are counter rotating, they can provide some additional propulsive force. This is good. But it also means that you may need to make a lot of small fin kicks to produce a lot of helpful counter-rotating vortex pairs....so you find that split-fin divers make fast, small-amplitude kicks. I don't know what Force-Fin divers do to maximize their propulsion.