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Posted by Dave on October 17, 2005 at 20:40:15:

In Reply to: I think he never swam through kelp with these! posted by Chris on October 17, 2005 at 18:21:51:

I hope the guy makes some money, he certainly has invested a lot of time and $.......BUT.......allow me to take exception to some of the statements made.

I notice the use of the term "vortices propulsion". This seems to be bad grammar for starters. Either hydrodynamic or aerodynamic vortices are both the more compressed side of a wing swirling from the higher compression side to the lower compression side. Both cause more drag and reduce effiiciency. That is why modern racing sailplanes and the latest efficiency designed jets and planes like the Lancair's use vertical flow fences at the tips to reduce the induced drag associated with tip vortices. More of the compressed upper layers stay there to create lift.

As to the claim that the "vortices trail" causes a reduction in drag, this is nonsense. In aerodynamics, tripping the boundary layer can cause a reduction in drag depending on the design parameters, but that is over the wing, not aft of it. The analogy is golf balls have dimples to create a dirty boundary layer of air to slip through which is easier for that shape to accomplish compared to smooth laminar flow.

But any boundary layer tripping done by a dolphin tail that is traveling forwards does not leave a tripped turbulent boundary layer that can be of any use unless the dolphin is swimming backwards.

The human body with all the dive gear we plaster all over ourselves underwater is as inefficient hydrodynamically as can be. All the various fin gimmicks that have come out over the years, between jet fins, split fins, etc is all marketing hype. One of the most hydrodynamically efficient large animals in the ocean are tuna-maybe they would notice a difference if they had different ins on them as they are so hydrodynamically clean, but not divers. Do you think you would notice a a 2% increase in speed if you are swimming 1.5mph?

This is all marketing hype....first they tellus that thin ties are in, then thick ties, then thin ties, then thick....narrow lapels, wide lapels, narrow ones, high ones......all designed to keep you buying products over and over.

I would guess that the shin based wedge will allow easier movement through a leg kick cycle, and that these fins may be easier on the foot tendons....but as to "vortices propulsion", sorry that just does scientifically past muster.

I put this right along that $90 ear dryer "designed by an M.D."




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