Help me understand the effects of current on fins

[Teamcasa]

First- speed test of fins have conclusively shown that monofins, freediving fins, and a few Force Fins are all faster than the fastest splits.

I'm still waiting for facts to back this statement up.

 

[meesier42]

From the World Records of Finswimming.
50meters
Monofins- 15.20
Stereo (Bi-fins)- 19.48
from that- its fairly easy to see that monofins are faster than any stereo fins.

but... alas these are only the mono's and bi's (long blades)
so I guess I have to post my information after-all, same setup at the finswimming (granted these times were back when I was 21 y/o, in college and in fantastic shape), all were done with dolphin kicks.

SpecialFins mono (fiberglass version)- 18.3
Force Fin Extra Force Tan Delta- 22.6
Cressi Gara HF2000*- 24.5
Mares Quattros- 25.2
Apollo Bio- 26.2

* I was unable to perform a good dolphin kick in these and had to use a flutter which is slower for all other fins.

doing flutter kicks
Force Fin Extra Force Tan Delta-24.6
Mares Quattros- 28.4
Apollo Bio- 27.8

of course, the Cressi Gara's are no where near the best long blades out there. And granted my info is a long way from "proof" of anything

 

[Bob Evans]

The Extra Force is the fin John Chatterton started his diving adventures in. A variable thrust fin and now in a cool youtube video.YouTube - Pool Bach Iknow my Mono fin will rock out with a faster number, back at the Fin Ranch the Hockey fin you asked me to make is going into production tomorrow. A real kicker, like a Donkey kick.

 

[Nemrod]

Current has no effect on a fins performance, the fin does not know there is current but the panicky out of shape diver who starts flailing away when he sees he is not making any ground, there lies the difference.

N

 

[Puffer Fish]

If you used a normal flutter kick with splits, it would make you really slow...which is seems to have done.

Scuba mag has videos of how they did their speed testing...you can see the differences in how they got those very fast times with them.

But they are doing their tests with scuba gear on, where one has to trade some the the raw speed for force.

Long fins, either mono or Bi, has long been acknowledged as being faster (just to total body length (standing wave issues).

Remember, you were also testing you particular finning method....

From the World Records of Finswimming.
50meters
Monofins- 15.20
Stereo (Bi-fins)- 19.48
from that- its fairly easy to see that monofins are faster than any stereo fins.

but... alas these are only the mono's and bi's (long blades)
so I guess I have to post my information after-all, same setup at the finswimming (granted these times were back when I was 21 y/o, in college and in fantastic shape), all were done with dolphin kicks.

SpecialFins mono (fiberglass version)- 18.3
Force Fin Extra Force Tan Delta- 22.6
Cressi Gara HF2000*- 24.5
Mares Quattros- 25.2
Apollo Bio- 26.2

* I was unable to perform a good dolphin kick in these and had to use a flutter which is slower for all other fins.

doing flutter kicks
Force Fin Extra Force Tan Delta-24.6
Mares Quattros- 28.4
Apollo Bio- 27.8

of course, the Cressi Gara's are no where near the best long blades out there. And granted my info is a long way from "proof" of anything

 

[danvolker]

From the World Records of Finswimming.
50meters
Monofins- 15.20
Stereo (Bi-fins)- 19.48
from that- its fairly easy to see that monofins are faster than any stereo fins.

but... alas these are only the mono's and bi's (long blades)
so I guess I have to post my information after-all, same setup at the finswimming (granted these times were back when I was 21 y/o, in college and in fantastic shape), all were done with dolphin kicks.

SpecialFins mono (fiberglass version)- 18.3
Force Fin Extra Force Tan Delta- 22.6
Cressi Gara HF2000*- 24.5
Mares Quattros- 25.2
Apollo Bio- 26.2

* I was unable to perform a good dolphin kick in these and had to use a flutter which is slower for all other fins.

doing flutter kicks
Force Fin Extra Force Tan Delta-24.6
Mares Quattros- 28.4
Apollo Bio- 27.8

of course, the Cressi Gara's are no where near the best long blades out there. And granted my info is a long way from "proof" of anything

VEry intersting Meesier, thanks for this.
I will add that in my own scuba diving with my C4 freediving fins, I use dolphin kick a good percentage of the time when I am moving from one reef to the next--when I want to cover distance easily. With the C4's, dolphin kick seems even more natural than flutter, but of course, it will work with any kick. I have also tried many other brands of freediving fins, and found many severely lacking--the cressi Gara 2000 's you mentioned are a good example of a freediving fin that does not perform well--which is wierd, because Cressi does know how to make a good fin---On a past Italy trip, I bought some cressi fins much longer, and much better than the gara 2000 or 3000's, but I had never seen this Cressi model in America. I have never used a good mares freedive blade, and "some" of the Omer fins are stiff without good return of power, making them undesirable as well. The specialfins.com fins seem the best for most divers, and of course, you will NEVER see them discussed in Rodales

Regards,
Dan V

 

[Susanne]

Dan, The subject of Split fin's reminds me how the whole rip off put my wife Susanne in Cottage Hospital, Santa Barbara. She was more important to me than being tied up with the land sharks. She is the one who can tell the whole story. Maybe, I can ask her again to set the records straight, it's truly a Amazing story.

I'm not sure why Dan Volker and you brought me into this thread, other than to say that Pufferfish's assessment is way over-simplified. The "V" shape of the Original Force Fin design is a split, balanced with blade surface area for load bearing leverage, and the Original patents filed in the mid-1980's are for a fin that snaps water behind and through that split. A lengthening of the split is disclosed in patents issued to Bob Evans in the mid-'80s and early 1990's. An Italian Patent with a different split blade configuration, much closer to the duo paddle blades most frequently seen marketed by many companies as split fins today, and there are more versions disclosed in patents before that. There is no reason to believe that the patent office does a better job than the SEC.

But, the "rip off" issue and whose patent is better than the other, and the issue of enforceability of them all, and whether or not I got sick because of this or that or other things, is a red herring.

The point of the thread is how one moves through currents, of which, Bob, you are much better equipped to answer than I.......

For scientific answers, I suggest approaching a step outside the diving industry and do a google search for "science magazine how fish move". There is a treasure trove of scientific analysis about how water interacts with a body moving through turbulent, or against water.... A few observations from these readings and my own experience shows a few things:

Highest speed is not the issue. Most of us who dive of are at least enough physical prowess to sprint a short distance. Whether or not one makes it back to the boat, or can relax and enjoy a dive in currents depends upon how long they can sustain that speed.

Nemrod and Dan are right about one thing, those who remain relaxed moving through water are the best equipped for moving through it. Those who can sustain their kick in a streamlined profile are better equipped than those whose fins and kick require that they bend their leg back, or swing their kick wide when water is moving against them.

Dan's favorite, free diving fins' length act as a safety that keeps them in a narrow profile, and as he accurately describes, their trailing edge action moves the water behind.

Whether a fin is stiff or flexible means more to the diver than the water. There is a certain optimal efficiency point under load or drag, where having a stiffer blade to leverage against is going to move one better than having a more flexible. Likewise, under lesser load or drag, a more flexible fin will require less energy to move. That is unique to the diver, his profile, endurance and strength. Its the movement of the fin that moves the water, and the better one can move their fin, the better they will move in the water.

My favorite, an original Force Fin, well, that and a flexible pair of ruby red Tan Delta's. Force Fins are designed to work optimally with a streamlined flutter kick, but with a kick back. You need only to work the blade in the forward kicking motion, where you have the most strength. At the end of your kick, the Force Fin blade snaps, rebounds, throws water behind, through the split "V" at its trailing edge, and that snap, resets and recovers your leg for the next power - downstroke. Each kick is a power and recovery. A fin that is flat, whether split or paddle, and requires that your work as hard on the upstroke and the down stroke is going to fatigue you faster than one that allows you to rest within in each kick. That's basic exercise physiology.

The Force Fin foot pocket forces one to power the blade from your strongest kicking muscles in the upper thigh, and limits the stress on the smaller muscles utilized when you kick with fins with blades that extend from the end of your foot.

IMHO, that is why a Force Fin belies its size and moves one well in a current.

I have to get going and get ready to jump in the pool now. Masters swim practice begins in about 1/2 hour, and I've yet to get my things together for work.

I'll leave it to others to address the remaining issue. That is the relationship between the integrity of blade surface area leveraged against when pushing oneself through water under load or drag. I think that is probably where Dan Volker is sensing the fall off of effectiveness when he sees some divers in some split fins having problems in currents that he thinks are related to the fin and not the divers.

 

[ps1mhd]

Dave has it right.



The kick required is so different from standard fins, that most people don't know how to do it.

There has been a huge amount of testing regarding this, but there are a lot of people that still try to use them as if they were jets, because that is what they believe fins are supposed to be.

One of the more interesting speed records for fin testing is that a pair of split fins has the fastest speed doing the frog kick (also every other type of kick, but that should be expected)... even after seeing a video of it, I cannot do that kick, but clearly at least one person could..

Do you or anyone else have a link to the video?

Mike

 

[Nemrod]

Correlations between fish and scuba divers are essentially useless. They swim at entirely different speeds and Reynolds numbers, their (fish) entire body provides propulsion, they have a slime coating, their design is optimized by millions of years of competitive evolution not marketing quackery. N

 

[ickis]

i usually go freediving with either monos or nothing (i know, call me primitive but its fun) but i do occasionally rent fins and am planning on buying the FF excellerators when i get enough money (and also the OPS- whenever they will be released ).
one thing i learned from this is that facing a current is mostly dependant on the divers attitude and strength- a strong willed and strong bodied diver can go through currents with ease wearing even the simplest splits or paddles or sometimes nothing at all.
i guess its quite clear that the dolphin kick is the fastest underwater movement there is (and also the funnest).
oh and another funny fact, source sandals make pretty decent makeshift fins if you adjust them correctly (i tried when i was without fins on a boat and we went freediving)