Pervasive Fallacy about Split Fins

[Tigerman]

View attachment 38499
Preparing for a running giant stride.

No photoshop in this computer. phear my ms paint skills

Now thats badass!!
He probably WOULD do a running giant stride as well, landing on his already prepared gear tahts in the water

 

[djanni]

View attachment 38499
Preparing for a running giant stride.

Jack Bauer wears split fins... cool!

 

[ToddK]

I think there maybe room for a couple of optimum fins.

Rather than talk about energy, as was said in the original Point #2, I'd rather use Power. Power = Force * Distance / Time. Distance/Time is how quickly the fins move. A diver that has a given degree of physical fitness puts out a certain amount of Power. Some of that power might be wasted by inefficiencies in the fin design, as was noted. But going back to the equation, you can either move the fins slowly with a lot of force (Paddle fins), or quickly with little force (Split fins).

I know that the gearbox in the car analogy isn't too loved in this thread, but I think it is appropriate. Why don't cars only come with a single high gear? Because there are times that you need more force to get the car moving.

I think this is directly what is going on in diving. If you are in a swimsuit or wetsuit and single tank, you don't have a lot of drag, a lot of force isn't required- maybe the Split fin is best. (Incidently, I'd being willing to bet that this is the kind of conditions used in the tests that were quoted above). If you are diving with a lot of bulky gear (drysuit, double tanks, etc), you might need the extra force of a paddle fin.

Regards, -Todd.

 

[Temple of Doom]

I know that the gearbox in the car analogy isn't too loved in this thread, but I think it is appropriate. Why don't cars only come with a single high gear? Because there are times that you need more force to get the car moving.

I think this is directly what is going on in diving. If you are in a swimsuit or wetsuit and single tank, you don't have a lot of drag, a lot of force isn't required- maybe the Split fin is best. (Incidently, I'd being willing to bet that this is the kind of conditions used in the tests that were quoted above). If you are diving with a lot of bulky gear (drysuit, double tanks, etc), you might need the extra force of a paddle fin.

Regards, -Todd.

If you think it through, or if you care to discuss further, you'll see that gearing on a car is not applicable as an analogy. A car needs gears to provide the same thrust at differnet speeds.

Swiming with fins provides the same thrust at all swiming speeds (very, very nearly). Further, even if it were applicable, splitfins are low gear, paddle fins are high gear!

If you were able to input the same energy into two gears, you'd get the same thrust and car speed coming out. The 'high/low gear' aspects of fins doens't affect thrust at all. What affects thrust is efficency of energy required in vs energy output as thrust. If you could design split fins to be less efficient, so that they were the same efficiency as paddle fins, then they'd both move you at the same speed, they'd have the same power. Paddle fins would be like a car in high gear in that you'd kick harder, but less than these low efficiency splits, but you'd still be going the same speed.

There is no such thing as extra force of a paddle fin. It just feels harder, but you kick less, but that's unrelated to the thrust differences. The reason splits offer more power is because they more efficiently use the energy your kicking gives them, this is what's been tested over and over again for the past few years.

If you take a look at the tests they ran, you'd see that they tested split fins while the diver was tied to a stationary object, thus effectively infinite drag (diver drag has pretty much zero effect on fin thrust output). They measured the force that split-fins were outputting in this 'infinite drag' scenario, it was higher than paddle fins, just like it was in 'normal drag' scenarios.

Please let's put this one myth to rest...

Craig

 

[MauiScubaSteve]

The reason this issue will never be put to rest is because many people who actually dive in the ocean regularly, with good paddle fin skills, put splits on and do not see more thrust and/or less air used. I am one of those people. My twin jets were forgotten by some tourist diver, thank goodness I didn't pay for them. To me they feel like they are broken. I would rather use my freedive fins!

Split fins require more skill to extract their full performance, and a semi-panicked diver's natural response will cause the performance of split fins to degrade dramatically.

Charlie Allen

I don't trust dive magazine tests where advertisers most expensive equipment get's the highest ratings. Since most divers do not know how to use fins properly, a smart engineer would design for the most thrust from bad technique. I would not be supprised if a person with terrible technique went faster in splits. Why would a manufacturer put out an expensive product that requires more skill to achieve results, when the target market has no skill? Much more likely the product gives noticible results to the unskilled masses.

 

[Temple of Doom]

I don't trust dive magazine tests where advertisers most expensive equipment get's the highest ratings. Since most divers do not know how to use fins properly, a smart engineer would design for the most thrust from bad technique. I would not be supprised if a person with terrible technique went faster in splits. Why would a manufacturer put out an expensive product that requires more skill to achieve results, when the target market has no skill? Much more likely the product gives noticible results to the unskilled masses.

If you use 'bad technique' and you move through the water more efficiently, I beg you what does 'good technique' mean!

Scientific tests by universities, magazines, and independant divers have repeatedly shown that split fins are more efficient (deliver more thrust for the same effort) while swimming forward.

Is there a reason that people refuse to believe that? You can believe that and still dislike splits. Is it that people find some aspect of all these tests that is poor science (if so what is it)? Could it be that if they believe those test results then they would think splits would be better than their paddles, and they don't want that?

There's no need for people to stick their heads in the sand. It's OK to dislike splits, even if they're more efficient swimming forward (as everybody agrees, swimming forward is only one part of diving). There's plenty of other reasons why they not be the better fin for any given situation, but refusing to believe the results confirmed by test after test is curious to me.

Craig

 

[Old Diver]

Try this: get out the Gorilla tape and tape the split shut and see what happens! Point 2: the Seals are the srongest, baddest, SOB's on the planet, and they won't gripe if they wring their foot off at the ankle. My old bones like less load. 3: the ultimate paddles were tried in the 70's, made by Faralon, with the ankle brace, about 3 feet long, 4 tall reinforcing ribs, solid rubber. If you were man enough you could plane on your chest. I notice that they aren't made anymore. Blast...everyone doesen't use the same fins, let's get over it.

 

[Tigerman]

...
Point 2: the Seals are the srongest, baddest, SOB's on the planet, and they won't gripe if they wring their foot off at the ankle.
...

*COUGH!*

 

[Old Diver]

One last thought...Humans are about as hydrodynamic as a brick. A boxfish can swim away from the fittest swimmer, about like us swimming in a steamer trunk, with our knees sticking out. You gotta smile, WE: are the biggest pigmies.

 

[in_cavediver]

If you use 'bad technique' and you move through the water more efficiently, I beg you what does 'good technique' mean!

Craig,

I neither care whether split fins are more effiecient or not under all conditions or this or that. I look at the proper techniques diving. What defines proper technique is environment specific. (although I do agree with you that if a bicycle kick with splits and clean and effecient form or propulsion, its OK)

As for technique, in many cases, a true flutter kick is a bad choice due to silting. So, now we say we need multiple kick styles for different situations. Lets evaluate the fins in a true diving scenarios employing the different restrictions and required techniques and see which come out best. I will guarantee paddles win some, splits win some. What does that mean, depending on what your want/need, your fin choice will differ.

Splits aren't evil. Paddles aren't evil. They both are tools for diving and should be treated as such. Each tool has its best place. I personally have paddles and blades. I'd like to get a set of splits to dink around with in places where silting isn't an issue and see how they work. I'm just to cheap to drop the cash on them.