Pervasive Fallacy about Split Fins

[Diver Dennis]

You should try a pair. Then you'll know what all the hype is about.

Don, I think I'll do that. We have a MEGA Dive-O-Rama coming up here in 2 weeks at Puerto Galera and I'm going to rent a pair. I take pictures and dive pretty slow. I also frog kick almost all the time to keep the sand where it should be, on the bottom, so it will be interesting to see how they work for my style of diving.

 

[BuoyantC]

A couple observations I've made:

#1 As I've posted before, everyone's physiology is different and a reason someone loves every type of fin out there. It works for them.

#2 Splits work for me in current, finning backwards, frog kick etc. It took a while to get used to them, but definitely easier on the knee.

#3 Splits do create long vortexes and horizontal positioning is important in avoiding silting. You should see the overweighted Asian tourist divers here!

#4 I hate hearing the "mantra" recited about Jetfins being the only fin as much as I hate hearing that bp/wings are the only suitable bcd system.....even if I use them myself!

Dennis

 

[MauiScubaSteve]

If you can go faster/pull harder with splits by using the same energy as you do with paddles, then you're going to use less energy to go the same speed.

This isn't a matter of opinion, it's fact.

Does any test say by using the same energy? How many callories were burned, how much air was consumed, what time of day was each fin tested, how many beers did the testers have each night before testing, did they have sex on the day of the game?

In the test videos, they are not simulating recreational diving, they are simulating 007 movie stunts. At 80mph, a 'Vette in 4th gear will probably use less energy than a Bug in 5th, but which will be more efficient around town?

Do you really think all those variables really matter as to whether one fin is more efficient than another?

All these variables make it highly unlikely we will ever have anything other than anecdotal evidence, just like with Nitrox. The fact is it's really hard to come up with facts that mean anything in diving!

 

[Temple of Doom]

All these variables make it highly unlikely we will ever have anything other than anecdotal evidence, just like with Nitrox.

That's where the scientific method comes in. If you design a test that removes all the variables except the fins, you'll have an experiment which tells you with good confidence, the difference between the fins.

Does any test say by using the same energy? How many callories were burned, how much air was consumed, what time of day was each fin tested, how many beers did the testers have each night before testing, did they have sex on the day of the game?

It sure sounds like you haven't read any descriptions of the tests you're casting doubts upon. Why not Take a look at the ScubaLab test that have been posted several times in this thread:
http://www.scubadiving.com/fins

From that page the 2005 test data: http://www.scubadiving.com/upload/images/pdf/200510_scubalab.pdf
(Look at the right side of the second page for details of how the tests were conducted.)

Please highlight where the test data is invalid for those tests.

A note about energy: Different fins aren't going to change the energy output of your body. You're going to put out the same energy whether you're wearing splits or paddles. It's the efficiency of the fins turning your body's energy into thrust that translates into faster or slower fins. If the same diver under the same conditions can swim 65 feet faster in splits than paddles, it's because the splits are more efficient at translating that divers energy into thrust.

 

[in_cavediver]

That's where the scientific method comes in. If you design a test that removes all the variables except the fins, you'll have an experiment which tells you with good confidence, the difference between the fins.

Please highlight where the test data is invalid for those tests.

Craig,

I will happily say flutter kicks, splits better than paddles. That though does NOT say splits better than paddles overall. Only in this one case.

If you want objective tests and true facts to support the supposition splits are more efficient than paddles, lets do the same tests but with a frog kick. Then with the modified frog, modified flutter and dolphin kicks and see where we are at. You might be very suprised to see splits do not excel in kicks other than the flutter and that data from those tests might very well say splits have much *lower* thrust than paddles.

 

[HenrikBP]

Just a data point and personal experience with Atomic Splits;

While they did frog kicks and heli turns just fine for me, they didn't feel great doing short stroke flutter kicks while going slow. I blame my lacking technique for not being able to do back kicks

They were fine for straight swimming at a decent clip, but felt like they weren't "loading up" when I was just taking it easy. My thinking is that since the blades of these fins are quite stiff they need a more powerful kick to flex and work efficiently.

So as with many other things it's probably not fair to lump all fins of a particular kind into one pile

Henrik

 

[radinator]

Do you really think all those variables really matter as to whether one fin is more efficient than another?

No, they don't. However, they certainly matter when determining which is more efficient than the other. If you don't see that you don't understand the basic principles of scientific research.

 

[sandmanz32]

i think this whole thread can be summed up by saying: try them, if you like them fine, if not thats fine to. dive what you like to use and what makes you comfortable in the water. personally, i dive paddles.....but im open to trying splits......im just not about to spend the $$$$$ on them first.....but if someone wants to loan me a pair! lol

 

[Temple of Doom]

Craig,

I will happily say flutter kicks, splits better than paddles. That though does NOT say splits better than paddles overall. Only in this one case.

If you want objective tests and true facts to support the supposition splits are more efficient than paddles, lets do the same tests but with a frog kick. Then with the modified frog, modified flutter and dolphin kicks and see where we are at. You might be very suprised to see splits do not excel in kicks other than the flutter and that data from those tests might very well say splits have much *lower* thrust than paddles.

You're preaching to the choir, here's some of the stuff you missed coming to the party late.

HOWEVER, That isn't to say that paddles will always silt more! I have no idea of the efficiency of frog kicks vs flutter kicks at slower speeds, I haven't seen any data. It could be very likely that frog kicks using paddles are more efficient than the flutter kicks of splits at low speed. Naturally frog kicks can't propel you as fast as flutter kicks, but they may be more efficient at slow speeds. If the frog kick were more efficient at caving speeds, then they would allow for the lower amount of silting at that speed. This isn't disputible either.
(There, now that the cavers have untied their long hose nooses, I can continue. )

There's multiple factors for determining which fin is 'better'. I don't think you could ever say that one fin is 'better' for all people or situations. What you can do is understand the objective qualities of both fins. In the case of splits, it's been demonstrated consistently and objectively that they are more efficient at forward swimming (and that of course holds true in any drag/current situation).

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.

Of course it doesn't mean that split fins are better, or that you can maneuver better in them, or that they silt less, or they have less entanglement issues. Some of these other 'strikes' against split fins are debateable and personal preference, others are indisputable. Those are valid reasons to not like them. The myth that somehow you get less power out of a split fin is simply wrong.

Etc...

 

[radinator]

A note about energy: Different fins aren't going to change the energy output of your body. You're going to put out the same energy whether you're wearing splits or paddles. It's the efficiency of the fins turning your body's energy into thrust that translates into faster or slower fins. If the same diver under the same conditions can swim 65 feet faster in splits than paddles, it's because the splits are more efficient at translating that divers energy into thrust.

Sorry, this is just plain inaccurate about energy expended.

The work performed is force x distance. So, when I move my leg, the work performed is the force I am pushing with multiplied by the distance I am moving it.

When I use paddle fins, I feel them 'bite' against the water. There is more force.

When I tried split fins, it felt like I had no fins at all. They didn't 'bite' the water. My leg moved the same distance, but there was less force.

Thus there was more energy expended using the paddle fin. W = F x d.

So a kick with the paddle fin requires more work. Your body is expending more energy.

You are accurate that when talking about efficiency (a term some here seem to use loosely), you have to consider what you get for the expended energy. But the expended energy is not independent of the fin used.

On the balance I prefer paddle fins. I tried the splits, and found that I needed 30% more kicks to get across the pool. Each kick was easier, in that there was less resistance due to the fin not 'biting' the water, but the result was there had to be more of them to get there.