Pervasive Fallacy about Split Fins

[Diver Dennis]

I wonder if any free divers use splits? They need a lot more propulsion than rec divers usually. I do know photographers who use free dive fins.

 

[Meister481]

I'm one of those silly people that use both. I have a set of turtles and a set of v-12's. I use both regularly, but in class I use the splits exclusively. I like the splits in the pool because they are lighter and more flexible. My last pool session I let the students try both sets to see the difference and some said they felt broken, some noticed that their thrust was more linear compared to the standard fins. My v-12's are extremely soft so they aren't the most efficient split, but they are comfortable. All the students thought the turtles threw off their buoyancy and were too stiff. The instructor really liked the idea and wants to keep doing things like that on the last day of OW class.

I guess I'm trying to make the point that it really doesn't matter, personal preference is the most important thing. If you don't like them, don't use them.

 

[Diver Dennis]

Since what's important in determining net velocity relative to the ground, you have to add the water's velocity relative to the ground (-4.0kts) and your velocity relative to the water (3.0kts). That gives you a -1.0kt velocity relative to the ground, but you can just as easily calculate both as relative velocities to a lobster you're chasing:
..

Craig

That is exactly what I said in my previous post. Less the lobster chase.

 

[Meister481]

Note that a frog kick, reverse kick, turns ect use the fin exactly as we use boat oars (paddles). Next time you go out in a canoe, try using paddles with splits in them and let me know how they work for you.

When paddling a canoe it would be a totally different force exerted on the fin than it would with a flutter kick. Cave divers know that splits ARE inferior to paddle design fins when alternate kicks are used. I believe the OP is trying to get that point across that the splits aren't useless or evil in the right environment. Proper tool for the job. I use my splits in warm water, use the turtles in caves, cold water, wrecks and when silt is a big issue.

 

[Charlie99]

There have been several tests that show that divers can sustain higher speed through the water with split fins than with paddle fins. With proper technique they are both faster and more efficient than paddle fins.

So why are split fins not universally accepted?

IMO, it comes down to two problems -----

1. Paddle fins give more control and manueverablity. This is because large paddle fins "grab" the water more effectively and are more easily used to change one's orientation and to do things like back kicks.

2. If you don't use proper technique, then split fins perform poorly. I strongly suspect that this is the reason behind the claims of "paddle fins don't do well in currents". From a physics point of view, the original poster is correct --- there is no difference from the diver's point of view whether he is moving at 4kts in still water, or making 1kt headway against a 3kt current. OTOH, if a diver in a current does not have the discipline to maintain the proper narrow flutter kick and starts trying to use wide powerful kicks, then he will lose speed.
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

 

[under water]

Ahhh. You didn't say this was based on the theory that splits are faster and more efficient. Are there tests that give credence to that theory?

Actually to say you have forward motion, I think you have to use a stationary object to measure it.

Hi Dennis,

http://www.scubadiving.com/upload/im...0_scubalab.pdf

They used divers pulling on guages tied to a pier as one of their tests.

They did concentrate on flutter kicks for most of their test, but they did evaluate alternative kicks as well​

This page has several years worth of tests.

http://www.scubadiving.com/fins​

Splits seem to be on top of the scoring.​

 

[Vie]

I use Jet Fins and Bio-fins. I love them both and they have their uses. The Jets I use for diving. The Bio-fins I use for snorkelling and messing around with my kids in the pool.

 

[highdesert]

When I took the Equipment Specialty class, my instructor (he's a sailor and I'm and ex-sailboat designer) said that splits employ the same kind of high pressure/low pressure physics that creates lift on an airplane wing or a sail, so that in addition to the "pushing" of water that you get with a paddle fin, you are also creating lift that "pulls" you through the water. This supposedly balances the fact that you have lost some of the "push" due to water escaping through the split.

In either style of fin, a stroke creates "tip vortices", which are really lost energy. The fin that reduces this kind of vortex, and conserves the energy in the stroke, overcomes part of the inefficiency of a fin.

 

[Diver Dennis]

Hi Dennis,

http://www.scubadiving.com/upload/im...0_scubalab.pdf

They used divers pulling on guages tied to a pier as one of their tests.

They did concentrate on flutter kicks for most of their test, but they did evaluate alternative kicks as well​

This page has several years worth of tests.

http://www.scubadiving.com/fins​

Splits seem to be on top of the scoring.​

Thanks Frank. I'll take a look.

 

[Ice9]

Would Chuck Norris ever use split fins?