A vortex?

[elmer fudd]

Having owned about six different fins I can without a second thought that I loved the split fins for speed and no cramps. When it comes to strong current or pushing an excessive amount of gear they feel like mush and really can't compare to paddle fins like the Hollis F1s.
He the diver holding a knife in his right hand?
I have only been into a vertical vortex on thr Cooper river but have never seen anything like this. Do we have some one that can do some translation from the facebook page to tell us what the OP said?

This I don't get. If you like the splits for speed, then why not for current? My split fin diving buddies seem to do just as well in current as I do in my paddles.

The only difference I notice in terms of speed is that paddles accelerate you instantly, whereas with splits it seems to take a few seconds before you reach full speed. Eventually though they both seem to reach about the same velocity.

 

[BVickery]

This I don't get. If you like the splits for speed, then why not for current? My split fin diving buddies seem to do just as well in current as I do in my paddles.

The only difference I notice in terms of speed is that paddles accelerate you instantly, whereas with splits it seems to take a few seconds before you reach full speed. Eventually though they both seem to reach about the same velocity.

I am wondering what the physical exertion between the two would be, which is the real question. I heard that splits aren't good in storng currents because the force needed is more than you would with a paddle. Anyone else hear or know if this is true?

 

[danvolker]

I came across this video this morning. I wonder what causes this, it was obviously hard for the diver to finally free himself.

https://www.facebook.com/photo.php?v=10151501528543380&set=vb.721338379&type=3&theater

I have never seen anything like this...I would love to get in one and experience it myself.

One thing about the severity of this though....most of these divers showed terrible propulsion skills....which is fairly typical of open water divers at normal training levels. One even used his hands as a primary propulsion solution, which speaks volumes about his lack of skill and poor training.
The others had "kick shapes" that were terrible for propulsion, and with such a lack of coordination, even freedive fins would not help.

I am going to say this again...PADI and NAUI and most agencies do not train kick shape or kicking skill to the masses that get certified...some of the individual instructors do...some of the instructors here may....but most divers just do this badly. I would love to blame this on split fins, but the guy on the left probably was using split fins, because his kick shape was so bad, that only fins as forgiving of bad technique as split fins, would allow him to get around. And with this weird vortex effect, these divers would just have needed to know how to kick properly.

 

[elmer fudd]

I am wondering what the physical exertion between the two would be, which is the real question. I heard that splits aren't good in storng currents because the force needed is more than you would with a paddle. Anyone else hear or know if this is true?

There is a world of difference between the way the two styles feel and perform, but in my experience they both work tolerably well. I don't think one style is faster or more powerful than the other and every real test I have read about seems to bear this out. I've also never noticed that my air consumption is much different, but it's been a couple years since I last dove splits.

What I do notice is that split fins are more of a one trick pony. They seem effortless to kick with a small short flutter kick, but when it comes to frog kicks turns and other things they just don't perform as well as paddles.

I have heard claims that splits are more efficient when used with a short kick because it keeps your legs and fins more within your slipstream and helps streamline you.

I've also heard claims that they actually act like propellers, which might be alright if we had propeller shafts instead of feet.

 

[danvolker]

Tests on all the print rags are basically paid for by big advertisers, AND the print rags would NEVER say that a big advertiser ( say the Biofin) is a piss poor fin....even if it obviously was.

On the other hand...we will be doing a DEMO Day at the BHB Marine Park in July, where divers will be able to try the major fins, and compare splits to Force Fins to Jet fins to hollis fins to normal freedive fins and even to the exotic composite freedive fins ( the Lamborghini Gallardo of Fins...in performance AND price).

I can pretty much guarantee that the people that have good kicking coordination, will be blown away by how much more efficient non-split fins can be.

 

[scubafied]

How do split fins enter into this? I have done pool tests lap swimming a variety of fins both in full gear and not and I can tell you that split fins are at least as fast as as paddle fins, as a generic quality. To be more specific about fin qualities and the ability to push a scuba diver we would have to talk about a specific fin, not fin type.

I doubt seriously either that the mini-votices that emanate from splits would inititate an underwater malstrom.

So you do not use splits because of underwater vortices, okay. With all the arm swimming I saw in that video, I doubt split fins were their issue.

N

That is pretty damn funny. I did not mean to imply that his split fins caused the vortice. If they did I would be running out to get some so I too could experience this phenomenon.

I have also had plenty of opportunities to use both. I prefer paddle fins as (for me) they are far more effective in every scenario but more importantly, in current. Dan brings up some very good points, not only about the 2 types of fins but about the divers in the video. You can see well before anyone is stuck that they do not seem to have very good propulsion skills to begin with.

I did not intend to turn this into another fin war. I couldn't care less what kind of fins someone is using, so long as I don't have to come help you should your fins prove ineffective. When that happens I will speak my peace on the boat.

 

[danvolker]

From my diving at the BHB Marine Park, and on charter boats, I have shot a lot of video of divers and groups with terrible propulsion skills.....one thing that is really beginning to stand out for me is the common denominator here with the worst of the kicking shapes, and worst , bicycling type kicks.....the Split Fins apparently allow propulsion to be arrived at, almost no matter how they are kicked---using almost any kick shape. I think this is the over-riding reason they have grown so much in popularity. Between the instructors and agency position that they did not want to spend the time with precision kick shape and techniques, and divers that are poorly coordinated, and with divers that JUST DON'T CARE TO LEARN PROPER KICK SHAPES AND IDEAL BIO0MECHANICS, I think Split fins end up the fin of choice, because they alone require no coordination..
Clearly a diver with GOOD coordination can do much more with split fins than an uncoordinated diver, but the real issue here is the instant access to propulsion a split fin delivers. The opposite would be a free dive fin....with this, you really need to understand how the hip and knee should be angled at all times, how they change throughout the kick cycle, in order to gain efficient use of this style of fin....if you do, the freedive fin wearing diver could literally swim at twice the speed of his evil split fin wearing twin, at a lower exertion level than the evil twin....

With SP Jet, the stiffness demands the correct kick shape, or the fins just won't get you anywhere, and the muscles will fatigue immediately from incorrect use with the fins.

I will be illustrating all of this with a video....and there will be a DEMO day where you can see this yourself

 

[Wolfie_47]

That does look like fun. I wonder though if the diver couldn't have just vented his BC a litttle and dropped out of it... or would it have had enough power to hold you in the current?

 

[elmer fudd]

Clearly a diver with GOOD coordination can do much more with split fins than an uncoordinated diver, but the real issue here is the instant access to propulsion a split fin delivers. The opposite would be a free dive fin....with this, you really need to understand how the hip and knee should be angled at all times, how they change throughout the kick cycle, in order to gain efficient use of this style of fin....if you do, the freedive fin wearing diver could literally swim at twice the speed of his evil split fin wearing twin, at a lower exertion level than the evil twin....

With SP Jet, the stiffness demands the correct kick shape, or the fins just won't get you anywhere, and the muscles will fatigue immediately from incorrect use with the fins.

I will be illustrating all of this with a video....and there will be a DEMO day where you can see this yourself

I have all the types of fins mentioned above, and I don't really find the speed thing to be true...using scuba gear.

The limiting factor for speed is water resistance, much more than thrust. The typical diver finning hard can go about 2 mph using fins that generate about 3 ft lbs of thrust. Some scooters on the other hand can generate in excess of 60 ft lbs of thrust, yet multiplying the amount of thrust by a factor of 20 only results in a doubling of the speed, if that. Freedive fins almost certainly are the most efficient fins out there, but they provide nowhere near the thrust of a scooter.

Free divers themselves are another story. They take streamlining and efficiency extremely seriously, sometimes even opting for things like monofins and fluid goggles. I think they also tend to be much more serious divers and athletes than scuba divers.


I'm also no fan of split fins. I probably do 80% of my dives with paddles and the other 20% with freedive fins, but I do dive with buddies that use split fins and they have no trouble keeping up or dealing with current and their air consumption is no worse than mine. They also seem to really like their fins, so I've got to concede that split fins really are adequate for scuba diving.

 

[OkByMe]

That does look like fun. I wonder though if the diver couldn't have just vented his BC a litttle and dropped out of it... or would it have had enough power to hold you in the current?

Good question... I have used the BC to rise and drop into different currents without so much as a kick. But it looks like they were into the experience and did not want out. It also looks like they were blowing through some air too.

FINS What is that about?