Split fin kick style?

[fnfalman]

Ah, this is the root of the issue with me. This totally jibes with my experience - I felt like I was riding a bike in first gear - lots and lots of really easy kicks with no speed. The natural response is to take bigger kicks, but that won't work in splits. It seems the downside to that is you are using only a small percentage of muscle, but then again, maybe that is a good thing? Less oxygen usage? Less nitrogen absorption? I don't know - which uses more air - using a larger portion of muscle slowly or a smaller portion of muscle quickly?

I don't know about you but the few times I got caught in the current and had to kick like mad with my split fins, I used plenty of air and my leg muscles turned to mush afterward. :shocked2: When you generate speed and thrust, you can either do it with big, powerful, long throw kicks with a paddle fin or you do it with fast cycles on a split fin. The energy required to generate speed is going to be prodigious.

As far as no speed goes, I think that Scubalab's measurements tells otherwise when they tested split fins. Notice that No.1 standing belongs to a solid fin, but before the solid fin people start clapping their hands, also notice that the Atomic split fins destroyed a host of other solid fins. And the solid fin champs of this particular test were full-footed models which are well known to be more efficient than open-heels models just because the legs can transfer the energy directly to the fins instead of losing out to open heels design.

18 New Fins | Scuba Diving Magazine

 

[TSandM]

First, many people think current matters in the performance of fins, but I don't think that's true. Fin performance and your speed relative to the water is the same regardless of current. Your speed relative to the bottom is the sum of your swimming speed relative to the water and the current. Long, floppy fins produce less power "against a current" because they produce less power, period. Divers notice this more when they are struggling against a current because they are kicking harder and they can measure their lack of progress better.

Second, as can be seen in the "29-lb lift" video, to produce the same power, a long, floppy fin requires a faster kick cycle or a larger amplitude (up-and-down motion) kick, or both. A larger amplitude will generate a larger wake pattern and more turbulence behind the diver. This may be why many divers report that split fins seem to kick up more silt.

Ah, so beautifully said! It's the airspeed versus ground speed principle

My personal belief, which is mine and isn't going to change at all, is that split fins are a way to reduce swimming effort at the expense of reducing the force you can apply to the water.

Which is not to say that there aren't fin designs that improve efficiency over stiff, paddle fins. I just redid my mask and snorkel swim for my PADI DM class. I did it the first time in paddle fins and got a time that was worth two points. I redid the swim in Seawing Novas, borrowed from a student, and if I hadn't messed up the first couple of turns, I would have gotten four this time. It wasn't fitness that changed . . .

 

[gcbryan]

Originally Posted by gcbryan
Maybe some divers don't need to frog kick into high current, or back kick or do helicopter turns.

Those aren't divers, they are rototillers and coral killers

No one needs to frog kick into high current. Being able to back kick or to do helicopter turns is nice not not necessary. None of this has to result in rototilling and coral killing.

If you are fighting high current you probably aren't going to be within rototilling distance of the bottom and if you are frog kicking into high current you are just using the wrong kick for the circumstances.

Frog kicking on the bottom will eliminate the rototilling and this could be done with splits.

Splits are like the high gear on a bike and paddles are like the low gear. If there are no hills you can use the low gear for everything if you slow down. If there are no steep valleys you can use the high gear for everything within reason.

I only want to carry one pair of fins with me on a dive and I use paddles but for a long, long surface swim with little current I would greatly prefer to be in splits. Instead I use Jets and have to work harder and try to avoid very long surface swims in the first place but it is a choice of power and control over ease of use in some circumstances.

 

[mdb]

This discussion comes up again and again. It is worthwhile for the new diver to have some opinions from all us SB "experts".

As pointed out, many times, some divers will prefer a low torque stiffer paddle fin, others a split style fin with less resistance, less strain, and higher top end speeds. Depends on the task at hand and the divers personal preference.

All split fins are not created equal. The same for paddle fins.

We manufacture a stiffer version of our bio-fin in the XT model. This is my favorite. The XT is much stiffer than the bio-fin pro. It feels and reacts much like a traditional paddle fin with the benefit of power on both strokes.

I learned to dive with Scuba-Pro Jet fins, then on to Voit duck feet, various Mares fins etc. I am used to a wider scissors style kick and I like the "bite" and feed back of a stiffer fin. It is all a matter of individual choice.

Our most efficient fin, with the least resistance and highest test speeds, is the original bio-fin pro. The most effective kick with the bio-fin pro is a small flutter kick.

Some video is @:
Apollo Sports: Dive Gear

 

[scjoe]

In discussing split fins and blades, I think most people would benefit by reading Pendergast’s studies. These were not studies done for a magazine so the frequent dismissal of those studies by various SB posters as just being designed to sell new fins doesn’t fly. Also, Pendergast included in his studies the beloved Jet Fin as well as Quattros, Apollo split fins, Oceanic Ocean Pro, U.S. Divers Compro, Mares Attack and US Divers Blades. He also separated his studies between male and female participants. His male subjects were scuba instructors in their thirties averaging 100 hours of diving a year and his female subjects were in their twenties averaging 30 hours of diving a year.

He found that the Apollo had a significantly lower energy cost for women than the Jets or Quattros. In the case of men, he found that the Mares Attack, Apollo and Jets had the lowest energy cost among the fins tested with the Jet being the lowest. The maximum thrust developed by women using the Apollo, Jet or Quattro fin was about the same. This was true for men as well. Maximum thrust is a combination of distance per kick and kick frequency. Although fin stiffness does affect distance per kick, the distance per kick for the Apollo, Jet and Quatro was about the same for women. Only the Attack fin, which was the stiffest, had a significantly greater distance per kick than the other fins. The Attack fin generated the highest velocity for both men and women, but the velocity of the Apollo, Jet and Quattros was about the same. All four produced similar speeds.

A couple of quotes from the male study may be helpful:

“In our studies, the divers invariably ranked the stiff fins as the best and the flexible fins as the worse, which did not correlate with objective evaluation of these fins.”

“This comparison indicates that both drag (kick depth) and efficiency (kick frequency) have to optimized to minimize the energy cost of swimming and accounts for the similar performance of the Attack and Apollo fins.”

“The proposition that rigid fins develop more thrust and speed was not supported by this work.” “…the most rigid and most flexible fin had similar performances.”

 

[TSandM]

I wonder if the difference with the Jets between men and women in the study had more to do with the fact that the women tested were diving far less than the men?

 

[gcbryan]

I don't think anyone doubts that without current you get a higher top end speed with splits (maybe someone does but I don't) but anyone who has tried to battle high current and have adequate control under those circumstances will also more than likely have no doubt that paddles were much more effective.

In between those two scenarios the differences are less. My point is that for the many people who have used both you don't really need a study. I own both Jets and Twin Jets.

There used to be a dive site here (Edmonds Oil Dock) that involved a rather long surface swim. I've done it many times in both Jets and Twin Jets. You have to kick more cycles I'm sure in Twins but your legs will be much less tired at the end of the day than with Jets.

On the other hand, we have many deep rock wall dives here where there is frequently (even when well timed) a light current pushing you along. You can do the dive with Twin Jets but you will have much more control being able to use one or two paddles to keep you in place or to allow your body to rotate or speed up/slow down relative to your buddy.

We also have sites where you may be on the surface and have to battle not insignificant current on your way in to shore. It's simply much easier and effective to do this with Jets rather than Twin Jets.

No study would change my mind on these points.

 

[H2O 70]

It is not a problem of your fins I bet. Atomic split is quite stiff fin and gives enough thrust. I know as I had one in the past. Pay closer attention to your trim and streamlining of your gear. It makes a huge difference. All unnecessary staff hanging of you will slow you down.

Well, my BCD at the time was too big for me (I lost weight over winter) and it was not fitting well. I am switching to a BP/W and looking forward to a tighter streamline - i have a Balance and it is nice, but it still feels bulky. Trim was pretty good and weight was maybe a little heavy, but not too much. The splits worked well for slow movement - which I prefer for just watching the life - it was when we hit current (1-2 kts) that I noticed a distinct lack of propulsion. I was able to frog kick (of sorts - still working that one out) and that worked well. Not so much on the back kick.

I think you and elan have answered the question on why, at least in this case, the dive leader was gliding through the water.

When leading OW Checkout tours, I have to go, what feels to me, insanely slow, even diving doubles. I do one frog kick to the students 3-4 flutter kicks. Big difference is when I look back at them, I can see their whole body. They aren't trimmed right just yet and for sure they are a wee bit heavy.

In general, split fins are very efficient but low torque and paddle fins are not as efficient but provide a lot of torque.

Which if you think about swimming in current as you described, makes sense.

I'll let everyone else continue to hash out the old split vs. paddle thing.

 

[lulubelle]

Thanks everyone for your comments. I've seen this debate many times and many places, but generally it has deteriorated into a "I'm right" discussion. I appreciate the discussion which gives me some food for thought.

I have both Atomic Splits and TUSA Imprex Tri Ex paddles which are quite long. I have wickedly skinny feet, so my choices are somewhat limited.

For Carribean diving, even drift diving, I prefer the splits. I have tiny ankles and I just don't get the ankle fatigue I get with paddles. I cannot do a frog kick with them however, I'll have to work on that.

But for diving here in NC, I can't stand to wear the splits. I am a former competitive swimmer. When there is a strong current to power through, it is just easier and more intuitive for me to get where I need to get in paddles. I find it much easier to modify my kick style for the circumstances too. I also haven't seen anyone in splits go inside of a wreck without making a mess.

What I would really prefer though is fins that FIT. My shoe size is 10AAAA.

 

[jstamets]

Just a reminder that the original question is not which fin is better, but rather, what is the correct way to use the fin - in my case, splits. I think it is fair to discuss fin differences, given that I was wearing splits and the guide was wearing paddles, but there are other factors that weigh into that - he is 19, I am 44, he dives daily, I have 15 dives and live in Ohio (not a lot of swimming going on right now). So fitness may play into that as well. The motivation for my question was the difference I seemed to experience within my own fins going from still water to a mild current with surge. I could keep up when in still water, but not as easily when the water started moving.

Many of the posts here are quite helpful. The big takeaway for me so far is that the fin styles are different and I was treating my splits more like paddles. One post early on suggested I may be better suited to paddles. Since I am looking at GUE for continuing education (no DIR rabbit trails please), I do have a set of paddles on the way. With both, I should be able to make my own decisions regarding "which is best" (or more accurately, which is more preferable to me), but unless a diver knows how to correctly use the fins he or she is using, regardless of the style, then it is not likely to be a very useful comparison.

That being said, I have a lot more understanding of the nature of both styles now as well as the kick styles that may be better suited to each fin type and I think I can get more out of the splits, should the need arise.